Adding upstream version 7.0.14-dfsg.upstream/7.0.14-dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

16 files changed, 11935 insertions, 0 deletions

diff --git a/src/VBox/GuestHost/SharedClipboard/ClipboardDataObjectImpl-win.cpp b/src/VBox/GuestHost/SharedClipboard/ClipboardDataObjectImpl-win.cpp
new file mode 100644
index 00000000..edf9d6e7
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/ClipboardDataObjectImpl-win.cpp
@@ -0,0 +1,978 @@
+/* $Id: ClipboardDataObjectImpl-win.cpp $ */
+/** @file
+ * ClipboardDataObjectImpl-win.cpp - Shared Clipboard IDataObject implementation.
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/GuestHost/SharedClipboard-win.h>
+#include <VBox/GuestHost/SharedClipboard-transfers.h>
+
+#include <iprt/win/windows.h>
+#include <iprt/win/shlobj.h>
+#include <iprt/win/shlwapi.h>
+
+#include <iprt/asm.h>
+#include <iprt/err.h>
+#include <iprt/path.h>
+#include <iprt/semaphore.h>
+#include <iprt/uri.h>
+#include <iprt/utf16.h>
+
+#include <iprt/errcore.h>
+#include <VBox/log.h>
+
+/** @todo Also handle Unicode entries.
+ *        !!! WARNING: Buggy, doesn't work yet (some memory corruption / garbage in the file name descriptions) !!! */
+//#define VBOX_CLIPBOARD_WITH_UNICODE_SUPPORT 1
+
+SharedClipboardWinDataObject::SharedClipboardWinDataObject(PSHCLTRANSFER pTransfer,
+                                                           LPFORMATETC pFormatEtc, LPSTGMEDIUM pStgMed, ULONG cFormats)
+    : m_enmStatus(Uninitialized)
+    , m_lRefCount(0)
+    , m_cFormats(0)
+    , m_pTransfer(pTransfer)
+    , m_pStream(NULL)
+    , m_uObjIdx(0)
+    , m_fRunning(false)
+    , m_EventListComplete(NIL_RTSEMEVENT)
+    , m_EventTransferComplete(NIL_RTSEMEVENT)
+{
+    AssertPtr(m_pTransfer);
+
+    HRESULT hr;
+
+    ULONG cFixedFormats = 3; /* CFSTR_FILEDESCRIPTORA + CFSTR_FILECONTENTS + CFSTR_PERFORMEDDROPEFFECT */
+#ifdef VBOX_CLIPBOARD_WITH_UNICODE_SUPPORT
+    cFixedFormats++; /* CFSTR_FILEDESCRIPTORW */
+#endif
+    const ULONG cAllFormats   = cFormats + cFixedFormats;
+
+    try
+    {
+        m_pFormatEtc = new FORMATETC[cAllFormats];
+        RT_BZERO(m_pFormatEtc, sizeof(FORMATETC) * cAllFormats);
+        m_pStgMedium = new STGMEDIUM[cAllFormats];
+        RT_BZERO(m_pStgMedium, sizeof(STGMEDIUM) * cAllFormats);
+
+        /** @todo Do we need CFSTR_FILENAME / CFSTR_SHELLIDLIST here? */
+
+        /*
+         * Register fixed formats.
+         */
+        unsigned uIdx = 0;
+
+        LogFlowFunc(("Registering CFSTR_FILEDESCRIPTORA ...\n"));
+        m_cfFileDescriptorA = RegisterClipboardFormat(CFSTR_FILEDESCRIPTORA);
+        registerFormat(&m_pFormatEtc[uIdx++], m_cfFileDescriptorA);
+#ifdef VBOX_CLIPBOARD_WITH_UNICODE_SUPPORT
+        LogFlowFunc(("Registering CFSTR_FILEDESCRIPTORW ...\n"));
+        m_cfFileDescriptorW = RegisterClipboardFormat(CFSTR_FILEDESCRIPTORW);
+        registerFormat(&m_pFormatEtc[uIdx++], m_cfFileDescriptorW);
+#endif
+
+        /* IStream interface, implemented in ClipboardStreamImpl-win.cpp. */
+        LogFlowFunc(("Registering CFSTR_FILECONTENTS ...\n"));
+        m_cfFileContents = RegisterClipboardFormat(CFSTR_FILECONTENTS);
+        registerFormat(&m_pFormatEtc[uIdx++], m_cfFileContents, TYMED_ISTREAM, 0 /* lIndex */);
+
+        /* We want to know from the target what the outcome of the operation was to react accordingly (e.g. abort a transfer). */
+        LogFlowFunc(("Registering CFSTR_PERFORMEDDROPEFFECT ...\n"));
+        m_cfPerformedDropEffect = RegisterClipboardFormat(CFSTR_PERFORMEDDROPEFFECT);
+        registerFormat(&m_pFormatEtc[uIdx++], m_cfPerformedDropEffect, TYMED_HGLOBAL, -1 /* lIndex */, DVASPECT_CONTENT);
+
+        /*
+         * Registration of dynamic formats needed?
+         */
+        LogFlowFunc(("%RU32 dynamic formats\n", cFormats));
+        if (cFormats)
+        {
+            AssertPtr(pFormatEtc);
+            AssertPtr(pStgMed);
+
+            for (ULONG i = 0; i < cFormats; i++)
+            {
+                LogFlowFunc(("Format %RU32: cfFormat=%RI16, tyMed=%RU32, dwAspect=%RU32\n",
+                             i, pFormatEtc[i].cfFormat, pFormatEtc[i].tymed, pFormatEtc[i].dwAspect));
+                m_pFormatEtc[cFixedFormats + i] = pFormatEtc[i];
+                m_pStgMedium[cFixedFormats + i] = pStgMed[i];
+            }
+        }
+
+        hr = S_OK;
+    }
+    catch (std::bad_alloc &)
+    {
+        hr = E_OUTOFMEMORY;
+    }
+
+    if (SUCCEEDED(hr))
+    {
+        m_cFormats  = cAllFormats;
+        m_enmStatus = Initialized;
+
+        int rc2 = RTSemEventCreate(&m_EventListComplete);
+        AssertRC(rc2);
+        rc2 = RTSemEventCreate(&m_EventTransferComplete);
+        AssertRC(rc2);
+    }
+
+    LogFlowFunc(("cAllFormats=%RU32, hr=%Rhrc\n", cAllFormats, hr));
+}
+
+SharedClipboardWinDataObject::~SharedClipboardWinDataObject(void)
+{
+    LogFlowFuncEnter();
+
+    RTSemEventDestroy(m_EventListComplete);
+    m_EventListComplete = NIL_RTSEMEVENT;
+
+    RTSemEventDestroy(m_EventTransferComplete);
+    m_EventTransferComplete = NIL_RTSEMEVENT;
+
+    if (m_pStream)
+        m_pStream->Release();
+
+    if (m_pFormatEtc)
+        delete[] m_pFormatEtc;
+
+    if (m_pStgMedium)
+        delete[] m_pStgMedium;
+
+    LogFlowFunc(("mRefCount=%RI32\n", m_lRefCount));
+}
+
+/*
+ * IUnknown methods.
+ */
+
+STDMETHODIMP_(ULONG) SharedClipboardWinDataObject::AddRef(void)
+{
+    LONG lCount = InterlockedIncrement(&m_lRefCount);
+    LogFlowFunc(("lCount=%RI32\n", lCount));
+    return lCount;
+}
+
+STDMETHODIMP_(ULONG) SharedClipboardWinDataObject::Release(void)
+{
+    LONG lCount = InterlockedDecrement(&m_lRefCount);
+    LogFlowFunc(("lCount=%RI32\n", m_lRefCount));
+    if (lCount == 0)
+    {
+        delete this;
+        return 0;
+    }
+
+    return lCount;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::QueryInterface(REFIID iid, void **ppvObject)
+{
+    AssertPtrReturn(ppvObject, E_INVALIDARG);
+
+    if (   iid == IID_IDataObject
+        || iid == IID_IUnknown)
+    {
+        AddRef();
+        *ppvObject = this;
+        return S_OK;
+    }
+
+    *ppvObject = 0;
+    return E_NOINTERFACE;
+}
+
+/**
+ * Copies a chunk of data into a HGLOBAL object.
+ *
+ * @returns VBox status code.
+ * @param   pvData              Data to copy.
+ * @param   cbData              Size (in bytes) to copy.
+ * @param   fFlags              GlobalAlloc flags, used for allocating the HGLOBAL block.
+ * @param   phGlobal            Where to store the allocated HGLOBAL object.
+ */
+int SharedClipboardWinDataObject::copyToHGlobal(const void *pvData, size_t cbData, UINT fFlags, HGLOBAL *phGlobal)
+{
+    AssertPtrReturn(phGlobal, VERR_INVALID_POINTER);
+
+    HGLOBAL hGlobal = GlobalAlloc(fFlags, cbData);
+    if (!hGlobal)
+        return VERR_NO_MEMORY;
+
+    void *pvAlloc = GlobalLock(hGlobal);
+    if (pvAlloc)
+    {
+        CopyMemory(pvAlloc, pvData, cbData);
+        GlobalUnlock(hGlobal);
+
+        *phGlobal = hGlobal;
+
+        return VINF_SUCCESS;
+    }
+
+    GlobalFree(hGlobal);
+    return VERR_ACCESS_DENIED;
+}
+
+/**
+ * Reads (handles) a specific directory reursively and inserts its entry into the
+ * objects's entry list.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Shared Clipboard transfer object to handle.
+ * @param   strDir              Directory path to handle.
+ */
+int SharedClipboardWinDataObject::readDir(PSHCLTRANSFER pTransfer, const Utf8Str &strDir)
+{
+    LogFlowFunc(("strDir=%s\n", strDir.c_str()));
+
+    SHCLLISTOPENPARMS openParmsList;
+    int rc = ShClTransferListOpenParmsInit(&openParmsList);
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTStrCopy(openParmsList.pszPath, openParmsList.cbPath, strDir.c_str());
+        if (RT_SUCCESS(rc))
+        {
+            SHCLLISTHANDLE hList;
+            rc = ShClTransferListOpen(pTransfer, &openParmsList, &hList);
+            if (RT_SUCCESS(rc))
+            {
+                LogFlowFunc(("strDir=%s -> hList=%RU64\n", strDir.c_str(), hList));
+
+                SHCLLISTHDR hdrList;
+                rc = ShClTransferListGetHeader(pTransfer, hList, &hdrList);
+                if (RT_SUCCESS(rc))
+                {
+                    LogFlowFunc(("cTotalObjects=%RU64, cbTotalSize=%RU64\n\n",
+                                 hdrList.cTotalObjects, hdrList.cbTotalSize));
+
+                    for (uint64_t o = 0; o < hdrList.cTotalObjects; o++)
+                    {
+                        SHCLLISTENTRY entryList;
+                        rc = ShClTransferListEntryInit(&entryList);
+                        if (RT_SUCCESS(rc))
+                        {
+                            rc = ShClTransferListRead(pTransfer, hList, &entryList);
+                            if (RT_SUCCESS(rc))
+                            {
+                                if (ShClTransferListEntryIsValid(&entryList))
+                                {
+                                    PSHCLFSOBJINFO pFsObjInfo = (PSHCLFSOBJINFO)entryList.pvInfo;
+                                    Assert(entryList.cbInfo == sizeof(SHCLFSOBJINFO));
+
+                                    Utf8Str strPath = strDir + Utf8Str("\\") + Utf8Str(entryList.pszName);
+
+                                    LogFlowFunc(("\t%s (%RU64 bytes) -> %s\n",
+                                                 entryList.pszName, pFsObjInfo->cbObject, strPath.c_str()));
+
+                                    if (RTFS_IS_DIRECTORY(pFsObjInfo->Attr.fMode))
+                                    {
+                                        FSOBJENTRY objEntry = { strPath.c_str(), *pFsObjInfo };
+
+                                        m_lstEntries.push_back(objEntry); /** @todo Can this throw? */
+
+                                        rc = readDir(pTransfer, strPath.c_str());
+                                    }
+                                    else if (RTFS_IS_FILE(pFsObjInfo->Attr.fMode))
+                                    {
+                                        FSOBJENTRY objEntry = { strPath.c_str(), *pFsObjInfo };
+
+                                        m_lstEntries.push_back(objEntry); /** @todo Can this throw? */
+                                    }
+                                    else
+                                        rc = VERR_NOT_SUPPORTED;
+
+                                    /** @todo Handle symlinks. */
+                                }
+                                else
+                                    rc = VERR_INVALID_PARAMETER;
+                            }
+
+                            ShClTransferListEntryDestroy(&entryList);
+                        }
+
+                        if (   RT_FAILURE(rc)
+                            && pTransfer->Thread.fStop)
+                            break;
+                    }
+                }
+
+                ShClTransferListClose(pTransfer, hList);
+            }
+        }
+
+        ShClTransferListOpenParmsDestroy(&openParmsList);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Thread for reading transfer data.
+ * The data object needs the (high level, root) transfer listing at the time of ::GetData(), so we need
+ * to block and wait until we have this data (via this thread) and continue.
+ *
+ * @returns VBox status code.
+ * @param   ThreadSelf          Thread handle. Unused at the moment.
+ * @param   pvUser              Pointer to user-provided data. Of type SharedClipboardWinDataObject.
+ */
+/* static */
+DECLCALLBACK(int) SharedClipboardWinDataObject::readThread(RTTHREAD ThreadSelf, void *pvUser)
+{
+    RT_NOREF(ThreadSelf);
+
+    LogFlowFuncEnter();
+
+    SharedClipboardWinDataObject *pThis = (SharedClipboardWinDataObject *)pvUser;
+
+    PSHCLTRANSFER pTransfer = pThis->m_pTransfer;
+    AssertPtr(pTransfer);
+
+    pTransfer->Thread.fStarted = true;
+    pTransfer->Thread.fStop    = false;
+
+    RTThreadUserSignal(RTThreadSelf());
+
+    LogRel2(("Shared Clipboard: Calculating transfer ...\n"));
+
+    PSHCLROOTLIST pRootList;
+    int rc = ShClTransferRootsGet(pTransfer, &pRootList);
+    if (RT_SUCCESS(rc))
+    {
+        LogFlowFunc(("cRoots=%RU32\n\n", pRootList->Hdr.cRoots));
+
+        for (uint32_t i = 0; i < pRootList->Hdr.cRoots; i++)
+        {
+            PSHCLLISTENTRY pRootEntry = &pRootList->paEntries[i];
+            AssertPtr(pRootEntry);
+
+            Assert(pRootEntry->cbInfo == sizeof(SHCLFSOBJINFO));
+            PSHCLFSOBJINFO pFsObjInfo = (PSHCLFSOBJINFO)pRootEntry->pvInfo;
+
+            LogFlowFunc(("pszRoot=%s, fMode=0x%x\n", pRootEntry->pszName, pFsObjInfo->Attr.fMode));
+
+            if (RTFS_IS_DIRECTORY(pFsObjInfo->Attr.fMode))
+            {
+                FSOBJENTRY objEntry = { pRootEntry->pszName, *pFsObjInfo };
+
+                pThis->m_lstEntries.push_back(objEntry); /** @todo Can this throw? */
+
+                rc = pThis->readDir(pTransfer, pRootEntry->pszName);
+            }
+            else if (RTFS_IS_FILE(pFsObjInfo->Attr.fMode))
+            {
+                FSOBJENTRY objEntry = { pRootEntry->pszName, *pFsObjInfo };
+
+                pThis->m_lstEntries.push_back(objEntry); /** @todo Can this throw? */
+            }
+            else
+                rc = VERR_NOT_SUPPORTED;
+
+            if (ASMAtomicReadBool(&pTransfer->Thread.fStop))
+            {
+                LogRel2(("Shared Clipboard: Stopping transfer calculation ...\n"));
+                break;
+            }
+
+            if (RT_FAILURE(rc))
+                break;
+        }
+
+        ShClTransferRootListFree(pRootList);
+        pRootList = NULL;
+
+        if (   RT_SUCCESS(rc)
+            && !ASMAtomicReadBool(&pTransfer->Thread.fStop))
+        {
+            LogRel2(("Shared Clipboard: Transfer calculation complete (%zu root entries)\n", pThis->m_lstEntries.size()));
+
+            /*
+             * Signal the "list complete" event so that this data object can return (valid) data via ::GetData().
+             * This in turn then will create IStream instances (by the OS) for each file system object to handle.
+             */
+            int rc2 = RTSemEventSignal(pThis->m_EventListComplete);
+            AssertRC(rc2);
+
+            if (pThis->m_lstEntries.size())
+            {
+                LogRel2(("Shared Clipboard: Waiting for transfer to complete ...\n"));
+
+                LogFlowFunc(("Waiting for transfer to complete ...\n"));
+
+                /* Transferring stuff can take a while, so don't use any timeout here. */
+                rc2 = RTSemEventWait(pThis->m_EventTransferComplete, RT_INDEFINITE_WAIT);
+                AssertRC(rc2);
+
+                switch (pThis->m_enmStatus)
+                {
+                    case Completed:
+                        LogRel2(("Shared Clipboard: Transfer complete\n"));
+                        break;
+
+                    case Canceled:
+                        LogRel2(("Shared Clipboard: Transfer canceled\n"));
+                        break;
+
+                    case Error:
+                        LogRel2(("Shared Clipboard: Transfer error occurred\n"));
+                        break;
+
+                    default:
+                        break;
+                }
+            }
+            else
+               LogRel(("Shared Clipboard: No transfer root entries found -- should not happen, please file a bug report\n"));
+        }
+        else if (RT_FAILURE(rc))
+            LogRel(("Shared Clipboard: Transfer failed with %Rrc\n", rc));
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Creates a FILEGROUPDESCRIPTOR object from a given Shared Clipboard transfer and stores the result into an HGLOBAL object.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Shared Clipboard transfer to create file grou desciprtor for.
+ * @param   fUnicode            Whether the FILEGROUPDESCRIPTOR object shall contain Unicode data or not.
+ * @param   phGlobal            Where to store the allocated HGLOBAL object on success.
+ */
+int SharedClipboardWinDataObject::createFileGroupDescriptorFromTransfer(PSHCLTRANSFER pTransfer,
+                                                                        bool fUnicode, HGLOBAL *phGlobal)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+    AssertPtrReturn(phGlobal,  VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    const size_t cbFileGroupDescriptor = fUnicode ? sizeof(FILEGROUPDESCRIPTORW) : sizeof(FILEGROUPDESCRIPTORA);
+    const size_t cbFileDescriptor = fUnicode ? sizeof(FILEDESCRIPTORW) : sizeof(FILEDESCRIPTORA);
+
+    const UINT   cItems = (UINT)m_lstEntries.size(); /** UINT vs. size_t. */
+    if (!cItems)
+        return VERR_NOT_FOUND;
+
+    UINT         curIdx = 0; /* Current index of the handled file group descriptor (FGD). */
+
+    const size_t cbFGD  = cbFileGroupDescriptor + (cbFileDescriptor * (cItems - 1));
+
+    LogFunc(("fUnicode=%RTbool, cItems=%u, cbFileDescriptor=%zu\n", fUnicode, cItems, cbFileDescriptor));
+
+    /* FILEGROUPDESCRIPTORA / FILEGROUPDESCRIPTOR matches except the cFileName member (TCHAR vs. WCHAR). */
+    FILEGROUPDESCRIPTOR *pFGD = (FILEGROUPDESCRIPTOR *)RTMemAllocZ(cbFGD);
+    if (!pFGD)
+        return VERR_NO_MEMORY;
+
+    int rc = VINF_SUCCESS;
+
+    pFGD->cItems = cItems;
+
+    char *pszFileSpec = NULL;
+
+    FsObjEntryList::const_iterator itRoot = m_lstEntries.begin();
+    while (itRoot != m_lstEntries.end())
+    {
+        FILEDESCRIPTOR *pFD = &pFGD->fgd[curIdx];
+        RT_BZERO(pFD, cbFileDescriptor);
+
+        const char *pszFile = itRoot->strPath.c_str();
+        AssertPtr(pszFile);
+
+        pszFileSpec = RTStrDup(pszFile);
+        AssertBreakStmt(pszFileSpec != NULL, rc = VERR_NO_MEMORY);
+
+        if (fUnicode)
+        {
+            PRTUTF16 pwszFileSpec;
+            rc = RTStrToUtf16(pszFileSpec, &pwszFileSpec);
+            if (RT_SUCCESS(rc))
+            {
+                rc = RTUtf16CopyEx((PRTUTF16 )pFD->cFileName, sizeof(pFD->cFileName) / sizeof(WCHAR),
+                                   pwszFileSpec, RTUtf16Len(pwszFileSpec));
+                RTUtf16Free(pwszFileSpec);
+
+                LogFlowFunc(("pFD->cFileNameW=%ls\n", pFD->cFileName));
+            }
+        }
+        else
+        {
+            rc = RTStrCopy(pFD->cFileName, sizeof(pFD->cFileName), pszFileSpec);
+            LogFlowFunc(("pFD->cFileNameA=%s\n", pFD->cFileName));
+        }
+
+        RTStrFree(pszFileSpec);
+        pszFileSpec = NULL;
+
+        if (RT_FAILURE(rc))
+            break;
+
+        pFD->dwFlags          = FD_PROGRESSUI | FD_ATTRIBUTES;
+        if (fUnicode) /** @todo Only >= Vista. */
+            pFD->dwFlags     |= FD_UNICODE;
+        pFD->dwFileAttributes = FILE_ATTRIBUTE_NORMAL;
+
+        const SHCLFSOBJINFO *pObjInfo = &itRoot->objInfo;
+
+        if (RTFS_IS_DIRECTORY(pObjInfo->Attr.fMode))
+        {
+            pFD->dwFileAttributes |= FILE_ATTRIBUTE_DIRECTORY;
+        }
+        else if (RTFS_IS_FILE(pObjInfo->Attr.fMode))
+        {
+            pFD->dwFlags |= FD_FILESIZE;
+
+            const uint64_t cbObjSize = pObjInfo->cbObject;
+
+            pFD->nFileSizeHigh = RT_HI_U32(cbObjSize);
+            pFD->nFileSizeLow  = RT_LO_U32(cbObjSize);
+        }
+        else if (RTFS_IS_SYMLINK(pObjInfo->Attr.fMode))
+        {
+            /** @todo Implement. */
+        }
+#if 0 /** @todo Implement this. */
+        pFD->dwFlags = FD_ATTRIBUTES | FD_CREATETIME | FD_ACCESSTIME | FD_WRITESTIME | FD_FILESIZE;
+        pFD->dwFileAttributes =
+        pFD->ftCreationTime   =
+        pFD->ftLastAccessTime =
+        pFD->ftLastWriteTime  =
+#endif
+        ++curIdx;
+        ++itRoot;
+    }
+
+    if (pszFileSpec)
+        RTStrFree(pszFileSpec);
+
+    if (RT_SUCCESS(rc))
+        rc = copyToHGlobal(pFGD, cbFGD, GMEM_MOVEABLE, phGlobal);
+
+    RTMemFree(pFGD);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Retrieves the data stored in this object and store the result in
+ * pMedium.
+ *
+ * @return  IPRT status code.
+ * @return  HRESULT
+ * @param   pFormatEtc
+ * @param   pMedium
+ */
+STDMETHODIMP SharedClipboardWinDataObject::GetData(LPFORMATETC pFormatEtc, LPSTGMEDIUM pMedium)
+{
+    AssertPtrReturn(pFormatEtc, DV_E_FORMATETC);
+    AssertPtrReturn(pMedium, DV_E_FORMATETC);
+
+    LogFlowFuncEnter();
+
+    LogFlowFunc(("lIndex=%RI32\n", pFormatEtc->lindex));
+
+    /*
+     * Initialize default values.
+     */
+    RT_BZERO(pMedium, sizeof(STGMEDIUM));
+
+    HRESULT hr = DV_E_FORMATETC; /* Play safe. */
+
+    if (   pFormatEtc->cfFormat == m_cfFileDescriptorA
+#ifdef VBOX_CLIPBOARD_WITH_UNICODE_SUPPORT
+        || pFormatEtc->cfFormat == m_cfFileDescriptorW
+#endif
+       )
+    {
+        const bool fUnicode = pFormatEtc->cfFormat == m_cfFileDescriptorW;
+
+        const uint32_t enmTransferStatus = ShClTransferGetStatus(m_pTransfer);
+        RT_NOREF(enmTransferStatus);
+
+        LogFlowFunc(("FormatIndex_FileDescriptor%s, enmTransferStatus=%s, m_fRunning=%RTbool\n",
+                     fUnicode ? "W" : "A", ShClTransferStatusToStr(enmTransferStatus), m_fRunning));
+
+        int rc;
+
+        /* The caller can call GetData() several times, so make sure we don't do the same transfer multiple times. */
+        if (!m_fRunning)
+        {
+            /* Start the transfer asynchronously in a separate thread. */
+            rc = ShClTransferRun(m_pTransfer, &SharedClipboardWinDataObject::readThread, this);
+            if (RT_SUCCESS(rc))
+            {
+                m_fRunning = true;
+
+                /* Don't block for too long here, as this also will screw other apps running on the OS. */
+                LogFunc(("Waiting for listing to arrive ...\n"));
+                rc = RTSemEventWait(m_EventListComplete, 30 * 1000 /* 30s timeout */);
+                if (RT_SUCCESS(rc))
+                {
+                    LogFunc(("Listing complete\n"));
+                }
+            }
+        }
+        else
+            rc = VINF_SUCCESS;
+
+        if (RT_SUCCESS(rc))
+        {
+            HGLOBAL hGlobal;
+            rc = createFileGroupDescriptorFromTransfer(m_pTransfer, fUnicode, &hGlobal);
+            if (RT_SUCCESS(rc))
+            {
+                pMedium->tymed   = TYMED_HGLOBAL;
+                pMedium->hGlobal = hGlobal;
+                /* Note: hGlobal now is being owned by pMedium / the caller. */
+
+                hr = S_OK;
+            }
+            else /* We can't tell any better to the caller, unfortunately. */
+                hr = E_UNEXPECTED;
+        }
+
+        if (RT_FAILURE(rc))
+            LogRel(("Shared Clipboard: Data object unable to get data, rc=%Rrc\n", rc));
+    }
+
+    if (pFormatEtc->cfFormat == m_cfFileContents)
+    {
+        if (          pFormatEtc->lindex >= 0
+            && (ULONG)pFormatEtc->lindex <  m_lstEntries.size())
+        {
+            m_uObjIdx = pFormatEtc->lindex; /* lIndex of FormatEtc contains the actual index to the object being handled. */
+
+            FSOBJENTRY &fsObjEntry = m_lstEntries.at(m_uObjIdx);
+
+            LogFlowFunc(("FormatIndex_FileContents: m_uObjIdx=%u (entry '%s')\n", m_uObjIdx, fsObjEntry.strPath.c_str()));
+
+            LogRel2(("Shared Clipboard: Receiving object '%s' ...\n", fsObjEntry.strPath.c_str()));
+
+            /* Hand-in the provider so that our IStream implementation can continue working with it. */
+            hr = SharedClipboardWinStreamImpl::Create(this /* pParent */, m_pTransfer,
+                                                      fsObjEntry.strPath.c_str()/* File name */, &fsObjEntry.objInfo /* PSHCLFSOBJINFO */,
+                                                      &m_pStream);
+            if (SUCCEEDED(hr))
+            {
+                /* Hand over the stream to the caller. */
+                pMedium->tymed = TYMED_ISTREAM;
+                pMedium->pstm  = m_pStream;
+            }
+        }
+    }
+    else if (pFormatEtc->cfFormat == m_cfPerformedDropEffect)
+    {
+        HGLOBAL hGlobal = GlobalAlloc(GHND, sizeof(DWORD));
+
+        DWORD* pdwDropEffect = (DWORD*)GlobalLock(hGlobal);
+        *pdwDropEffect = DROPEFFECT_COPY;
+
+        GlobalUnlock(hGlobal);
+
+        pMedium->tymed          = TYMED_HGLOBAL;
+        pMedium->hGlobal        = hGlobal;
+        pMedium->pUnkForRelease = NULL;
+    }
+
+    if (   FAILED(hr)
+        && hr != DV_E_FORMATETC) /* Can happen if the caller queries unknown / unhandled formats. */
+    {
+        LogRel(("Shared Clipboard: Error returning data from data object (%Rhrc)\n", hr));
+    }
+
+    LogFlowFunc(("hr=%Rhrc\n", hr));
+    return hr;
+}
+
+/**
+ * Only required for IStream / IStorage interfaces.
+ *
+ * @return  IPRT status code.
+ * @return  HRESULT
+ * @param   pFormatEtc
+ * @param   pMedium
+ */
+STDMETHODIMP SharedClipboardWinDataObject::GetDataHere(LPFORMATETC pFormatEtc, LPSTGMEDIUM pMedium)
+{
+    RT_NOREF(pFormatEtc, pMedium);
+    LogFlowFunc(("\n"));
+    return E_NOTIMPL;
+}
+
+/**
+ * Query if this objects supports a specific format.
+ *
+ * @return  IPRT status code.
+ * @return  HRESULT
+ * @param   pFormatEtc
+ */
+STDMETHODIMP SharedClipboardWinDataObject::QueryGetData(LPFORMATETC pFormatEtc)
+{
+    LogFlowFunc(("\n"));
+    return lookupFormatEtc(pFormatEtc, NULL /* puIndex */) ? S_OK : DV_E_FORMATETC;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::GetCanonicalFormatEtc(LPFORMATETC pFormatEtc, LPFORMATETC pFormatEtcOut)
+{
+    RT_NOREF(pFormatEtc);
+    LogFlowFunc(("\n"));
+
+    /* Set this to NULL in any case. */
+    pFormatEtcOut->ptd = NULL;
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::SetData(LPFORMATETC pFormatEtc, LPSTGMEDIUM pMedium, BOOL fRelease)
+{
+    if (   pFormatEtc == NULL
+        || pMedium    == NULL)
+        return E_INVALIDARG;
+
+    if (pFormatEtc->lindex != -1)
+        return DV_E_LINDEX;
+
+    if (pFormatEtc->tymed != TYMED_HGLOBAL)
+        return DV_E_TYMED;
+
+    if (pFormatEtc->dwAspect != DVASPECT_CONTENT)
+        return DV_E_DVASPECT;
+
+    LogFlowFunc(("cfFormat=%RU16, lookupFormatEtc=%RTbool\n",
+                 pFormatEtc->cfFormat, lookupFormatEtc(pFormatEtc, NULL /* puIndex */)));
+
+    /* CFSTR_PERFORMEDDROPEFFECT is used by the drop target (caller of this IDataObject) to communicate
+     * the outcome of the overall operation. */
+    if (   pFormatEtc->cfFormat == m_cfPerformedDropEffect
+        && pMedium->tymed       == TYMED_HGLOBAL)
+    {
+        DWORD dwEffect = *(DWORD *)GlobalLock(pMedium->hGlobal);
+        GlobalUnlock(pMedium->hGlobal);
+
+        LogFlowFunc(("dwEffect=%RI32\n", dwEffect));
+
+        /* Did the user cancel the operation via UI (shell)? This also might happen when overwriting an existing file
+         * and the user doesn't want to allow this. */
+        if (dwEffect == DROPEFFECT_NONE)
+        {
+            LogRel2(("Shared Clipboard: Transfer canceled by user interaction\n"));
+
+            OnTransferCanceled();
+        }
+        /** @todo Detect move / overwrite actions here. */
+
+        if (fRelease)
+            ReleaseStgMedium(pMedium);
+
+        return S_OK;
+    }
+
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::EnumFormatEtc(DWORD dwDirection, IEnumFORMATETC **ppEnumFormatEtc)
+{
+    LogFlowFunc(("dwDirection=%RI32, mcFormats=%RI32, mpFormatEtc=%p\n", dwDirection, m_cFormats, m_pFormatEtc));
+
+    HRESULT hr;
+    if (dwDirection == DATADIR_GET)
+        hr = SharedClipboardWinEnumFormatEtc::CreateEnumFormatEtc(m_cFormats, m_pFormatEtc, ppEnumFormatEtc);
+    else
+        hr = E_NOTIMPL;
+
+    LogFlowFunc(("hr=%Rhrc\n", hr));
+    return hr;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::DAdvise(LPFORMATETC pFormatEtc, DWORD fAdvise, IAdviseSink *pAdvSink, DWORD *pdwConnection)
+{
+    RT_NOREF(pFormatEtc, fAdvise, pAdvSink, pdwConnection);
+    return OLE_E_ADVISENOTSUPPORTED;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::DUnadvise(DWORD dwConnection)
+{
+    RT_NOREF(dwConnection);
+    return OLE_E_ADVISENOTSUPPORTED;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::EnumDAdvise(IEnumSTATDATA **ppEnumAdvise)
+{
+    RT_NOREF(ppEnumAdvise);
+    return OLE_E_ADVISENOTSUPPORTED;
+}
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_WIN_ASYNC
+/*
+ * IDataObjectAsyncCapability methods.
+ */
+
+STDMETHODIMP SharedClipboardWinDataObject::EndOperation(HRESULT hResult, IBindCtx *pbcReserved, DWORD dwEffects)
+{
+     RT_NOREF(hResult, pbcReserved, dwEffects);
+     return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::GetAsyncMode(BOOL *pfIsOpAsync)
+{
+     RT_NOREF(pfIsOpAsync);
+     return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::InOperation(BOOL *pfInAsyncOp)
+{
+     RT_NOREF(pfInAsyncOp);
+     return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::SetAsyncMode(BOOL fDoOpAsync)
+{
+     RT_NOREF(fDoOpAsync);
+     return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinDataObject::StartOperation(IBindCtx *pbcReserved)
+{
+     RT_NOREF(pbcReserved);
+     return E_NOTIMPL;
+}
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_WIN_ASYNC */
+
+/*
+ * Own stuff.
+ */
+
+int SharedClipboardWinDataObject::Init(void)
+{
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+    return VINF_SUCCESS;
+}
+
+void SharedClipboardWinDataObject::OnTransferComplete(int rc /* = VINF_SUCESS */)
+{
+    RT_NOREF(rc);
+
+    LogFlowFunc(("m_uObjIdx=%RU32 (total: %zu)\n", m_uObjIdx, m_lstEntries.size()));
+
+    if (RT_SUCCESS(rc))
+    {
+        const bool fComplete = m_uObjIdx == m_lstEntries.size() - 1 /* Object index is zero-based */;
+        if (fComplete)
+        {
+            m_enmStatus = Completed;
+        }
+    }
+    else
+        m_enmStatus = Error;
+
+    if (m_enmStatus != Initialized)
+    {
+        if (m_EventTransferComplete != NIL_RTSEMEVENT)
+        {
+            int rc2 = RTSemEventSignal(m_EventTransferComplete);
+            AssertRC(rc2);
+        }
+    }
+
+    LogFlowFuncLeaveRC(rc);
+}
+
+void SharedClipboardWinDataObject::OnTransferCanceled(void)
+{
+    LogFlowFuncEnter();
+
+    m_enmStatus = Canceled;
+
+    if (m_EventTransferComplete != NIL_RTSEMEVENT)
+    {
+        int rc2 = RTSemEventSignal(m_EventTransferComplete);
+        AssertRC(rc2);
+    }
+
+    LogFlowFuncLeave();
+}
+
+/* static */
+void SharedClipboardWinDataObject::logFormat(CLIPFORMAT fmt)
+{
+    char szFormat[128];
+    if (GetClipboardFormatName(fmt, szFormat, sizeof(szFormat)))
+    {
+        LogFlowFunc(("clipFormat=%RI16 -> %s\n", fmt, szFormat));
+    }
+    else
+        LogFlowFunc(("clipFormat=%RI16 is unknown\n", fmt));
+}
+
+bool SharedClipboardWinDataObject::lookupFormatEtc(LPFORMATETC pFormatEtc, ULONG *puIndex)
+{
+    AssertReturn(pFormatEtc, false);
+    /* puIndex is optional. */
+
+    for (ULONG i = 0; i < m_cFormats; i++)
+    {
+        if(    (pFormatEtc->tymed & m_pFormatEtc[i].tymed)
+            && pFormatEtc->cfFormat == m_pFormatEtc[i].cfFormat)
+            /* Note: Do *not* compare dwAspect here, as this can be dynamic, depending on how the object should be represented. */
+            //&& pFormatEtc->dwAspect == m_pFormatEtc[i].dwAspect)
+        {
+            LogRel2(("Shared Clipboard: Format found: tyMed=%RI32, cfFormat=%RI16, dwAspect=%RI32, ulIndex=%RU32\n",
+                     pFormatEtc->tymed, pFormatEtc->cfFormat, pFormatEtc->dwAspect, i));
+            if (puIndex)
+                *puIndex = i;
+            return true;
+        }
+    }
+
+    LogRel2(("Shared Clipboard: Format NOT found: tyMed=%RI32, cfFormat=%RI16, dwAspect=%RI32\n",
+             pFormatEtc->tymed, pFormatEtc->cfFormat, pFormatEtc->dwAspect));
+
+    logFormat(pFormatEtc->cfFormat);
+
+    return false;
+}
+
+void SharedClipboardWinDataObject::registerFormat(LPFORMATETC pFormatEtc, CLIPFORMAT clipFormat,
+                                                  TYMED tyMed, LONG lIndex, DWORD dwAspect,
+                                                  DVTARGETDEVICE *pTargetDevice)
+{
+    AssertPtr(pFormatEtc);
+
+    pFormatEtc->cfFormat = clipFormat;
+    pFormatEtc->tymed    = tyMed;
+    pFormatEtc->lindex   = lIndex;
+    pFormatEtc->dwAspect = dwAspect;
+    pFormatEtc->ptd      = pTargetDevice;
+
+    LogFlowFunc(("Registered format=%ld\n", pFormatEtc->cfFormat));
+
+    logFormat(pFormatEtc->cfFormat);
+}
diff --git a/src/VBox/GuestHost/SharedClipboard/ClipboardEnumFormatEtcImpl-win.cpp b/src/VBox/GuestHost/SharedClipboard/ClipboardEnumFormatEtcImpl-win.cpp
new file mode 100644
index 00000000..3e517a90
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/ClipboardEnumFormatEtcImpl-win.cpp
@@ -0,0 +1,205 @@
+/* $Id: ClipboardEnumFormatEtcImpl-win.cpp $ */
+/** @file
+ * ClipboardEnumFormatEtcImpl-win.cpp - Shared Clipboard IEnumFORMATETC ("Format et cetera") implementation.
+ */
+
+/*
+ * Copyright (C) 2013-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include <new> /* For bad_alloc. */
+
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/GuestHost/SharedClipboard-win.h>
+
+#include <iprt/win/windows.h>
+
+#include <VBox/log.h>
+
+
+
+SharedClipboardWinEnumFormatEtc::SharedClipboardWinEnumFormatEtc(LPFORMATETC pFormatEtc, ULONG cFormats)
+    : m_lRefCount(1),
+      m_nIndex(0)
+{
+    HRESULT hr;
+
+    try
+    {
+        LogFlowFunc(("pFormatEtc=%p, cFormats=%RU32\n", pFormatEtc, cFormats));
+        m_pFormatEtc  = new FORMATETC[cFormats];
+
+        for (ULONG i = 0; i < cFormats; i++)
+        {
+            LogFlowFunc(("Format %RU32: cfFormat=%RI16, tyMed=%RU32, dwAspect=%RU32\n",
+                         i, pFormatEtc[i].cfFormat, pFormatEtc[i].tymed, pFormatEtc[i].dwAspect));
+
+            SharedClipboardWinDataObject::logFormat(pFormatEtc[i].cfFormat);
+
+            SharedClipboardWinEnumFormatEtc::CopyFormat(&m_pFormatEtc[i], &pFormatEtc[i]);
+        }
+
+        m_nNumFormats = cFormats;
+        hr = S_OK;
+    }
+    catch (std::bad_alloc &)
+    {
+        hr = E_OUTOFMEMORY;
+    }
+
+    LogFlowFunc(("hr=%Rhrc\n", hr));
+}
+
+SharedClipboardWinEnumFormatEtc::~SharedClipboardWinEnumFormatEtc(void)
+{
+    if (m_pFormatEtc)
+    {
+        for (ULONG i = 0; i < m_nNumFormats; i++)
+        {
+            if(m_pFormatEtc[i].ptd)
+                CoTaskMemFree(m_pFormatEtc[i].ptd);
+        }
+
+        delete[] m_pFormatEtc;
+        m_pFormatEtc = NULL;
+    }
+
+    LogFlowFunc(("m_lRefCount=%RI32\n", m_lRefCount));
+}
+
+/*
+ * IUnknown methods.
+ */
+
+STDMETHODIMP_(ULONG) SharedClipboardWinEnumFormatEtc::AddRef(void)
+{
+    return InterlockedIncrement(&m_lRefCount);
+}
+
+STDMETHODIMP_(ULONG) SharedClipboardWinEnumFormatEtc::Release(void)
+{
+    LONG lCount = InterlockedDecrement(&m_lRefCount);
+    if (lCount == 0)
+    {
+        LogFlowFunc(("Delete\n"));
+        delete this;
+        return 0;
+    }
+
+    return lCount;
+}
+
+STDMETHODIMP SharedClipboardWinEnumFormatEtc::QueryInterface(REFIID iid, void **ppvObject)
+{
+    if (   iid == IID_IEnumFORMATETC
+        || iid == IID_IUnknown)
+    {
+        AddRef();
+        *ppvObject = this;
+        return S_OK;
+    }
+
+    *ppvObject = 0;
+    return E_NOINTERFACE;
+}
+
+STDMETHODIMP SharedClipboardWinEnumFormatEtc::Next(ULONG cFormats, LPFORMATETC pFormatEtc, ULONG *pcFetched)
+{
+    ULONG ulCopied  = 0;
+
+    if(cFormats == 0 || pFormatEtc == 0)
+        return E_INVALIDARG;
+
+    while (   m_nIndex < m_nNumFormats
+           && ulCopied < cFormats)
+    {
+        SharedClipboardWinEnumFormatEtc::CopyFormat(&pFormatEtc[ulCopied], &m_pFormatEtc[m_nIndex]);
+        ulCopied++;
+        m_nIndex++;
+    }
+
+    if (pcFetched)
+        *pcFetched = ulCopied;
+
+    return (ulCopied == cFormats) ? S_OK : S_FALSE;
+}
+
+STDMETHODIMP SharedClipboardWinEnumFormatEtc::Skip(ULONG cFormats)
+{
+    m_nIndex += cFormats;
+    return (m_nIndex <= m_nNumFormats) ? S_OK : S_FALSE;
+}
+
+STDMETHODIMP SharedClipboardWinEnumFormatEtc::Reset(void)
+{
+    m_nIndex = 0;
+    return S_OK;
+}
+
+STDMETHODIMP SharedClipboardWinEnumFormatEtc::Clone(IEnumFORMATETC **ppEnumFormatEtc)
+{
+    HRESULT hResult = CreateEnumFormatEtc(m_nNumFormats, m_pFormatEtc, ppEnumFormatEtc);
+    if (hResult == S_OK)
+        ((SharedClipboardWinEnumFormatEtc *) *ppEnumFormatEtc)->m_nIndex = m_nIndex;
+
+    return hResult;
+}
+
+/* static */
+void SharedClipboardWinEnumFormatEtc::CopyFormat(LPFORMATETC pDest, LPFORMATETC pSource)
+{
+    AssertPtrReturnVoid(pDest);
+    AssertPtrReturnVoid(pSource);
+
+    *pDest = *pSource;
+
+    if (pSource->ptd)
+    {
+        pDest->ptd = (DVTARGETDEVICE*)CoTaskMemAlloc(sizeof(DVTARGETDEVICE));
+        *(pDest->ptd) = *(pSource->ptd);
+    }
+}
+
+/* static */
+HRESULT SharedClipboardWinEnumFormatEtc::CreateEnumFormatEtc(UINT nNumFormats, LPFORMATETC pFormatEtc, IEnumFORMATETC **ppEnumFormatEtc)
+{
+    AssertReturn(nNumFormats, E_INVALIDARG);
+    AssertPtrReturn(pFormatEtc, E_INVALIDARG);
+    AssertPtrReturn(ppEnumFormatEtc, E_INVALIDARG);
+
+    HRESULT hr;
+    try
+    {
+        *ppEnumFormatEtc = new SharedClipboardWinEnumFormatEtc(pFormatEtc, nNumFormats);
+        hr = S_OK;
+    }
+    catch(std::bad_alloc &)
+    {
+        hr = E_OUTOFMEMORY;
+    }
+
+    return hr;
+}
+
diff --git a/src/VBox/GuestHost/SharedClipboard/ClipboardMIME.cpp b/src/VBox/GuestHost/SharedClipboard/ClipboardMIME.cpp
new file mode 100644
index 00000000..e8c800b8
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/ClipboardMIME.cpp
@@ -0,0 +1,53 @@
+/* $Id: ClipboardMIME.cpp $ */
+/** @file
+ * Shared Clipboard - Path list class.
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/GuestHost/SharedClipboard-transfers.h>
+
+#include <iprt/string.h>
+
+
+bool ShClMIMEHasFileURLs(const char *pcszFormat, size_t cchFormatMax)
+{
+    /** @todo "text/uri" also an official variant? */
+    return (   RTStrNICmp(pcszFormat, "text/uri-list", cchFormatMax)             == 0
+            || RTStrNICmp(pcszFormat, "x-special/gnome-icon-list", cchFormatMax) == 0);
+}
+
+bool ShClMIMENeedsCache(const char *pcszFormat, size_t cchFormatMax)
+{
+    bool fNeedsDropDir = false;
+    if (!RTStrNICmp(pcszFormat, "text/uri-list", cchFormatMax)) /** @todo Add "x-special/gnome-icon-list"? */
+        fNeedsDropDir = true;
+
+    return fNeedsDropDir;
+}
+
diff --git a/src/VBox/GuestHost/SharedClipboard/ClipboardPath.cpp b/src/VBox/GuestHost/SharedClipboard/ClipboardPath.cpp
new file mode 100644
index 00000000..bb9cc3d3
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/ClipboardPath.cpp
@@ -0,0 +1,92 @@
+/* $Id: ClipboardPath.cpp $ */
+/** @file
+ * Shared Clipboard - Path handling.
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/GuestHost/SharedClipboard-transfers.h>
+
+#include <iprt/err.h>
+#include <iprt/path.h>
+#include <iprt/string.h>
+
+
+/**
+ * Sanitizes the file name component so that unsupported characters
+ * will be replaced by an underscore ("_").
+ *
+ * @return  IPRT status code.
+ * @param   pszPath             Path to sanitize.
+ * @param   cbPath              Size (in bytes) of path to sanitize.
+ */
+int ShClPathSanitizeFilename(char *pszPath, size_t cbPath)
+{
+    int rc = VINF_SUCCESS;
+#ifdef RT_OS_WINDOWS
+    RT_NOREF1(cbPath);
+    /* Replace out characters not allowed on Windows platforms, put in by RTTimeSpecToString(). */
+    /** @todo Use something like RTPathSanitize() if available later some time. */
+    static const RTUNICP s_uszValidRangePairs[] =
+    {
+        ' ', ' ',
+        '(', ')',
+        '-', '.',
+        '0', '9',
+        'A', 'Z',
+        'a', 'z',
+        '_', '_',
+        0xa0, 0xd7af,
+        '\0'
+    };
+    ssize_t cReplaced = RTStrPurgeComplementSet(pszPath, s_uszValidRangePairs, '_' /* chReplacement */);
+    if (cReplaced < 0)
+        rc = VERR_INVALID_UTF8_ENCODING;
+#else
+    RT_NOREF2(pszPath, cbPath);
+#endif
+    return rc;
+}
+
+/**
+ * Sanitizes a given path regarding invalid / unhandled characters.
+ * Currently not implemented.
+ *
+ * @returns VBox status code.
+ * @param   pszPath             Path to sanitize. UTF-8.
+ * @param   cbPath              Size (in bytes) of the path to sanitize.
+ */
+int ShClPathSanitize(char *pszPath, size_t cbPath)
+{
+    RT_NOREF(pszPath, cbPath);
+
+    /** @todo */
+
+    return VINF_SUCCESS;
+}
+
diff --git a/src/VBox/GuestHost/SharedClipboard/ClipboardStreamImpl-win.cpp b/src/VBox/GuestHost/SharedClipboard/ClipboardStreamImpl-win.cpp
new file mode 100644
index 00000000..38626873
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/ClipboardStreamImpl-win.cpp
@@ -0,0 +1,382 @@
+/* $Id: ClipboardStreamImpl-win.cpp $ */
+/** @file
+ * ClipboardStreamImpl-win.cpp - Shared Clipboard IStream object implementation (guest and host side).
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/GuestHost/SharedClipboard-win.h>
+
+#include <iprt/asm.h>
+#include <iprt/ldr.h>
+#include <iprt/thread.h>
+
+#include <VBox/GuestHost/SharedClipboard.h>
+#include <VBox/GuestHost/SharedClipboard-win.h>
+#include <strsafe.h>
+
+#include <VBox/log.h>
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+
+
+
+/*********************************************************************************************************************************
+*   Static variables                                                                                                             *
+*********************************************************************************************************************************/
+
+
+
+SharedClipboardWinStreamImpl::SharedClipboardWinStreamImpl(SharedClipboardWinDataObject *pParent, PSHCLTRANSFER pTransfer,
+                                                           const Utf8Str &strPath, PSHCLFSOBJINFO pObjInfo)
+    : m_pParent(pParent)
+    , m_lRefCount(1) /* Our IDataObjct *always* holds the last reference to this object; needed for the callbacks. */
+    , m_pTransfer(pTransfer)
+    , m_hObj(SHCLOBJHANDLE_INVALID)
+    , m_strPath(strPath)
+    , m_objInfo(*pObjInfo)
+    , m_cbProcessed(0)
+    , m_fIsComplete(false)
+{
+    AssertPtr(m_pTransfer);
+
+    LogFunc(("m_strPath=%s\n", m_strPath.c_str()));
+}
+
+SharedClipboardWinStreamImpl::~SharedClipboardWinStreamImpl(void)
+{
+    LogFlowThisFuncEnter();
+}
+
+/*
+ * IUnknown methods.
+ */
+
+STDMETHODIMP SharedClipboardWinStreamImpl::QueryInterface(REFIID iid, void **ppvObject)
+{
+    AssertPtrReturn(ppvObject, E_INVALIDARG);
+
+    if (iid == IID_IUnknown)
+    {
+        LogFlowFunc(("IID_IUnknown\n"));
+        *ppvObject = (IUnknown *)(ISequentialStream *)this;
+    }
+    else if (iid == IID_ISequentialStream)
+    {
+        LogFlowFunc(("IID_ISequentialStream\n"));
+        *ppvObject = (ISequentialStream *)this;
+    }
+    else if (iid == IID_IStream)
+    {
+        LogFlowFunc(("IID_IStream\n"));
+        *ppvObject = (IStream *)this;
+    }
+    else
+    {
+        *ppvObject = NULL;
+        return E_NOINTERFACE;
+    }
+
+    AddRef();
+    return S_OK;
+}
+
+STDMETHODIMP_(ULONG) SharedClipboardWinStreamImpl::AddRef(void)
+{
+    LONG lCount = InterlockedIncrement(&m_lRefCount);
+    LogFlowFunc(("lCount=%RI32\n", lCount));
+    return lCount;
+}
+
+STDMETHODIMP_(ULONG) SharedClipboardWinStreamImpl::Release(void)
+{
+    LONG lCount = InterlockedDecrement(&m_lRefCount);
+    LogFlowFunc(("lCount=%RI32\n", m_lRefCount));
+    if (lCount == 0)
+    {
+        delete this;
+        return 0;
+    }
+
+    return lCount;
+}
+
+/*
+ * IStream methods.
+ */
+
+STDMETHODIMP SharedClipboardWinStreamImpl::Clone(IStream** ppStream)
+{
+    RT_NOREF(ppStream);
+
+    LogFlowFuncEnter();
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::Commit(DWORD dwFrags)
+{
+    RT_NOREF(dwFrags);
+
+    LogFlowThisFuncEnter();
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::CopyTo(IStream *pDestStream, ULARGE_INTEGER nBytesToCopy, ULARGE_INTEGER *nBytesRead,
+                                                  ULARGE_INTEGER *nBytesWritten)
+{
+    RT_NOREF(pDestStream, nBytesToCopy, nBytesRead, nBytesWritten);
+
+    LogFlowThisFuncEnter();
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::LockRegion(ULARGE_INTEGER nStart, ULARGE_INTEGER nBytes,DWORD dwFlags)
+{
+    RT_NOREF(nStart, nBytes, dwFlags);
+
+    LogFlowThisFuncEnter();
+    return STG_E_INVALIDFUNCTION;
+}
+
+/* Note: Windows seems to assume EOF if nBytesRead < nBytesToRead. */
+STDMETHODIMP SharedClipboardWinStreamImpl::Read(void *pvBuffer, ULONG nBytesToRead, ULONG *nBytesRead)
+{
+    LogFlowThisFunc(("Enter: m_cbProcessed=%RU64\n", m_cbProcessed));
+
+    /** @todo Is there any locking required so that parallel reads aren't possible? */
+
+    if (!pvBuffer)
+        return STG_E_INVALIDPOINTER;
+
+    if (   nBytesToRead == 0
+        || m_fIsComplete)
+    {
+        if (nBytesRead)
+            *nBytesRead = 0;
+        return S_OK;
+    }
+
+    int rc;
+
+    try
+    {
+        if (   m_hObj == SHCLOBJHANDLE_INVALID
+            && m_pTransfer->ProviderIface.pfnObjOpen)
+        {
+            SHCLOBJOPENCREATEPARMS openParms;
+            rc = ShClTransferObjOpenParmsInit(&openParms);
+            if (RT_SUCCESS(rc))
+            {
+                openParms.fCreate = SHCL_OBJ_CF_ACCESS_READ
+                                  | SHCL_OBJ_CF_ACCESS_DENYWRITE;
+
+                rc = RTStrCopy(openParms.pszPath, openParms.cbPath, m_strPath.c_str());
+                if (RT_SUCCESS(rc))
+                {
+                    rc = m_pTransfer->ProviderIface.pfnObjOpen(&m_pTransfer->ProviderCtx, &openParms, &m_hObj);
+                }
+
+                ShClTransferObjOpenParmsDestroy(&openParms);
+            }
+        }
+        else
+            rc = VINF_SUCCESS;
+
+        uint32_t cbRead = 0;
+
+        const uint64_t cbSize   = (uint64_t)m_objInfo.cbObject;
+        const uint32_t cbToRead = RT_MIN(cbSize - m_cbProcessed, nBytesToRead);
+
+        if (RT_SUCCESS(rc))
+        {
+            if (cbToRead)
+            {
+                rc = m_pTransfer->ProviderIface.pfnObjRead(&m_pTransfer->ProviderCtx, m_hObj,
+                                                           pvBuffer, cbToRead, 0 /* fFlags */, &cbRead);
+                if (RT_SUCCESS(rc))
+                {
+                    m_cbProcessed += cbRead;
+                    Assert(m_cbProcessed <= cbSize);
+                }
+            }
+
+            /* Transfer complete? Make sure to close the object again. */
+            m_fIsComplete = m_cbProcessed == cbSize;
+
+            if (m_fIsComplete)
+            {
+                if (m_pTransfer->ProviderIface.pfnObjClose)
+                {
+                    int rc2 = m_pTransfer->ProviderIface.pfnObjClose(&m_pTransfer->ProviderCtx, m_hObj);
+                    AssertRC(rc2);
+                }
+
+                if (m_pParent)
+                    m_pParent->OnTransferComplete();
+            }
+        }
+
+        LogFlowThisFunc(("Leave: rc=%Rrc, cbSize=%RU64, cbProcessed=%RU64 -> nBytesToRead=%RU32, cbToRead=%RU32, cbRead=%RU32\n",
+                         rc, cbSize, m_cbProcessed, nBytesToRead, cbToRead, cbRead));
+
+        if (nBytesRead)
+            *nBytesRead = (ULONG)cbRead;
+
+        if (nBytesToRead != cbRead)
+            return S_FALSE;
+
+        return S_OK;
+    }
+    catch (...)
+    {
+        LogFunc(("Caught exception\n"));
+    }
+
+    return E_FAIL;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::Revert(void)
+{
+    LogFlowThisFuncEnter();
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::Seek(LARGE_INTEGER nMove, DWORD dwOrigin, ULARGE_INTEGER* nNewPos)
+{
+    RT_NOREF(nMove, dwOrigin, nNewPos);
+
+    LogFlowThisFunc(("nMove=%RI64, dwOrigin=%RI32\n", nMove, dwOrigin));
+
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::SetSize(ULARGE_INTEGER nNewSize)
+{
+    RT_NOREF(nNewSize);
+
+    LogFlowThisFuncEnter();
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::Stat(STATSTG *pStatStg, DWORD dwFlags)
+{
+    HRESULT hr = S_OK;
+
+    if (pStatStg)
+    {
+        RT_ZERO(*pStatStg);
+
+        switch (dwFlags)
+        {
+            case STATFLAG_NONAME:
+                pStatStg->pwcsName = NULL;
+                break;
+
+            case STATFLAG_DEFAULT:
+            {
+                /** @todo r=bird: This is using the wrong allocator.  According to MSDN the
+                 * caller will pass this to CoTaskMemFree, so we should use CoTaskMemAlloc to
+                 * allocate it. */
+                int rc2 = RTStrToUtf16(m_strPath.c_str(), &pStatStg->pwcsName);
+                if (RT_FAILURE(rc2))
+                    hr = E_FAIL;
+                break;
+            }
+
+            default:
+                hr = STG_E_INVALIDFLAG;
+                break;
+        }
+
+        if (SUCCEEDED(hr))
+        {
+            pStatStg->type              = STGTY_STREAM;
+            pStatStg->grfMode           = STGM_READ;
+            pStatStg->grfLocksSupported = 0;
+            pStatStg->cbSize.QuadPart   = (uint64_t)m_objInfo.cbObject;
+        }
+    }
+    else
+       hr = STG_E_INVALIDPOINTER;
+
+    LogFlowThisFunc(("hr=%Rhrc\n", hr));
+    return hr;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::UnlockRegion(ULARGE_INTEGER nStart, ULARGE_INTEGER nBytes, DWORD dwFlags)
+{
+    RT_NOREF(nStart, nBytes, dwFlags);
+
+    LogFlowThisFuncEnter();
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP SharedClipboardWinStreamImpl::Write(const void *pvBuffer, ULONG nBytesToRead, ULONG *nBytesRead)
+{
+    RT_NOREF(pvBuffer, nBytesToRead, nBytesRead);
+
+    LogFlowThisFuncEnter();
+    return E_NOTIMPL;
+}
+
+/*
+ * Own stuff.
+ */
+
+/**
+ * Factory to create our own IStream implementation.
+ *
+ * @returns HRESULT
+ * @param   pParent             Pointer to the parent data object.
+ * @param   pTransfer           Pointer to Shared Clipboard transfer object to use.
+ * @param   strPath             Path of object to handle for the stream.
+ * @param   pObjInfo            Pointer to object information.
+ * @param   ppStream            Where to return the created stream object on success.
+ */
+/* static */
+HRESULT SharedClipboardWinStreamImpl::Create(SharedClipboardWinDataObject *pParent, PSHCLTRANSFER pTransfer,
+                                             const Utf8Str &strPath, PSHCLFSOBJINFO pObjInfo,
+                                             IStream **ppStream)
+{
+    AssertPtrReturn(pTransfer, E_POINTER);
+
+    SharedClipboardWinStreamImpl *pStream = new SharedClipboardWinStreamImpl(pParent, pTransfer, strPath, pObjInfo);
+    if (pStream)
+    {
+        pStream->AddRef();
+
+        *ppStream = pStream;
+        return S_OK;
+    }
+
+    return E_FAIL;
+}
+
diff --git a/src/VBox/GuestHost/SharedClipboard/Makefile.kmk b/src/VBox/GuestHost/SharedClipboard/Makefile.kmk
new file mode 100644
index 00000000..aa3cdc96
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/Makefile.kmk
@@ -0,0 +1,36 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the VirtualBox Shared Clipboard guest/host code.
+#
+
+#
+# Copyright (C) 2020-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+ifdef VBOX_WITH_TESTCASES
+ include $(PATH_SUB_CURRENT)/testcase/Makefile.kmk
+endif
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp b/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp
new file mode 100644
index 00000000..c1886d31
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp
@@ -0,0 +1,1226 @@
+/* $Id: clipboard-common.cpp $ */
+/** @file
+ * Shared Clipboard: Some helper function for converting between the various eol.
+ */
+
+/*
+ * Includes contributions from François Revol
+ *
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+
+#include <iprt/alloc.h>
+#include <iprt/assert.h>
+#include <iprt/semaphore.h>
+#include <iprt/path.h>
+#include <iprt/rand.h>
+#include <iprt/utf16.h>
+
+#include <iprt/formats/bmp.h>
+
+#include <iprt/errcore.h>
+#include <VBox/log.h>
+#include <VBox/GuestHost/clipboard-helper.h>
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+
+
+/*********************************************************************************************************************************
+*   Prototypes                                                                                                                   *
+*********************************************************************************************************************************/
+static void shClEventSourceResetInternal(PSHCLEVENTSOURCE pSource);
+
+static void shClEventDestroy(PSHCLEVENT pEvent);
+DECLINLINE(PSHCLEVENT) shclEventGet(PSHCLEVENTSOURCE pSource, SHCLEVENTID idEvent);
+
+
+/*********************************************************************************************************************************
+*   Implementation                                                                                                               *
+*********************************************************************************************************************************/
+
+/**
+ * Allocates a new event payload.
+ *
+ * @returns VBox status code.
+ * @param   uID                 Payload ID to set for this payload. Useful for consequtive payloads.
+ * @param   pvData              Data block to associate to this payload.
+ * @param   cbData              Size (in bytes) of data block to associate.
+ * @param   ppPayload           Where to store the allocated event payload on success.
+ */
+int ShClPayloadAlloc(uint32_t uID, const void *pvData, uint32_t cbData,
+                     PSHCLEVENTPAYLOAD *ppPayload)
+{
+    AssertPtrReturn(pvData, VERR_INVALID_POINTER);
+    AssertReturn(cbData > 0, VERR_INVALID_PARAMETER);
+
+    PSHCLEVENTPAYLOAD pPayload = (PSHCLEVENTPAYLOAD)RTMemAlloc(sizeof(SHCLEVENTPAYLOAD));
+    if (pPayload)
+    {
+        pPayload->pvData = RTMemDup(pvData, cbData);
+        if (pPayload->pvData)
+        {
+            pPayload->cbData = cbData;
+            pPayload->uID    = uID;
+
+            *ppPayload = pPayload;
+            return VINF_SUCCESS;
+        }
+
+        RTMemFree(pPayload);
+    }
+    return VERR_NO_MEMORY;
+}
+
+/**
+ * Frees an event payload.
+ *
+ * @returns VBox status code.
+ * @param   pPayload            Event payload to free.
+ */
+void ShClPayloadFree(PSHCLEVENTPAYLOAD pPayload)
+{
+    if (!pPayload)
+        return;
+
+    if (pPayload->pvData)
+    {
+        Assert(pPayload->cbData);
+        RTMemFree(pPayload->pvData);
+        pPayload->pvData = NULL;
+    }
+
+    pPayload->cbData = 0;
+    pPayload->uID = UINT32_MAX;
+
+    RTMemFree(pPayload);
+}
+
+/**
+ * Creates a new event source.
+ *
+ * @returns VBox status code.
+ * @param   pSource             Event source to create.
+ * @param   uID                 ID to use for event source.
+ */
+int ShClEventSourceCreate(PSHCLEVENTSOURCE pSource, SHCLEVENTSOURCEID uID)
+{
+    LogFlowFunc(("pSource=%p, uID=%RU16\n", pSource, uID));
+    AssertPtrReturn(pSource, VERR_INVALID_POINTER);
+
+    int rc = RTCritSectInit(&pSource->CritSect);
+    AssertRCReturn(rc, rc);
+
+    RTListInit(&pSource->lstEvents);
+
+    pSource->uID          = uID;
+    /* Choose a random event ID starting point. */
+    pSource->idNextEvent  = RTRandU32Ex(1, VBOX_SHCL_MAX_EVENTS - 1);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys an event source.
+ *
+ * @returns VBox status code.
+ * @param   pSource             Event source to destroy.
+ */
+int ShClEventSourceDestroy(PSHCLEVENTSOURCE pSource)
+{
+    if (!pSource)
+        return VINF_SUCCESS;
+
+    LogFlowFunc(("ID=%RU32\n", pSource->uID));
+
+    int rc = RTCritSectEnter(&pSource->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        shClEventSourceResetInternal(pSource);
+
+        rc = RTCritSectLeave(&pSource->CritSect);
+        AssertRC(rc);
+
+        RTCritSectDelete(&pSource->CritSect);
+
+        pSource->uID          = UINT16_MAX;
+        pSource->idNextEvent  = UINT32_MAX;
+    }
+
+    return rc;
+}
+
+/**
+ * Resets an event source, internal version.
+ *
+ * @param   pSource             Event source to reset.
+ */
+static void shClEventSourceResetInternal(PSHCLEVENTSOURCE pSource)
+{
+    LogFlowFunc(("ID=%RU32\n", pSource->uID));
+
+    PSHCLEVENT pEvIt;
+    PSHCLEVENT pEvItNext;
+    RTListForEachSafe(&pSource->lstEvents, pEvIt, pEvItNext, SHCLEVENT, Node)
+    {
+        RTListNodeRemove(&pEvIt->Node);
+
+        shClEventDestroy(pEvIt);
+
+        RTMemFree(pEvIt);
+        pEvIt = NULL;
+    }
+}
+
+/**
+ * Resets an event source.
+ *
+ * @param   pSource             Event source to reset.
+ */
+void ShClEventSourceReset(PSHCLEVENTSOURCE pSource)
+{
+    int rc2 = RTCritSectEnter(&pSource->CritSect);
+    if (RT_SUCCESS(rc2))
+    {
+        shClEventSourceResetInternal(pSource);
+
+        rc2 = RTCritSectLeave(&pSource->CritSect);
+        AssertRC(rc2);
+    }
+}
+
+/**
+ * Generates a new event ID for a specific event source and registers it.
+ *
+ * @returns VBox status code.
+ * @param   pSource             Event source to generate event for.
+ * @param   ppEvent             Where to return the new event generated on success.
+ */
+int ShClEventSourceGenerateAndRegisterEvent(PSHCLEVENTSOURCE pSource, PSHCLEVENT *ppEvent)
+{
+    AssertPtrReturn(pSource, VERR_INVALID_POINTER);
+    AssertPtrReturn(ppEvent, VERR_INVALID_POINTER);
+
+    PSHCLEVENT pEvent = (PSHCLEVENT)RTMemAllocZ(sizeof(SHCLEVENT));
+    AssertReturn(pEvent, VERR_NO_MEMORY);
+    int rc = RTSemEventMultiCreate(&pEvent->hEvtMulSem);
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTCritSectEnter(&pSource->CritSect);
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Allocate an unique event ID.
+             */
+            for (uint32_t cTries = 0;; cTries++)
+            {
+                SHCLEVENTID idEvent = ++pSource->idNextEvent;
+                if (idEvent < VBOX_SHCL_MAX_EVENTS)
+                { /* likely */ }
+                else
+                    pSource->idNextEvent = idEvent = 1; /* zero == error, remember! */
+
+                if (shclEventGet(pSource, idEvent) == NULL)
+                {
+                    pEvent->pParent = pSource;
+                    pEvent->idEvent = idEvent;
+                    RTListAppend(&pSource->lstEvents, &pEvent->Node);
+
+                    rc = RTCritSectLeave(&pSource->CritSect);
+                    AssertRC(rc);
+
+                    LogFlowFunc(("uSource=%RU16: New event: %#x\n", pSource->uID, idEvent));
+
+                    ShClEventRetain(pEvent);
+                    *ppEvent = pEvent;
+
+                    return VINF_SUCCESS;
+                }
+
+                AssertBreak(cTries < 4096);
+            }
+
+            rc = RTCritSectLeave(&pSource->CritSect);
+            AssertRC(rc);
+        }
+    }
+
+    AssertMsgFailed(("Unable to register a new event ID for event source %RU16\n", pSource->uID));
+
+    RTSemEventMultiDestroy(pEvent->hEvtMulSem);
+    pEvent->hEvtMulSem = NIL_RTSEMEVENTMULTI;
+    RTMemFree(pEvent);
+    return rc;
+}
+
+/**
+ * Destroys an event.
+ *
+ * @param   pEvent              Event to destroy.
+ */
+static void shClEventDestroy(PSHCLEVENT pEvent)
+{
+    if (!pEvent)
+        return;
+
+    AssertMsgReturnVoid(pEvent->cRefs == 0, ("Event %RU32 still has %RU32 references\n",
+                                             pEvent->idEvent, pEvent->cRefs));
+
+    LogFlowFunc(("Event %RU32\n", pEvent->idEvent));
+
+    if (pEvent->hEvtMulSem != NIL_RTSEMEVENT)
+    {
+        RTSemEventMultiDestroy(pEvent->hEvtMulSem);
+        pEvent->hEvtMulSem = NIL_RTSEMEVENT;
+    }
+
+    ShClPayloadFree(pEvent->pPayload);
+
+    pEvent->idEvent = NIL_SHCLEVENTID;
+}
+
+/**
+ * Unregisters an event.
+ *
+ * @returns VBox status code.
+ * @param   pSource             Event source to unregister event for.
+ * @param   pEvent              Event to unregister. On success the pointer will be invalid.
+ */
+static int shClEventSourceUnregisterEventInternal(PSHCLEVENTSOURCE pSource, PSHCLEVENT pEvent)
+{
+    LogFlowFunc(("idEvent=%RU32, cRefs=%RU32\n", pEvent->idEvent, pEvent->cRefs));
+
+    AssertReturn(pEvent->cRefs == 0, VERR_WRONG_ORDER);
+
+    int rc = RTCritSectEnter(&pSource->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        RTListNodeRemove(&pEvent->Node);
+
+        shClEventDestroy(pEvent);
+
+        rc = RTCritSectLeave(&pSource->CritSect);
+        if (RT_SUCCESS(rc))
+        {
+            RTMemFree(pEvent);
+            pEvent = NULL;
+        }
+    }
+
+    return rc;
+}
+
+/**
+ * Returns a specific event of a event source. Inlined version.
+ *
+ * @returns Pointer to event if found, or NULL if not found.
+ * @param   pSource             Event source to get event from.
+ * @param   uID                 Event ID to get.
+ */
+DECLINLINE(PSHCLEVENT) shclEventGet(PSHCLEVENTSOURCE pSource, SHCLEVENTID idEvent)
+{
+    PSHCLEVENT pEvent;
+    RTListForEach(&pSource->lstEvents, pEvent, SHCLEVENT, Node)
+    {
+        if (pEvent->idEvent == idEvent)
+            return pEvent;
+    }
+
+    return NULL;
+}
+
+/**
+ * Returns a specific event of a event source.
+ *
+ * @returns Pointer to event if found, or NULL if not found.
+ * @param   pSource             Event source to get event from.
+ * @param   idEvent             ID of event to return.
+ */
+PSHCLEVENT ShClEventSourceGetFromId(PSHCLEVENTSOURCE pSource, SHCLEVENTID idEvent)
+{
+    AssertPtrReturn(pSource, NULL);
+
+    int rc = RTCritSectEnter(&pSource->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+         PSHCLEVENT pEvent = shclEventGet(pSource, idEvent);
+
+         rc = RTCritSectLeave(&pSource->CritSect);
+         AssertRC(rc);
+
+         return pEvent;
+    }
+
+    return NULL;
+}
+
+/**
+ * Returns the last (newest) event ID which has been registered for an event source.
+ *
+ * @returns Pointer to last registered event, or NULL if not found.
+ * @param   pSource             Event source to get last registered event from.
+ */
+PSHCLEVENT ShClEventSourceGetLast(PSHCLEVENTSOURCE pSource)
+{
+    AssertPtrReturn(pSource, NULL);
+
+    int rc = RTCritSectEnter(&pSource->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        PSHCLEVENT pEvent = RTListGetLast(&pSource->lstEvents, SHCLEVENT, Node);
+
+        rc = RTCritSectLeave(&pSource->CritSect);
+        AssertRC(rc);
+
+        return pEvent;
+    }
+
+    return NULL;
+}
+
+/**
+ * Returns the current reference count for a specific event.
+ *
+ * @returns Reference count.
+ * @param   pSource             Event source the specific event is part of.
+ * @param   idEvent             Event ID to return reference count for.
+ */
+uint32_t ShClEventGetRefs(PSHCLEVENT pEvent)
+{
+    AssertPtrReturn(pEvent, 0);
+
+    return ASMAtomicReadU32(&pEvent->cRefs);
+}
+
+/**
+ * Detaches a payload from an event, internal version.
+ *
+ * @returns Pointer to the detached payload. Can be NULL if the payload has no payload.
+ * @param   pEvent              Event to detach payload for.
+ */
+static PSHCLEVENTPAYLOAD shclEventPayloadDetachInternal(PSHCLEVENT pEvent)
+{
+#ifdef VBOX_STRICT
+    AssertPtrReturn(pEvent, NULL);
+#endif
+
+    PSHCLEVENTPAYLOAD pPayload = pEvent->pPayload;
+
+    pEvent->pPayload = NULL;
+
+    return pPayload;
+}
+
+/**
+ * Waits for an event to get signalled.
+ *
+ * @returns VBox status code.
+ * @param   pEvent              Event to wait for.
+ * @param   uTimeoutMs          Timeout (in ms) to wait.
+ * @param   ppPayload           Where to store the (allocated) event payload on success. Needs to be free'd with
+ *                              SharedClipboardPayloadFree(). Optional.
+ */
+int ShClEventWait(PSHCLEVENT pEvent, RTMSINTERVAL uTimeoutMs, PSHCLEVENTPAYLOAD *ppPayload)
+{
+    AssertPtrReturn(pEvent, VERR_INVALID_POINTER);
+    AssertPtrNullReturn(ppPayload, VERR_INVALID_POINTER);
+    LogFlowFuncEnter();
+
+    int rc = RTSemEventMultiWait(pEvent->hEvtMulSem, uTimeoutMs);
+    if (RT_SUCCESS(rc))
+    {
+        if (ppPayload)
+        {
+            /* Make sure to detach payload here, as the caller now owns the data. */
+            *ppPayload = shclEventPayloadDetachInternal(pEvent);
+        }
+    }
+
+    if (RT_FAILURE(rc))
+        LogRel2(("Shared Clipboard: Waiting for event %RU32 failed, rc=%Rrc\n", pEvent->idEvent, rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Retains an event by increasing its reference count.
+ *
+ * @returns New reference count, or UINT32_MAX if failed.
+ * @param   pEvent              Event to retain.
+ */
+uint32_t ShClEventRetain(PSHCLEVENT pEvent)
+{
+    AssertPtrReturn(pEvent, UINT32_MAX);
+    AssertReturn(ASMAtomicReadU32(&pEvent->cRefs) < 64, UINT32_MAX);
+    return ASMAtomicIncU32(&pEvent->cRefs);
+}
+
+/**
+ * Releases an event by decreasing its reference count.
+ *
+ * @returns New reference count, or UINT32_MAX if failed.
+ * @param   pEvent              Event to release.
+ *                              If the reference count reaches 0, the event will
+ *                              be destroyed and \a pEvent will be invalid.
+ */
+uint32_t ShClEventRelease(PSHCLEVENT pEvent)
+{
+    if (!pEvent)
+        return 0;
+
+    AssertReturn(ASMAtomicReadU32(&pEvent->cRefs) > 0, UINT32_MAX);
+
+    uint32_t const cRefs = ASMAtomicDecU32(&pEvent->cRefs);
+    if (cRefs == 0)
+    {
+        AssertPtr(pEvent->pParent);
+        int rc2 = shClEventSourceUnregisterEventInternal(pEvent->pParent, pEvent);
+        AssertRC(rc2);
+
+        return RT_SUCCESS(rc2) ? 0 : UINT32_MAX;
+    }
+
+    return cRefs;
+}
+
+/**
+ * Signals an event.
+ *
+ * @returns VBox status code.
+ * @param   pEvent              Event to signal.
+ * @param   pPayload            Event payload to associate. Takes ownership on
+ *                              success. Optional.
+ */
+int ShClEventSignal(PSHCLEVENT pEvent, PSHCLEVENTPAYLOAD pPayload)
+{
+    AssertPtrReturn(pEvent, VERR_INVALID_POINTER);
+
+    Assert(pEvent->pPayload == NULL);
+
+    pEvent->pPayload = pPayload;
+
+    int rc = RTSemEventMultiSignal(pEvent->hEvtMulSem);
+    if (RT_FAILURE(rc))
+        pEvent->pPayload = NULL; /* (no race condition if consumer also enters the critical section) */
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClUtf16LenUtf8(PCRTUTF16 pcwszSrc, size_t cwcSrc, size_t *pchLen)
+{
+    AssertPtrReturn(pcwszSrc, VERR_INVALID_POINTER);
+    AssertPtrReturn(pchLen, VERR_INVALID_POINTER);
+
+    size_t chLen = 0;
+    int rc = RTUtf16CalcUtf8LenEx(pcwszSrc, cwcSrc, &chLen);
+    if (RT_SUCCESS(rc))
+        *pchLen = chLen;
+    return rc;
+}
+
+int ShClConvUtf16CRLFToUtf8LF(PCRTUTF16 pcwszSrc, size_t cwcSrc,
+                              char *pszBuf, size_t cbBuf, size_t *pcbLen)
+{
+    AssertPtrReturn(pcwszSrc, VERR_INVALID_POINTER);
+    AssertReturn   (cwcSrc,   VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pszBuf,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pcbLen,   VERR_INVALID_POINTER);
+
+    int rc;
+
+    PRTUTF16 pwszTmp = NULL;
+    size_t   cchTmp  = 0;
+
+    size_t   cbLen = 0;
+
+    /* How long will the converted text be? */
+    rc = ShClUtf16CRLFLenUtf8(pcwszSrc, cwcSrc, &cchTmp);
+    if (RT_SUCCESS(rc))
+    {
+        cchTmp++; /* Add space for terminator. */
+
+        pwszTmp = (PRTUTF16)RTMemAlloc(cchTmp * sizeof(RTUTF16));
+        if (pwszTmp)
+        {
+            rc = ShClConvUtf16CRLFToLF(pcwszSrc, cwcSrc, pwszTmp, cchTmp);
+            if (RT_SUCCESS(rc))
+                rc = RTUtf16ToUtf8Ex(pwszTmp + 1, cchTmp - 1, &pszBuf, cbBuf, &cbLen);
+
+            RTMemFree(reinterpret_cast<void *>(pwszTmp));
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        *pcbLen = cbLen;
+    }
+
+    return rc;
+}
+
+int ShClConvUtf16LFToCRLFA(PCRTUTF16 pcwszSrc, size_t cwcSrc,
+                           PRTUTF16 *ppwszDst, size_t *pcwDst)
+{
+    AssertPtrReturn(pcwszSrc, VERR_INVALID_POINTER);
+    AssertPtrReturn(ppwszDst, VERR_INVALID_POINTER);
+    AssertPtrReturn(pcwDst,   VERR_INVALID_POINTER);
+
+    PRTUTF16 pwszDst = NULL;
+    size_t   cchDst;
+
+    int rc = ShClUtf16LFLenUtf8(pcwszSrc, cwcSrc, &cchDst);
+    if (RT_SUCCESS(rc))
+    {
+        pwszDst = (PRTUTF16)RTMemAlloc((cchDst + 1 /* Leave space for terminator */) * sizeof(RTUTF16));
+        if (pwszDst)
+        {
+            rc = ShClConvUtf16LFToCRLF(pcwszSrc, cwcSrc, pwszDst, cchDst + 1 /* Include terminator */);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        *ppwszDst = pwszDst;
+        *pcwDst   = cchDst;
+    }
+    else
+        RTMemFree(pwszDst);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClConvUtf8LFToUtf16CRLF(const char *pcszSrc, size_t cbSrc,
+                              PRTUTF16 *ppwszDst, size_t *pcwDst)
+{
+    AssertPtrReturn(pcszSrc,  VERR_INVALID_POINTER);
+    AssertReturn(cbSrc,       VERR_INVALID_PARAMETER);
+    AssertPtrReturn(ppwszDst, VERR_INVALID_POINTER);
+    AssertPtrReturn(pcwDst,   VERR_INVALID_POINTER);
+
+    /* Intermediate conversion to UTF-16. */
+    size_t   cwcTmp;
+    PRTUTF16 pwcTmp = NULL;
+    int rc = RTStrToUtf16Ex(pcszSrc, cbSrc, &pwcTmp, 0, &cwcTmp);
+    if (RT_SUCCESS(rc))
+    {
+        rc = ShClConvUtf16LFToCRLFA(pwcTmp, cwcTmp, ppwszDst, pcwDst);
+        RTUtf16Free(pwcTmp);
+    }
+
+    return rc;
+}
+
+/**
+ * Converts a Latin-1 string with LF line endings into an UTF-16 string with CRLF endings.
+ *
+ * @returns VBox status code.
+ * @param   pcszSrc             Latin-1 string to convert.
+ * @param   cbSrc               Size (in bytes) of Latin-1 string to convert.
+ * @param   ppwszDst            Where to return the converted UTF-16 string on success.
+ * @param   pcwDst              Where to return the length (in UTF-16 characters) on success.
+ *
+ * @note    Only converts the source until the string terminator is found (or length limit is hit).
+ */
+int ShClConvLatin1LFToUtf16CRLF(const char *pcszSrc, size_t cbSrc,
+                                PRTUTF16 *ppwszDst, size_t *pcwDst)
+{
+    AssertPtrReturn(pcszSrc,  VERR_INVALID_POINTER);
+    AssertReturn(cbSrc,       VERR_INVALID_PARAMETER);
+    AssertPtrReturn(ppwszDst, VERR_INVALID_POINTER);
+    AssertPtrReturn(pcwDst,   VERR_INVALID_POINTER);
+
+    size_t chSrc = 0;
+
+    PRTUTF16 pwszDst = NULL;
+
+    /* Calculate the space needed. */
+    size_t cwDst = 0;
+    for (size_t i = 0; i < cbSrc && pcszSrc[i] != '\0'; ++i)
+    {
+        if (pcszSrc[i] == VBOX_SHCL_LINEFEED)
+            cwDst += 2; /* Space for VBOX_SHCL_CARRIAGERETURN + VBOX_SHCL_LINEFEED. */
+        else
+            ++cwDst;
+        chSrc++;
+    }
+
+    pwszDst = (PRTUTF16)RTMemAlloc((cwDst + 1 /* Leave space for the terminator */) * sizeof(RTUTF16));
+    AssertPtrReturn(pwszDst, VERR_NO_MEMORY);
+
+    /* Do the conversion, bearing in mind that Latin-1 expands "naturally" to UTF-16. */
+    for (size_t i = 0, j = 0; i < chSrc; ++i, ++j)
+    {
+        AssertMsg(j <= cwDst, ("cbSrc=%zu, j=%u vs. cwDst=%u\n", cbSrc, j, cwDst));
+        if (pcszSrc[i] != VBOX_SHCL_LINEFEED)
+            pwszDst[j] = pcszSrc[i];
+        else
+        {
+            pwszDst[j]     = VBOX_SHCL_CARRIAGERETURN;
+            pwszDst[j + 1] = VBOX_SHCL_LINEFEED;
+            ++j;
+        }
+    }
+
+    pwszDst[cwDst] = '\0';  /* Make sure we are zero-terminated. */
+
+    *ppwszDst = pwszDst;
+    *pcwDst   = cwDst;
+
+    return VINF_SUCCESS;
+}
+
+int ShClConvUtf16ToUtf8HTML(PCRTUTF16 pcwszSrc, size_t cwcSrc, char **ppszDst, size_t *pcbDst)
+{
+    AssertPtrReturn(pcwszSrc, VERR_INVALID_POINTER);
+    AssertReturn   (cwcSrc,   VERR_INVALID_PARAMETER);
+    AssertPtrReturn(ppszDst,  VERR_INVALID_POINTER);
+    AssertPtrReturn(pcbDst,   VERR_INVALID_POINTER);
+
+    int rc = VINF_SUCCESS;
+
+    size_t    cwTmp = cwcSrc;
+    PCRTUTF16 pwTmp = pcwszSrc;
+
+    char  *pchDst = NULL;
+    size_t cbDst  = 0;
+
+    size_t i = 0;
+    while (i < cwTmp)
+    {
+        /* Find  zero symbol (end of string). */
+        for (; i < cwTmp && pcwszSrc[i] != 0; i++)
+            ;
+
+        /* Convert found string. */
+        char  *psz = NULL;
+        size_t cch = 0;
+        rc = RTUtf16ToUtf8Ex(pwTmp, cwTmp, &psz, pwTmp - pcwszSrc, &cch);
+        if (RT_FAILURE(rc))
+            break;
+
+        /* Append new substring. */
+        char *pchNew = (char *)RTMemRealloc(pchDst, cbDst + cch + 1);
+        if (!pchNew)
+        {
+            RTStrFree(psz);
+            rc = VERR_NO_MEMORY;
+            break;
+        }
+
+        pchDst = pchNew;
+        memcpy(pchDst + cbDst, psz, cch + 1);
+
+        RTStrFree(psz);
+
+        cbDst += cch + 1;
+
+        /* Skip zero symbols. */
+        for (; i < cwTmp && pcwszSrc[i] == 0; i++)
+            ;
+
+        /* Remember start of string. */
+        pwTmp += i;
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        *ppszDst = pchDst;
+        *pcbDst  = cbDst;
+
+        return VINF_SUCCESS;
+    }
+
+    RTMemFree(pchDst);
+
+    return rc;
+}
+
+int ShClUtf16LFLenUtf8(PCRTUTF16 pcwszSrc, size_t cwSrc, size_t *pchLen)
+{
+    AssertPtrReturn(pcwszSrc, VERR_INVALID_POINTER);
+    AssertPtrReturn(pchLen, VERR_INVALID_POINTER);
+
+    AssertMsgReturn(pcwszSrc[0] != VBOX_SHCL_UTF16BEMARKER,
+                    ("Big endian UTF-16 not supported yet\n"), VERR_NOT_SUPPORTED);
+
+    size_t cLen = 0;
+
+    /* Don't copy the endian marker. */
+    size_t i = pcwszSrc[0] == VBOX_SHCL_UTF16LEMARKER ? 1 : 0;
+
+    /* Calculate the size of the destination text string. */
+    /* Is this Utf16 or Utf16-LE? */
+    for (; i < cwSrc; ++i, ++cLen)
+    {
+        /* Check for a single line feed */
+        if (pcwszSrc[i] == VBOX_SHCL_LINEFEED)
+            ++cLen;
+#ifdef RT_OS_DARWIN
+        /* Check for a single carriage return (MacOS) */
+        if (pcwszSrc[i] == VBOX_SHCL_CARRIAGERETURN)
+            ++cLen;
+#endif
+        if (pcwszSrc[i] == 0)
+        {
+            /* Don't count this, as we do so below. */
+            break;
+        }
+    }
+
+    *pchLen = cLen;
+
+    return VINF_SUCCESS;
+}
+
+int ShClUtf16CRLFLenUtf8(PCRTUTF16 pcwszSrc, size_t cwSrc, size_t *pchLen)
+{
+    AssertPtrReturn(pcwszSrc, VERR_INVALID_POINTER);
+    AssertReturn(cwSrc, VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pchLen, VERR_INVALID_POINTER);
+
+    AssertMsgReturn(pcwszSrc[0] != VBOX_SHCL_UTF16BEMARKER,
+                    ("Big endian UTF-16 not supported yet\n"), VERR_NOT_SUPPORTED);
+
+    size_t cLen = 0;
+
+    /* Calculate the size of the destination text string. */
+    /* Is this Utf16 or Utf16-LE? */
+    if (pcwszSrc[0] == VBOX_SHCL_UTF16LEMARKER)
+        cLen = 0;
+    else
+        cLen = 1;
+
+    for (size_t i = 0; i < cwSrc; ++i, ++cLen)
+    {
+        if (   (i + 1 < cwSrc)
+            && (pcwszSrc[i]     == VBOX_SHCL_CARRIAGERETURN)
+            && (pcwszSrc[i + 1] == VBOX_SHCL_LINEFEED))
+        {
+            ++i;
+        }
+        if (pcwszSrc[i] == 0)
+            break;
+    }
+
+    *pchLen = cLen;
+
+    return VINF_SUCCESS;
+}
+
+int ShClConvUtf16LFToCRLF(PCRTUTF16 pcwszSrc, size_t cwcSrc, PRTUTF16 pu16Dst, size_t cwDst)
+{
+    AssertPtrReturn(pcwszSrc, VERR_INVALID_POINTER);
+    AssertPtrReturn(pu16Dst, VERR_INVALID_POINTER);
+    AssertReturn(cwDst, VERR_INVALID_PARAMETER);
+
+    AssertMsgReturn(pcwszSrc[0] != VBOX_SHCL_UTF16BEMARKER,
+                    ("Big endian UTF-16 not supported yet\n"), VERR_NOT_SUPPORTED);
+
+    int rc = VINF_SUCCESS;
+
+    /* Don't copy the endian marker. */
+    size_t i = pcwszSrc[0] == VBOX_SHCL_UTF16LEMARKER ? 1 : 0;
+    size_t j = 0;
+
+    for (; i < cwcSrc; ++i, ++j)
+    {
+        /* Don't copy the null byte, as we add it below. */
+        if (pcwszSrc[i] == 0)
+            break;
+
+        /* Not enough space in destination? */
+        if (j == cwDst)
+        {
+            rc = VERR_BUFFER_OVERFLOW;
+            break;
+        }
+
+        if (pcwszSrc[i] == VBOX_SHCL_LINEFEED)
+        {
+            pu16Dst[j] = VBOX_SHCL_CARRIAGERETURN;
+            ++j;
+
+            /* Not enough space in destination? */
+            if (j == cwDst)
+            {
+                rc = VERR_BUFFER_OVERFLOW;
+                break;
+            }
+        }
+#ifdef RT_OS_DARWIN
+        /* Check for a single carriage return (MacOS) */
+        else if (pcwszSrc[i] == VBOX_SHCL_CARRIAGERETURN)
+        {
+            /* Set CR.r */
+            pu16Dst[j] = VBOX_SHCL_CARRIAGERETURN;
+            ++j;
+
+            /* Not enough space in destination? */
+            if (j == cwDst)
+            {
+                rc = VERR_BUFFER_OVERFLOW;
+                break;
+            }
+
+            /* Add line feed. */
+            pu16Dst[j] = VBOX_SHCL_LINEFEED;
+            continue;
+        }
+#endif
+        pu16Dst[j] = pcwszSrc[i];
+    }
+
+    if (j == cwDst)
+        rc = VERR_BUFFER_OVERFLOW;
+
+    if (RT_SUCCESS(rc))
+    {
+        /* Add terminator. */
+        pu16Dst[j] = 0;
+    }
+
+    return rc;
+}
+
+int ShClConvUtf16CRLFToLF(PCRTUTF16 pcwszSrc, size_t cwcSrc, PRTUTF16 pu16Dst, size_t cwDst)
+{
+    AssertPtrReturn(pcwszSrc, VERR_INVALID_POINTER);
+    AssertReturn(cwcSrc,      VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pu16Dst,  VERR_INVALID_POINTER);
+    AssertReturn(cwDst,       VERR_INVALID_PARAMETER);
+
+    AssertMsgReturn(pcwszSrc[0] != VBOX_SHCL_UTF16BEMARKER,
+                    ("Big endian UTF-16 not supported yet\n"), VERR_NOT_SUPPORTED);
+
+    /* Prepend the Utf16 byte order marker if it is missing. */
+    size_t cwDstPos;
+    if (pcwszSrc[0] == VBOX_SHCL_UTF16LEMARKER)
+    {
+        cwDstPos = 0;
+    }
+    else
+    {
+        pu16Dst[0] = VBOX_SHCL_UTF16LEMARKER;
+        cwDstPos = 1;
+    }
+
+    for (size_t i = 0; i < cwcSrc; ++i, ++cwDstPos)
+    {
+        if (pcwszSrc[i] == 0)
+            break;
+
+        if (cwDstPos == cwDst)
+            return VERR_BUFFER_OVERFLOW;
+
+        if (   (i + 1 < cwcSrc)
+            && (pcwszSrc[i]     == VBOX_SHCL_CARRIAGERETURN)
+            && (pcwszSrc[i + 1] == VBOX_SHCL_LINEFEED))
+        {
+            ++i;
+        }
+
+        pu16Dst[cwDstPos] = pcwszSrc[i];
+    }
+
+    if (cwDstPos == cwDst)
+        return VERR_BUFFER_OVERFLOW;
+
+    /* Add terminating zero. */
+    pu16Dst[cwDstPos] = 0;
+
+    return VINF_SUCCESS;
+}
+
+int ShClDibToBmp(const void *pvSrc, size_t cbSrc, void **ppvDest, size_t *pcbDest)
+{
+    AssertPtrReturn(pvSrc,   VERR_INVALID_POINTER);
+    AssertReturn(cbSrc,      VERR_INVALID_PARAMETER);
+    AssertPtrReturn(ppvDest, VERR_INVALID_POINTER);
+    AssertPtrReturn(pcbDest, VERR_INVALID_POINTER);
+
+    PBMPWIN3XINFOHDR coreHdr = (PBMPWIN3XINFOHDR)pvSrc;
+    /** @todo Support all the many versions of the DIB headers. */
+    if (   cbSrc < sizeof(BMPWIN3XINFOHDR)
+        || RT_LE2H_U32(coreHdr->cbSize) < sizeof(BMPWIN3XINFOHDR)
+        || RT_LE2H_U32(coreHdr->cbSize) != sizeof(BMPWIN3XINFOHDR))
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    size_t offPixel = sizeof(BMPFILEHDR)
+                    + RT_LE2H_U32(coreHdr->cbSize)
+                    + RT_LE2H_U32(coreHdr->cClrUsed) * sizeof(uint32_t);
+    if (cbSrc < offPixel)
+        return VERR_INVALID_PARAMETER;
+
+    size_t cbDst = sizeof(BMPFILEHDR) + cbSrc;
+
+    void *pvDest = RTMemAlloc(cbDst);
+    if (!pvDest)
+        return VERR_NO_MEMORY;
+
+    PBMPFILEHDR fileHdr = (PBMPFILEHDR)pvDest;
+
+    fileHdr->uType       = BMP_HDR_MAGIC;
+    fileHdr->cbFileSize  = (uint32_t)RT_H2LE_U32(cbDst);
+    fileHdr->Reserved1   = 0;
+    fileHdr->Reserved2   = 0;
+    fileHdr->offBits     = (uint32_t)RT_H2LE_U32(offPixel);
+
+    memcpy((uint8_t *)pvDest + sizeof(BMPFILEHDR), pvSrc, cbSrc);
+
+    *ppvDest = pvDest;
+    *pcbDest = cbDst;
+
+    return VINF_SUCCESS;
+}
+
+int ShClBmpGetDib(const void *pvSrc, size_t cbSrc, const void **ppvDest, size_t *pcbDest)
+{
+    AssertPtrReturn(pvSrc,   VERR_INVALID_POINTER);
+    AssertReturn(cbSrc,      VERR_INVALID_PARAMETER);
+    AssertPtrReturn(ppvDest, VERR_INVALID_POINTER);
+    AssertPtrReturn(pcbDest, VERR_INVALID_POINTER);
+
+    PBMPFILEHDR pBmpHdr = (PBMPFILEHDR)pvSrc;
+    if (   cbSrc < sizeof(BMPFILEHDR)
+        || pBmpHdr->uType != BMP_HDR_MAGIC
+        || RT_LE2H_U32(pBmpHdr->cbFileSize) != cbSrc)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    *ppvDest = ((uint8_t *)pvSrc) + sizeof(BMPFILEHDR);
+    *pcbDest = cbSrc - sizeof(BMPFILEHDR);
+
+    return VINF_SUCCESS;
+}
+
+#ifdef LOG_ENABLED
+
+int ShClDbgDumpHtml(const char *pcszSrc, size_t cbSrc)
+{
+    int rc = VINF_SUCCESS;
+    char *pszBuf = (char *)RTMemTmpAllocZ(cbSrc + 1);
+    if (pszBuf)
+    {
+        memcpy(pszBuf, pcszSrc, cbSrc);
+        pszBuf[cbSrc] = '\0';
+        for (size_t off = 0; off < cbSrc; ++off)
+            if (pszBuf[off] == '\n' || pszBuf[off] == '\r')
+                pszBuf[off] = ' ';
+        LogFunc(("Removed \\r\\n: %s\n", pszBuf));
+        RTMemTmpFree(pszBuf);
+    }
+    else
+        rc = VERR_NO_MEMORY;
+    return rc;
+}
+
+void ShClDbgDumpData(const void *pv, size_t cb, SHCLFORMAT uFormat)
+{
+    if (LogIsEnabled())
+    {
+        if (uFormat & VBOX_SHCL_FMT_UNICODETEXT)
+        {
+            LogFunc(("VBOX_SHCL_FMT_UNICODETEXT:\n"));
+            if (pv && cb)
+                LogFunc(("%ls\n", pv));
+            else
+                LogFunc(("%p %zu\n", pv, cb));
+        }
+        else if (uFormat & VBOX_SHCL_FMT_BITMAP)
+            LogFunc(("VBOX_SHCL_FMT_BITMAP\n"));
+        else if (uFormat & VBOX_SHCL_FMT_HTML)
+        {
+            LogFunc(("VBOX_SHCL_FMT_HTML:\n"));
+            if (pv && cb)
+            {
+                LogFunc(("%s\n", pv));
+                ShClDbgDumpHtml((const char *)pv, cb);
+            }
+            else
+                LogFunc(("%p %zu\n", pv, cb));
+        }
+        else
+            LogFunc(("Invalid format %02X\n", uFormat));
+    }
+}
+
+#endif /* LOG_ENABLED */
+
+/**
+ * Translates a Shared Clipboard host function number to a string.
+ *
+ * @returns Function ID string name.
+ * @param   uFn                 The function to translate.
+ */
+const char *ShClHostFunctionToStr(uint32_t uFn)
+{
+    switch (uFn)
+    {
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_FN_SET_MODE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_FN_SET_HEADLESS);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_FN_CANCEL);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_FN_ERROR);
+    }
+    return "Unknown";
+}
+
+/**
+ * Translates a Shared Clipboard host message enum to a string.
+ *
+ * @returns Message ID string name.
+ * @param   uMsg                The message to translate.
+ */
+const char *ShClHostMsgToStr(uint32_t uMsg)
+{
+    switch (uMsg)
+    {
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_QUIT);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_READ_DATA);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_FORMATS_REPORT);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_CANCELED);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_READ_DATA_CID);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_STATUS);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_ROOT_LIST_HDR_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_ROOT_LIST_HDR_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_ROOT_LIST_ENTRY_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_ROOT_LIST_ENTRY_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_LIST_OPEN);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_LIST_CLOSE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_LIST_HDR_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_LIST_HDR_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_LIST_ENTRY_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_LIST_ENTRY_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_OBJ_OPEN);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_OBJ_CLOSE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_OBJ_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_OBJ_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_CANCEL);
+        RT_CASE_RET_STR(VBOX_SHCL_HOST_MSG_TRANSFER_ERROR);
+    }
+    return "Unknown";
+}
+
+/**
+ * Translates a Shared Clipboard guest message enum to a string.
+ *
+ * @returns Message ID string name.
+ * @param   uMsg                The message to translate.
+ */
+const char *ShClGuestMsgToStr(uint32_t uMsg)
+{
+    switch (uMsg)
+    {
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_REPORT_FORMATS);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_DATA_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_DATA_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_CONNECT);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_REPORT_FEATURES);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_QUERY_FEATURES);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_MSG_PEEK_NOWAIT);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_MSG_PEEK_WAIT);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_MSG_GET);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_MSG_CANCEL);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_REPLY);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_ROOT_LIST_HDR_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_ROOT_LIST_HDR_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_ROOT_LIST_ENTRY_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_ROOT_LIST_ENTRY_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_LIST_OPEN);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_LIST_CLOSE);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_LIST_HDR_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_LIST_HDR_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_LIST_ENTRY_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_LIST_ENTRY_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_OBJ_OPEN);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_OBJ_CLOSE);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_OBJ_READ);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_OBJ_WRITE);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_ERROR);
+        RT_CASE_RET_STR(VBOX_SHCL_GUEST_FN_NEGOTIATE_CHUNK_SIZE);
+    }
+    return "Unknown";
+}
+
+/**
+ * Converts Shared Clipboard formats to a string.
+ *
+ * @returns Stringified Shared Clipboard formats, or NULL on failure. Must be free'd with RTStrFree().
+ * @param   fFormats            Shared Clipboard formats to convert.
+ *
+ */
+char *ShClFormatsToStrA(SHCLFORMATS fFormats)
+{
+#define APPEND_FMT_TO_STR(_aFmt)                \
+    if (fFormats & VBOX_SHCL_FMT_##_aFmt)       \
+    {                                           \
+        if (pszFmts)                            \
+        {                                       \
+            rc2 = RTStrAAppend(&pszFmts, ", "); \
+            if (RT_FAILURE(rc2))                \
+                break;                          \
+        }                                       \
+                                                \
+        rc2 = RTStrAAppend(&pszFmts, #_aFmt);   \
+        if (RT_FAILURE(rc2))                    \
+            break;                              \
+    }
+
+    char *pszFmts = NULL;
+    int rc2 = VINF_SUCCESS;
+
+    do
+    {
+        APPEND_FMT_TO_STR(UNICODETEXT);
+        APPEND_FMT_TO_STR(BITMAP);
+        APPEND_FMT_TO_STR(HTML);
+# ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+        APPEND_FMT_TO_STR(URI_LIST);
+# endif
+
+    } while (0);
+
+    if (!pszFmts)
+        rc2 = RTStrAAppend(&pszFmts, "NONE");
+
+    if (   RT_FAILURE(rc2)
+        && pszFmts)
+    {
+        RTStrFree(pszFmts);
+        pszFmts = NULL;
+    }
+
+#undef APPEND_FMT_TO_STR
+
+    return pszFmts;
+}
+
diff --git a/src/VBox/GuestHost/SharedClipboard/clipboard-transfers-http.cpp b/src/VBox/GuestHost/SharedClipboard/clipboard-transfers-http.cpp
new file mode 100644
index 00000000..71504151
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/clipboard-transfers-http.cpp
@@ -0,0 +1,862 @@
+/* $Id: clipboard-transfers-http.cpp $ */
+/** @file
+ * Shared Clipboard: HTTP server implementation for Shared Clipboard transfers on UNIX-y guests / hosts.
+ */
+
+/*
+ * Copyright (C) 2020-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include <signal.h>
+
+#include <iprt/http.h>
+#include <iprt/http-server.h>
+
+#include <iprt/net.h> /* To make use of IPv4Addr in RTGETOPTUNION. */
+
+#include <iprt/asm.h>
+#include <iprt/assert.h>
+#include <iprt/ctype.h>
+#include <iprt/errcore.h>
+#include <iprt/file.h>
+#include <iprt/getopt.h>
+#include <iprt/initterm.h>
+#include <iprt/list.h>
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <iprt/log.h>
+#include <iprt/mem.h>
+#include <iprt/message.h>
+#include <iprt/path.h>
+#include <iprt/rand.h>
+#include <iprt/stream.h>
+#include <iprt/string.h>
+#include <iprt/thread.h>
+#include <iprt/uuid.h>
+#include <iprt/vfs.h>
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <VBox/GuestHost/SharedClipboard-x11.h>
+#include <VBox/GuestHost/SharedClipboard-transfers.h>
+
+
+/*********************************************************************************************************************************
+*   Definitations                                                                                                                *
+*********************************************************************************************************************************/
+
+typedef struct _SHCLHTTPSERVERTRANSFER
+{
+    /** The node list. */
+    RTLISTNODE          Node;
+    /** Pointer to associated transfer. */
+    PSHCLTRANSFER       pTransfer;
+    /** The (cached) root list of the transfer. NULL if not cached yet. */
+    PSHCLROOTLIST       pRootList;
+    /** Critical section for serializing access. */
+    RTCRITSECT          CritSect;
+    /** The handle we're going to use for this HTTP transfer. */
+    SHCLOBJHANDLE       hObj;
+    /** The virtual path of the HTTP server's root directory for this transfer. */
+    char                szPathVirtual[RTPATH_MAX];
+} SHCLHTTPSERVERTRANSFER;
+typedef SHCLHTTPSERVERTRANSFER *PSHCLHTTPSERVERTRANSFER;
+
+
+/*********************************************************************************************************************************
+*   Prototypes                                                                                                                   *
+*********************************************************************************************************************************/
+static int shClTransferHttpServerDestroyInternal(PSHCLHTTPSERVER pThis);
+static const char *shClTransferHttpServerGetHost(PSHCLHTTPSERVER pSrv);
+
+
+/*********************************************************************************************************************************
+*   Public Shared Clipboard HTTP transfer functions                                                                              *
+*********************************************************************************************************************************/
+
+/**
+ * Registers a Shared Clipboard transfer to a HTTP context.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                HTTP context to register transfer for.
+ * @param   pTransfer           Transfer to register.
+ */
+int ShClHttpTransferRegister(PSHCLHTTPCONTEXT pCtx, PSHCLTRANSFER pTransfer)
+{
+    int rc = VINF_SUCCESS;
+
+    /* Start the built-in HTTP server to serve file(s). */
+    if (!ShClTransferHttpServerIsRunning(&pCtx->HttpServer)) /* Only one HTTP server per transfer context. */
+        rc = ShClTransferHttpServerCreate(&pCtx->HttpServer, NULL /* puPort */);
+
+    if (RT_SUCCESS(rc))
+        rc = ShClTransferHttpServerRegisterTransfer(&pCtx->HttpServer, pTransfer);
+
+    return rc;
+}
+
+/**
+ * Unregisters a formerly registered Shared Clipboard transfer.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                HTTP context to unregister transfer from.
+ * @param   pTransfer           Transfer to unregister.
+ */
+int ShClHttpTransferUnregister(PSHCLHTTPCONTEXT pCtx, PSHCLTRANSFER pTransfer)
+{
+    int rc = VINF_SUCCESS;
+
+    if (ShClTransferHttpServerIsRunning(&pCtx->HttpServer))
+    {
+        /* Try unregistering transfer (if it was registered before). */
+        rc = ShClTransferHttpServerUnregisterTransfer(&pCtx->HttpServer, pTransfer);
+        if (RT_SUCCESS(rc))
+        {
+            /* No more registered transfers left? Tear down the HTTP server instance then. */
+            if (ShClTransferHttpServerGetTransferCount(&pCtx->HttpServer) == 0)
+                rc = ShClTransferHttpServerDestroy(&pCtx->HttpServer);
+        }
+        AssertRC(rc);
+    }
+
+    return rc;
+}
+
+
+/*********************************************************************************************************************************
+*   Internal Shared Clipboard HTTP transfer functions                                                                            *
+*********************************************************************************************************************************/
+
+DECLINLINE(void) shClHttpTransferLock(PSHCLHTTPSERVERTRANSFER pSrvTx)
+{
+    int rc2 = RTCritSectEnter(&pSrvTx->CritSect);
+    AssertRC(rc2);
+}
+
+DECLINLINE(void) shClHttpTransferUnlock(PSHCLHTTPSERVERTRANSFER pSrvTx)
+{
+    int rc2 = RTCritSectEnter(&pSrvTx->CritSect);
+    AssertRC(rc2);
+}
+
+/**
+ * Return the HTTP server transfer for a specific transfer ID.
+ *
+ * @returns Pointer to HTTP server transfer if found, NULL if not found.
+ * @param   pSrv                HTTP server instance.
+ * @param   idTransfer          Transfer ID to return HTTP server transfer for.
+ */
+static PSHCLHTTPSERVERTRANSFER shClTransferHttpServerGetTransferById(PSHCLHTTPSERVER pSrv, SHCLTRANSFERID idTransfer)
+{
+    PSHCLHTTPSERVERTRANSFER pSrvTx;
+    RTListForEach(&pSrv->lstTransfers, pSrvTx, SHCLHTTPSERVERTRANSFER, Node) /** @todo Slow O(n) lookup, but does it for now. */
+    {
+        if (pSrvTx->pTransfer->State.uID == idTransfer)
+            return pSrvTx;
+    }
+
+    return NULL;
+}
+
+/**
+ * Returns a HTTP server transfer from a given URL.
+ *
+ * @returns Pointer to HTTP server transfer if found, NULL if not found.
+ * @param   pThis               HTTP server instance data.
+ * @param   pszUrl              URL to validate.
+ */
+DECLINLINE(PSHCLHTTPSERVERTRANSFER) shClTransferHttpGetTransferFromUrl(PSHCLHTTPSERVER pThis, const char *pszUrl)
+{
+    AssertPtrReturn(pszUrl, NULL);
+
+    PSHCLHTTPSERVERTRANSFER pSrvTx = NULL;
+
+    PSHCLHTTPSERVERTRANSFER pSrvTxCur;
+    RTListForEach(&pThis->lstTransfers, pSrvTxCur, SHCLHTTPSERVERTRANSFER, Node)
+    {
+        AssertPtr(pSrvTxCur->pTransfer);
+
+        LogFlowFunc(("pSrvTxCur=%s\n", pSrvTxCur->szPathVirtual));
+
+        /* Be picky here, do a case sensitive comparison. */
+        if (RTStrStartsWith(pszUrl, pSrvTxCur->szPathVirtual))
+        {
+            pSrvTx = pSrvTxCur;
+            break;
+        }
+    }
+
+    if (!pSrvTx)
+        LogRel2(("Shared Clipboard: HTTP URL '%s' not valid\n", pszUrl));
+
+    LogFlowFunc(("pszUrl=%s, pSrvTx=%p\n", pszUrl, pSrvTx));
+    return pSrvTx;
+}
+
+/**
+ * Returns a HTTP server transfer from an internal HTTP handle.
+ *
+ * @returns Pointer to HTTP server transfer if found, NULL if not found.
+ * @param   pThis               HTTP server instance data.
+ * @param   pvHandle            Handle to return transfer for.
+ */
+DECLINLINE(PSHCLHTTPSERVERTRANSFER) shClTransferHttpGetTransferFromHandle(PSHCLHTTPSERVER pThis, void *pvHandle)
+{
+    AssertPtrReturn(pvHandle, NULL);
+
+    const SHCLTRANSFERID uHandle = *(uint16_t *)pvHandle;
+
+    /** @ŧodo Use a handle lookup table (map) later. */
+    PSHCLHTTPSERVERTRANSFER pSrvTxCur;
+    RTListForEach(&pThis->lstTransfers, pSrvTxCur, SHCLHTTPSERVERTRANSFER, Node)
+    {
+        AssertPtr(pSrvTxCur->pTransfer);
+
+        if (pSrvTxCur->pTransfer->State.uID == uHandle) /** @ŧodo We're using the transfer ID as handle for now. */
+            return pSrvTxCur;
+    }
+
+    return NULL;
+}
+
+static int shClTransferHttpGetTransferRoots(PSHCLHTTPSERVER pThis, PSHCLHTTPSERVERTRANSFER pSrvTx)
+{
+    RT_NOREF(pThis);
+
+    int rc = VINF_SUCCESS;
+
+    if (pSrvTx->pRootList == NULL)
+    {
+        AssertPtr(pSrvTx->pTransfer);
+        rc = ShClTransferRootsGet(pSrvTx->pTransfer, &pSrvTx->pRootList);
+    }
+
+    return rc;
+}
+
+
+/*********************************************************************************************************************************
+*   HTTP server callback implementations                                                                                         *
+*********************************************************************************************************************************/
+
+/** @copydoc RTHTTPSERVERCALLBACKS::pfnOpen */
+static DECLCALLBACK(int) shClTransferHttpOpen(PRTHTTPCALLBACKDATA pData, PRTHTTPSERVERREQ pReq, void **ppvHandle)
+{
+    PSHCLHTTPSERVER pThis = (PSHCLHTTPSERVER)pData->pvUser;
+    Assert(pData->cbUser == sizeof(SHCLHTTPSERVER));
+
+    int rc;
+
+    PSHCLHTTPSERVERTRANSFER pSrvTx = shClTransferHttpGetTransferFromUrl(pThis, pReq->pszUrl);
+    if (pSrvTx)
+    {
+        shClHttpTransferLock(pSrvTx);
+
+        AssertPtr(pSrvTx->pTransfer);
+
+        SHCLOBJOPENCREATEPARMS openParms;
+        rc = ShClTransferObjOpenParmsInit(&openParms);
+        if (RT_SUCCESS(rc))
+        {
+            openParms.fCreate = SHCL_OBJ_CF_ACCESS_READ
+                              | SHCL_OBJ_CF_ACCESS_DENYWRITE;
+
+            rc = RTStrCopy(openParms.pszPath, openParms.cbPath, "foo"); /** @ŧodo BUGBUG !!!! */
+            if (RT_SUCCESS(rc))
+            {
+                rc = ShClTransferObjOpen(pSrvTx->pTransfer, &openParms, &pSrvTx->hObj);
+                if (RT_SUCCESS(rc))
+                {
+                    *ppvHandle = &pSrvTx->hObj;
+                    LogRel2(("Shared Clipboard: HTTP transfer (handle %RU64) started ...\n", pSrvTx->hObj));
+                }
+            }
+
+            ShClTransferObjOpenParmsDestroy(&openParms);
+        }
+
+        shClHttpTransferUnlock(pSrvTx);
+    }
+    else
+        rc = VERR_NOT_FOUND;
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Error starting HTTP transfer for '%s', rc=%Rrc\n", pReq->pszUrl, rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/** @copydoc RTHTTPSERVERCALLBACKS::pfnRead */
+static DECLCALLBACK(int) shClTransferHttpRead(PRTHTTPCALLBACKDATA pData, void *pvHandle, void *pvBuf, size_t cbBuf, size_t *pcbRead)
+{
+    PSHCLHTTPSERVER pThis = (PSHCLHTTPSERVER)pData->pvUser;
+    Assert(pData->cbUser == sizeof(SHCLHTTPSERVER));
+
+    RT_NOREF(pvBuf, cbBuf, pcbRead);
+
+    int rc;
+
+    PSHCLHTTPSERVERTRANSFER pSrvTx = shClTransferHttpGetTransferFromHandle(pThis, pvHandle);
+    if (pSrvTx)
+    {
+        Assert(pSrvTx->hObj != SHCLOBJHANDLE_INVALID);
+
+        uint32_t cbRead;
+        rc = ShClTransferObjRead(pSrvTx->pTransfer, pSrvTx->hObj, pvBuf, cbBuf, 0 /* fFlags */, &cbRead);
+        if (RT_SUCCESS(rc))
+        {
+            *pcbRead = (uint32_t)cbRead;
+        }
+
+        if (RT_FAILURE(rc))
+            LogRel(("Shared Clipboard: Error reading HTTP transfer (handle %RU64), rc=%Rrc\n", pSrvTx->hObj, rc));
+    }
+    else
+        rc = VERR_NOT_FOUND;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/** @copydoc RTHTTPSERVERCALLBACKS::pfnClose */
+static DECLCALLBACK(int) shClTransferHttpClose(PRTHTTPCALLBACKDATA pData, void *pvHandle)
+{
+    PSHCLHTTPSERVER pThis = (PSHCLHTTPSERVER)pData->pvUser;
+    Assert(pData->cbUser == sizeof(SHCLHTTPSERVER));
+
+    int rc;
+
+    PSHCLHTTPSERVERTRANSFER pSrvTx = shClTransferHttpGetTransferFromHandle(pThis, pvHandle);
+    if (pSrvTx)
+    {
+        shClHttpTransferLock(pSrvTx);
+
+        Assert(pSrvTx->hObj != SHCLOBJHANDLE_INVALID);
+        rc = ShClTransferObjClose(pSrvTx->pTransfer, pSrvTx->hObj);
+        if (RT_SUCCESS(rc))
+        {
+            pSrvTx->hObj = SHCLOBJHANDLE_INVALID;
+            LogRel2(("Shared Clipboard: HTTP transfer %RU16 done\n", pSrvTx->pTransfer->State.uID));
+        }
+
+        if (RT_FAILURE(rc))
+            LogRel(("Shared Clipboard: Error closing HTTP transfer (handle %RU64), rc=%Rrc\n", pSrvTx->hObj, rc));
+
+        shClHttpTransferUnlock(pSrvTx);
+    }
+    else
+        rc = VERR_NOT_FOUND;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/** @copydoc RTHTTPSERVERCALLBACKS::pfnQueryInfo */
+static DECLCALLBACK(int) shClTransferHttpQueryInfo(PRTHTTPCALLBACKDATA pData,
+                                                   PRTHTTPSERVERREQ pReq, PRTFSOBJINFO pObjInfo, char **ppszMIMEHint)
+{
+    PSHCLHTTPSERVER pThis = (PSHCLHTTPSERVER)pData->pvUser;
+    Assert(pData->cbUser == sizeof(SHCLHTTPSERVER));
+
+    int rc;
+
+    PSHCLHTTPSERVERTRANSFER pSrvTx = shClTransferHttpGetTransferFromUrl(pThis, pReq->pszUrl);
+    if (pSrvTx)
+    {
+        shClHttpTransferLock(pSrvTx);
+
+        rc = shClTransferHttpGetTransferRoots(pThis, pSrvTx);
+
+        shClHttpTransferUnlock(pSrvTx);
+    }
+    else
+        rc = VERR_NOT_FOUND;
+
+    RT_NOREF(pObjInfo, ppszMIMEHint);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/** @copydoc RTHTTPSERVERCALLBACKS::pfnDestroy */
+static DECLCALLBACK(int) shClTransferHttpDestroy(PRTHTTPCALLBACKDATA pData)
+{
+    PSHCLHTTPSERVER pThis = (PSHCLHTTPSERVER)pData->pvUser;
+    Assert(pData->cbUser == sizeof(SHCLHTTPSERVER));
+
+    return shClTransferHttpServerDestroyInternal(pThis);
+}
+
+
+/*********************************************************************************************************************************
+*   Internal Shared Clipboard HTTP server functions                                                                              *
+*********************************************************************************************************************************/
+
+/**
+ * Destroys a Shared Clipboard HTTP server instance, internal version.
+ *
+ * @returns VBox status code.
+ * @param   pSrv                Shared Clipboard HTTP server instance to destroy.
+ */
+static int shClTransferHttpServerDestroyInternal(PSHCLHTTPSERVER pSrv)
+{
+    PSHCLHTTPSERVERTRANSFER pSrvTx, pSrvTxNext;
+    RTListForEachSafe(&pSrv->lstTransfers, pSrvTx, pSrvTxNext, SHCLHTTPSERVERTRANSFER, Node)
+    {
+        RTListNodeRemove(&pSrvTx->Node);
+
+        RTMemFree(pSrvTx);
+        pSrvTx = NULL;
+    }
+
+    RTHttpServerResponseDestroy(&pSrv->Resp);
+
+    pSrv->hHTTPServer = NIL_RTHTTPSERVER;
+
+    int rc = VINF_SUCCESS;
+
+    if (RTCritSectIsInitialized(&pSrv->CritSect))
+        rc = RTCritSectDelete(&pSrv->CritSect);
+
+    return rc;
+}
+
+/**
+ * Locks the critical section of a Shared Clipboard HTTP server instance.
+ *
+ * @param   pSrv                Shared Clipboard HTTP server instance to lock.
+ */
+DECLINLINE(void) shClTransferHttpServerLock(PSHCLHTTPSERVER pSrv)
+{
+    int rc2 = RTCritSectEnter(&pSrv->CritSect);
+    AssertRC(rc2);
+}
+
+/**
+ * Unlocks the critical section of a Shared Clipboard HTTP server instance.
+ *
+ * @param   pSrv                Shared Clipboard HTTP server instance to unlock.
+ */
+DECLINLINE(void) shClTransferHttpServerUnlock(PSHCLHTTPSERVER pSrv)
+{
+    int rc2 = RTCritSectLeave(&pSrv->CritSect);
+    AssertRC(rc2);
+}
+
+/**
+ * Initializes a new Shared Clipboard HTTP server instance.
+ *
+ * @param   pSrv                HTTP server instance to initialize.
+ */
+static void shClTransferHttpServerInitInternal(PSHCLHTTPSERVER pSrv)
+{
+    pSrv->hHTTPServer = NIL_RTHTTPSERVER;
+    pSrv->uPort       = 0;
+    RTListInit(&pSrv->lstTransfers);
+    pSrv->cTransfers  = 0;
+    int rc2 = RTHttpServerResponseInit(&pSrv->Resp);
+    AssertRC(rc2);
+}
+
+
+/*********************************************************************************************************************************
+*   Public Shared Clipboard HTTP server functions                                                                                *
+*********************************************************************************************************************************/
+
+/**
+ * Initializes a new Shared Clipboard HTTP server instance.
+ *
+ * @param   pSrv                HTTP server instance to initialize.
+ */
+void ShClTransferHttpServerInit(PSHCLHTTPSERVER pSrv)
+{
+    AssertPtrReturnVoid(pSrv);
+
+    shClTransferHttpServerInitInternal(pSrv);
+}
+
+/**
+ * Creates a new Shared Clipboard HTTP server instance, extended version.
+ *
+ * @returns VBox status code.
+ * @param   pSrv                HTTP server instance to create.
+ * @param   uPort               TCP port number to use.
+ */
+int ShClTransferHttpServerCreateEx(PSHCLHTTPSERVER pSrv, uint16_t uPort)
+{
+    AssertPtrReturn(pSrv, VERR_INVALID_POINTER);
+
+    RTHTTPSERVERCALLBACKS Callbacks;
+    RT_ZERO(Callbacks);
+
+    Callbacks.pfnOpen          = shClTransferHttpOpen;
+    Callbacks.pfnRead          = shClTransferHttpRead;
+    Callbacks.pfnClose         = shClTransferHttpClose;
+    Callbacks.pfnQueryInfo     = shClTransferHttpQueryInfo;
+    Callbacks.pfnDestroy       = shClTransferHttpDestroy;
+
+    /* Note: The server always and *only* runs against the localhost interface. */
+    int rc = RTHttpServerCreate(&pSrv->hHTTPServer, "localhost", uPort, &Callbacks,
+                                pSrv, sizeof(SHCLHTTPSERVER));
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTCritSectInit(&pSrv->CritSect);
+        AssertRCReturn(rc, rc);
+
+        pSrv->uPort = uPort;
+
+        LogRel2(("Shared Clipboard: HTTP server running at port %RU16\n", pSrv->uPort));
+    }
+    else
+    {
+        int rc2 = shClTransferHttpServerDestroyInternal(pSrv);
+        AssertRC(rc2);
+    }
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: HTTP server failed to run, rc=%Rrc\n", rc));
+
+    return rc;
+}
+
+/**
+ * Creates a new Shared Clipboard HTTP server instance.
+ *
+ * This does automatic probing of TCP ports if one already is being used.
+ *
+ * @returns VBox status code.
+ * @param   pSrv                HTTP server instance to create.
+ * @param   puPort              Where to return the TCP port number being used on success. Optional.
+ */
+int ShClTransferHttpServerCreate(PSHCLHTTPSERVER pSrv, uint16_t *puPort)
+{
+    AssertPtrReturn(pSrv, VERR_INVALID_POINTER);
+    /* puPort is optional. */
+
+    /** @todo Try favorite ports first (e.g. 8080, 8000, ...)? */
+
+    RTRAND hRand;
+    int rc = RTRandAdvCreateSystemFaster(&hRand); /* Should be good enough for this task. */
+    if (RT_SUCCESS(rc))
+    {
+        uint16_t uPort;
+        for (int i = 0; i < 32; i++)
+        {
+#ifdef DEBUG_andy
+            uPort = 8080; /* Make the port predictable, but only for me, mwahaha! :-). */
+#else
+            uPort = RTRandAdvU32Ex(hRand, 1024, UINT16_MAX);
+#endif
+            rc = ShClTransferHttpServerCreateEx(pSrv, (uint32_t)uPort);
+            if (RT_SUCCESS(rc))
+            {
+                if (puPort)
+                    *puPort = uPort;
+                break;
+            }
+        }
+
+        RTRandAdvDestroy(hRand);
+    }
+
+    return rc;
+}
+
+/**
+ * Destroys a Shared Clipboard HTTP server instance.
+ *
+ * @returns VBox status code.
+ * @param   pSrv                HTTP server instance to destroy.
+ */
+int ShClTransferHttpServerDestroy(PSHCLHTTPSERVER pSrv)
+{
+    AssertPtrReturn(pSrv, VERR_INVALID_POINTER);
+
+    if (pSrv->hHTTPServer == NIL_RTHTTPSERVER)
+        return VINF_SUCCESS;
+
+    Assert(pSrv->cTransfers == 0); /* Sanity. */
+
+    int rc = RTHttpServerDestroy(pSrv->hHTTPServer);
+    if (RT_SUCCESS(rc))
+        rc = shClTransferHttpServerDestroyInternal(pSrv);
+
+    if (RT_SUCCESS(rc))
+        LogRel2(("Shared Clipboard: HTTP server stopped\n"));
+    else
+        LogRel(("Shared Clipboard: HTTP server failed to stop, rc=%Rrc\n", rc));
+
+    return rc;
+}
+
+/**
+ * Registers a Shared Clipboard transfer to a HTTP server instance.
+ *
+ * @returns VBox status code.
+ * @param   pSrv                HTTP server instance to register transfer for.
+ * @param   pTransfer           Transfer to register.
+ */
+int ShClTransferHttpServerRegisterTransfer(PSHCLHTTPSERVER pSrv, PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pSrv, VERR_INVALID_POINTER);
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    AssertReturn(pTransfer->State.uID, VERR_INVALID_PARAMETER); /* Paranoia. */
+
+    shClTransferHttpServerLock(pSrv);
+
+    PSHCLHTTPSERVERTRANSFER pSrvTx = (PSHCLHTTPSERVERTRANSFER)RTMemAllocZ(sizeof(SHCLHTTPSERVERTRANSFER));
+    AssertPtrReturn(pSrvTx, VERR_NO_MEMORY);
+
+    RTUUID Uuid;
+    int rc = RTUuidCreate(&Uuid);
+    if (RT_SUCCESS(rc))
+    {
+        char szUuid[64];
+        rc = RTUuidToStr(&Uuid, szUuid, sizeof(szUuid));
+        if (RT_SUCCESS(rc))
+        {
+            rc = RTCritSectInit(&pSrvTx->CritSect);
+            AssertRC(rc);
+
+            /* Create the virtual HTTP path for the transfer.
+             * Every transfer has a dedicated HTTP path. */
+#ifdef DEBUG_andy
+            ssize_t cch = RTStrPrintf2(pSrvTx->szPathVirtual, sizeof(pSrvTx->szPathVirtual), "/d1bbda60-80b7-45dc-a41c-ac4686c1d988/10664");
+#else
+            ssize_t cch = RTStrPrintf2(pSrvTx->szPathVirtual, sizeof(pSrvTx->szPathVirtual), "%s/%RU16/", szUuid, pTransfer->State.uID);
+#endif
+            AssertReturn(cch, VERR_BUFFER_OVERFLOW);
+
+            pSrvTx->pTransfer = pTransfer;
+            pSrvTx->pRootList = NULL;
+            pSrvTx->hObj      = SHCLOBJHANDLE_INVALID;
+
+            RTListAppend(&pSrv->lstTransfers, &pSrvTx->Node);
+            pSrv->cTransfers++;
+
+            LogFunc(("pTransfer=%p, idTransfer=%RU16, szPath=%s -> %RU32 transfers\n",
+                     pSrvTx->pTransfer, pSrvTx->pTransfer->State.uID, pSrvTx->szPathVirtual, pSrv->cTransfers));
+
+            LogRel2(("Shared Clipboard: Registered HTTP transfer %RU16, now %RU32 HTTP transfers total\n",
+                     pTransfer->State.uID, pSrv->cTransfers));
+        }
+    }
+
+    if (RT_FAILURE(rc))
+        RTMemFree(pSrvTx);
+
+    shClTransferHttpServerUnlock(pSrv);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Unregisters a formerly registered Shared Clipboard transfer.
+ *
+ * @returns VBox status code.
+ * @param   pSrv                HTTP server instance to unregister transfer from.
+ * @param   pTransfer           Transfer to unregister.
+ */
+int ShClTransferHttpServerUnregisterTransfer(PSHCLHTTPSERVER pSrv, PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pSrv, VERR_INVALID_POINTER);
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    shClTransferHttpServerLock(pSrv);
+
+    AssertReturn(pSrv->cTransfers, VERR_WRONG_ORDER);
+
+    int rc = VINF_SUCCESS;
+
+    PSHCLHTTPSERVERTRANSFER pSrvTx;
+    RTListForEach(&pSrv->lstTransfers, pSrvTx, SHCLHTTPSERVERTRANSFER, Node)
+    {
+        AssertPtr(pSrvTx->pTransfer);
+        if (pSrvTx->pTransfer->State.uID == pTransfer->State.uID)
+        {
+            RTListNodeRemove(&pSrvTx->Node);
+
+            Assert(pSrv->cTransfers);
+            pSrv->cTransfers--;
+
+            LogFunc(("pTransfer=%p, idTransfer=%RU16, szPath=%s -> %RU32 transfers\n",
+                     pSrvTx->pTransfer, pSrvTx->pTransfer->State.uID, pSrvTx->szPathVirtual, pSrv->cTransfers));
+
+            LogRel2(("Shared Clipboard: Unregistered HTTP transfer %RU16, now %RU32 HTTP transfers total\n",
+                     pTransfer->State.uID, pSrv->cTransfers));
+
+            rc = RTCritSectDelete(&pSrvTx->CritSect);
+            AssertRC(rc);
+
+            RTMemFree(pSrvTx);
+            pSrvTx = NULL;
+
+            rc = VINF_SUCCESS;
+            break;
+        }
+    }
+
+    shClTransferHttpServerUnlock(pSrv);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Returns whether a specific transfer ID is registered with a HTTP server instance or not.
+ *
+ * @returns \c true if the transfer ID is registered, \c false if not.
+ * @param   pSrv                HTTP server instance.
+ * @param   idTransfer          Transfer ID to check for.
+ */
+bool ShClTransferHttpServerHasTransfer(PSHCLHTTPSERVER pSrv, SHCLTRANSFERID idTransfer)
+{
+    AssertPtrReturn(pSrv, false);
+
+    shClTransferHttpServerLock(pSrv);
+
+    const bool fRc = shClTransferHttpServerGetTransferById(pSrv, idTransfer) != NULL;
+
+    shClTransferHttpServerUnlock(pSrv);
+
+    return fRc;
+}
+
+/**
+ * Returns the used TCP port number of a HTTP server instance.
+ *
+ * @returns TCP port number. 0 if not specified yet.
+ * @param   pSrv                HTTP server instance to return port for.
+ */
+uint16_t ShClTransferHttpServerGetPort(PSHCLHTTPSERVER pSrv)
+{
+    AssertPtrReturn(pSrv, 0);
+
+    shClTransferHttpServerLock(pSrv);
+
+    const uint16_t uPort = pSrv->uPort;
+
+    shClTransferHttpServerUnlock(pSrv);
+
+    return uPort;
+}
+
+/**
+ * Returns the number of registered HTTP server transfers of a HTTP server instance.
+ *
+ * @returns Number of registered transfers.
+ * @param   pSrv                HTTP server instance to return registered transfers for.
+ */
+uint32_t ShClTransferHttpServerGetTransferCount(PSHCLHTTPSERVER pSrv)
+{
+    AssertPtrReturn(pSrv, 0);
+
+    shClTransferHttpServerLock(pSrv);
+
+    const uint32_t cTransfers = pSrv->cTransfers;
+
+    shClTransferHttpServerUnlock(pSrv);
+
+    return cTransfers;
+}
+
+/**
+ * Returns the host name (scheme) of a HTTP server instance.
+ *
+ * @param   pSrv                HTTP server instance to return host name (scheme) for.
+ *
+ * @returns Host name (scheme).
+ */
+static const char *shClTransferHttpServerGetHost(PSHCLHTTPSERVER pSrv)
+{
+    RT_NOREF(pSrv);
+    return "http://localhost"; /* Hardcoded for now. */
+}
+
+/**
+ * Returns an allocated string with a HTTP server instance's address.
+ *
+ * @returns Allocated string with a HTTP server instance's address, or NULL on OOM.
+ *          Needs to be free'd by the caller using RTStrFree().
+ * @param   pSrv                HTTP server instance to return address for.
+ */
+char *ShClTransferHttpServerGetAddressA(PSHCLHTTPSERVER pSrv)
+{
+    AssertPtrReturn(pSrv, NULL);
+
+    shClTransferHttpServerLock(pSrv);
+
+    char *pszAddress = RTStrAPrintf2("%s:%RU16", shClTransferHttpServerGetHost(pSrv), pSrv->uPort);
+    AssertPtr(pszAddress);
+
+    shClTransferHttpServerUnlock(pSrv);
+
+    return pszAddress;
+}
+
+/**
+ * Returns an allocated string with the URL of a given Shared Clipboard transfer ID.
+ *
+ * @returns Allocated string with the URL of a given Shared Clipboard transfer ID, or NULL if not found.
+ *          Needs to be free'd by the caller using RTStrFree().
+ * @param   pSrv                HTTP server instance to return URL for.
+ */
+char *ShClTransferHttpServerGetUrlA(PSHCLHTTPSERVER pSrv, SHCLTRANSFERID idTransfer)
+{
+    AssertPtrReturn(pSrv, NULL);
+    AssertReturn(idTransfer != NIL_SHCLTRANSFERID, NULL);
+
+    shClTransferHttpServerLock(pSrv);
+
+    PSHCLHTTPSERVERTRANSFER pSrvTx = shClTransferHttpServerGetTransferById(pSrv, idTransfer);
+    if (!pSrvTx)
+    {
+        AssertFailed();
+        shClTransferHttpServerUnlock(pSrv);
+        return NULL;
+    }
+
+    AssertReturn(RTStrNLen(pSrvTx->szPathVirtual, RTPATH_MAX), NULL);
+    char *pszUrl = RTStrAPrintf2("%s:%RU16/%s", shClTransferHttpServerGetHost(pSrv), pSrv->uPort, pSrvTx->szPathVirtual);
+    AssertPtr(pszUrl);
+
+    shClTransferHttpServerUnlock(pSrv);
+
+    return pszUrl;
+}
+
+/**
+ * Returns whether a given HTTP server instance is running or not.
+ *
+ * @returns \c true if running, or \c false if not.
+ * @param   pSrv                HTTP server instance to check running state for.
+ */
+bool ShClTransferHttpServerIsRunning(PSHCLHTTPSERVER pSrv)
+{
+    AssertPtrReturn(pSrv, false);
+
+    return (pSrv->hHTTPServer != NIL_RTHTTPSERVER); /* Seems enough for now. */
+}
diff --git a/src/VBox/GuestHost/SharedClipboard/clipboard-transfers.cpp b/src/VBox/GuestHost/SharedClipboard/clipboard-transfers.cpp
new file mode 100644
index 00000000..f0a0453d
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/clipboard-transfers.cpp
@@ -0,0 +1,3132 @@
+/* $Id: clipboard-transfers.cpp $ */
+/** @file
+ * Shared Clipboard: Common Shared Clipboard transfer handling code.
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/log.h>
+
+#include <iprt/dir.h>
+#include <iprt/file.h>
+#include <iprt/list.h>
+#include <iprt/path.h>
+#include <iprt/rand.h>
+#include <iprt/semaphore.h>
+
+#include <VBox/err.h>
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <VBox/GuestHost/SharedClipboard-transfers.h>
+
+
+static int shClTransferThreadCreate(PSHCLTRANSFER pTransfer, PFNRTTHREAD pfnThreadFunc, void *pvUser);
+static int shClTransferThreadDestroy(PSHCLTRANSFER pTransfer, RTMSINTERVAL uTimeoutMs);
+
+static void shclTransferCtxTransferRemoveAndUnregister(PSHCLTRANSFERCTX pTransferCtx, PSHCLTRANSFER pTransfer);
+static PSHCLTRANSFER shClTransferCtxGetTransferByIdInternal(PSHCLTRANSFERCTX pTransferCtx, uint32_t uId);
+static PSHCLTRANSFER shClTransferCtxGetTransferByIndexInternal(PSHCLTRANSFERCTX pTransferCtx, uint32_t uIdx);
+static int shClConvertFileCreateFlags(uint32_t fShClFlags, uint64_t *pfOpen);
+static int shClTransferResolvePathAbs(PSHCLTRANSFER pTransfer, const char *pszPath, uint32_t fFlags, char **ppszResolved);
+
+/** @todo Split this file up in different modules. */
+
+/**
+ * Allocates a new transfer root list.
+ *
+ * @returns Allocated transfer root list on success, or NULL on failure.
+ */
+PSHCLROOTLIST ShClTransferRootListAlloc(void)
+{
+    PSHCLROOTLIST pRootList = (PSHCLROOTLIST)RTMemAllocZ(sizeof(SHCLROOTLIST));
+
+    return pRootList;
+}
+
+/**
+ * Frees a transfer root list.
+ *
+ * @param   pRootList           transfer root list to free. The pointer will be
+ *                              invalid after returning from this function.
+ */
+void ShClTransferRootListFree(PSHCLROOTLIST pRootList)
+{
+    if (!pRootList)
+        return;
+
+    for (uint32_t i = 0; i < pRootList->Hdr.cRoots; i++)
+        ShClTransferListEntryInit(&pRootList->paEntries[i]);
+
+    RTMemFree(pRootList);
+    pRootList = NULL;
+}
+
+/**
+ * Initializes a transfer root list header.
+ *
+ * @returns VBox status code.
+ * @param   pRootLstHdr         Root list header to initialize.
+ */
+int ShClTransferRootListHdrInit(PSHCLROOTLISTHDR pRootLstHdr)
+{
+    AssertPtrReturn(pRootLstHdr, VERR_INVALID_POINTER);
+
+    RT_BZERO(pRootLstHdr, sizeof(SHCLROOTLISTHDR));
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys a transfer root list header.
+ *
+ * @param   pRootLstHdr         Root list header to destroy.
+ */
+void ShClTransferRootListHdrDestroy(PSHCLROOTLISTHDR pRootLstHdr)
+{
+    if (!pRootLstHdr)
+        return;
+
+    pRootLstHdr->fRoots = 0;
+    pRootLstHdr->cRoots = 0;
+}
+
+/**
+ * Duplicates a transfer list header.
+ *
+ * @returns Duplicated transfer list header on success, or NULL on failure.
+ * @param   pRootLstHdr         Root list header to duplicate.
+ */
+PSHCLROOTLISTHDR ShClTransferRootListHdrDup(PSHCLROOTLISTHDR pRootLstHdr)
+{
+    AssertPtrReturn(pRootLstHdr, NULL);
+
+    int rc = VINF_SUCCESS;
+
+    PSHCLROOTLISTHDR pRootsDup = (PSHCLROOTLISTHDR)RTMemAllocZ(sizeof(SHCLROOTLISTHDR));
+    if (pRootsDup)
+    {
+        *pRootsDup = *pRootLstHdr;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    if (RT_FAILURE(rc))
+    {
+        ShClTransferRootListHdrDestroy(pRootsDup);
+        pRootsDup = NULL;
+    }
+
+    return pRootsDup;
+}
+
+/**
+ * (Deep) Copies a clipboard root list entry structure.
+ *
+ * @returns VBox status code.
+ * @param   pDst                Where to copy the source root list entry to.
+ * @param   pSrc                Source root list entry to copy.
+ */
+int ShClTransferRootListEntryCopy(PSHCLROOTLISTENTRY pDst, PSHCLROOTLISTENTRY pSrc)
+{
+    return ShClTransferListEntryCopy(pDst, pSrc);
+}
+
+/**
+ * Initializes a clipboard root list entry structure.
+ *
+ * @param   pRootListEntry      Clipboard root list entry structure to destroy.
+ */
+int ShClTransferRootListEntryInit(PSHCLROOTLISTENTRY pRootListEntry)
+{
+    return ShClTransferListEntryInit(pRootListEntry);
+}
+
+/**
+ * Destroys a clipboard root list entry structure.
+ *
+ * @param   pRootListEntry      Clipboard root list entry structure to destroy.
+ */
+void ShClTransferRootListEntryDestroy(PSHCLROOTLISTENTRY pRootListEntry)
+{
+    return ShClTransferListEntryDestroy(pRootListEntry);
+}
+
+/**
+ * Duplicates (allocates) a clipboard root list entry structure.
+ *
+ * @returns Duplicated clipboard root list entry structure on success.
+ * @param   pRootListEntry      Clipboard root list entry to duplicate.
+ */
+PSHCLROOTLISTENTRY ShClTransferRootListEntryDup(PSHCLROOTLISTENTRY pRootListEntry)
+{
+    return ShClTransferListEntryDup(pRootListEntry);
+}
+
+/**
+ * Initializes an list handle info structure.
+ *
+ * @returns VBox status code.
+ * @param   pInfo               List handle info structure to initialize.
+ */
+int ShClTransferListHandleInfoInit(PSHCLLISTHANDLEINFO pInfo)
+{
+    AssertPtrReturn(pInfo, VERR_INVALID_POINTER);
+
+    pInfo->hList   = SHCLLISTHANDLE_INVALID;
+    pInfo->enmType = SHCLOBJTYPE_INVALID;
+
+    pInfo->pszPathLocalAbs = NULL;
+
+    RT_ZERO(pInfo->u);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys a list handle info structure.
+ *
+ * @param   pInfo               List handle info structure to destroy.
+ */
+void ShClTransferListHandleInfoDestroy(PSHCLLISTHANDLEINFO pInfo)
+{
+    if (!pInfo)
+        return;
+
+    if (pInfo->pszPathLocalAbs)
+    {
+        RTStrFree(pInfo->pszPathLocalAbs);
+        pInfo->pszPathLocalAbs = NULL;
+    }
+}
+
+/**
+ * Allocates a transfer list header structure.
+ *
+ * @returns VBox status code.
+ * @param   ppListHdr           Where to store the allocated transfer list header structure on success.
+ */
+int ShClTransferListHdrAlloc(PSHCLLISTHDR *ppListHdr)
+{
+    int rc;
+
+    PSHCLLISTHDR pListHdr = (PSHCLLISTHDR)RTMemAllocZ(sizeof(SHCLLISTHDR));
+    if (pListHdr)
+    {
+        *ppListHdr = pListHdr;
+        rc = VINF_SUCCESS;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Frees a transfer list header structure.
+ *
+ * @param   pListEntry          Transfer list header structure to free.
+ */
+void ShClTransferListHdrFree(PSHCLLISTHDR pListHdr)
+{
+    if (!pListHdr)
+        return;
+
+    LogFlowFuncEnter();
+
+    ShClTransferListHdrDestroy(pListHdr);
+
+    RTMemFree(pListHdr);
+    pListHdr = NULL;
+}
+
+/**
+ * Duplicates (allocates) a transfer list header structure.
+ *
+ * @returns Duplicated transfer list header structure on success.
+ * @param   pListHdr            Transfer list header to duplicate.
+ */
+PSHCLLISTHDR ShClTransferListHdrDup(PSHCLLISTHDR pListHdr)
+{
+    AssertPtrReturn(pListHdr, NULL);
+
+    PSHCLLISTHDR pListHdrDup = (PSHCLLISTHDR)RTMemAlloc(sizeof(SHCLLISTHDR));
+    if (pListHdrDup)
+    {
+        *pListHdrDup = *pListHdr;
+    }
+
+    return pListHdrDup;
+}
+
+/**
+ * Initializes a transfer list header structure.
+ *
+ * @returns VBox status code.
+ * @param   pListHdr            Transfer list header struct to initialize.
+ */
+int ShClTransferListHdrInit(PSHCLLISTHDR pListHdr)
+{
+    AssertPtrReturn(pListHdr, VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    ShClTransferListHdrReset(pListHdr);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys a transfer list header structure.
+ *
+ * @param   pListHdr            Transfer list header struct to destroy.
+ */
+void ShClTransferListHdrDestroy(PSHCLLISTHDR pListHdr)
+{
+    if (!pListHdr)
+        return;
+
+    LogFlowFuncEnter();
+}
+
+/**
+ * Resets a transfer list header structure.
+ *
+ * @returns VBox status code.
+ * @param   pListHdr            Transfer list header struct to reset.
+ */
+void ShClTransferListHdrReset(PSHCLLISTHDR pListHdr)
+{
+    AssertPtrReturnVoid(pListHdr);
+
+    LogFlowFuncEnter();
+
+    RT_BZERO(pListHdr, sizeof(SHCLLISTHDR));
+}
+
+/**
+ * Returns whether a given transfer list header is valid or not.
+ *
+ * @returns \c true if valid, \c false if not.
+ * @param   pListHdr            Transfer list header to validate.
+ */
+bool ShClTransferListHdrIsValid(PSHCLLISTHDR pListHdr)
+{
+    RT_NOREF(pListHdr);
+    return true; /** @todo Implement this. */
+}
+
+int ShClTransferListOpenParmsCopy(PSHCLLISTOPENPARMS pDst, PSHCLLISTOPENPARMS pSrc)
+{
+    AssertPtrReturn(pDst, VERR_INVALID_POINTER);
+    AssertPtrReturn(pSrc, VERR_INVALID_POINTER);
+
+    int rc = VINF_SUCCESS;
+
+    if (pSrc->pszFilter)
+    {
+        pDst->pszFilter = RTStrDup(pSrc->pszFilter);
+        if (!pDst->pszFilter)
+            rc = VERR_NO_MEMORY;
+    }
+
+    if (   RT_SUCCESS(rc)
+        && pSrc->pszPath)
+    {
+        pDst->pszPath = RTStrDup(pSrc->pszPath);
+        if (!pDst->pszPath)
+            rc = VERR_NO_MEMORY;
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        pDst->fList    = pDst->fList;
+        pDst->cbFilter = pSrc->cbFilter;
+        pDst->cbPath   = pSrc->cbPath;
+    }
+
+    return rc;
+}
+
+/**
+ * Duplicates a transfer list open parameters structure.
+ *
+ * @returns Duplicated transfer list open parameters structure on success, or NULL on failure.
+ * @param   pParms              Transfer list open parameters structure to duplicate.
+ */
+PSHCLLISTOPENPARMS ShClTransferListOpenParmsDup(PSHCLLISTOPENPARMS pParms)
+{
+    AssertPtrReturn(pParms, NULL);
+
+    PSHCLLISTOPENPARMS pParmsDup = (PSHCLLISTOPENPARMS)RTMemAllocZ(sizeof(SHCLLISTOPENPARMS));
+    if (!pParmsDup)
+        return NULL;
+
+    int rc = ShClTransferListOpenParmsCopy(pParmsDup, pParms);
+    if (RT_FAILURE(rc))
+    {
+        ShClTransferListOpenParmsDestroy(pParmsDup);
+
+        RTMemFree(pParmsDup);
+        pParmsDup = NULL;
+    }
+
+    return pParmsDup;
+}
+
+/**
+ * Initializes a transfer list open parameters structure.
+ *
+ * @returns VBox status code.
+ * @param   pParms              Transfer list open parameters structure to initialize.
+ */
+int ShClTransferListOpenParmsInit(PSHCLLISTOPENPARMS pParms)
+{
+    AssertPtrReturn(pParms, VERR_INVALID_POINTER);
+
+    RT_BZERO(pParms, sizeof(SHCLLISTOPENPARMS));
+
+    pParms->cbFilter  = SHCL_TRANSFER_PATH_MAX; /** @todo Make this dynamic. */
+    pParms->pszFilter = RTStrAlloc(pParms->cbFilter);
+
+    pParms->cbPath    = SHCL_TRANSFER_PATH_MAX; /** @todo Make this dynamic. */
+    pParms->pszPath   = RTStrAlloc(pParms->cbPath);
+
+    LogFlowFuncLeave();
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys a transfer list open parameters structure.
+ *
+ * @param   pParms              Transfer list open parameters structure to destroy.
+ */
+void ShClTransferListOpenParmsDestroy(PSHCLLISTOPENPARMS pParms)
+{
+    if (!pParms)
+        return;
+
+    if (pParms->pszFilter)
+    {
+        RTStrFree(pParms->pszFilter);
+        pParms->pszFilter = NULL;
+    }
+
+    if (pParms->pszPath)
+    {
+        RTStrFree(pParms->pszPath);
+        pParms->pszPath = NULL;
+    }
+}
+
+/**
+ * Creates (allocates) and initializes a clipboard list entry structure.
+ *
+ * @param   ppDirData           Where to return the created clipboard list entry structure on success.
+ */
+int ShClTransferListEntryAlloc(PSHCLLISTENTRY *ppListEntry)
+{
+    PSHCLLISTENTRY pListEntry = (PSHCLLISTENTRY)RTMemAlloc(sizeof(SHCLLISTENTRY));
+    if (!pListEntry)
+        return VERR_NO_MEMORY;
+
+    int rc = ShClTransferListEntryInit(pListEntry);
+    if (RT_SUCCESS(rc))
+        *ppListEntry = pListEntry;
+
+    return rc;
+}
+
+/**
+ * Frees a clipboard list entry structure.
+ *
+ * @param   pListEntry         Clipboard list entry structure to free.
+ */
+void ShClTransferListEntryFree(PSHCLLISTENTRY pListEntry)
+{
+    if (!pListEntry)
+        return;
+
+    ShClTransferListEntryDestroy(pListEntry);
+    RTMemFree(pListEntry);
+}
+
+/**
+ * (Deep) Copies a clipboard list entry structure.
+ *
+ * @returns VBox status code.
+ * @param   pListEntry          Clipboard list entry to copy.
+ */
+int ShClTransferListEntryCopy(PSHCLLISTENTRY pDst, PSHCLLISTENTRY pSrc)
+{
+    AssertPtrReturn(pDst, VERR_INVALID_POINTER);
+    AssertPtrReturn(pSrc, VERR_INVALID_POINTER);
+
+    int rc = VINF_SUCCESS;
+
+    *pDst = *pSrc;
+
+    if (pSrc->pszName)
+    {
+        pDst->pszName = RTStrDup(pSrc->pszName);
+        if (!pDst->pszName)
+            rc = VERR_NO_MEMORY;
+    }
+
+    if (   RT_SUCCESS(rc)
+        && pSrc->pvInfo)
+    {
+        pDst->pvInfo = RTMemDup(pSrc->pvInfo, pSrc->cbInfo);
+        if (pDst->pvInfo)
+        {
+            pDst->cbInfo = pSrc->cbInfo;
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+
+    if (RT_FAILURE(rc))
+    {
+        if (pDst->pvInfo)
+        {
+            RTMemFree(pDst->pvInfo);
+            pDst->pvInfo = NULL;
+            pDst->cbInfo = 0;
+        }
+    }
+
+    return rc;
+}
+
+/**
+ * Duplicates (allocates) a clipboard list entry structure.
+ *
+ * @returns Duplicated clipboard list entry structure on success.
+ * @param   pListEntry          Clipboard list entry to duplicate.
+ */
+PSHCLLISTENTRY ShClTransferListEntryDup(PSHCLLISTENTRY pListEntry)
+{
+    AssertPtrReturn(pListEntry, NULL);
+
+    int rc = VINF_SUCCESS;
+
+    PSHCLLISTENTRY pListEntryDup = (PSHCLLISTENTRY)RTMemAllocZ(sizeof(SHCLLISTENTRY));
+    if (pListEntryDup)
+        rc = ShClTransferListEntryCopy(pListEntryDup, pListEntry);
+
+    if (RT_FAILURE(rc))
+    {
+        ShClTransferListEntryDestroy(pListEntryDup);
+
+        RTMemFree(pListEntryDup);
+        pListEntryDup = NULL;
+    }
+
+    return pListEntryDup;
+}
+
+/**
+ * Initializes a clipboard list entry structure.
+ *
+ * @returns VBox status code.
+ * @param   pListEntry          Clipboard list entry structure to initialize.
+ */
+int ShClTransferListEntryInit(PSHCLLISTENTRY pListEntry)
+{
+    AssertPtrReturn(pListEntry, VERR_INVALID_POINTER);
+
+    RT_BZERO(pListEntry, sizeof(SHCLLISTENTRY));
+
+    pListEntry->pszName = RTStrAlloc(SHCLLISTENTRY_MAX_NAME);
+    if (!pListEntry->pszName)
+        return VERR_NO_MEMORY;
+
+    pListEntry->cbName = SHCLLISTENTRY_MAX_NAME;
+
+    pListEntry->pvInfo = (PSHCLFSOBJINFO)RTMemAlloc(sizeof(SHCLFSOBJINFO));
+    if (pListEntry->pvInfo)
+    {
+        pListEntry->cbInfo = sizeof(SHCLFSOBJINFO);
+        pListEntry->fInfo  = VBOX_SHCL_INFO_FLAG_FSOBJINFO;
+
+        return VINF_SUCCESS;
+    }
+
+    return VERR_NO_MEMORY;
+}
+
+/**
+ * Destroys a clipboard list entry structure.
+ *
+ * @param   pListEntry          Clipboard list entry structure to destroy.
+ */
+void ShClTransferListEntryDestroy(PSHCLLISTENTRY pListEntry)
+{
+    if (!pListEntry)
+        return;
+
+    if (pListEntry->pszName)
+    {
+        RTStrFree(pListEntry->pszName);
+
+        pListEntry->pszName = NULL;
+        pListEntry->cbName  = 0;
+    }
+
+    if (pListEntry->pvInfo)
+    {
+        RTMemFree(pListEntry->pvInfo);
+        pListEntry->pvInfo = NULL;
+        pListEntry->cbInfo = 0;
+    }
+}
+
+/**
+ * Returns whether a given clipboard list entry is valid or not.
+ *
+ * @returns \c true if valid, \c false if not.
+ * @param   pListEntry          Clipboard list entry to validate.
+ */
+bool ShClTransferListEntryIsValid(PSHCLLISTENTRY pListEntry)
+{
+    AssertPtrReturn(pListEntry, false);
+
+    if (   !pListEntry->pszName
+        || !pListEntry->cbName
+        || strlen(pListEntry->pszName) == 0
+        || strlen(pListEntry->pszName) > pListEntry->cbName /* Includes zero termination */ - 1)
+    {
+        return false;
+    }
+
+    if (pListEntry->cbInfo) /* cbInfo / pvInfo is optional. */
+    {
+        if (!pListEntry->pvInfo)
+            return false;
+    }
+
+    return true;
+}
+
+/**
+ * Initializes a transfer object context.
+ *
+ * @returns VBox status code.
+ * @param   pObjCtx             transfer object context to initialize.
+ */
+int ShClTransferObjCtxInit(PSHCLCLIENTTRANSFEROBJCTX pObjCtx)
+{
+    AssertPtrReturn(pObjCtx, VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    pObjCtx->uHandle  = SHCLOBJHANDLE_INVALID;
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys a transfer object context.
+ *
+ * @param   pObjCtx             transfer object context to destroy.
+ */
+void ShClTransferObjCtxDestroy(PSHCLCLIENTTRANSFEROBJCTX pObjCtx)
+{
+    AssertPtrReturnVoid(pObjCtx);
+
+    LogFlowFuncEnter();
+}
+
+/**
+ * Returns if a transfer object context is valid or not.
+ *
+ * @returns \c true if valid, \c false if not.
+ * @param   pObjCtx             transfer object context to check.
+ */
+bool ShClTransferObjCtxIsValid(PSHCLCLIENTTRANSFEROBJCTX pObjCtx)
+{
+    return (   pObjCtx
+            && pObjCtx->uHandle != SHCLOBJHANDLE_INVALID);
+}
+
+/**
+ * Initializes an object handle info structure.
+ *
+ * @returns VBox status code.
+ * @param   pInfo               Object handle info structure to initialize.
+ */
+int ShClTransferObjHandleInfoInit(PSHCLOBJHANDLEINFO pInfo)
+{
+    AssertPtrReturn(pInfo, VERR_INVALID_POINTER);
+
+    pInfo->hObj    = SHCLOBJHANDLE_INVALID;
+    pInfo->enmType = SHCLOBJTYPE_INVALID;
+
+    pInfo->pszPathLocalAbs = NULL;
+
+    RT_ZERO(pInfo->u);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys an object handle info structure.
+ *
+ * @param   pInfo               Object handle info structure to destroy.
+ */
+void ShClTransferObjHandleInfoDestroy(PSHCLOBJHANDLEINFO pInfo)
+{
+    if (!pInfo)
+        return;
+
+    if (pInfo->pszPathLocalAbs)
+    {
+        RTStrFree(pInfo->pszPathLocalAbs);
+        pInfo->pszPathLocalAbs = NULL;
+    }
+}
+
+/**
+ * Initializes a transfer object open parameters structure.
+ *
+ * @returns VBox status code.
+ * @param   pParms              transfer object open parameters structure to initialize.
+ */
+int ShClTransferObjOpenParmsInit(PSHCLOBJOPENCREATEPARMS pParms)
+{
+    AssertPtrReturn(pParms, VERR_INVALID_POINTER);
+
+    int rc;
+
+    RT_BZERO(pParms, sizeof(SHCLOBJOPENCREATEPARMS));
+
+    pParms->cbPath    = RTPATH_MAX; /** @todo Make this dynamic. */
+    pParms->pszPath   = RTStrAlloc(pParms->cbPath);
+    if (pParms->pszPath)
+    {
+        rc = VINF_SUCCESS;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Copies a transfer object open parameters structure from source to destination.
+ *
+ * @returns VBox status code.
+ * @param   pParmsDst           Where to copy the source transfer object open parameters to.
+ * @param   pParmsSrc           Which source transfer object open parameters to copy.
+ */
+int ShClTransferObjOpenParmsCopy(PSHCLOBJOPENCREATEPARMS pParmsDst, PSHCLOBJOPENCREATEPARMS pParmsSrc)
+{
+    int rc;
+
+    *pParmsDst = *pParmsSrc;
+
+    if (pParmsSrc->pszPath)
+    {
+        Assert(pParmsSrc->cbPath);
+        pParmsDst->pszPath = RTStrDup(pParmsSrc->pszPath);
+        if (pParmsDst->pszPath)
+        {
+            rc = VINF_SUCCESS;
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+    else
+        rc = VINF_SUCCESS;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Destroys a transfer object open parameters structure.
+ *
+ * @param   pParms              transfer object open parameters structure to destroy.
+ */
+void ShClTransferObjOpenParmsDestroy(PSHCLOBJOPENCREATEPARMS pParms)
+{
+    if (!pParms)
+        return;
+
+    if (pParms->pszPath)
+    {
+        RTStrFree(pParms->pszPath);
+        pParms->pszPath = NULL;
+    }
+}
+
+/**
+ * Returns a specific object handle info of a transfer.
+ *
+ * @returns Pointer to object handle info if found, or NULL if not found.
+ * @param   pTransfer           Clipboard transfer to get object handle info from.
+ * @param   hObj                Object handle of the object to get handle info for.
+ */
+DECLINLINE(PSHCLOBJHANDLEINFO) shClTransferObjGet(PSHCLTRANSFER pTransfer, SHCLOBJHANDLE hObj)
+{
+    PSHCLOBJHANDLEINFO pIt;
+    RTListForEach(&pTransfer->lstObj, pIt, SHCLOBJHANDLEINFO, Node) /** @todo Slooow ...but works for now. */
+    {
+        if (pIt->hObj == hObj)
+            return pIt;
+    }
+
+    return NULL;
+}
+
+/**
+ * Opens a transfer object.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to open the object for.
+ * @param   pOpenCreateParms    Open / create parameters of transfer object to open / create.
+ * @param   phObj               Where to store the handle of transfer object opened on success.
+ */
+int ShClTransferObjOpen(PSHCLTRANSFER pTransfer, PSHCLOBJOPENCREATEPARMS pOpenCreateParms, PSHCLOBJHANDLE phObj)
+{
+    AssertPtrReturn(pTransfer,        VERR_INVALID_POINTER);
+    AssertPtrReturn(pOpenCreateParms, VERR_INVALID_POINTER);
+    AssertPtrReturn(phObj,            VERR_INVALID_POINTER);
+    AssertMsgReturn(pTransfer->pszPathRootAbs, ("Transfer has no root path set\n"), VERR_INVALID_PARAMETER);
+    AssertMsgReturn(pOpenCreateParms->pszPath, ("No path in open/create params set\n"), VERR_INVALID_PARAMETER);
+
+    if (pTransfer->cObjHandles >= pTransfer->cMaxObjHandles)
+        return VERR_SHCLPB_MAX_OBJECTS_REACHED;
+
+    LogFlowFunc(("pszPath=%s, fCreate=0x%x\n", pOpenCreateParms->pszPath, pOpenCreateParms->fCreate));
+
+    int rc;
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        PSHCLOBJHANDLEINFO pInfo = (PSHCLOBJHANDLEINFO)RTMemAllocZ(sizeof(SHCLOBJHANDLEINFO));
+        if (pInfo)
+        {
+            rc = ShClTransferObjHandleInfoInit(pInfo);
+            if (RT_SUCCESS(rc))
+            {
+                uint64_t fOpen;
+                rc = shClConvertFileCreateFlags(pOpenCreateParms->fCreate, &fOpen);
+                if (RT_SUCCESS(rc))
+                {
+                    rc = shClTransferResolvePathAbs(pTransfer, pOpenCreateParms->pszPath, 0 /* fFlags */,
+                                                    &pInfo->pszPathLocalAbs);
+                    if (RT_SUCCESS(rc))
+                    {
+                        rc = RTFileOpen(&pInfo->u.Local.hFile, pInfo->pszPathLocalAbs, fOpen);
+                        if (RT_SUCCESS(rc))
+                            LogRel2(("Shared Clipboard: Opened file '%s'\n", pInfo->pszPathLocalAbs));
+                        else
+                            LogRel(("Shared Clipboard: Error opening file '%s': rc=%Rrc\n", pInfo->pszPathLocalAbs, rc));
+                    }
+                }
+            }
+
+            if (RT_SUCCESS(rc))
+            {
+                pInfo->hObj    = pTransfer->uObjHandleNext++;
+                pInfo->enmType = SHCLOBJTYPE_FILE;
+
+                RTListAppend(&pTransfer->lstObj, &pInfo->Node);
+                pTransfer->cObjHandles++;
+
+                LogFlowFunc(("cObjHandles=%RU32\n", pTransfer->cObjHandles));
+
+                *phObj = pInfo->hObj;
+            }
+            else
+            {
+                ShClTransferObjHandleInfoDestroy(pInfo);
+                RTMemFree(pInfo);
+            }
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnObjOpen)
+            rc = pTransfer->ProviderIface.pfnObjOpen(&pTransfer->ProviderCtx, pOpenCreateParms, phObj);
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+    else
+        AssertFailedStmt(rc = VERR_NOT_IMPLEMENTED);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Closes a transfer object.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer that contains the object to close.
+ * @param   hObj                Handle of transfer object to close.
+ */
+int ShClTransferObjClose(PSHCLTRANSFER pTransfer, SHCLOBJHANDLE hObj)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    int rc = VINF_SUCCESS;
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        PSHCLOBJHANDLEINFO pInfo = shClTransferObjGet(pTransfer, hObj);
+        if (pInfo)
+        {
+            switch (pInfo->enmType)
+            {
+                case SHCLOBJTYPE_DIRECTORY:
+                {
+                    rc = RTDirClose(pInfo->u.Local.hDir);
+                    if (RT_SUCCESS(rc))
+                    {
+                        pInfo->u.Local.hDir = NIL_RTDIR;
+
+                        LogRel2(("Shared Clipboard: Closed directory '%s'\n", pInfo->pszPathLocalAbs));
+                    }
+                    else
+                        LogRel(("Shared Clipboard: Closing directory '%s' failed with %Rrc\n", pInfo->pszPathLocalAbs, rc));
+                    break;
+                }
+
+                case SHCLOBJTYPE_FILE:
+                {
+                    rc = RTFileClose(pInfo->u.Local.hFile);
+                    if (RT_SUCCESS(rc))
+                    {
+                        pInfo->u.Local.hFile = NIL_RTFILE;
+
+                        LogRel2(("Shared Clipboard: Closed file '%s'\n", pInfo->pszPathLocalAbs));
+                    }
+                    else
+                        LogRel(("Shared Clipboard: Closing file '%s' failed with %Rrc\n", pInfo->pszPathLocalAbs, rc));
+                    break;
+                }
+
+                default:
+                    rc = VERR_NOT_IMPLEMENTED;
+                    break;
+            }
+
+            RTListNodeRemove(&pInfo->Node);
+
+            Assert(pTransfer->cObjHandles);
+            pTransfer->cObjHandles--;
+
+            ShClTransferObjHandleInfoDestroy(pInfo);
+
+            RTMemFree(pInfo);
+            pInfo = NULL;
+        }
+        else
+            rc = VERR_NOT_FOUND;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnObjClose)
+        {
+            rc = pTransfer->ProviderIface.pfnObjClose(&pTransfer->ProviderCtx, hObj);
+        }
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+    else
+        AssertFailedStmt(rc = VERR_NOT_IMPLEMENTED);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Reads from a transfer object.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer that contains the object to read from.
+ * @param   hObj                Handle of transfer object to read from.
+ * @param   pvBuf               Buffer for where to store the read data.
+ * @param   cbBuf               Size (in bytes) of buffer.
+ * @param   fFlags              Read flags. Optional.
+ * @param   pcbRead             Where to return how much bytes were read on success. Optional.
+ */
+int ShClTransferObjRead(PSHCLTRANSFER pTransfer,
+                        SHCLOBJHANDLE hObj, void *pvBuf, uint32_t cbBuf, uint32_t fFlags, uint32_t *pcbRead)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+    AssertPtrReturn(pvBuf,     VERR_INVALID_POINTER);
+    AssertReturn   (cbBuf,     VERR_INVALID_PARAMETER);
+    /* pcbRead is optional. */
+    /** @todo Validate fFlags. */
+
+    int rc = VINF_SUCCESS;
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        PSHCLOBJHANDLEINFO pInfo = shClTransferObjGet(pTransfer, hObj);
+        if (pInfo)
+        {
+            switch (pInfo->enmType)
+            {
+                case SHCLOBJTYPE_FILE:
+                {
+                    size_t cbRead;
+                    rc = RTFileRead(pInfo->u.Local.hFile, pvBuf, cbBuf, &cbRead);
+                    if (RT_SUCCESS(rc))
+                    {
+                        if (pcbRead)
+                            *pcbRead = (uint32_t)cbRead;
+                    }
+                    break;
+                }
+
+                default:
+                    rc = VERR_NOT_SUPPORTED;
+                    break;
+            }
+        }
+        else
+            rc = VERR_NOT_FOUND;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnObjRead)
+        {
+            rc = pTransfer->ProviderIface.pfnObjRead(&pTransfer->ProviderCtx, hObj, pvBuf, cbBuf, fFlags, pcbRead);
+        }
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+    else
+        AssertFailedStmt(rc = VERR_NOT_IMPLEMENTED);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Writes to a transfer object.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer that contains the object to write to.
+ * @param   hObj                Handle of transfer object to write to.
+ * @param   pvBuf               Buffer of data to write.
+ * @param   cbBuf               Size (in bytes) of buffer to write.
+ * @param   fFlags              Write flags. Optional.
+ * @param   pcbWritten          How much bytes were writtenon success. Optional.
+ */
+int ShClTransferObjWrite(PSHCLTRANSFER pTransfer,
+                         SHCLOBJHANDLE hObj, void *pvBuf, uint32_t cbBuf, uint32_t fFlags, uint32_t *pcbWritten)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+    AssertPtrReturn(pvBuf,     VERR_INVALID_POINTER);
+    AssertReturn   (cbBuf,     VERR_INVALID_PARAMETER);
+    /* pcbWritten is optional. */
+
+    int rc = VINF_SUCCESS;
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        PSHCLOBJHANDLEINFO pInfo = shClTransferObjGet(pTransfer, hObj);
+        if (pInfo)
+        {
+            switch (pInfo->enmType)
+            {
+                case SHCLOBJTYPE_FILE:
+                {
+                    rc = RTFileWrite(pInfo->u.Local.hFile, pvBuf, cbBuf, (size_t *)pcbWritten);
+                    break;
+                }
+
+                default:
+                    rc = VERR_NOT_SUPPORTED;
+                    break;
+            }
+        }
+        else
+            rc = VERR_NOT_FOUND;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnObjWrite)
+        {
+            rc = pTransfer->ProviderIface.pfnObjWrite(&pTransfer->ProviderCtx, hObj, pvBuf, cbBuf, fFlags, pcbWritten);
+        }
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+    else
+        AssertFailedStmt(rc = VERR_NOT_IMPLEMENTED);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Duplicates a transfer object data chunk.
+ *
+ * @returns Duplicated object data chunk on success, or NULL on failure.
+ * @param   pDataChunk          transfer object data chunk to duplicate.
+ */
+PSHCLOBJDATACHUNK ShClTransferObjDataChunkDup(PSHCLOBJDATACHUNK pDataChunk)
+{
+    if (!pDataChunk)
+        return NULL;
+
+    PSHCLOBJDATACHUNK pDataChunkDup = (PSHCLOBJDATACHUNK)RTMemAllocZ(sizeof(SHCLOBJDATACHUNK));
+    if (!pDataChunkDup)
+        return NULL;
+
+    if (pDataChunk->pvData)
+    {
+        Assert(pDataChunk->cbData);
+
+        pDataChunkDup->uHandle = pDataChunk->uHandle;
+        pDataChunkDup->pvData  = RTMemDup(pDataChunk->pvData, pDataChunk->cbData);
+        pDataChunkDup->cbData  = pDataChunk->cbData;
+    }
+
+    return pDataChunkDup;
+}
+
+/**
+ * Destroys a transfer object data chunk.
+ *
+ * @param   pDataChunk          transfer object data chunk to destroy.
+ */
+void ShClTransferObjDataChunkDestroy(PSHCLOBJDATACHUNK pDataChunk)
+{
+    if (!pDataChunk)
+        return;
+
+    if (pDataChunk->pvData)
+    {
+        Assert(pDataChunk->cbData);
+
+        RTMemFree(pDataChunk->pvData);
+
+        pDataChunk->pvData = NULL;
+        pDataChunk->cbData = 0;
+    }
+
+    pDataChunk->uHandle = 0;
+}
+
+/**
+ * Frees a transfer object data chunk.
+ *
+ * @param   pDataChunk          transfer object data chunk to free. The handed-in pointer will
+ *                              be invalid after calling this function.
+ */
+void ShClTransferObjDataChunkFree(PSHCLOBJDATACHUNK pDataChunk)
+{
+    if (!pDataChunk)
+        return;
+
+    ShClTransferObjDataChunkDestroy(pDataChunk);
+
+    RTMemFree(pDataChunk);
+    pDataChunk = NULL;
+}
+
+/**
+ * Creates a clipboard transfer.
+ *
+ * @returns VBox status code.
+ * @param   ppTransfer          Where to return the created Shared Clipboard transfer struct.
+ *                              Must be destroyed by ShClTransferDestroy().
+ */
+int ShClTransferCreate(PSHCLTRANSFER *ppTransfer)
+{
+    AssertPtrReturn(ppTransfer, VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    PSHCLTRANSFER pTransfer = (PSHCLTRANSFER)RTMemAllocZ(sizeof(SHCLTRANSFER));
+    AssertPtrReturn(pTransfer, VERR_NO_MEMORY);
+
+    pTransfer->State.uID       = 0;
+    pTransfer->State.enmStatus = SHCLTRANSFERSTATUS_NONE;
+    pTransfer->State.enmDir    = SHCLTRANSFERDIR_UNKNOWN;
+    pTransfer->State.enmSource = SHCLSOURCE_INVALID;
+
+    pTransfer->Thread.hThread    = NIL_RTTHREAD;
+    pTransfer->Thread.fCancelled = false;
+    pTransfer->Thread.fStarted   = false;
+    pTransfer->Thread.fStop      = false;
+
+    pTransfer->pszPathRootAbs    = NULL;
+
+#ifdef DEBUG_andy
+    pTransfer->uTimeoutMs     = RT_MS_5SEC;
+#else
+    pTransfer->uTimeoutMs     = RT_MS_30SEC;
+#endif
+    pTransfer->cbMaxChunkSize  = _64K; /** @todo Make this configurable. */
+    pTransfer->cMaxListHandles = _4K;  /** @todo Ditto. */
+    pTransfer->cMaxObjHandles  = _4K;  /** @todo Ditto. */
+
+    pTransfer->pvUser = NULL;
+    pTransfer->cbUser = 0;
+
+    RTListInit(&pTransfer->lstList);
+    RTListInit(&pTransfer->lstObj);
+
+    pTransfer->cRoots = 0;
+    RTListInit(&pTransfer->lstRoots);
+
+    int rc = ShClEventSourceCreate(&pTransfer->Events, 0 /* uID */);
+    if (RT_SUCCESS(rc))
+    {
+        *ppTransfer = pTransfer;
+    }
+    else
+    {
+        if (pTransfer)
+        {
+            ShClTransferDestroy(pTransfer);
+            RTMemFree(pTransfer);
+        }
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Destroys a clipboard transfer context struct.
+ *
+ * @returns VBox status code.
+ * @param   pTransferCtx                Clipboard transfer to destroy.
+ */
+int ShClTransferDestroy(PSHCLTRANSFER pTransfer)
+{
+    if (!pTransfer)
+        return VINF_SUCCESS;
+
+    LogFlowFuncEnter();
+
+    int rc = shClTransferThreadDestroy(pTransfer, 30 * 1000 /* Timeout in ms */);
+    if (RT_FAILURE(rc))
+        return rc;
+
+    ShClTransferReset(pTransfer);
+
+    ShClEventSourceDestroy(&pTransfer->Events);
+
+    LogFlowFuncLeave();
+    return VINF_SUCCESS;
+}
+
+/**
+ * Initializes a Shared Clipboard transfer object.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Transfer to initialize.
+ * @param   enmDir              Specifies the transfer direction of this transfer.
+ * @param   enmSource           Specifies the data source of the transfer.
+ */
+int ShClTransferInit(PSHCLTRANSFER pTransfer, SHCLTRANSFERDIR enmDir, SHCLSOURCE enmSource)
+{
+    pTransfer->State.enmDir    = enmDir;
+    pTransfer->State.enmSource = enmSource;
+
+    LogFlowFunc(("uID=%RU32, enmDir=%RU32, enmSource=%RU32\n",
+                 pTransfer->State.uID, pTransfer->State.enmDir, pTransfer->State.enmSource));
+
+    pTransfer->State.enmStatus = SHCLTRANSFERSTATUS_INITIALIZED; /* Now we're ready to run. */
+
+    pTransfer->cListHandles    = 0;
+    pTransfer->uListHandleNext = 1;
+
+    pTransfer->cObjHandles     = 0;
+    pTransfer->uObjHandleNext  = 1;
+
+    int rc = VINF_SUCCESS;
+
+    if (pTransfer->Callbacks.pfnOnInitialize)
+        rc = pTransfer->Callbacks.pfnOnInitialize(&pTransfer->CallbackCtx);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Returns a specific list handle info of a transfer.
+ *
+ * @returns Pointer to list handle info if found, or NULL if not found.
+ * @param   pTransfer           Clipboard transfer to get list handle info from.
+ * @param   hList               List handle of the list to get handle info for.
+ */
+DECLINLINE(PSHCLLISTHANDLEINFO) shClTransferListGetByHandle(PSHCLTRANSFER pTransfer, SHCLLISTHANDLE hList)
+{
+    PSHCLLISTHANDLEINFO pIt;
+    RTListForEach(&pTransfer->lstList, pIt, SHCLLISTHANDLEINFO, Node) /** @todo Sloooow ... improve this. */
+    {
+        if (pIt->hList == hList)
+            return pIt;
+    }
+
+    return NULL;
+}
+
+/**
+ * Creates a new list handle (local only).
+ *
+ * @returns New List handle on success, or SHCLLISTHANDLE_INVALID on error.
+ * @param   pTransfer           Clipboard transfer to create new list handle for.
+ */
+DECLINLINE(SHCLLISTHANDLE) shClTransferListHandleNew(PSHCLTRANSFER pTransfer)
+{
+    return pTransfer->uListHandleNext++; /** @todo Good enough for now. Improve this later. */
+}
+
+/**
+ * Validates whether a given path matches our set of rules or not.
+ *
+ * @returns VBox status code.
+ * @param   pcszPath            Path to validate.
+ * @param   fMustExist          Whether the path to validate also must exist.
+ */
+static int shClTransferValidatePath(const char *pcszPath, bool fMustExist)
+{
+    int rc = VINF_SUCCESS;
+
+    if (!strlen(pcszPath))
+        rc = VERR_INVALID_PARAMETER;
+
+    if (   RT_SUCCESS(rc)
+        && !RTStrIsValidEncoding(pcszPath))
+    {
+        rc = VERR_INVALID_UTF8_ENCODING;
+    }
+
+    if (   RT_SUCCESS(rc)
+        && RTStrStr(pcszPath, ".."))
+    {
+        rc = VERR_INVALID_PARAMETER;
+    }
+
+    if (   RT_SUCCESS(rc)
+        && fMustExist)
+    {
+        RTFSOBJINFO objInfo;
+        rc = RTPathQueryInfo(pcszPath, &objInfo, RTFSOBJATTRADD_NOTHING);
+        if (RT_SUCCESS(rc))
+        {
+            if (RTFS_IS_DIRECTORY(objInfo.Attr.fMode))
+            {
+                if (!RTDirExists(pcszPath)) /* Path must exist. */
+                    rc = VERR_PATH_NOT_FOUND;
+            }
+            else if (RTFS_IS_FILE(objInfo.Attr.fMode))
+            {
+                if (!RTFileExists(pcszPath)) /* File must exist. */
+                    rc = VERR_FILE_NOT_FOUND;
+            }
+            else /* Everything else (e.g. symbolic links) are not supported. */
+            {
+                LogRel2(("Shared Clipboard: Path '%s' contains a symbolic link or junktion, which are not supported\n", pcszPath));
+                rc = VERR_NOT_SUPPORTED;
+            }
+        }
+    }
+
+    if (RT_FAILURE(rc))
+        LogRel2(("Shared Clipboard: Validating path '%s' failed: %Rrc\n", pcszPath, rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Resolves a relative path of a specific transfer to its absolute path.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to resolve path for.
+ * @param   pszPath             Path to resolve.
+ * @param   fFlags              Resolve flags. Currently not used and must be 0.
+ * @param   ppszResolved        Where to store the allocated resolved path. Must be free'd by the called using RTStrFree().
+ */
+static int shClTransferResolvePathAbs(PSHCLTRANSFER pTransfer, const char *pszPath, uint32_t fFlags,
+                                      char **ppszResolved)
+{
+    AssertPtrReturn(pTransfer,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pszPath,     VERR_INVALID_POINTER);
+    AssertReturn   (fFlags == 0, VERR_INVALID_PARAMETER);
+
+    LogFlowFunc(("pszPathRootAbs=%s, pszPath=%s\n", pTransfer->pszPathRootAbs, pszPath));
+
+    int rc = shClTransferValidatePath(pszPath, false /* fMustExist */);
+    if (RT_SUCCESS(rc))
+    {
+        char *pszPathAbs = RTPathJoinA(pTransfer->pszPathRootAbs, pszPath);
+        if (pszPathAbs)
+        {
+            char   szResolved[RTPATH_MAX];
+            size_t cbResolved = sizeof(szResolved);
+            rc = RTPathAbsEx(pTransfer->pszPathRootAbs, pszPathAbs, RTPATH_STR_F_STYLE_HOST, szResolved, &cbResolved);
+
+            RTStrFree(pszPathAbs);
+
+            if (RT_SUCCESS(rc))
+            {
+                LogFlowFunc(("pszResolved=%s\n", szResolved));
+
+                rc = VERR_PATH_NOT_FOUND; /* Play safe by default. */
+
+                /* Make sure the resolved path is part of the set of root entries. */
+                PSHCLLISTROOT pListRoot;
+                RTListForEach(&pTransfer->lstRoots, pListRoot, SHCLLISTROOT, Node)
+                {
+                    if (RTPathStartsWith(szResolved, pListRoot->pszPathAbs))
+                    {
+                        rc = VINF_SUCCESS;
+                        break;
+                    }
+                }
+
+                if (RT_SUCCESS(rc))
+                    *ppszResolved = RTStrDup(szResolved);
+            }
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Resolving absolute path '%s' failed, rc=%Rrc\n", pszPath, rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Opens a list.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to handle.
+ * @param   pOpenParms          List open parameters to use for opening.
+ * @param   phList              Where to store the List handle of opened list on success.
+ */
+int ShClTransferListOpen(PSHCLTRANSFER pTransfer, PSHCLLISTOPENPARMS pOpenParms,
+                         PSHCLLISTHANDLE phList)
+{
+    AssertPtrReturn(pTransfer,  VERR_INVALID_POINTER);
+    AssertPtrReturn(pOpenParms, VERR_INVALID_POINTER);
+    AssertPtrReturn(phList,     VERR_INVALID_POINTER);
+
+    int rc;
+
+    if (pTransfer->cListHandles == pTransfer->cMaxListHandles)
+        return VERR_SHCLPB_MAX_LISTS_REACHED;
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        LogFlowFunc(("pszPath=%s\n", pOpenParms->pszPath));
+
+        PSHCLLISTHANDLEINFO pInfo
+            = (PSHCLLISTHANDLEINFO)RTMemAllocZ(sizeof(SHCLLISTHANDLEINFO));
+        if (pInfo)
+        {
+            rc = ShClTransferListHandleInfoInit(pInfo);
+            if (RT_SUCCESS(rc))
+            {
+                rc = shClTransferResolvePathAbs(pTransfer, pOpenParms->pszPath, 0 /* fFlags */, &pInfo->pszPathLocalAbs);
+                if (RT_SUCCESS(rc))
+                {
+                    RTFSOBJINFO objInfo;
+                    rc = RTPathQueryInfo(pInfo->pszPathLocalAbs, &objInfo, RTFSOBJATTRADD_NOTHING);
+                    if (RT_SUCCESS(rc))
+                    {
+                        if (RTFS_IS_DIRECTORY(objInfo.Attr.fMode))
+                        {
+                            rc = RTDirOpen(&pInfo->u.Local.hDir, pInfo->pszPathLocalAbs);
+                            if (RT_SUCCESS(rc))
+                            {
+                                pInfo->enmType = SHCLOBJTYPE_DIRECTORY;
+
+                                LogRel2(("Shared Clipboard: Opening directory '%s'\n", pInfo->pszPathLocalAbs));
+                            }
+                            else
+                                LogRel(("Shared Clipboard: Opening directory '%s' failed with %Rrc\n", pInfo->pszPathLocalAbs, rc));
+
+                        }
+                        else if (RTFS_IS_FILE(objInfo.Attr.fMode))
+                        {
+                            rc = RTFileOpen(&pInfo->u.Local.hFile, pInfo->pszPathLocalAbs,
+                                            RTFILE_O_OPEN | RTFILE_O_READ | RTFILE_O_DENY_WRITE);
+                            if (RT_SUCCESS(rc))
+                            {
+                                pInfo->enmType = SHCLOBJTYPE_FILE;
+
+                                LogRel2(("Shared Clipboard: Opening file '%s'\n", pInfo->pszPathLocalAbs));
+                            }
+                            else
+                                LogRel(("Shared Clipboard: Opening file '%s' failed with %Rrc\n", pInfo->pszPathLocalAbs, rc));
+                        }
+                        else
+                            rc = VERR_NOT_SUPPORTED;
+
+                        if (RT_SUCCESS(rc))
+                        {
+                            pInfo->hList = shClTransferListHandleNew(pTransfer);
+
+                            RTListAppend(&pTransfer->lstList, &pInfo->Node);
+                            pTransfer->cListHandles++;
+
+                            if (phList)
+                                *phList = pInfo->hList;
+
+                            LogFlowFunc(("pszPathLocalAbs=%s, hList=%RU64, cListHandles=%RU32\n",
+                                         pInfo->pszPathLocalAbs, pInfo->hList, pTransfer->cListHandles));
+                        }
+                        else
+                        {
+                            if (RTFS_IS_DIRECTORY(objInfo.Attr.fMode))
+                            {
+                                if (RTDirIsValid(pInfo->u.Local.hDir))
+                                    RTDirClose(pInfo->u.Local.hDir);
+                            }
+                            else if (RTFS_IS_FILE(objInfo.Attr.fMode))
+                            {
+                                if (RTFileIsValid(pInfo->u.Local.hFile))
+                                    RTFileClose(pInfo->u.Local.hFile);
+                            }
+                        }
+                    }
+                }
+            }
+
+            if (RT_FAILURE(rc))
+            {
+                ShClTransferListHandleInfoDestroy(pInfo);
+
+                RTMemFree(pInfo);
+                pInfo = NULL;
+            }
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnListOpen)
+        {
+            rc = pTransfer->ProviderIface.pfnListOpen(&pTransfer->ProviderCtx, pOpenParms, phList);
+        }
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+    else
+        AssertFailedStmt(rc = VERR_NOT_IMPLEMENTED);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Closes a list.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to handle.
+ * @param   hList               Handle of list to close.
+ */
+int ShClTransferListClose(PSHCLTRANSFER pTransfer, SHCLLISTHANDLE hList)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    if (hList == SHCLLISTHANDLE_INVALID)
+        return VINF_SUCCESS;
+
+    int rc = VINF_SUCCESS;
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        PSHCLLISTHANDLEINFO pInfo = shClTransferListGetByHandle(pTransfer, hList);
+        if (pInfo)
+        {
+            switch (pInfo->enmType)
+            {
+                case SHCLOBJTYPE_DIRECTORY:
+                {
+                    if (RTDirIsValid(pInfo->u.Local.hDir))
+                    {
+                        RTDirClose(pInfo->u.Local.hDir);
+                        pInfo->u.Local.hDir = NIL_RTDIR;
+                    }
+                    break;
+                }
+
+                default:
+                    rc = VERR_NOT_SUPPORTED;
+                    break;
+            }
+
+            RTListNodeRemove(&pInfo->Node);
+
+            Assert(pTransfer->cListHandles);
+            pTransfer->cListHandles--;
+
+            RTMemFree(pInfo);
+        }
+        else
+            rc = VERR_NOT_FOUND;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnListClose)
+        {
+            rc = pTransfer->ProviderIface.pfnListClose(&pTransfer->ProviderCtx, hList);
+        }
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Adds a file to a list heaer.
+ *
+ * @returns VBox status code.
+ * @param   pHdr                List header to add file to.
+ * @param   pszPath             Path of file to add.
+ */
+static int shclTransferListHdrAddFile(PSHCLLISTHDR pHdr, const char *pszPath)
+{
+    uint64_t cbSize = 0;
+    int rc = RTFileQuerySizeByPath(pszPath, &cbSize);
+    if (RT_SUCCESS(rc))
+    {
+        pHdr->cbTotalSize  += cbSize;
+        pHdr->cTotalObjects++;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Builds a list header, internal version.
+ *
+ * @returns VBox status code.
+ * @param   pHdr                Where to store the build list header.
+ * @param   pcszSrcPath         Source path of list.
+ * @param   pcszDstPath         Destination path of list.
+ * @param   pcszDstBase         Destination base path.
+ * @param   cchDstBase          Number of charaters of destination base path.
+ */
+static int shclTransferListHdrFromDir(PSHCLLISTHDR pHdr, const char *pcszPathAbs)
+{
+    AssertPtrReturn(pcszPathAbs, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("pcszPathAbs=%s\n", pcszPathAbs));
+
+    RTFSOBJINFO objInfo;
+    int rc = RTPathQueryInfo(pcszPathAbs, &objInfo, RTFSOBJATTRADD_NOTHING);
+    if (RT_SUCCESS(rc))
+    {
+        if (RTFS_IS_DIRECTORY(objInfo.Attr.fMode))
+        {
+            RTDIR hDir;
+            rc = RTDirOpen(&hDir, pcszPathAbs);
+            if (RT_SUCCESS(rc))
+            {
+                size_t        cbDirEntry = 0;
+                PRTDIRENTRYEX pDirEntry  = NULL;
+                do
+                {
+                    /* Retrieve the next directory entry. */
+                    rc = RTDirReadExA(hDir, &pDirEntry, &cbDirEntry, RTFSOBJATTRADD_NOTHING, RTPATH_F_ON_LINK);
+                    if (RT_FAILURE(rc))
+                    {
+                        if (rc == VERR_NO_MORE_FILES)
+                            rc = VINF_SUCCESS;
+                        break;
+                    }
+
+                    switch (pDirEntry->Info.Attr.fMode & RTFS_TYPE_MASK)
+                    {
+                        case RTFS_TYPE_DIRECTORY:
+                        {
+                            /* Skip "." and ".." entries. */
+                            if (RTDirEntryExIsStdDotLink(pDirEntry))
+                                break;
+
+                            pHdr->cTotalObjects++;
+                            break;
+                        }
+                        case RTFS_TYPE_FILE:
+                        {
+                            char *pszSrc = RTPathJoinA(pcszPathAbs, pDirEntry->szName);
+                            if (pszSrc)
+                            {
+                                rc = shclTransferListHdrAddFile(pHdr, pszSrc);
+                                RTStrFree(pszSrc);
+                            }
+                            else
+                                rc = VERR_NO_MEMORY;
+                            break;
+                        }
+                        case RTFS_TYPE_SYMLINK:
+                        {
+                            /** @todo Not implemented yet. */
+                        }
+
+                        default:
+                            break;
+                    }
+
+                } while (RT_SUCCESS(rc));
+
+                RTDirReadExAFree(&pDirEntry, &cbDirEntry);
+                RTDirClose(hDir);
+            }
+        }
+        else if (RTFS_IS_FILE(objInfo.Attr.fMode))
+        {
+            rc = shclTransferListHdrAddFile(pHdr, pcszPathAbs);
+        }
+        else if (RTFS_IS_SYMLINK(objInfo.Attr.fMode))
+        {
+            /** @todo Not implemented yet. */
+        }
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Retrieves the header of a Shared Clipboard list.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to handle.
+ * @param   hList               Handle of list to get header for.
+ * @param   pHdr                Where to store the returned list header information.
+ */
+int ShClTransferListGetHeader(PSHCLTRANSFER pTransfer, SHCLLISTHANDLE hList,
+                              PSHCLLISTHDR pHdr)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+    AssertPtrReturn(pHdr,      VERR_INVALID_POINTER);
+
+    int rc;
+
+    LogFlowFunc(("hList=%RU64\n", hList));
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        PSHCLLISTHANDLEINFO pInfo = shClTransferListGetByHandle(pTransfer, hList);
+        if (pInfo)
+        {
+            rc = ShClTransferListHdrInit(pHdr);
+            if (RT_SUCCESS(rc))
+            {
+                switch (pInfo->enmType)
+                {
+                    case SHCLOBJTYPE_DIRECTORY:
+                    {
+                        LogFlowFunc(("DirAbs: %s\n", pInfo->pszPathLocalAbs));
+
+                        rc = shclTransferListHdrFromDir(pHdr, pInfo->pszPathLocalAbs);
+                        break;
+                    }
+
+                    case SHCLOBJTYPE_FILE:
+                    {
+                        LogFlowFunc(("FileAbs: %s\n", pInfo->pszPathLocalAbs));
+
+                        pHdr->cTotalObjects = 1;
+
+                        RTFSOBJINFO objInfo;
+                        rc = RTFileQueryInfo(pInfo->u.Local.hFile, &objInfo, RTFSOBJATTRADD_NOTHING);
+                        if (RT_SUCCESS(rc))
+                        {
+                            pHdr->cbTotalSize = objInfo.cbObject;
+                        }
+                        break;
+                    }
+
+                    default:
+                        rc = VERR_NOT_SUPPORTED;
+                        break;
+                }
+            }
+
+            LogFlowFunc(("cTotalObj=%RU64, cbTotalSize=%RU64\n", pHdr->cTotalObjects, pHdr->cbTotalSize));
+        }
+        else
+            rc = VERR_NOT_FOUND;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnListHdrRead)
+        {
+            rc = pTransfer->ProviderIface.pfnListHdrRead(&pTransfer->ProviderCtx, hList, pHdr);
+        }
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+    else
+        AssertFailedStmt(rc = VERR_NOT_IMPLEMENTED);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Returns the current transfer object for a Shared Clipboard transfer list.
+ *
+ * Currently not implemented and wil return NULL.
+ *
+ * @returns Pointer to transfer object, or NULL if not found / invalid.
+ * @param   pTransfer           Clipboard transfer to return transfer object for.
+ * @param   hList               Handle of Shared Clipboard transfer list to get object for.
+ * @param   uIdx                Index of object to get.
+ */
+PSHCLTRANSFEROBJ ShClTransferListGetObj(PSHCLTRANSFER pTransfer,
+                                        SHCLLISTHANDLE hList, uint64_t uIdx)
+{
+    AssertPtrReturn(pTransfer, NULL);
+
+    RT_NOREF(hList, uIdx);
+
+    LogFlowFunc(("hList=%RU64\n", hList));
+
+    return NULL;
+}
+
+/**
+ * Reads a single Shared Clipboard list entry.
+ *
+ * @returns VBox status code or VERR_NO_MORE_FILES if the end of the list has been reached.
+ * @param   pTransfer           Clipboard transfer to handle.
+ * @param   hList               List handle of list to read from.
+ * @param   pEntry              Where to store the read information.
+ */
+int ShClTransferListRead(PSHCLTRANSFER pTransfer, SHCLLISTHANDLE hList,
+                         PSHCLLISTENTRY pEntry)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+    AssertPtrReturn(pEntry,    VERR_INVALID_POINTER);
+
+    int rc = VINF_SUCCESS;
+
+    LogFlowFunc(("hList=%RU64\n", hList));
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        PSHCLLISTHANDLEINFO pInfo = shClTransferListGetByHandle(pTransfer, hList);
+        if (pInfo)
+        {
+            switch (pInfo->enmType)
+            {
+                case SHCLOBJTYPE_DIRECTORY:
+                {
+                    LogFlowFunc(("\tDirectory: %s\n", pInfo->pszPathLocalAbs));
+
+                    for (;;)
+                    {
+                        bool fSkipEntry = false; /* Whether to skip an entry in the enumeration. */
+
+                        size_t        cbDirEntry = 0;
+                        PRTDIRENTRYEX pDirEntry  = NULL;
+                        rc = RTDirReadExA(pInfo->u.Local.hDir, &pDirEntry, &cbDirEntry, RTFSOBJATTRADD_NOTHING, RTPATH_F_ON_LINK);
+                        if (RT_SUCCESS(rc))
+                        {
+                            switch (pDirEntry->Info.Attr.fMode & RTFS_TYPE_MASK)
+                            {
+                                case RTFS_TYPE_DIRECTORY:
+                                {
+                                    /* Skip "." and ".." entries. */
+                                    if (RTDirEntryExIsStdDotLink(pDirEntry))
+                                    {
+                                        fSkipEntry = true;
+                                        break;
+                                    }
+
+                                    LogFlowFunc(("Directory: %s\n", pDirEntry->szName));
+                                    break;
+                                }
+
+                                case RTFS_TYPE_FILE:
+                                {
+                                    LogFlowFunc(("File: %s\n", pDirEntry->szName));
+                                    break;
+                                }
+
+                                case RTFS_TYPE_SYMLINK:
+                                {
+                                    rc = VERR_NOT_IMPLEMENTED; /** @todo Not implemented yet. */
+                                    break;
+                                }
+
+                                default:
+                                    break;
+                            }
+
+                            if (   RT_SUCCESS(rc)
+                                && !fSkipEntry)
+                            {
+                                rc = RTStrCopy(pEntry->pszName, pEntry->cbName, pDirEntry->szName);
+                                if (RT_SUCCESS(rc))
+                                {
+                                    pEntry->cbName = (uint32_t)strlen(pEntry->pszName) + 1; /* Include termination. */
+
+                                    AssertPtr(pEntry->pvInfo);
+                                    Assert   (pEntry->cbInfo == sizeof(SHCLFSOBJINFO));
+
+                                    ShClFsObjFromIPRT(PSHCLFSOBJINFO(pEntry->pvInfo), &pDirEntry->Info);
+
+                                    LogFlowFunc(("Entry pszName=%s, pvInfo=%p, cbInfo=%RU32\n",
+                                                 pEntry->pszName, pEntry->pvInfo, pEntry->cbInfo));
+                                }
+                            }
+
+                            RTDirReadExAFree(&pDirEntry, &cbDirEntry);
+                        }
+
+                        if (   !fSkipEntry /* Do we have a valid entry? Bail out. */
+                            || RT_FAILURE(rc))
+                        {
+                            break;
+                        }
+                    }
+
+                    break;
+                }
+
+                case SHCLOBJTYPE_FILE:
+                {
+                    LogFlowFunc(("\tSingle file: %s\n", pInfo->pszPathLocalAbs));
+
+                    RTFSOBJINFO objInfo;
+                    rc = RTFileQueryInfo(pInfo->u.Local.hFile, &objInfo, RTFSOBJATTRADD_NOTHING);
+                    if (RT_SUCCESS(rc))
+                    {
+                        pEntry->pvInfo = (PSHCLFSOBJINFO)RTMemAlloc(sizeof(SHCLFSOBJINFO));
+                        if (pEntry->pvInfo)
+                        {
+                            rc = RTStrCopy(pEntry->pszName, pEntry->cbName, pInfo->pszPathLocalAbs);
+                            if (RT_SUCCESS(rc))
+                            {
+                                ShClFsObjFromIPRT(PSHCLFSOBJINFO(pEntry->pvInfo), &objInfo);
+
+                                pEntry->cbInfo = sizeof(SHCLFSOBJINFO);
+                                pEntry->fInfo  = VBOX_SHCL_INFO_FLAG_FSOBJINFO;
+                            }
+                        }
+                        else
+                            rc = VERR_NO_MEMORY;
+                    }
+
+                    break;
+                }
+
+                default:
+                    rc = VERR_NOT_SUPPORTED;
+                    break;
+            }
+        }
+        else
+            rc = VERR_NOT_FOUND;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnListEntryRead)
+            rc = pTransfer->ProviderIface.pfnListEntryRead(&pTransfer->ProviderCtx, hList, pEntry);
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+    else
+        AssertFailedStmt(rc = VERR_NOT_IMPLEMENTED);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClTransferListWrite(PSHCLTRANSFER pTransfer, SHCLLISTHANDLE hList,
+                          PSHCLLISTENTRY pEntry)
+{
+    RT_NOREF(pTransfer, hList, pEntry);
+
+    int rc = VINF_SUCCESS;
+
+#if 0
+    if (pTransfer->ProviderIface.pfnListEntryWrite)
+        rc = pTransfer->ProviderIface.pfnListEntryWrite(&pTransfer->ProviderCtx, hList, pEntry);
+#endif
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Returns whether a given list handle is valid or not.
+ *
+ * @returns \c true if list handle is valid, \c false if not.
+ * @param   pTransfer           Clipboard transfer to handle.
+ * @param   hList               List handle to check.
+ */
+bool ShClTransferListHandleIsValid(PSHCLTRANSFER pTransfer, SHCLLISTHANDLE hList)
+{
+    bool fIsValid = false;
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        fIsValid = shClTransferListGetByHandle(pTransfer, hList) != NULL;
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        AssertFailed(); /** @todo Implement. */
+    }
+    else
+        AssertFailedStmt(fIsValid = false);
+
+    return fIsValid;
+}
+
+/**
+ * Copies a transfer callback table from source to destination.
+ *
+ * @param   pCallbacksDst       Callback destination.
+ * @param   pCallbacksSrc       Callback source. If set to NULL, the
+ *                              destination callback table will be unset.
+ */
+void ShClTransferCopyCallbacks(PSHCLTRANSFERCALLBACKTABLE pCallbacksDst,
+                               PSHCLTRANSFERCALLBACKTABLE pCallbacksSrc)
+{
+    AssertPtrReturnVoid(pCallbacksDst);
+
+    if (pCallbacksSrc) /* Set */
+    {
+#define SET_CALLBACK(a_pfnCallback) \
+        if (pCallbacksSrc->a_pfnCallback) \
+            pCallbacksDst->a_pfnCallback = pCallbacksSrc->a_pfnCallback
+
+        SET_CALLBACK(pfnOnInitialize);
+        SET_CALLBACK(pfnOnStart);
+        SET_CALLBACK(pfnOnCompleted);
+        SET_CALLBACK(pfnOnError);
+        SET_CALLBACK(pfnOnRegistered);
+        SET_CALLBACK(pfnOnUnregistered);
+
+#undef SET_CALLBACK
+
+        pCallbacksDst->pvUser = pCallbacksSrc->pvUser;
+        pCallbacksDst->cbUser = pCallbacksSrc->cbUser;
+    }
+    else /* Unset */
+        RT_BZERO(pCallbacksDst, sizeof(SHCLTRANSFERCALLBACKTABLE));
+}
+
+/**
+ * Sets or unsets the callback table to be used for a Shared Clipboard transfer.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to set callbacks for.
+ * @param   pCallbacks          Pointer to callback table to set. If set to NULL,
+ *                              existing callbacks for this transfer will be unset.
+ */
+void ShClTransferSetCallbacks(PSHCLTRANSFER pTransfer,
+                              PSHCLTRANSFERCALLBACKTABLE pCallbacks)
+{
+    AssertPtrReturnVoid(pTransfer);
+    /* pCallbacks can be NULL. */
+
+    ShClTransferCopyCallbacks(&pTransfer->Callbacks, pCallbacks);
+}
+
+/**
+ * Sets the transfer provider interface for a given transfer.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Transfer to create transfer provider for.
+ * @param   pCreationCtx        Provider creation context to use for provider creation.
+ */
+int ShClTransferSetProviderIface(PSHCLTRANSFER pTransfer,
+                                 PSHCLTXPROVIDERCREATIONCTX pCreationCtx)
+{
+    AssertPtrReturn(pTransfer,    VERR_INVALID_POINTER);
+    AssertPtrReturn(pCreationCtx, VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    int rc = VINF_SUCCESS;
+
+    pTransfer->ProviderIface         = pCreationCtx->Interface;
+    pTransfer->ProviderCtx.pTransfer = pTransfer;
+    pTransfer->ProviderCtx.pvUser    = pCreationCtx->pvUser;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Clears (resets) the root list of a Shared Clipboard transfer.
+ *
+ * @param   pTransfer           Transfer to clear transfer root list for.
+ */
+static void shClTransferListRootsClear(PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturnVoid(pTransfer);
+
+    if (pTransfer->pszPathRootAbs)
+    {
+        RTStrFree(pTransfer->pszPathRootAbs);
+        pTransfer->pszPathRootAbs = NULL;
+    }
+
+    PSHCLLISTROOT pListRoot, pListRootNext;
+    RTListForEachSafe(&pTransfer->lstRoots, pListRoot, pListRootNext, SHCLLISTROOT, Node)
+    {
+        RTStrFree(pListRoot->pszPathAbs);
+
+        RTListNodeRemove(&pListRoot->Node);
+
+        RTMemFree(pListRoot);
+        pListRoot = NULL;
+    }
+
+    pTransfer->cRoots = 0;
+}
+
+/**
+ * Resets a Shared Clipboard transfer.
+ *
+ * @param   pTransfer           Clipboard transfer to reset.
+ */
+void ShClTransferReset(PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturnVoid(pTransfer);
+
+    LogFlowFuncEnter();
+
+    shClTransferListRootsClear(pTransfer);
+
+    PSHCLLISTHANDLEINFO pItList, pItListNext;
+    RTListForEachSafe(&pTransfer->lstList, pItList, pItListNext, SHCLLISTHANDLEINFO, Node)
+    {
+        ShClTransferListHandleInfoDestroy(pItList);
+
+        RTListNodeRemove(&pItList->Node);
+
+        RTMemFree(pItList);
+    }
+
+    PSHCLOBJHANDLEINFO pItObj, pItObjNext;
+    RTListForEachSafe(&pTransfer->lstObj, pItObj, pItObjNext, SHCLOBJHANDLEINFO, Node)
+    {
+        ShClTransferObjHandleInfoDestroy(pItObj);
+
+        RTListNodeRemove(&pItObj->Node);
+
+        RTMemFree(pItObj);
+    }
+}
+
+/**
+ * Returns the number of transfer root list entries.
+ *
+ * @returns Root list entry count.
+ * @param   pTransfer           Clipboard transfer to return root entry count for.
+ */
+uint32_t ShClTransferRootsCount(PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pTransfer, 0);
+
+    LogFlowFunc(("[Transfer %RU32] cRoots=%RU64\n", pTransfer->State.uID, pTransfer->cRoots));
+    return (uint32_t)pTransfer->cRoots;
+}
+
+/**
+ * Returns a specific root list entry of a transfer.
+ *
+ * @returns Pointer to root list entry if found, or NULL if not found.
+ * @param   pTransfer           Clipboard transfer to get root list entry from.
+ * @param   uIdx                Index of root list entry to return.
+ */
+DECLINLINE(PSHCLLISTROOT) shClTransferRootsGetInternal(PSHCLTRANSFER pTransfer, uint32_t uIdx)
+{
+    if (uIdx >= pTransfer->cRoots)
+        return NULL;
+
+    PSHCLLISTROOT pIt = RTListGetFirst(&pTransfer->lstRoots, SHCLLISTROOT, Node);
+    while (uIdx--) /** @todo Slow, but works for now. */
+        pIt = RTListGetNext(&pTransfer->lstRoots, pIt, SHCLLISTROOT, Node);
+
+    return pIt;
+}
+
+/**
+ * Get a specific root list entry.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to get root list entry of.
+ * @param   uIndex              Index (zero-based) of entry to get.
+ * @param   pEntry              Where to store the returned entry on success.
+ */
+int ShClTransferRootsEntry(PSHCLTRANSFER pTransfer,
+                           uint64_t uIndex, PSHCLROOTLISTENTRY pEntry)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+    AssertPtrReturn(pEntry,    VERR_INVALID_POINTER);
+
+    if (uIndex >= pTransfer->cRoots)
+        return VERR_INVALID_PARAMETER;
+
+    int rc;
+
+    PSHCLLISTROOT pRoot = shClTransferRootsGetInternal(pTransfer, uIndex);
+    AssertPtrReturn(pRoot, VERR_INVALID_PARAMETER);
+
+    /* Make sure that we only advertise relative source paths, not absolute ones. */
+    const char *pcszSrcPath = pRoot->pszPathAbs;
+
+    char *pszFileName = RTPathFilename(pcszSrcPath);
+    if (pszFileName)
+    {
+        Assert(pszFileName >= pcszSrcPath);
+        size_t cchDstBase = pszFileName - pcszSrcPath;
+        const char *pszDstPath = &pcszSrcPath[cchDstBase];
+
+        LogFlowFunc(("pcszSrcPath=%s, pszDstPath=%s\n", pcszSrcPath, pszDstPath));
+
+        rc = ShClTransferListEntryInit(pEntry);
+        if (RT_SUCCESS(rc))
+        {
+            rc = RTStrCopy(pEntry->pszName, pEntry->cbName, pszDstPath);
+            if (RT_SUCCESS(rc))
+            {
+                pEntry->cbInfo = sizeof(SHCLFSOBJINFO);
+                pEntry->pvInfo = (PSHCLFSOBJINFO)RTMemAlloc(pEntry->cbInfo);
+                if (pEntry->pvInfo)
+                {
+                    RTFSOBJINFO fsObjInfo;
+                    rc = RTPathQueryInfo(pcszSrcPath, &fsObjInfo, RTFSOBJATTRADD_NOTHING);
+                    if (RT_SUCCESS(rc))
+                    {
+                        ShClFsObjFromIPRT(PSHCLFSOBJINFO(pEntry->pvInfo), &fsObjInfo);
+
+                        pEntry->fInfo = VBOX_SHCL_INFO_FLAG_FSOBJINFO;
+                    }
+                }
+                else
+                    rc = VERR_NO_MEMORY;
+            }
+        }
+    }
+    else
+        rc = VERR_INVALID_POINTER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Returns the root entries of a Shared Clipboard transfer.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to return root entries for.
+ * @param   ppRootList          Where to store the root list on success.
+ */
+int ShClTransferRootsGet(PSHCLTRANSFER pTransfer, PSHCLROOTLIST *ppRootList)
+{
+    AssertPtrReturn(pTransfer,  VERR_INVALID_POINTER);
+    AssertPtrReturn(ppRootList, VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    int rc = VINF_SUCCESS;
+
+    if (pTransfer->State.enmSource == SHCLSOURCE_LOCAL)
+    {
+        PSHCLROOTLIST pRootList = ShClTransferRootListAlloc();
+        if (!pRootList)
+            return VERR_NO_MEMORY;
+
+        const uint64_t cRoots = (uint32_t)pTransfer->cRoots;
+
+        LogFlowFunc(("cRoots=%RU64\n", cRoots));
+
+        if (cRoots)
+        {
+            PSHCLROOTLISTENTRY paRootListEntries
+                = (PSHCLROOTLISTENTRY)RTMemAllocZ(cRoots * sizeof(SHCLROOTLISTENTRY));
+            if (paRootListEntries)
+            {
+                for (uint64_t i = 0; i < cRoots; ++i)
+                {
+                    rc = ShClTransferRootsEntry(pTransfer, i, &paRootListEntries[i]);
+                    if (RT_FAILURE(rc))
+                        break;
+                }
+
+                if (RT_SUCCESS(rc))
+                    pRootList->paEntries = paRootListEntries;
+            }
+            else
+                rc = VERR_NO_MEMORY;
+        }
+        else
+            rc = VERR_NOT_FOUND;
+
+        if (RT_SUCCESS(rc))
+        {
+            pRootList->Hdr.cRoots = cRoots;
+            pRootList->Hdr.fRoots = 0; /** @todo Implement this. */
+
+            *ppRootList = pRootList;
+        }
+    }
+    else if (pTransfer->State.enmSource == SHCLSOURCE_REMOTE)
+    {
+        if (pTransfer->ProviderIface.pfnRootsGet)
+            rc = pTransfer->ProviderIface.pfnRootsGet(&pTransfer->ProviderCtx, ppRootList);
+        else
+            rc = VERR_NOT_SUPPORTED;
+    }
+    else
+        AssertFailedStmt(rc = VERR_NOT_IMPLEMENTED);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Sets transfer root list entries for a given transfer.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Transfer to set transfer list entries for.
+ * @param   pszRoots            String list (separated by CRLF) of root entries to set.
+ *                              All entries must have the same root path.
+ * @param   cbRoots             Size (in bytes) of string list.
+ */
+int ShClTransferRootsSet(PSHCLTRANSFER pTransfer, const char *pszRoots, size_t cbRoots)
+{
+    AssertPtrReturn(pTransfer,      VERR_INVALID_POINTER);
+    AssertPtrReturn(pszRoots,       VERR_INVALID_POINTER);
+    AssertReturn(cbRoots,           VERR_INVALID_PARAMETER);
+
+    if (!RTStrIsValidEncoding(pszRoots))
+        return VERR_INVALID_UTF8_ENCODING;
+
+    int rc = VINF_SUCCESS;
+
+    shClTransferListRootsClear(pTransfer);
+
+    char  *pszPathRootAbs = NULL;
+
+    RTCList<RTCString> lstRootEntries = RTCString(pszRoots, cbRoots - 1).split("\r\n");
+    for (size_t i = 0; i < lstRootEntries.size(); ++i)
+    {
+        PSHCLLISTROOT pListRoot = (PSHCLLISTROOT)RTMemAlloc(sizeof(SHCLLISTROOT));
+        AssertPtrBreakStmt(pListRoot, rc = VERR_NO_MEMORY);
+
+        const char *pszPathCur = RTStrDup(lstRootEntries.at(i).c_str());
+
+        LogFlowFunc(("pszPathCur=%s\n", pszPathCur));
+
+        /* No root path determined yet? */
+        if (!pszPathRootAbs)
+        {
+            pszPathRootAbs = RTStrDup(pszPathCur);
+            if (pszPathRootAbs)
+            {
+                RTPathStripFilename(pszPathRootAbs);
+
+                LogFlowFunc(("pszPathRootAbs=%s\n", pszPathRootAbs));
+
+                /* We don't want to have a relative directory here. */
+                if (RTPathStartsWithRoot(pszPathRootAbs))
+                {
+                    rc = shClTransferValidatePath(pszPathRootAbs, true /* Path must exist */);
+                }
+                else
+                    rc = VERR_INVALID_PARAMETER;
+            }
+            else
+                rc = VERR_NO_MEMORY;
+        }
+
+        if (RT_FAILURE(rc))
+            break;
+
+        pListRoot->pszPathAbs = RTStrDup(pszPathCur);
+        if (!pListRoot->pszPathAbs)
+        {
+            rc = VERR_NO_MEMORY;
+            break;
+        }
+
+        RTListAppend(&pTransfer->lstRoots, &pListRoot->Node);
+
+        pTransfer->cRoots++;
+    }
+
+    /* No (valid) root directory found? Bail out early. */
+    if (!pszPathRootAbs)
+        rc = VERR_PATH_NOT_FOUND;
+
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Step 2:
+         * Go through the created list and make sure all entries have the same root path.
+         */
+        PSHCLLISTROOT pListRoot;
+        RTListForEach(&pTransfer->lstRoots, pListRoot, SHCLLISTROOT, Node)
+        {
+            if (!RTStrStartsWith(pListRoot->pszPathAbs, pszPathRootAbs))
+            {
+                rc = VERR_INVALID_PARAMETER;
+                break;
+            }
+
+            rc = shClTransferValidatePath(pListRoot->pszPathAbs, true /* Path must exist */);
+            if (RT_FAILURE(rc))
+                break;
+        }
+    }
+
+    /** @todo Entry rollback on failure? */
+
+    if (RT_SUCCESS(rc))
+    {
+        pTransfer->pszPathRootAbs = pszPathRootAbs;
+        LogFlowFunc(("pszPathRootAbs=%s, cRoots=%zu\n", pTransfer->pszPathRootAbs, pTransfer->cRoots));
+
+        LogRel2(("Shared Clipboard: Transfer uses root '%s'\n", pTransfer->pszPathRootAbs));
+    }
+    else
+    {
+        LogRel(("Shared Clipboard: Unable to set roots for transfer, rc=%Rrc\n", rc));
+        RTStrFree(pszPathRootAbs);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Returns the transfer's ID.
+ *
+ * @returns The transfer's ID.
+ * @param   pTransfer           Clipboard transfer to return ID for.
+ */
+SHCLTRANSFERID ShClTransferGetID(PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pTransfer, 0);
+
+    return pTransfer->State.uID;
+}
+
+/**
+ * Returns the transfer's direction.
+ *
+ * @returns The transfer's direction.
+ * @param   pTransfer           Clipboard transfer to return direction for.
+ */
+SHCLTRANSFERDIR ShClTransferGetDir(PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pTransfer, SHCLTRANSFERDIR_UNKNOWN);
+
+    LogFlowFunc(("[Transfer %RU32] enmDir=%RU32\n", pTransfer->State.uID, pTransfer->State.enmDir));
+    return pTransfer->State.enmDir;
+}
+
+/**
+ * Returns the transfer's source.
+ *
+ * @returns The transfer's source.
+ * @param   pTransfer           Clipboard transfer to return source for.
+ */
+SHCLSOURCE ShClTransferGetSource(PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pTransfer, SHCLSOURCE_INVALID);
+
+    LogFlowFunc(("[Transfer %RU32] enmSource=%RU32\n", pTransfer->State.uID, pTransfer->State.enmSource));
+    return pTransfer->State.enmSource;
+}
+
+/**
+ * Returns the current transfer status.
+ *
+ * @returns Current transfer status.
+ * @param   pTransfer           Clipboard transfer to return status for.
+ */
+SHCLTRANSFERSTATUS ShClTransferGetStatus(PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pTransfer, SHCLTRANSFERSTATUS_NONE);
+
+    LogFlowFunc(("[Transfer %RU32] enmStatus=%RU32\n", pTransfer->State.uID, pTransfer->State.enmStatus));
+    return pTransfer->State.enmStatus;
+}
+
+/**
+ * Runs a started Shared Clipboard transfer in a dedicated thread.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to run.
+ * @param   pfnThreadFunc       Pointer to thread function to use.
+ * @param   pvUser              Pointer to user-provided data. Optional.
+ */
+int ShClTransferRun(PSHCLTRANSFER pTransfer, PFNRTTHREAD pfnThreadFunc, void *pvUser)
+{
+    AssertPtrReturn(pTransfer,     VERR_INVALID_POINTER);
+    AssertPtrReturn(pfnThreadFunc, VERR_INVALID_POINTER);
+    /* pvUser is optional. */
+
+    AssertMsgReturn(pTransfer->State.enmStatus == SHCLTRANSFERSTATUS_STARTED,
+                    ("Wrong status (currently is %s)\n", ShClTransferStatusToStr(pTransfer->State.enmStatus)),
+                    VERR_WRONG_ORDER);
+
+    int rc = shClTransferThreadCreate(pTransfer, pfnThreadFunc, pvUser);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Starts an initialized transfer.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to start.
+ */
+int ShClTransferStart(PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    /* Ready to start? */
+    AssertMsgReturn(pTransfer->State.enmStatus == SHCLTRANSFERSTATUS_INITIALIZED,
+                    ("Wrong status (currently is %s)\n", ShClTransferStatusToStr(pTransfer->State.enmStatus)),
+                    VERR_WRONG_ORDER);
+
+    int rc;
+
+    if (pTransfer->Callbacks.pfnOnStart)
+    {
+        rc = pTransfer->Callbacks.pfnOnStart(&pTransfer->CallbackCtx);
+    }
+    else
+        rc = VINF_SUCCESS;
+
+    if (RT_SUCCESS(rc))
+    {
+        pTransfer->State.enmStatus = SHCLTRANSFERSTATUS_STARTED;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Creates a thread for a Shared Clipboard transfer.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to create thread for.
+ * @param   pfnThreadFunc       Thread function to use for this transfer.
+ * @param   pvUser              Pointer to user-provided data.
+ */
+static int shClTransferThreadCreate(PSHCLTRANSFER pTransfer, PFNRTTHREAD pfnThreadFunc, void *pvUser)
+
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    /* Already marked for stopping? */
+    AssertMsgReturn(pTransfer->Thread.fStop == false,
+                    ("Transfer thread already marked for stopping"), VERR_WRONG_ORDER);
+    /* Already started? */
+    AssertMsgReturn(pTransfer->Thread.fStarted == false,
+                    ("Transfer thread already started"), VERR_WRONG_ORDER);
+
+    /* Spawn a worker thread, so that we don't block the window thread for too long. */
+    int rc = RTThreadCreate(&pTransfer->Thread.hThread, pfnThreadFunc,
+                            pvUser, 0, RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE,
+                            "shclp");
+    if (RT_SUCCESS(rc))
+    {
+        int rc2 = RTThreadUserWait(pTransfer->Thread.hThread, 30 * 1000 /* Timeout in ms */);
+        AssertRC(rc2);
+
+        if (pTransfer->Thread.fStarted) /* Did the thread indicate that it started correctly? */
+        {
+            /* Nothing to do in here. */
+        }
+        else
+            rc = VERR_GENERAL_FAILURE; /** @todo Find a better rc. */
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Destroys a thread of a Shared Clipboard transfer.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Clipboard transfer to destroy thread for.
+ * @param   uTimeoutMs          Timeout (in ms) to wait for thread creation.
+ */
+static int shClTransferThreadDestroy(PSHCLTRANSFER pTransfer, RTMSINTERVAL uTimeoutMs)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    if (pTransfer->Thread.hThread == NIL_RTTHREAD)
+        return VINF_SUCCESS;
+
+    LogFlowFuncEnter();
+
+    /* Set stop indicator. */
+    pTransfer->Thread.fStop = true;
+
+    int rcThread = VERR_WRONG_ORDER;
+    int rc = RTThreadWait(pTransfer->Thread.hThread, uTimeoutMs, &rcThread);
+
+    LogFlowFunc(("Waiting for thread resulted in %Rrc (thread exited with %Rrc)\n", rc, rcThread));
+
+    return rc;
+}
+
+/**
+ * Initializes a Shared Clipboard transfer context.
+ *
+ * @returns VBox status code.
+ * @param   pTransferCtx                Transfer context to initialize.
+ */
+int ShClTransferCtxInit(PSHCLTRANSFERCTX pTransferCtx)
+{
+    AssertPtrReturn(pTransferCtx, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("pTransferCtx=%p\n", pTransferCtx));
+
+    int rc = RTCritSectInit(&pTransferCtx->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        RTListInit(&pTransferCtx->List);
+
+        pTransferCtx->cTransfers  = 0;
+        pTransferCtx->cRunning    = 0;
+        pTransferCtx->cMaxRunning = 64; /** @todo Make this configurable? */
+
+        RT_ZERO(pTransferCtx->bmTransferIds);
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS_HTTP
+        ShClTransferHttpServerInit(&pTransferCtx->HttpServer);
+#endif
+        ShClTransferCtxReset(pTransferCtx);
+    }
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys a Shared Clipboard transfer context struct.
+ *
+ * @param   pTransferCtx                Transfer context to destroy.
+ */
+void ShClTransferCtxDestroy(PSHCLTRANSFERCTX pTransferCtx)
+{
+    if (!pTransferCtx)
+        return;
+
+    LogFlowFunc(("pTransferCtx=%p\n", pTransferCtx));
+
+    if (RTCritSectIsInitialized(&pTransferCtx->CritSect))
+        RTCritSectDelete(&pTransferCtx->CritSect);
+
+    PSHCLTRANSFER pTransfer, pTransferNext;
+    RTListForEachSafe(&pTransferCtx->List, pTransfer, pTransferNext, SHCLTRANSFER, Node)
+    {
+        ShClTransferDestroy(pTransfer);
+
+        shclTransferCtxTransferRemoveAndUnregister(pTransferCtx, pTransfer);
+
+        RTMemFree(pTransfer);
+        pTransfer = NULL;
+    }
+
+    pTransferCtx->cRunning   = 0;
+    pTransferCtx->cTransfers = 0;
+}
+
+/**
+ * Resets a Shared Clipboard transfer.
+ *
+ * @param   pTransferCtx                Transfer context to reset.
+ */
+void ShClTransferCtxReset(PSHCLTRANSFERCTX pTransferCtx)
+{
+    AssertPtrReturnVoid(pTransferCtx);
+
+    LogFlowFuncEnter();
+
+    PSHCLTRANSFER pTransfer;
+    RTListForEach(&pTransferCtx->List, pTransfer, SHCLTRANSFER, Node)
+        ShClTransferReset(pTransfer);
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS_HTTP
+    /** @todo Anything to do here? */
+#endif
+}
+
+/**
+ * Returns a specific Shared Clipboard transfer, internal version.
+ *
+ * @returns Shared Clipboard transfer, or NULL if not found.
+ * @param   pTransferCtx                Transfer context to return transfer for.
+ * @param   uID                         ID of the transfer to return.
+ */
+static PSHCLTRANSFER shClTransferCtxGetTransferByIdInternal(PSHCLTRANSFERCTX pTransferCtx, uint32_t uID)
+{
+    PSHCLTRANSFER pTransfer;
+    RTListForEach(&pTransferCtx->List, pTransfer, SHCLTRANSFER, Node) /** @todo Slow, but works for now. */
+    {
+        if (pTransfer->State.uID == uID)
+            return pTransfer;
+    }
+
+    return NULL;
+}
+
+/**
+ * Returns a specific Shared Clipboard transfer by index, internal version.
+ *
+ * @returns Shared Clipboard transfer, or NULL if not found.
+ * @param   pTransferCtx                Transfer context to return transfer for.
+ * @param   uIdx                        Index of the transfer to return.
+ */
+static PSHCLTRANSFER shClTransferCtxGetTransferByIndexInternal(PSHCLTRANSFERCTX pTransferCtx, uint32_t uIdx)
+{
+    uint32_t idx = 0;
+
+    PSHCLTRANSFER pTransfer;
+    RTListForEach(&pTransferCtx->List, pTransfer, SHCLTRANSFER, Node) /** @todo Slow, but works for now. */
+    {
+        if (uIdx == idx)
+            return pTransfer;
+        idx++;
+    }
+
+    return NULL;
+}
+
+/**
+ * Returns a Shared Clipboard transfer for a specific transfer ID.
+ *
+ * @returns Shared Clipboard transfer, or NULL if not found.
+ * @param   pTransferCtx                Transfer context to return transfer for.
+ * @param   uID                         ID of the transfer to return.
+ */
+PSHCLTRANSFER ShClTransferCtxGetTransferById(PSHCLTRANSFERCTX pTransferCtx, uint32_t uID)
+{
+    return shClTransferCtxGetTransferByIdInternal(pTransferCtx, uID);
+}
+
+/**
+ * Returns a Shared Clipboard transfer for a specific list index.
+ *
+ * @returns Shared Clipboard transfer, or NULL if not found.
+ * @param   pTransferCtx                Transfer context to return transfer for.
+ * @param   uIdx                        List index of the transfer to return.
+ */
+PSHCLTRANSFER ShClTransferCtxGetTransferByIndex(PSHCLTRANSFERCTX pTransferCtx, uint32_t uIdx)
+{
+    return shClTransferCtxGetTransferByIndexInternal(pTransferCtx, uIdx);
+}
+
+/**
+ * Returns the number of running Shared Clipboard transfers.
+ *
+ * @returns Number of running transfers.
+ * @param   pTransferCtx                Transfer context to return number for.
+ */
+uint32_t ShClTransferCtxGetRunningTransfers(PSHCLTRANSFERCTX pTransferCtx)
+{
+    AssertPtrReturn(pTransferCtx, 0);
+    return pTransferCtx->cRunning;
+}
+
+/**
+ * Returns the number of total Shared Clipboard transfers.
+ *
+ * @returns Number of total transfers.
+ * @param   pTransferCtx                Transfer context to return number for.
+ */
+uint32_t ShClTransferCtxGetTotalTransfers(PSHCLTRANSFERCTX pTransferCtx)
+{
+    AssertPtrReturn(pTransferCtx, 0);
+    return pTransferCtx->cTransfers;
+}
+
+/**
+ * Registers a Shared Clipboard transfer with a transfer context, i.e. allocates a transfer ID.
+ *
+ * @return  VBox status code.
+ * @retval  VERR_SHCLPB_MAX_TRANSFERS_REACHED if the maximum of concurrent transfers
+ *          is reached.
+ * @param   pTransferCtx        Transfer context to register transfer to.
+ * @param   pTransfer           Transfer to register.
+ * @param   pidTransfer         Where to return the transfer ID on success. Optional.
+ */
+int ShClTransferCtxTransferRegister(PSHCLTRANSFERCTX pTransferCtx, PSHCLTRANSFER pTransfer, SHCLTRANSFERID *pidTransfer)
+{
+    AssertPtrReturn(pTransferCtx, VERR_INVALID_POINTER);
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+    /* pidTransfer is optional. */
+
+    /*
+     * Pick a random bit as starting point.  If it's in use, search forward
+     * for a free one, wrapping around.  We've reserved both the zero'th and
+     * max-1 IDs.
+     */
+    SHCLTRANSFERID idTransfer = RTRandU32Ex(1, VBOX_SHCL_MAX_TRANSFERS - 2);
+
+    if (!ASMBitTestAndSet(&pTransferCtx->bmTransferIds[0], idTransfer))
+    { /* likely */ }
+    else if (pTransferCtx->cTransfers < VBOX_SHCL_MAX_TRANSFERS - 2 /* First and last are not used */)
+    {
+        /* Forward search. */
+        int iHit = ASMBitNextClear(&pTransferCtx->bmTransferIds[0], VBOX_SHCL_MAX_TRANSFERS, idTransfer);
+        if (iHit < 0)
+            iHit = ASMBitFirstClear(&pTransferCtx->bmTransferIds[0], VBOX_SHCL_MAX_TRANSFERS);
+        AssertLogRelMsgReturn(iHit >= 0, ("Transfer count: %RU16\n", pTransferCtx->cTransfers), VERR_SHCLPB_MAX_TRANSFERS_REACHED);
+        idTransfer = iHit;
+        AssertLogRelMsgReturn(!ASMBitTestAndSet(&pTransferCtx->bmTransferIds[0], idTransfer), ("idObject=%#x\n", idTransfer), VERR_INTERNAL_ERROR_2);
+    }
+    else
+    {
+        LogFunc(("Maximum number of transfers reached (%RU16 transfers)\n", pTransferCtx->cTransfers));
+        return VERR_SHCLPB_MAX_TRANSFERS_REACHED;
+    }
+
+    Log2Func(("pTransfer=%p, idTransfer=%RU32 (%RU16 transfers)\n", pTransfer, idTransfer, pTransferCtx->cTransfers));
+
+    pTransfer->State.uID = idTransfer;
+
+    RTListAppend(&pTransferCtx->List, &pTransfer->Node);
+
+    pTransferCtx->cTransfers++;
+
+    if (pTransfer->Callbacks.pfnOnRegistered)
+        pTransfer->Callbacks.pfnOnRegistered(&pTransfer->CallbackCtx, pTransferCtx);
+
+    if (pidTransfer)
+        *pidTransfer = idTransfer;
+
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+    return VINF_SUCCESS;
+}
+
+/**
+ * Registers a Shared Clipboard transfer with a transfer context by specifying an ID for the transfer.
+ *
+ * @return  VBox status code.
+ * @retval  VERR_ALREADY_EXISTS if a transfer with the given ID already exists.
+ * @retval  VERR_SHCLPB_MAX_TRANSFERS_REACHED if the maximum of concurrent transfers for this context has been reached.
+ * @param   pTransferCtx                Transfer context to register transfer to.
+ * @param   pTransfer           Transfer to register.
+ * @param   idTransfer          Transfer ID to use for registration.
+ */
+int ShClTransferCtxTransferRegisterById(PSHCLTRANSFERCTX pTransferCtx, PSHCLTRANSFER pTransfer, SHCLTRANSFERID idTransfer)
+{
+    LogFlowFunc(("cTransfers=%RU16, idTransfer=%RU32\n", pTransferCtx->cTransfers, idTransfer));
+
+    if (pTransferCtx->cTransfers < VBOX_SHCL_MAX_TRANSFERS - 2 /* First and last are not used */)
+    {
+        if (!ASMBitTestAndSet(&pTransferCtx->bmTransferIds[0], idTransfer))
+        {
+            RTListAppend(&pTransferCtx->List, &pTransfer->Node);
+
+            pTransfer->State.uID = idTransfer;
+
+            if (pTransfer->Callbacks.pfnOnRegistered)
+                pTransfer->Callbacks.pfnOnRegistered(&pTransfer->CallbackCtx, pTransferCtx);
+
+            pTransferCtx->cTransfers++;
+            return VINF_SUCCESS;
+        }
+
+        return VERR_ALREADY_EXISTS;
+    }
+
+    LogFunc(("Maximum number of transfers reached (%RU16 transfers)\n", pTransferCtx->cTransfers));
+    return VERR_SHCLPB_MAX_TRANSFERS_REACHED;
+}
+
+/**
+ * Removes and unregisters a transfer from a transfer context.
+ *
+ * @param   pTransferCtx        Transfer context to remove transfer from.
+ * @param   pTransfer           Transfer to remove.
+ */
+static void shclTransferCtxTransferRemoveAndUnregister(PSHCLTRANSFERCTX pTransferCtx, PSHCLTRANSFER pTransfer)
+{
+    RTListNodeRemove(&pTransfer->Node);
+
+    Assert(pTransferCtx->cTransfers);
+    pTransferCtx->cTransfers--;
+
+    Assert(pTransferCtx->cTransfers >= pTransferCtx->cRunning);
+
+    if (pTransfer->Callbacks.pfnOnUnregistered)
+        pTransfer->Callbacks.pfnOnUnregistered(&pTransfer->CallbackCtx, pTransferCtx);
+
+    LogFlowFunc(("Now %RU32 transfers left\n", pTransferCtx->cTransfers));
+}
+
+/**
+ * Unregisters a transfer from an Transfer context.
+ *
+ * @retval  VINF_SUCCESS on success.
+ * @retval  VERR_NOT_FOUND if the transfer ID was not found.
+ * @param   pTransferCtx        Transfer context to unregister transfer from.
+ * @param   idTransfer          Transfer ID to unregister.
+ */
+int ShClTransferCtxTransferUnregister(PSHCLTRANSFERCTX pTransferCtx, SHCLTRANSFERID idTransfer)
+{
+    int rc = VINF_SUCCESS;
+    AssertMsgStmt(ASMBitTestAndClear(&pTransferCtx->bmTransferIds, idTransfer), ("idTransfer=%#x\n", idTransfer), rc = VERR_NOT_FOUND);
+
+    LogFlowFunc(("idTransfer=%RU32\n", idTransfer));
+
+    PSHCLTRANSFER pTransfer = shClTransferCtxGetTransferByIdInternal(pTransferCtx, idTransfer);
+    if (pTransfer)
+    {
+        shclTransferCtxTransferRemoveAndUnregister(pTransferCtx, pTransfer);
+    }
+    else
+        rc = VERR_NOT_FOUND;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Cleans up all associated transfers which are not needed (anymore).
+ * This can be due to transfers which only have been announced but not / never being run.
+ *
+ * @param   pTransferCtx        Transfer context to cleanup transfers for.
+ */
+void ShClTransferCtxCleanup(PSHCLTRANSFERCTX pTransferCtx)
+{
+    AssertPtrReturnVoid(pTransferCtx);
+
+    LogFlowFunc(("pTransferCtx=%p, cTransfers=%RU16 cRunning=%RU16\n",
+                 pTransferCtx, pTransferCtx->cTransfers, pTransferCtx->cRunning));
+
+    if (pTransferCtx->cTransfers == 0)
+        return;
+
+    /* Remove all transfers which are not in a running state (e.g. only announced). */
+    PSHCLTRANSFER pTransfer, pTransferNext;
+    RTListForEachSafe(&pTransferCtx->List, pTransfer, pTransferNext, SHCLTRANSFER, Node)
+    {
+        if (ShClTransferGetStatus(pTransfer) != SHCLTRANSFERSTATUS_STARTED)
+        {
+            shclTransferCtxTransferRemoveAndUnregister(pTransferCtx, pTransfer);
+
+            ShClTransferDestroy(pTransfer);
+
+            RTMemFree(pTransfer);
+            pTransfer = NULL;
+        }
+    }
+}
+
+/**
+ * Returns whether the maximum of concurrent transfers of a specific transfer contexthas been reached or not.
+ *
+ * @returns \c if maximum has been reached, \c false if not.
+ * @param   pTransferCtx        Transfer context to determine value for.
+ */
+bool ShClTransferCtxTransfersMaximumReached(PSHCLTRANSFERCTX pTransferCtx)
+{
+    AssertPtrReturn(pTransferCtx, true);
+
+    LogFlowFunc(("cRunning=%RU32, cMaxRunning=%RU32\n", pTransferCtx->cRunning, pTransferCtx->cMaxRunning));
+
+    Assert(pTransferCtx->cRunning <= pTransferCtx->cMaxRunning);
+    return pTransferCtx->cRunning == pTransferCtx->cMaxRunning;
+}
+
+/**
+ * Copies file system objinfo from IPRT to Shared Clipboard format.
+ *
+ * @param   pDst                The Shared Clipboard structure to convert data to.
+ * @param   pSrc                The IPRT structure to convert data from.
+ */
+void ShClFsObjFromIPRT(PSHCLFSOBJINFO pDst, PCRTFSOBJINFO pSrc)
+{
+    pDst->cbObject          = pSrc->cbObject;
+    pDst->cbAllocated       = pSrc->cbAllocated;
+    pDst->AccessTime        = pSrc->AccessTime;
+    pDst->ModificationTime  = pSrc->ModificationTime;
+    pDst->ChangeTime        = pSrc->ChangeTime;
+    pDst->BirthTime         = pSrc->BirthTime;
+    pDst->Attr.fMode        = pSrc->Attr.fMode;
+    /* Clear bits which we don't pass through for security reasons. */
+    pDst->Attr.fMode       &= ~(RTFS_UNIX_ISUID | RTFS_UNIX_ISGID | RTFS_UNIX_ISTXT);
+    RT_ZERO(pDst->Attr.u);
+    switch (pSrc->Attr.enmAdditional)
+    {
+        default:
+        case RTFSOBJATTRADD_NOTHING:
+            pDst->Attr.enmAdditional        = SHCLFSOBJATTRADD_NOTHING;
+            break;
+
+        case RTFSOBJATTRADD_UNIX:
+            pDst->Attr.enmAdditional        = SHCLFSOBJATTRADD_UNIX;
+            pDst->Attr.u.Unix.uid           = pSrc->Attr.u.Unix.uid;
+            pDst->Attr.u.Unix.gid           = pSrc->Attr.u.Unix.gid;
+            pDst->Attr.u.Unix.cHardlinks    = pSrc->Attr.u.Unix.cHardlinks;
+            pDst->Attr.u.Unix.INodeIdDevice = pSrc->Attr.u.Unix.INodeIdDevice;
+            pDst->Attr.u.Unix.INodeId       = pSrc->Attr.u.Unix.INodeId;
+            pDst->Attr.u.Unix.fFlags        = pSrc->Attr.u.Unix.fFlags;
+            pDst->Attr.u.Unix.GenerationId  = pSrc->Attr.u.Unix.GenerationId;
+            pDst->Attr.u.Unix.Device        = pSrc->Attr.u.Unix.Device;
+            break;
+
+        case RTFSOBJATTRADD_EASIZE:
+            pDst->Attr.enmAdditional        = SHCLFSOBJATTRADD_EASIZE;
+            pDst->Attr.u.EASize.cb          = pSrc->Attr.u.EASize.cb;
+            break;
+    }
+}
+
+/**
+ * Converts Shared Clipboard create flags (see SharedClipboard-transfers.h) into IPRT create flags.
+ *
+ * @returns IPRT status code.
+ * @param       fShClFlags  Shared clipboard create flags.
+ * @param[out]  pfOpen      Where to store the RTFILE_O_XXX flags for
+ *                          RTFileOpen.
+ *
+ * @sa Initially taken from vbsfConvertFileOpenFlags().
+ */
+static int shClConvertFileCreateFlags(uint32_t fShClFlags, uint64_t *pfOpen)
+{
+    AssertMsgReturnStmt(!(fShClFlags & ~SHCL_OBJ_CF_VALID_MASK), ("%#x4\n", fShClFlags), *pfOpen = 0, VERR_INVALID_FLAGS);
+
+    uint64_t fOpen = 0;
+
+    switch (fShClFlags & SHCL_OBJ_CF_ACCESS_MASK_RW)
+    {
+        case SHCL_OBJ_CF_ACCESS_NONE:
+        {
+#ifdef RT_OS_WINDOWS
+            if ((fShClFlags & SHCL_OBJ_CF_ACCESS_MASK_ATTR) != SHCL_OBJ_CF_ACCESS_ATTR_NONE)
+                fOpen |= RTFILE_O_OPEN | RTFILE_O_ATTR_ONLY;
+            else
+#endif
+                fOpen |= RTFILE_O_OPEN | RTFILE_O_READ;
+            LogFlowFunc(("SHCL_OBJ_CF_ACCESS_NONE\n"));
+            break;
+        }
+
+        case SHCL_OBJ_CF_ACCESS_READ:
+        {
+            fOpen |= RTFILE_O_OPEN | RTFILE_O_READ;
+            LogFlowFunc(("SHCL_OBJ_CF_ACCESS_READ\n"));
+            break;
+        }
+
+        default:
+            AssertFailedReturn(VERR_IPE_NOT_REACHED_DEFAULT_CASE);
+    }
+
+    switch (fShClFlags & SHCL_OBJ_CF_ACCESS_MASK_ATTR)
+    {
+        case SHCL_OBJ_CF_ACCESS_ATTR_NONE:
+        {
+            fOpen |= RTFILE_O_ACCESS_ATTR_DEFAULT;
+            LogFlowFunc(("SHCL_OBJ_CF_ACCESS_ATTR_NONE\n"));
+            break;
+        }
+
+        case SHCL_OBJ_CF_ACCESS_ATTR_READ:
+        {
+            fOpen |= RTFILE_O_ACCESS_ATTR_READ;
+            LogFlowFunc(("SHCL_OBJ_CF_ACCESS_ATTR_READ\n"));
+            break;
+        }
+
+        default:
+            AssertFailedReturn(VERR_IPE_NOT_REACHED_DEFAULT_CASE);
+    }
+
+    /* Sharing mask */
+    switch (fShClFlags & SHCL_OBJ_CF_ACCESS_MASK_DENY)
+    {
+        case SHCL_OBJ_CF_ACCESS_DENYNONE:
+            fOpen |= RTFILE_O_DENY_NONE;
+            LogFlowFunc(("SHCL_OBJ_CF_ACCESS_DENYNONE\n"));
+            break;
+
+        case SHCL_OBJ_CF_ACCESS_DENYWRITE:
+            fOpen |= RTFILE_O_DENY_WRITE;
+            LogFlowFunc(("SHCL_OBJ_CF_ACCESS_DENYWRITE\n"));
+            break;
+
+        default:
+            AssertFailedReturn(VERR_IPE_NOT_REACHED_DEFAULT_CASE);
+    }
+
+    *pfOpen = fOpen;
+
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+    return VINF_SUCCESS;
+}
+
+/**
+ * Translates a Shared Clipboard transfer status (SHCLTRANSFERSTATUS_XXX) into a string.
+ *
+ * @returns Transfer status string name.
+ * @param   enmStatus           The transfer status to translate.
+ */
+const char *ShClTransferStatusToStr(SHCLTRANSFERSTATUS enmStatus)
+{
+    switch (enmStatus)
+    {
+        RT_CASE_RET_STR(SHCLTRANSFERSTATUS_NONE);
+        RT_CASE_RET_STR(SHCLTRANSFERSTATUS_INITIALIZED);
+        RT_CASE_RET_STR(SHCLTRANSFERSTATUS_STARTED);
+        RT_CASE_RET_STR(SHCLTRANSFERSTATUS_STOPPED);
+        RT_CASE_RET_STR(SHCLTRANSFERSTATUS_CANCELED);
+        RT_CASE_RET_STR(SHCLTRANSFERSTATUS_KILLED);
+        RT_CASE_RET_STR(SHCLTRANSFERSTATUS_ERROR);
+    }
+    return "Unknown";
+}
diff --git a/src/VBox/GuestHost/SharedClipboard/clipboard-win.cpp b/src/VBox/GuestHost/SharedClipboard/clipboard-win.cpp
new file mode 100644
index 00000000..bd2a50f1
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/clipboard-win.cpp
@@ -0,0 +1,1322 @@
+/* $Id: clipboard-win.cpp $ */
+/** @file
+ * Shared Clipboard: Windows-specific functions for clipboard handling.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/GuestHost/SharedClipboard.h>
+
+#include <iprt/assert.h>
+#include <iprt/errcore.h>
+#include <iprt/ldr.h>
+#include <iprt/mem.h>
+#include <iprt/thread.h>
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+# include <iprt/win/windows.h>
+# include <iprt/win/shlobj.h> /* For CFSTR_FILEDESCRIPTORXXX + CFSTR_FILECONTENTS. */
+# include <iprt/utf16.h>
+#endif
+
+#include <VBox/log.h>
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+# include <VBox/GuestHost/SharedClipboard-transfers.h>
+#endif
+#include <VBox/GuestHost/SharedClipboard-win.h>
+#include <VBox/GuestHost/clipboard-helper.h>
+
+
+/**
+ * Opens the clipboard of a specific window.
+ *
+ * @returns VBox status code.
+ * @param   hWnd                Handle of window to open clipboard for.
+ */
+int SharedClipboardWinOpen(HWND hWnd)
+{
+    /* "OpenClipboard fails if another window has the clipboard open."
+     * So try a few times and wait up to 1 second.
+     */
+    BOOL fOpened = FALSE;
+
+    LogFlowFunc(("hWnd=%p\n", hWnd));
+
+    int i = 0;
+    for (;;)
+    {
+        if (OpenClipboard(hWnd))
+        {
+            fOpened = TRUE;
+            break;
+        }
+
+        if (i >= 10) /* sleep interval = [1..512] ms */
+            break;
+
+        RTThreadSleep(1 << i);
+        ++i;
+    }
+
+#ifdef LOG_ENABLED
+    if (i > 0)
+        LogFlowFunc(("%d times tried to open clipboard\n", i + 1));
+#endif
+
+    int rc;
+    if (fOpened)
+        rc = VINF_SUCCESS;
+    else
+    {
+        const DWORD dwLastErr = GetLastError();
+        rc = RTErrConvertFromWin32(dwLastErr);
+        LogRel(("Failed to open clipboard, rc=%Rrc (0x%x)\n", rc, dwLastErr));
+    }
+
+    return rc;
+}
+
+/**
+ * Closes the clipboard for the current thread.
+ *
+ * @returns VBox status code.
+ */
+int SharedClipboardWinClose(void)
+{
+    int rc;
+
+    const BOOL fRc = CloseClipboard();
+    if (RT_UNLIKELY(!fRc))
+    {
+        const DWORD dwLastErr = GetLastError();
+        if (dwLastErr == ERROR_CLIPBOARD_NOT_OPEN)
+        {
+            rc = VINF_SUCCESS; /* Not important, so just report success instead. */
+        }
+        else
+        {
+            rc = RTErrConvertFromWin32(dwLastErr);
+            LogFunc(("Failed with %Rrc (0x%x)\n", rc, dwLastErr));
+        }
+    }
+    else
+        rc = VINF_SUCCESS;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Clears the clipboard for the current thread.
+ *
+ * @returns VBox status code.
+ */
+int SharedClipboardWinClear(void)
+{
+    LogFlowFuncEnter();
+    if (EmptyClipboard())
+        return VINF_SUCCESS;
+
+    const DWORD dwLastErr = GetLastError();
+    AssertReturn(dwLastErr != ERROR_CLIPBOARD_NOT_OPEN, VERR_INVALID_STATE);
+
+    int rc = RTErrConvertFromWin32(dwLastErr);
+    LogFunc(("Failed with %Rrc (0x%x)\n", rc, dwLastErr));
+    return rc;
+}
+
+/**
+ * Initializes a Shared Clipboard Windows context.
+ *
+ * @returns VBox status code.
+ * @param   pWinCtx             Shared Clipboard Windows context to initialize.
+ */
+int SharedClipboardWinCtxInit(PSHCLWINCTX pWinCtx)
+{
+    int rc = RTCritSectInit(&pWinCtx->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        /* Check that new Clipboard API is available. */
+        SharedClipboardWinCheckAndInitNewAPI(&pWinCtx->newAPI);
+        /* Do *not* check the rc, as the call might return VERR_SYMBOL_NOT_FOUND is the new API isn't available. */
+
+        pWinCtx->hWnd                 = NULL;
+        pWinCtx->hWndClipboardOwnerUs = NULL;
+        pWinCtx->hWndNextInChain      = NULL;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Destroys a Shared Clipboard Windows context.
+ *
+ * @param   pWinCtx             Shared Clipboard Windows context to destroy.
+ */
+void SharedClipboardWinCtxDestroy(PSHCLWINCTX pWinCtx)
+{
+    if (!pWinCtx)
+        return;
+
+    LogFlowFuncEnter();
+
+    if (RTCritSectIsInitialized(&pWinCtx->CritSect))
+    {
+        int rc2 = RTCritSectDelete(&pWinCtx->CritSect);
+        AssertRC(rc2);
+    }
+}
+
+/**
+ * Checks and initializes function pointer which are required for using
+ * the new clipboard API.
+ *
+ * @returns VBox status code, or VERR_SYMBOL_NOT_FOUND if the new API is not available.
+ * @param   pAPI                Where to store the retrieved function pointers.
+ *                              Will be set to NULL if the new API is not available.
+ */
+int SharedClipboardWinCheckAndInitNewAPI(PSHCLWINAPINEW pAPI)
+{
+    RTLDRMOD hUser32 = NIL_RTLDRMOD;
+    int rc = RTLdrLoadSystem("User32.dll", /* fNoUnload = */ true, &hUser32);
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTLdrGetSymbol(hUser32, "AddClipboardFormatListener", (void **)&pAPI->pfnAddClipboardFormatListener);
+        if (RT_SUCCESS(rc))
+        {
+            rc = RTLdrGetSymbol(hUser32, "RemoveClipboardFormatListener", (void **)&pAPI->pfnRemoveClipboardFormatListener);
+        }
+
+        RTLdrClose(hUser32);
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        LogRel(("Shared Clipboard: New Clipboard API enabled\n"));
+    }
+    else
+    {
+        RT_BZERO(pAPI, sizeof(SHCLWINAPINEW));
+        LogRel(("Shared Clipboard: New Clipboard API not available (%Rrc)\n", rc));
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Returns if the new clipboard API is available or not.
+ *
+ * @returns @c true if the new API is available, or @c false if not.
+ * @param   pAPI                Structure used for checking if the new clipboard API is available or not.
+ */
+bool SharedClipboardWinIsNewAPI(PSHCLWINAPINEW pAPI)
+{
+    if (!pAPI)
+        return false;
+    return pAPI->pfnAddClipboardFormatListener != NULL;
+}
+
+/**
+ * Adds ourselves into the chain of cliboard listeners.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                Windows clipboard context to use to add ourselves.
+ */
+int SharedClipboardWinChainAdd(PSHCLWINCTX pCtx)
+{
+    const PSHCLWINAPINEW pAPI = &pCtx->newAPI;
+
+    BOOL fRc;
+    if (SharedClipboardWinIsNewAPI(pAPI))
+        fRc = pAPI->pfnAddClipboardFormatListener(pCtx->hWnd);
+    else
+    {
+        SetLastError(NO_ERROR);
+        pCtx->hWndNextInChain = SetClipboardViewer(pCtx->hWnd);
+        fRc = pCtx->hWndNextInChain != NULL || GetLastError() == NO_ERROR;
+    }
+
+    int rc = VINF_SUCCESS;
+
+    if (!fRc)
+    {
+        const DWORD dwLastErr = GetLastError();
+        rc = RTErrConvertFromWin32(dwLastErr);
+        LogFunc(("Failed with %Rrc (0x%x)\n", rc, dwLastErr));
+    }
+
+    return rc;
+}
+
+/**
+ * Remove ourselves from the chain of cliboard listeners
+ *
+ * @returns VBox status code.
+ * @param   pCtx                Windows clipboard context to use to remove ourselves.
+ */
+int SharedClipboardWinChainRemove(PSHCLWINCTX pCtx)
+{
+    if (!pCtx->hWnd)
+        return VINF_SUCCESS;
+
+    const PSHCLWINAPINEW pAPI = &pCtx->newAPI;
+
+    BOOL fRc;
+    if (SharedClipboardWinIsNewAPI(pAPI))
+    {
+        fRc = pAPI->pfnRemoveClipboardFormatListener(pCtx->hWnd);
+    }
+    else
+    {
+        fRc = ChangeClipboardChain(pCtx->hWnd, pCtx->hWndNextInChain);
+        if (fRc)
+            pCtx->hWndNextInChain = NULL;
+    }
+
+    int rc = VINF_SUCCESS;
+
+    if (!fRc)
+    {
+        const DWORD dwLastErr = GetLastError();
+        rc = RTErrConvertFromWin32(dwLastErr);
+        LogFunc(("Failed with %Rrc (0x%x)\n", rc, dwLastErr));
+    }
+
+    return rc;
+}
+
+/**
+ * Callback which is invoked when we have successfully pinged ourselves down the
+ * clipboard chain.  We simply unset a boolean flag to say that we are responding.
+ * There is a race if a ping returns after the next one is initiated, but nothing
+ * very bad is likely to happen.
+ *
+ * @param   hWnd                Window handle to use for this callback. Not used currently.
+ * @param   uMsg                Message to handle. Not used currently.
+ * @param   dwData              Pointer to user-provided data. Contains our Windows clipboard context.
+ * @param   lResult             Additional data to pass. Not used currently.
+ */
+VOID CALLBACK SharedClipboardWinChainPingProc(HWND hWnd, UINT uMsg, ULONG_PTR dwData, LRESULT lResult) RT_NOTHROW_DEF
+{
+    RT_NOREF(hWnd);
+    RT_NOREF(uMsg);
+    RT_NOREF(lResult);
+
+    /** @todo r=andy Why not using SetWindowLongPtr for keeping the context? */
+    PSHCLWINCTX pCtx = (PSHCLWINCTX)dwData;
+    AssertPtrReturnVoid(pCtx);
+
+    pCtx->oldAPI.fCBChainPingInProcess = FALSE;
+}
+
+/**
+ * Passes a window message to the next window in the clipboard chain.
+ *
+ * @returns LRESULT
+ * @param   pWinCtx             Window context to use.
+ * @param   msg                 Window message to pass.
+ * @param   wParam              WPARAM to pass.
+ * @param   lParam              LPARAM to pass.
+ */
+LRESULT SharedClipboardWinChainPassToNext(PSHCLWINCTX pWinCtx,
+                                          UINT msg, WPARAM wParam, LPARAM lParam)
+{
+    LogFlowFuncEnter();
+
+    LRESULT lresultRc = 0;
+
+    if (pWinCtx->hWndNextInChain)
+    {
+        LogFunc(("hWndNextInChain=%p\n", pWinCtx->hWndNextInChain));
+
+        /* Pass the message to next window in the clipboard chain. */
+        DWORD_PTR dwResult;
+        lresultRc = SendMessageTimeout(pWinCtx->hWndNextInChain, msg, wParam, lParam, 0,
+                                       SHCL_WIN_CBCHAIN_TIMEOUT_MS, &dwResult);
+        if (!lresultRc)
+            lresultRc = dwResult;
+    }
+
+    LogFlowFunc(("lresultRc=%ld\n", lresultRc));
+    return lresultRc;
+}
+
+/**
+ * Converts a (registered or standard) Windows clipboard format to a VBox clipboard format.
+ *
+ * @returns Converted VBox clipboard format, or VBOX_SHCL_FMT_NONE if not found.
+ * @param   uFormat             Windows clipboard format to convert.
+ */
+SHCLFORMAT SharedClipboardWinClipboardFormatToVBox(UINT uFormat)
+{
+    /* Insert the requested clipboard format data into the clipboard. */
+    SHCLFORMAT vboxFormat = VBOX_SHCL_FMT_NONE;
+
+    switch (uFormat)
+    {
+        case CF_UNICODETEXT:
+            vboxFormat = VBOX_SHCL_FMT_UNICODETEXT;
+            break;
+
+        case CF_DIB:
+            vboxFormat = VBOX_SHCL_FMT_BITMAP;
+            break;
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+        /* CF_HDROP handles file system entries which are locally present
+         * on source for transferring to the target.
+         *
+         * This does *not* invoke any IDataObject / IStream implementations! */
+        case CF_HDROP:
+            vboxFormat = VBOX_SHCL_FMT_URI_LIST;
+            break;
+#endif
+
+        default:
+            if (uFormat >= 0xC000) /** Formats registered with RegisterClipboardFormat() start at this index. */
+            {
+                TCHAR szFormatName[256]; /** @todo r=andy Do we need Unicode support here as well? */
+                int cActual = GetClipboardFormatName(uFormat, szFormatName, sizeof(szFormatName) / sizeof(TCHAR));
+                if (cActual)
+                {
+                    LogFlowFunc(("uFormat=%u -> szFormatName=%s\n", uFormat, szFormatName));
+
+                    if (RTStrCmp(szFormatName, SHCL_WIN_REGFMT_HTML) == 0)
+                        vboxFormat = VBOX_SHCL_FMT_HTML;
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+                    /* These types invoke our IDataObject / IStream implementations. */
+                    else if (   (RTStrCmp(szFormatName, CFSTR_FILEDESCRIPTORA) == 0)
+                             || (RTStrCmp(szFormatName, CFSTR_FILECONTENTS)    == 0))
+                        vboxFormat = VBOX_SHCL_FMT_URI_LIST;
+                    /** @todo Do we need to handle CFSTR_FILEDESCRIPTORW here as well? */
+#endif
+                }
+            }
+            break;
+    }
+
+    LogFlowFunc(("uFormat=%u -> vboxFormat=0x%x\n", uFormat, vboxFormat));
+    return vboxFormat;
+}
+
+/**
+ * Retrieves all supported clipboard formats of a specific clipboard.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                Windows clipboard context to retrieve formats for.
+ * @param   pfFormats           Where to store the retrieved formats.
+ */
+int SharedClipboardWinGetFormats(PSHCLWINCTX pCtx, PSHCLFORMATS pfFormats)
+{
+    AssertPtrReturn(pCtx, VERR_INVALID_POINTER);
+    AssertPtrReturn(pfFormats, VERR_INVALID_POINTER);
+
+    SHCLFORMATS fFormats = VBOX_SHCL_FMT_NONE;
+
+    /* Query list of available formats and report to host. */
+    int rc = SharedClipboardWinOpen(pCtx->hWnd);
+    if (RT_SUCCESS(rc))
+    {
+        UINT uCurFormat = 0; /* Must be set to zero for EnumClipboardFormats(). */
+        while ((uCurFormat = EnumClipboardFormats(uCurFormat)) != 0)
+            fFormats |= SharedClipboardWinClipboardFormatToVBox(uCurFormat);
+
+        int rc2 = SharedClipboardWinClose();
+        AssertRC(rc2);
+        LogFlowFunc(("fFormats=%#x\n", fFormats));
+    }
+    else
+        LogFunc(("Failed with rc=%Rrc (fFormats=%#x)\n", rc, fFormats));
+
+    *pfFormats = fFormats;
+    return rc;
+}
+
+/**
+ * Extracts a field value from CF_HTML data.
+ *
+ * @returns VBox status code.
+ * @param   pszSrc      source in CF_HTML format.
+ * @param   pszOption   Name of CF_HTML field.
+ * @param   puValue     Where to return extracted value of CF_HTML field.
+ */
+int SharedClipboardWinGetCFHTMLHeaderValue(const char *pszSrc, const char *pszOption, uint32_t *puValue)
+{
+    AssertPtrReturn(pszSrc, VERR_INVALID_POINTER);
+    AssertPtrReturn(pszOption, VERR_INVALID_POINTER);
+
+    int rc = VERR_INVALID_PARAMETER;
+
+    const char *pszOptionValue = RTStrStr(pszSrc, pszOption);
+    if (pszOptionValue)
+    {
+        size_t cchOption = strlen(pszOption);
+        Assert(cchOption);
+
+        rc = RTStrToUInt32Ex(pszOptionValue + cchOption, NULL, 10, puValue);
+    }
+    return rc;
+}
+
+/**
+ * Check that the source string contains CF_HTML struct.
+ *
+ * @returns @c true if the @a pszSource string is in CF_HTML format.
+ * @param   pszSource   Source string to check.
+ */
+bool SharedClipboardWinIsCFHTML(const char *pszSource)
+{
+    return    RTStrStr(pszSource, "Version:") != NULL
+           && RTStrStr(pszSource, "StartHTML:") != NULL;
+}
+
+/**
+ * Converts clipboard data from CF_HTML format to MIME clipboard format.
+ *
+ * Returns allocated buffer that contains html converted to text/html mime type
+ *
+ * @returns VBox status code.
+ * @param   pszSource   The input.
+ * @param   cch         The length of the input.
+ * @param   ppszOutput  Where to return the result.  Free using RTMemFree.
+ * @param   pcbOutput   Where to the return length of the result (bytes/chars).
+ */
+int SharedClipboardWinConvertCFHTMLToMIME(const char *pszSource, const uint32_t cch, char **ppszOutput, uint32_t *pcbOutput)
+{
+    Assert(pszSource);
+    Assert(cch);
+    Assert(ppszOutput);
+    Assert(pcbOutput);
+
+    uint32_t offStart;
+    int rc = SharedClipboardWinGetCFHTMLHeaderValue(pszSource, "StartFragment:", &offStart);
+    if (RT_SUCCESS(rc))
+    {
+        uint32_t offEnd;
+        rc = SharedClipboardWinGetCFHTMLHeaderValue(pszSource, "EndFragment:", &offEnd);
+        if (RT_SUCCESS(rc))
+        {
+            if (   offStart > 0
+                && offEnd > 0
+                && offEnd >= offStart
+                && offEnd <= cch)
+            {
+                uint32_t cchSubStr = offEnd - offStart;
+                char *pszResult = (char *)RTMemAlloc(cchSubStr + 1);
+                if (pszResult)
+                {
+                    rc = RTStrCopyEx(pszResult, cchSubStr + 1, pszSource + offStart, cchSubStr);
+                    if (RT_SUCCESS(rc))
+                    {
+                        *ppszOutput = pszResult;
+                        *pcbOutput  = (uint32_t)(cchSubStr + 1);
+                        rc = VINF_SUCCESS;
+                    }
+                    else
+                    {
+                        LogRelFlowFunc(("Error: Unknown CF_HTML format. Expected EndFragment. rc = %Rrc\n", rc));
+                        RTMemFree(pszResult);
+                    }
+                }
+                else
+                {
+                    LogRelFlowFunc(("Error: Unknown CF_HTML format. Expected EndFragment\n"));
+                    rc = VERR_NO_MEMORY;
+                }
+            }
+            else
+            {
+                LogRelFlowFunc(("Error: CF_HTML out of bounds - offStart=%#x offEnd=%#x cch=%#x\n", offStart, offEnd, cch));
+                rc = VERR_INVALID_PARAMETER;
+            }
+        }
+        else
+        {
+            LogRelFlowFunc(("Error: Unknown CF_HTML format. Expected EndFragment. rc = %Rrc\n", rc));
+            rc = VERR_INVALID_PARAMETER;
+        }
+    }
+    else
+    {
+        LogRelFlowFunc(("Error: Unknown CF_HTML format. Expected StartFragment. rc = %Rrc\n", rc));
+        rc = VERR_INVALID_PARAMETER;
+    }
+
+    return rc;
+}
+
+/**
+ * Converts source UTF-8 MIME HTML clipboard data to UTF-8 CF_HTML format.
+ *
+ * This is just encapsulation work, slapping a header on the data.
+ *
+ * It allocates [..]
+ *
+ * Calculations:
+ *   Header length = format Length + (2*(10 - 5('%010d'))('digits')) - 2('%s') = format length + 8
+ *   EndHtml       = Header length + fragment length
+ *   StartHtml     = 105(constant)
+ *   StartFragment = 141(constant) may vary if the header html content will be extended
+ *   EndFragment   = Header length + fragment length - 38(ending length)
+ *
+ * For more format details, check out:
+ * https://docs.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/aa767917(v=vs.85)
+ *
+ * @returns VBox status code.
+ * @param   pszSource   Source buffer that contains utf-16 string in mime html format
+ * @param   cb          Size of source buffer in bytes
+ * @param   ppszOutput  Where to return the allocated output buffer to put converted UTF-8
+ *                      CF_HTML clipboard data.  This function allocates memory for this.
+ * @param   pcbOutput   Where to return the size of allocated result buffer in bytes/chars, including zero terminator
+ *
+ * @note    output buffer should be free using RTMemFree()
+ * @note    Everything inside of fragment can be UTF8. Windows allows it. Everything in header should be Latin1.
+ */
+int SharedClipboardWinConvertMIMEToCFHTML(const char *pszSource, size_t cb, char **ppszOutput, uint32_t *pcbOutput)
+{
+    Assert(ppszOutput);
+    Assert(pcbOutput);
+    Assert(pszSource);
+    Assert(cb);
+
+    /*
+     * Check that input UTF-8 and properly zero terminated.
+     * Note! The zero termination may come earlier than 'cb' - 1, that's fine.
+     */
+    int rc = RTStrValidateEncodingEx(pszSource, cb, RTSTR_VALIDATE_ENCODING_ZERO_TERMINATED);
+    if (RT_SUCCESS(rc))
+    { /* likely */ }
+    else
+    {
+        LogRelFlowFunc(("Error: invalid source fragment. rc = %Rrc\n", rc));
+        return rc;
+    }
+    size_t const cchFragment = strlen(pszSource); /* Unfortunately the validator doesn't return the length. */
+
+    /*
+     * @StartHtml     - Absolute offset of <html>
+     * @EndHtml       - Size of the whole resulting text (excluding ending zero char)
+     * @StartFragment - Absolute position after <!--StartFragment-->
+     * @EndFragment   - Absolute position of <!--EndFragment-->
+     *
+     * Note! The offset are zero padded to max width so we don't have any variations due to those.
+     * Note! All values includes CRLFs inserted into text.
+     *
+     * Calculations:
+     *   Header length = Format sample length - 2 ('%s')
+     *   EndHtml       = Header length + fragment length
+     *   StartHtml     = 101(constant)
+     *   StartFragment = 137(constant)
+     *   EndFragment   = Header length + fragment length - 38 (ending length)
+     */
+    static const char s_szFormatSample[] =
+    /*   0:   */ "Version:1.0\r\n"
+    /*  13:   */ "StartHTML:000000101\r\n"
+    /*  34:   */ "EndHTML:%0000009u\r\n" // END HTML = Header length + fragment length
+    /*  53:   */ "StartFragment:000000137\r\n"
+    /*  78:   */ "EndFragment:%0000009u\r\n"
+    /* 101:   */ "<html>\r\n"
+    /* 109:   */ "<body>\r\n"
+    /* 117:   */ "<!--StartFragment-->"
+    /* 137:   */ "%s"
+    /* 137+2: */ "<!--EndFragment-->\r\n"
+    /* 157+2: */ "</body>\r\n"
+    /* 166+2: */ "</html>\r\n"
+    /* 175+2: */ ;
+    AssertCompile(sizeof(s_szFormatSample) == 175 + 2 + 1);
+
+    /* Calculate parameters of the CF_HTML header */
+    size_t const cchHeader      = sizeof(s_szFormatSample) - 2 /*%s*/ - 1 /*'\0'*/;
+    size_t const offEndHtml     = cchHeader + cchFragment;
+    size_t const offEndFragment = cchHeader + cchFragment - 38; /* 175-137 = 38 */
+    char *pszResult = (char *)RTMemAlloc(offEndHtml + 1);
+    AssertLogRelReturn(pszResult, VERR_NO_MEMORY);
+
+    /* Format resulting CF_HTML string: */
+    size_t cchFormatted = RTStrPrintf(pszResult, offEndHtml + 1, s_szFormatSample, offEndHtml, offEndFragment, pszSource);
+    Assert(offEndHtml == cchFormatted);
+
+#ifdef VBOX_STRICT
+    /*
+     * Check the calculations.
+     */
+
+    /* check 'StartFragment:' value */
+    static const char s_szStartFragment[] = "<!--StartFragment-->";
+    const char *pszRealStartFragment = RTStrStr(pszResult, s_szStartFragment);
+    Assert(&pszRealStartFragment[sizeof(s_szStartFragment) - 1] - pszResult == 137);
+
+    /* check 'EndFragment:' value */
+    static const char s_szEndFragment[] = "<!--EndFragment-->";
+    const char *pszRealEndFragment = RTStrStr(pszResult, s_szEndFragment);
+    Assert((size_t)(pszRealEndFragment - pszResult) == offEndFragment);
+#endif
+
+    *ppszOutput = pszResult;
+    *pcbOutput = (uint32_t)cchFormatted + 1;
+    Assert(*pcbOutput == cchFormatted + 1);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Handles the WM_CHANGECBCHAIN code.
+ *
+ * @returns LRESULT
+ * @param   pWinCtx             Windows context to use.
+ * @param   hWnd                Window handle to use.
+ * @param   msg                 Message ID to pass on.
+ * @param   wParam              wParam to pass on
+ * @param   lParam              lParam to pass on.
+ */
+LRESULT SharedClipboardWinHandleWMChangeCBChain(PSHCLWINCTX pWinCtx,
+                                              HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
+{
+    LRESULT lresultRc = 0;
+
+    LogFlowFuncEnter();
+
+    if (SharedClipboardWinIsNewAPI(&pWinCtx->newAPI))
+    {
+        lresultRc = DefWindowProc(hWnd, msg, wParam, lParam);
+    }
+    else /* Old API */
+    {
+        HWND hwndRemoved = (HWND)wParam;
+        HWND hwndNext    = (HWND)lParam;
+
+        if (hwndRemoved == pWinCtx->hWndNextInChain)
+        {
+            /* The window that was next to our in the chain is being removed.
+             * Relink to the new next window.
+             */
+            pWinCtx->hWndNextInChain = hwndNext;
+        }
+        else
+        {
+            if (pWinCtx->hWndNextInChain)
+            {
+                /* Pass the message further. */
+                DWORD_PTR dwResult;
+                lresultRc = SendMessageTimeout(pWinCtx->hWndNextInChain, WM_CHANGECBCHAIN, wParam, lParam, 0,
+                                                SHCL_WIN_CBCHAIN_TIMEOUT_MS,
+                                                &dwResult);
+                if (!lresultRc)
+                    lresultRc = (LRESULT)dwResult;
+            }
+        }
+    }
+
+    LogFlowFunc(("lresultRc=%ld\n", lresultRc));
+    return lresultRc;
+}
+
+/**
+ * Handles the WM_DESTROY code.
+ *
+ * @returns VBox status code.
+ * @param   pWinCtx             Windows context to use.
+ */
+int SharedClipboardWinHandleWMDestroy(PSHCLWINCTX pWinCtx)
+{
+    LogFlowFuncEnter();
+
+    int rc = VINF_SUCCESS;
+
+    /* MS recommends to remove from Clipboard chain in this callback. */
+    SharedClipboardWinChainRemove(pWinCtx);
+
+    if (pWinCtx->oldAPI.timerRefresh)
+    {
+        Assert(pWinCtx->hWnd);
+        KillTimer(pWinCtx->hWnd, 0);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Handles the WM_RENDERALLFORMATS message.
+ *
+ * @returns VBox status code.
+ * @param   pWinCtx             Windows context to use.
+ * @param   hWnd                Window handle to use.
+ */
+int SharedClipboardWinHandleWMRenderAllFormats(PSHCLWINCTX pWinCtx, HWND hWnd)
+{
+    RT_NOREF(pWinCtx);
+
+    LogFlowFuncEnter();
+
+    /* Do nothing. The clipboard formats will be unavailable now, because the
+     * windows is to be destroyed and therefore the guest side becomes inactive.
+     */
+    int rc = SharedClipboardWinOpen(hWnd);
+    if (RT_SUCCESS(rc))
+    {
+        SharedClipboardWinClear();
+        SharedClipboardWinClose();
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Handles the WM_TIMER code, which is needed if we're running with the so-called "old" Windows clipboard API.
+ * Does nothing if we're running with the "new" Windows API.
+ *
+ * @returns VBox status code.
+ * @param   pWinCtx             Windows context to use.
+ */
+int SharedClipboardWinHandleWMTimer(PSHCLWINCTX pWinCtx)
+{
+    int rc = VINF_SUCCESS;
+
+    if (!SharedClipboardWinIsNewAPI(&pWinCtx->newAPI)) /* Only run when using the "old" Windows API. */
+    {
+        LogFlowFuncEnter();
+
+        HWND hViewer = GetClipboardViewer();
+
+        /* Re-register ourselves in the clipboard chain if our last ping
+         * timed out or there seems to be no valid chain. */
+        if (!hViewer || pWinCtx->oldAPI.fCBChainPingInProcess)
+        {
+            SharedClipboardWinChainRemove(pWinCtx);
+            SharedClipboardWinChainAdd(pWinCtx);
+       }
+
+       /* Start a new ping by passing a dummy WM_CHANGECBCHAIN to be
+        * processed by ourselves to the chain. */
+       pWinCtx->oldAPI.fCBChainPingInProcess = TRUE;
+
+       hViewer = GetClipboardViewer();
+       if (hViewer)
+           SendMessageCallback(hViewer, WM_CHANGECBCHAIN, (WPARAM)pWinCtx->hWndNextInChain, (LPARAM)pWinCtx->hWndNextInChain,
+                               SharedClipboardWinChainPingProc, (ULONG_PTR)pWinCtx);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Announces a clipboard format to the Windows clipboard.
+ *
+ * The actual rendering (setting) of the clipboard data will be done later with
+ * a separate WM_RENDERFORMAT message.
+ *
+ * @returns VBox status code. VERR_NOT_SUPPORTED if the format is not supported / handled.
+ * @param   pWinCtx             Windows context to use.
+ * @param   fFormats            Clipboard format(s) to announce.
+ */
+static int sharedClipboardWinAnnounceFormats(PSHCLWINCTX pWinCtx, SHCLFORMATS fFormats)
+{
+    LogFunc(("fFormats=0x%x\n", fFormats));
+
+    /*
+     * Set the clipboard formats.
+     */
+    static struct
+    {
+        uint32_t        fVBoxFormat;
+        UINT            uWinFormat;
+        const char     *pszWinFormat;
+        const char     *pszLog;
+    } s_aFormats[] =
+    {
+        { VBOX_SHCL_FMT_UNICODETEXT,    CF_UNICODETEXT, NULL,                 "CF_UNICODETEXT" },
+        { VBOX_SHCL_FMT_BITMAP,         CF_DIB,         NULL,                 "CF_DIB" },
+        { VBOX_SHCL_FMT_HTML,           0,              SHCL_WIN_REGFMT_HTML, "SHCL_WIN_REGFMT_HTML" },
+    };
+    unsigned    cSuccessfullySet = 0;
+    SHCLFORMATS fFormatsLeft     = fFormats;
+    int         rc               = VINF_SUCCESS;
+    for (uintptr_t i = 0; i < RT_ELEMENTS(s_aFormats) && fFormatsLeft != 0; i++)
+    {
+        if (fFormatsLeft & s_aFormats[i].fVBoxFormat)
+        {
+            LogFunc(("%s\n", s_aFormats[i].pszLog));
+            fFormatsLeft &= ~s_aFormats[i].fVBoxFormat;
+
+            /* Reg format if needed: */
+            UINT uWinFormat = s_aFormats[i].uWinFormat;
+            if (!uWinFormat)
+            {
+                uWinFormat = RegisterClipboardFormat(s_aFormats[i].pszWinFormat);
+                AssertContinue(uWinFormat != 0);
+            }
+
+            /* Tell the clipboard we've got data upon a request.  We check the
+               last error here as hClip will be NULL even on success (despite
+               what MSDN says). */
+            SetLastError(NO_ERROR);
+            HANDLE hClip = SetClipboardData(uWinFormat, NULL);
+            DWORD dwErr = GetLastError();
+            if (dwErr == NO_ERROR || hClip != NULL)
+                cSuccessfullySet++;
+            else
+            {
+                AssertMsgFailed(("%s/%u: %u\n", s_aFormats[i].pszLog, uWinFormat, dwErr));
+                rc = RTErrConvertFromWin32(dwErr);
+            }
+        }
+    }
+
+    /*
+     * Consider setting anything a success, converting any error into
+     * informational status.  Unsupport error only happens if all formats
+     * were unsupported.
+     */
+    if (cSuccessfullySet > 0)
+    {
+        pWinCtx->hWndClipboardOwnerUs = GetClipboardOwner();
+        if (RT_FAILURE(rc))
+            rc = -rc;
+    }
+    else if (RT_SUCCESS(rc) && fFormatsLeft != 0)
+    {
+        LogFunc(("Unsupported formats: %#x (%#x)\n", fFormatsLeft, fFormats));
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Opens the clipboard, clears it, announces @a fFormats and closes it.
+ *
+ * The actual rendering (setting) of the clipboard data will be done later with
+ * a separate WM_RENDERFORMAT message.
+ *
+ * @returns VBox status code. VERR_NOT_SUPPORTED if the format is not supported / handled.
+ * @param   pWinCtx     Windows context to use.
+ * @param   fFormats    Clipboard format(s) to announce.
+ * @param   hWnd        The window handle to use as owner.
+ */
+int SharedClipboardWinClearAndAnnounceFormats(PSHCLWINCTX pWinCtx, SHCLFORMATS fFormats, HWND hWnd)
+{
+    int rc = SharedClipboardWinOpen(hWnd);
+    if (RT_SUCCESS(rc))
+    {
+        SharedClipboardWinClear();
+
+        rc = sharedClipboardWinAnnounceFormats(pWinCtx, fFormats);
+        Assert(pWinCtx->hWndClipboardOwnerUs == hWnd || pWinCtx->hWndClipboardOwnerUs == NULL);
+
+        SharedClipboardWinClose();
+    }
+    return rc;
+}
+
+/**
+ * Writes (places) clipboard data into the Windows clipboard.
+ *
+ * @returns VBox status code.
+ * @param   cfFormat            Windows clipboard format to write data for.
+ * @param   pvData              Pointer to actual clipboard data to write.
+ * @param   cbData              Size (in bytes) of actual clipboard data to write.
+ *
+ * @note    ASSUMES that the clipboard has already been opened.
+ */
+int SharedClipboardWinDataWrite(UINT cfFormat, void *pvData, uint32_t cbData)
+{
+    AssertPtrReturn(pvData, VERR_INVALID_POINTER);
+    AssertReturn   (cbData, VERR_INVALID_PARAMETER);
+
+    int rc = VINF_SUCCESS;
+
+    HANDLE hMem = GlobalAlloc(GMEM_DDESHARE | GMEM_MOVEABLE, cbData);
+
+    LogFlowFunc(("hMem=%p\n", hMem));
+
+    if (hMem)
+    {
+        void *pMem = GlobalLock(hMem);
+
+        LogFlowFunc(("pMem=%p, GlobalSize=%zu\n", pMem, GlobalSize(hMem)));
+
+        if (pMem)
+        {
+            LogFlowFunc(("Setting data\n"));
+
+            memcpy(pMem, pvData, cbData);
+
+            /* The memory must be unlocked before inserting to the Clipboard. */
+            GlobalUnlock(hMem);
+
+            /* 'hMem' contains the host clipboard data.
+             * size is 'cb' and format is 'format'.
+             */
+            HANDLE hClip = SetClipboardData(cfFormat, hMem);
+
+            LogFlowFunc(("hClip=%p\n", hClip));
+
+            if (hClip)
+            {
+                /* The hMem ownership has gone to the system. Nothing to do. */
+            }
+            else
+                rc = RTErrConvertFromWin32(GetLastError());
+        }
+        else
+            rc = VERR_ACCESS_DENIED;
+
+        GlobalFree(hMem);
+    }
+    else
+        rc = RTErrConvertFromWin32(GetLastError());
+
+    if (RT_FAILURE(rc))
+        LogFunc(("Setting clipboard data failed with %Rrc\n", rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+
+/**
+ * Creates an Shared Clipboard transfer by announcing transfer data  (via IDataObject) to Windows.
+ *
+ * This creates the necessary IDataObject + IStream implementations and initiates the actual transfers required for getting
+ * the meta data. Whether or not the actual (file++) transfer(s) are happening is up to the user (at some point) later then.
+ *
+ * @returns VBox status code.
+ * @param   pWinCtx             Windows context to use.
+ * @param   pTransferCtxCtx     Transfer contextto use.
+ * @param   pTransfer           Shared Clipboard transfer to use.
+ */
+int SharedClipboardWinTransferCreate(PSHCLWINCTX pWinCtx, PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("pWinCtx=%p\n", pWinCtx));
+
+    AssertReturn(pTransfer->pvUser == NULL, VERR_WRONG_ORDER);
+
+    /* Make sure to enter the critical section before setting the clipboard data, as otherwise WM_CLIPBOARDUPDATE
+     * might get called *before* we had the opportunity to set pWinCtx->hWndClipboardOwnerUs below. */
+    int rc = RTCritSectEnter(&pWinCtx->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        SharedClipboardWinTransferCtx *pWinURITransferCtx = new SharedClipboardWinTransferCtx();
+        if (pWinURITransferCtx)
+        {
+            pTransfer->pvUser = pWinURITransferCtx;
+            pTransfer->cbUser = sizeof(SharedClipboardWinTransferCtx);
+
+            pWinURITransferCtx->pDataObj = new SharedClipboardWinDataObject(pTransfer);
+            if (pWinURITransferCtx->pDataObj)
+            {
+                rc = pWinURITransferCtx->pDataObj->Init();
+                if (RT_SUCCESS(rc))
+                {
+                    SharedClipboardWinClose();
+                    /* Note: Clipboard must be closed first before calling OleSetClipboard(). */
+
+                    /** @todo There is a potential race between SharedClipboardWinClose() and OleSetClipboard(),
+                     *        where another application could own the clipboard (open), and thus the call to
+                     *        OleSetClipboard() will fail. Needs (better) fixing. */
+                    HRESULT hr = S_OK;
+
+                    for (unsigned uTries = 0; uTries < 3; uTries++)
+                    {
+                        hr = OleSetClipboard(pWinURITransferCtx->pDataObj);
+                        if (SUCCEEDED(hr))
+                        {
+                            Assert(OleIsCurrentClipboard(pWinURITransferCtx->pDataObj) == S_OK); /* Sanity. */
+
+                            /*
+                             * Calling OleSetClipboard() changed the clipboard owner, which in turn will let us receive
+                             * a WM_CLIPBOARDUPDATE message. To not confuse ourselves with our own clipboard owner changes,
+                             * save a new window handle and deal with it in WM_CLIPBOARDUPDATE.
+                             */
+                            pWinCtx->hWndClipboardOwnerUs = GetClipboardOwner();
+
+                            LogFlowFunc(("hWndClipboardOwnerUs=%p\n", pWinCtx->hWndClipboardOwnerUs));
+                            break;
+                        }
+
+                        LogFlowFunc(("Failed with %Rhrc (try %u/3)\n", hr, uTries + 1));
+                        RTThreadSleep(500); /* Wait a bit. */
+                    }
+
+                    if (FAILED(hr))
+                    {
+                        rc = VERR_ACCESS_DENIED; /** @todo Fudge; fix this. */
+                        LogRel(("Shared Clipboard: Failed with %Rhrc when setting data object to clipboard\n", hr));
+                    }
+                }
+            }
+            else
+                rc = VERR_NO_MEMORY;
+        }
+        else
+            rc = VERR_NO_MEMORY;
+
+        int rc2 = RTCritSectLeave(&pWinCtx->CritSect);
+        AssertRC(rc2);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Destroys implementation-specific data for an Shared Clipboard transfer.
+ *
+ * @param   pWinCtx             Windows context to use.
+ * @param   pTransfer           Shared Clipboard transfer to create implementation-specific data for.
+ */
+void SharedClipboardWinTransferDestroy(PSHCLWINCTX pWinCtx, PSHCLTRANSFER pTransfer)
+{
+    RT_NOREF(pWinCtx);
+
+    if (!pTransfer)
+        return;
+
+    LogFlowFuncEnter();
+
+    if (pTransfer->pvUser)
+    {
+        Assert(pTransfer->cbUser == sizeof(SharedClipboardWinTransferCtx));
+        SharedClipboardWinTransferCtx *pWinURITransferCtx = (SharedClipboardWinTransferCtx *)pTransfer->pvUser;
+        Assert(pWinURITransferCtx);
+
+        if (pWinURITransferCtx->pDataObj)
+        {
+            delete pWinURITransferCtx->pDataObj;
+            pWinURITransferCtx->pDataObj = NULL;
+        }
+
+        delete pWinURITransferCtx;
+
+        pTransfer->pvUser = NULL;
+        pTransfer->cbUser = 0;
+    }
+}
+
+/**
+ * Retrieves the roots for a transfer by opening the clipboard and getting the clipboard data
+ * as string list (CF_HDROP), assigning it to the transfer as roots then.
+ *
+ * @returns VBox status code.
+ * @param   pWinCtx             Windows context to use.
+ * @param   pTransfer           Transfer to get roots for.
+ */
+int SharedClipboardWinGetRoots(PSHCLWINCTX pWinCtx, PSHCLTRANSFER pTransfer)
+{
+    AssertPtrReturn(pWinCtx,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+
+    Assert(ShClTransferGetSource(pTransfer) == SHCLSOURCE_LOCAL); /* Sanity. */
+
+    int rc = SharedClipboardWinOpen(pWinCtx->hWnd);
+    if (RT_SUCCESS(rc))
+    {
+        /* The data data in CF_HDROP format, as the files are locally present and don't need to be
+         * presented as a IDataObject or IStream. */
+        HANDLE hClip = hClip = GetClipboardData(CF_HDROP);
+        if (hClip)
+        {
+            HDROP hDrop = (HDROP)GlobalLock(hClip);
+            if (hDrop)
+            {
+                char    *papszList = NULL;
+                uint32_t cbList;
+                rc = SharedClipboardWinDropFilesToStringList((DROPFILES *)hDrop, &papszList, &cbList);
+
+                GlobalUnlock(hClip);
+
+                if (RT_SUCCESS(rc))
+                {
+                    rc = ShClTransferRootsSet(pTransfer,
+                                              papszList, cbList + 1 /* Include termination */);
+                    RTStrFree(papszList);
+                }
+            }
+            else
+                LogRel(("Shared Clipboard: Unable to lock clipboard data, last error: %ld\n", GetLastError()));
+        }
+        else
+            LogRel(("Shared Clipboard: Unable to retrieve clipboard data from clipboard (CF_HDROP), last error: %ld\n",
+                    GetLastError()));
+
+        SharedClipboardWinClose();
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Converts a DROPFILES (HDROP) structure to a string list, separated by \r\n.
+ * Does not do any locking on the input data.
+ *
+ * @returns VBox status code.
+ * @param   pDropFiles          Pointer to DROPFILES structure to convert.
+ * @param   papszList           Where to store the allocated string list.
+ * @param   pcbList             Where to store the size (in bytes) of the allocated string list.
+ */
+int SharedClipboardWinDropFilesToStringList(DROPFILES *pDropFiles, char **papszList, uint32_t *pcbList)
+{
+    AssertPtrReturn(pDropFiles, VERR_INVALID_POINTER);
+    AssertPtrReturn(papszList,  VERR_INVALID_POINTER);
+    AssertPtrReturn(pcbList,    VERR_INVALID_POINTER);
+
+    /* Do we need to do Unicode stuff? */
+    const bool fUnicode = RT_BOOL(pDropFiles->fWide);
+
+    /* Get the offset of the file list. */
+    Assert(pDropFiles->pFiles >= sizeof(DROPFILES));
+
+    /* Note: This is *not* pDropFiles->pFiles! DragQueryFile only
+     *       will work with the plain storage medium pointer! */
+    HDROP hDrop = (HDROP)(pDropFiles);
+
+    int rc = VINF_SUCCESS;
+
+    /* First, get the file count. */
+    /** @todo Does this work on Windows 2000 / NT4? */
+    char *pszFiles = NULL;
+    uint32_t cchFiles = 0;
+    UINT cFiles = DragQueryFile(hDrop, UINT32_MAX /* iFile */, NULL /* lpszFile */, 0 /* cchFile */);
+
+    LogFlowFunc(("Got %RU16 file(s), fUnicode=%RTbool\n", cFiles, fUnicode));
+
+    for (UINT i = 0; i < cFiles; i++)
+    {
+        UINT cchFile = DragQueryFile(hDrop, i /* File index */, NULL /* Query size first */, 0 /* cchFile */);
+        Assert(cchFile);
+
+        if (RT_FAILURE(rc))
+            break;
+
+        char *pszFileUtf8 = NULL; /* UTF-8 version. */
+        UINT cchFileUtf8 = 0;
+        if (fUnicode)
+        {
+            /* Allocate enough space (including terminator). */
+            WCHAR *pwszFile = (WCHAR *)RTMemAlloc((cchFile + 1) * sizeof(WCHAR));
+            if (pwszFile)
+            {
+                const UINT cwcFileUtf16 = DragQueryFileW(hDrop, i /* File index */,
+                                                         pwszFile, cchFile + 1 /* Include terminator */);
+
+                AssertMsg(cwcFileUtf16 == cchFile, ("cchFileUtf16 (%RU16) does not match cchFile (%RU16)\n",
+                                                    cwcFileUtf16, cchFile));
+                RT_NOREF(cwcFileUtf16);
+
+                rc = RTUtf16ToUtf8(pwszFile, &pszFileUtf8);
+                if (RT_SUCCESS(rc))
+                {
+                    cchFileUtf8 = (UINT)strlen(pszFileUtf8);
+                    Assert(cchFileUtf8);
+                }
+
+                RTMemFree(pwszFile);
+            }
+            else
+                rc = VERR_NO_MEMORY;
+        }
+        else /* ANSI */
+        {
+            /* Allocate enough space (including terminator). */
+            char *pszFileANSI = (char *)RTMemAlloc((cchFile + 1) * sizeof(char));
+            UINT  cchFileANSI = 0;
+            if (pszFileANSI)
+            {
+                cchFileANSI = DragQueryFileA(hDrop, i /* File index */,
+                                             pszFileANSI, cchFile + 1 /* Include terminator */);
+
+                AssertMsg(cchFileANSI == cchFile, ("cchFileANSI (%RU16) does not match cchFile (%RU16)\n",
+                                                   cchFileANSI, cchFile));
+
+                /* Convert the ANSI codepage to UTF-8. */
+                rc = RTStrCurrentCPToUtf8(&pszFileUtf8, pszFileANSI);
+                if (RT_SUCCESS(rc))
+                {
+                    cchFileUtf8 = (UINT)strlen(pszFileUtf8);
+                }
+            }
+            else
+                rc = VERR_NO_MEMORY;
+        }
+
+        if (RT_SUCCESS(rc))
+        {
+            LogFlowFunc(("\tFile: %s (cchFile=%RU16)\n", pszFileUtf8, cchFileUtf8));
+
+            LogRel2(("Shared Clipboard: Adding file '%s' to transfer\n", pszFileUtf8));
+
+            rc = RTStrAAppendExN(&pszFiles, 1 /* cPairs */, pszFileUtf8, strlen(pszFileUtf8));
+            cchFiles += (uint32_t)strlen(pszFileUtf8);
+        }
+
+        if (pszFileUtf8)
+            RTStrFree(pszFileUtf8);
+
+        if (RT_FAILURE(rc))
+        {
+            LogFunc(("Error handling file entry #%u, rc=%Rrc\n", i, rc));
+            break;
+        }
+
+        /* Add separation between filenames.
+         * Note: Also do this for the last element of the list. */
+        rc = RTStrAAppendExN(&pszFiles, 1 /* cPairs */, "\r\n", 2 /* Bytes */);
+        if (RT_SUCCESS(rc))
+            cchFiles += 2; /* Include \r\n */
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        cchFiles += 1; /* Add string termination. */
+        uint32_t cbFiles = cchFiles * sizeof(char); /* UTF-8. */
+
+        LogFlowFunc(("cFiles=%u, cchFiles=%RU32, cbFiles=%RU32, pszFiles=0x%p\n",
+                     cFiles, cchFiles, cbFiles, pszFiles));
+
+        *papszList = pszFiles;
+        *pcbList   = cbFiles;
+    }
+    else
+    {
+        if (pszFiles)
+            RTStrFree(pszFiles);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
diff --git a/src/VBox/GuestHost/SharedClipboard/clipboard-x11.cpp b/src/VBox/GuestHost/SharedClipboard/clipboard-x11.cpp
new file mode 100644
index 00000000..5e57d85e
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/clipboard-x11.cpp
@@ -0,0 +1,2428 @@
+/** @file
+ * Shared Clipboard: Common X11 code.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+/* Note: to automatically run regression tests on the Shared Clipboard,
+ * execute the tstClipboardGH-X11 testcase.  If you often make changes to the
+ * clipboard code, adding the line
+ *
+ *   OTHERS += $(PATH_tstClipboardGH-X11)/tstClipboardGH-X11.run
+ *
+ * to LocalConfig.kmk will cause the tests to be run every time the code is
+ * changed.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+
+#include <errno.h>
+
+#include <dlfcn.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#ifdef RT_OS_SOLARIS
+#include <tsol/label.h>
+#endif
+
+#include <X11/Xlib.h>
+#include <X11/Xatom.h>
+#include <X11/Intrinsic.h>
+#include <X11/Shell.h>
+#include <X11/Xproto.h>
+#include <X11/StringDefs.h>
+
+#include <iprt/assert.h>
+#include <iprt/types.h>
+#include <iprt/mem.h>
+#include <iprt/semaphore.h>
+#include <iprt/thread.h>
+#include <iprt/utf16.h>
+#include <iprt/uri.h>
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+# include <iprt/cpp/list.h>
+# include <iprt/cpp/ministring.h>
+# include <VBox/GuestHost/SharedClipboard-transfers.h>
+#endif
+
+#include <VBox/log.h>
+#include <VBox/version.h>
+
+#include <VBox/GuestHost/SharedClipboard.h>
+#include <VBox/GuestHost/SharedClipboard-x11.h>
+#include <VBox/GuestHost/clipboard-helper.h>
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+
+/** Own macro for declaring function visibility / linkage based on whether this
+ *  code runs as part of test cases or not. */
+#ifdef TESTCASE
+# define SHCL_X11_DECL(x) x
+#else
+# define SHCL_X11_DECL(x) static x
+#endif
+
+
+/*********************************************************************************************************************************
+*   Externals                                                                                                                    *
+*********************************************************************************************************************************/
+#ifdef TESTCASE
+extern void tstThreadScheduleCall(void (*proc)(void *, void *), void *client_data);
+extern void tstClipRequestData(SHCLX11CTX* pCtx, SHCLX11FMTIDX target, void *closure);
+extern void tstRequestTargets(SHCLX11CTX* pCtx);
+#endif
+
+
+/*********************************************************************************************************************************
+*   Prototypes                                                                                                                   *
+*********************************************************************************************************************************/
+class formats;
+SHCL_X11_DECL(Atom) clipGetAtom(PSHCLX11CTX pCtx, const char *pszName);
+SHCL_X11_DECL(void) clipQueryX11Targets(PSHCLX11CTX pCtx);
+
+static int          clipInitInternal(PSHCLX11CTX pCtx);
+static void         clipUninitInternal(PSHCLX11CTX pCtx);
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+
+/**
+ * The table maps X11 names to data formats
+ * and to the corresponding VBox clipboard formats.
+ */
+SHCL_X11_DECL(SHCLX11FMTTABLE) g_aFormats[] =
+{
+    { "INVALID",                            SHCLX11FMT_INVALID,     VBOX_SHCL_FMT_NONE },
+
+    { "UTF8_STRING",                        SHCLX11FMT_UTF8,        VBOX_SHCL_FMT_UNICODETEXT },
+    { "text/plain;charset=UTF-8",           SHCLX11FMT_UTF8,        VBOX_SHCL_FMT_UNICODETEXT },
+    { "text/plain;charset=utf-8",           SHCLX11FMT_UTF8,        VBOX_SHCL_FMT_UNICODETEXT },
+    { "STRING",                             SHCLX11FMT_TEXT,        VBOX_SHCL_FMT_UNICODETEXT },
+    { "TEXT",                               SHCLX11FMT_TEXT,        VBOX_SHCL_FMT_UNICODETEXT },
+    { "text/plain",                         SHCLX11FMT_TEXT,        VBOX_SHCL_FMT_UNICODETEXT },
+
+    { "text/html",                          SHCLX11FMT_HTML,        VBOX_SHCL_FMT_HTML },
+    { "text/html;charset=utf-8",            SHCLX11FMT_HTML,        VBOX_SHCL_FMT_HTML },
+    { "application/x-moz-nativehtml",       SHCLX11FMT_HTML,        VBOX_SHCL_FMT_HTML },
+
+    { "image/bmp",                          SHCLX11FMT_BMP,         VBOX_SHCL_FMT_BITMAP },
+    { "image/x-bmp",                        SHCLX11FMT_BMP,         VBOX_SHCL_FMT_BITMAP },
+    { "image/x-MS-bmp",                     SHCLX11FMT_BMP,         VBOX_SHCL_FMT_BITMAP },
+    /** @todo Inkscape exports image/png but not bmp... */
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    { "text/uri-list",                      SHCLX11FMT_URI_LIST,    VBOX_SHCL_FMT_URI_LIST },
+    { "x-special/gnome-copied-files",       SHCLX11FMT_URI_LIST,    VBOX_SHCL_FMT_URI_LIST },
+    { "x-special/nautilus-clipboard",       SHCLX11FMT_URI_LIST,    VBOX_SHCL_FMT_URI_LIST },
+    { "application/x-kde-cutselection",     SHCLX11FMT_URI_LIST,    VBOX_SHCL_FMT_URI_LIST },
+    /** @todo Anything else we need to add here? */
+    /** @todo Add Wayland / Weston support. */
+#endif
+};
+
+
+#ifdef TESTCASE
+# ifdef RT_OS_SOLARIS_10
+char XtStrings [] = "";
+WidgetClassRec* applicationShellWidgetClass;
+char XtShellStrings [] = "";
+int XmbTextPropertyToTextList(
+    Display*            /* display */,
+    XTextProperty*      /* text_prop */,
+    char***             /* list_return */,
+    int*                /* count_return */
+)
+{
+  return 0;
+}
+# else
+const char XtStrings [] = "";
+_WidgetClassRec* applicationShellWidgetClass;
+const char XtShellStrings [] = "";
+# endif /* RT_OS_SOLARIS_10 */
+#endif /* TESTCASE */
+
+
+/*********************************************************************************************************************************
+*   Defines                                                                                                                      *
+*********************************************************************************************************************************/
+
+#define SHCL_MAX_X11_FORMATS        RT_ELEMENTS(g_aFormats)
+
+
+/*********************************************************************************************************************************
+*   Internal structures                                                                                                          *
+*********************************************************************************************************************************/
+
+/**
+ * A structure containing information about where to store a request
+ * for the X11 clipboard contents.
+ */
+typedef struct _CLIPREADX11CBREQ
+{
+    /** The format VBox would like the data in. */
+    SHCLFORMAT       uFmtVBox;
+    /** The format we requested from X11. */
+    SHCLX11FMTIDX    idxFmtX11;
+    /** The clipboard context this request is associated with. */
+    SHCLX11CTX      *pCtx;
+    /** The request structure passed in from the backend. */
+    CLIPREADCBREQ   *pReq;
+} CLIPREADX11CBREQ;
+
+
+
+#ifdef TESTCASE
+/**
+ * Return the max. number of elements in the X11 format table.
+ * Used by the testing code in tstClipboardGH-X11.cpp
+ * which cannot use RT_ELEMENTS(g_aFormats) directly.
+ *
+ * @return size_t The number of elements in the g_aFormats array.
+ */
+SHCL_X11_DECL(size_t) clipReportMaxX11Formats(void)
+{
+    return (RT_ELEMENTS(g_aFormats));
+}
+#endif
+
+/**
+ * Returns the atom corresponding to a supported X11 format.
+ *
+ * @returns Found atom to the corresponding X11 format.
+ * @param   pCtx                The X11 clipboard context to use.
+ * @param   uFmtIdx             Format index to look up atom for.
+ */
+static Atom clipAtomForX11Format(PSHCLX11CTX pCtx, SHCLX11FMTIDX uFmtIdx)
+{
+    AssertReturn(uFmtIdx < RT_ELEMENTS(g_aFormats), 0);
+    return clipGetAtom(pCtx, g_aFormats[uFmtIdx].pcszAtom);
+}
+
+/**
+ * Returns the SHCLX11FMT corresponding to a supported X11 format.
+ *
+ * @return  SHCLX11FMT for a specific format index.
+ * @param   uFmtIdx             Format index to look up SHCLX11CLIPFMT for.
+ */
+SHCL_X11_DECL(SHCLX11FMT) clipRealFormatForX11Format(SHCLX11FMTIDX uFmtIdx)
+{
+    AssertReturn(uFmtIdx < RT_ELEMENTS(g_aFormats), SHCLX11FMT_INVALID);
+    return g_aFormats[uFmtIdx].enmFmtX11;
+}
+
+/**
+ * Returns the VBox format corresponding to a supported X11 format.
+ *
+ * @return  SHCLFORMAT for a specific format index.
+ * @param   uFmtIdx             Format index to look up VBox format for.
+ */
+static SHCLFORMAT clipVBoxFormatForX11Format(SHCLX11FMTIDX uFmtIdx)
+{
+    AssertReturn(uFmtIdx < RT_ELEMENTS(g_aFormats), VBOX_SHCL_FMT_NONE);
+    return g_aFormats[uFmtIdx].uFmtVBox;
+}
+
+/**
+ * Looks up the X11 format matching a given X11 atom.
+ *
+ * @returns The format on success, NIL_CLIPX11FORMAT on failure.
+ * @param   pCtx                The X11 clipboard context to use.
+ * @param   atomFormat          Atom to look up X11 format for.
+ */
+static SHCLX11FMTIDX clipFindX11FormatByAtom(PSHCLX11CTX pCtx, Atom atomFormat)
+{
+    for (unsigned i = 0; i < RT_ELEMENTS(g_aFormats); ++i)
+        if (clipAtomForX11Format(pCtx, i) == atomFormat)
+        {
+            LogFlowFunc(("Returning index %u for atom '%s'\n", i, g_aFormats[i].pcszAtom));
+            return i;
+        }
+    return NIL_CLIPX11FORMAT;
+}
+
+/**
+ * Enumerates supported X11 clipboard formats corresponding to given VBox formats.
+ *
+ * @returns The next matching X11 format index in the list, or NIL_CLIPX11FORMAT if there are no more.
+ * @param   uFormatsVBox            VBox formats to enumerate supported X11 clipboard formats for.
+ * @param   lastFmtIdx              The value returned from the last call of this function.
+ *                                  Use NIL_CLIPX11FORMAT to start the enumeration.
+ */
+static SHCLX11FMTIDX clipEnumX11Formats(SHCLFORMATS uFormatsVBox,
+                                        SHCLX11FMTIDX lastFmtIdx)
+{
+    for (unsigned i = lastFmtIdx + 1; i < RT_ELEMENTS(g_aFormats); ++i)
+    {
+        if (uFormatsVBox & clipVBoxFormatForX11Format(i))
+            return i;
+    }
+
+    return NIL_CLIPX11FORMAT;
+}
+
+/**
+ * Array of structures for mapping Xt widgets to context pointers.  We
+ * need this because the widget clipboard callbacks do not pass user data.
+ */
+static struct
+{
+    /** Pointer to widget we want to associate the context with. */
+    Widget      pWidget;
+    /** Pointer to X11 context associated with the widget. */
+    PSHCLX11CTX pCtx;
+} g_aContexts[VBOX_SHARED_CLIPBOARD_X11_CONNECTIONS_MAX];
+
+/**
+ * Registers a new X11 clipboard context.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                The X11 clipboard context to use.
+ */
+static int clipRegisterContext(PSHCLX11CTX pCtx)
+{
+    AssertPtrReturn(pCtx, VERR_INVALID_PARAMETER);
+
+    bool fFound = false;
+
+    Widget pWidget = pCtx->pWidget;
+    AssertReturn(pWidget != NULL, VERR_INVALID_PARAMETER);
+
+    for (unsigned i = 0; i < RT_ELEMENTS(g_aContexts); ++i)
+    {
+        AssertReturn(   (g_aContexts[i].pWidget != pWidget)
+                     && (g_aContexts[i].pCtx != pCtx), VERR_WRONG_ORDER);
+        if (g_aContexts[i].pWidget == NULL && !fFound)
+        {
+            AssertReturn(g_aContexts[i].pCtx == NULL, VERR_INTERNAL_ERROR);
+            g_aContexts[i].pWidget = pWidget;
+            g_aContexts[i].pCtx = pCtx;
+            fFound = true;
+        }
+    }
+
+    return fFound ? VINF_SUCCESS : VERR_OUT_OF_RESOURCES;
+}
+
+/**
+ * Unregister an X11 clipboard context.
+ *
+ * @param   pCtx                The X11 clipboard context to use.
+ */
+static void clipUnregisterContext(PSHCLX11CTX pCtx)
+{
+    AssertPtrReturnVoid(pCtx);
+
+    Widget pWidget = pCtx->pWidget;
+    AssertPtrReturnVoid(pWidget);
+
+    bool fFound = false;
+    for (unsigned i = 0; i < RT_ELEMENTS(g_aContexts); ++i)
+    {
+        Assert(!fFound || g_aContexts[i].pWidget != pWidget);
+        if (g_aContexts[i].pWidget == pWidget)
+        {
+            Assert(g_aContexts[i].pCtx != NULL);
+            g_aContexts[i].pWidget = NULL;
+            g_aContexts[i].pCtx = NULL;
+            fFound = true;
+        }
+    }
+}
+
+/**
+ * Finds a X11 clipboard context for a specific X11 widget.
+ *
+ * @returns Pointer to associated X11 clipboard context if found, or NULL if not found.
+ * @param   pWidget                 X11 widget to return X11 clipboard context for.
+ */
+static PSHCLX11CTX clipLookupContext(Widget pWidget)
+{
+    AssertPtrReturn(pWidget, NULL);
+
+    for (unsigned i = 0; i < RT_ELEMENTS(g_aContexts); ++i)
+    {
+        if (g_aContexts[i].pWidget == pWidget)
+        {
+            Assert(g_aContexts[i].pCtx != NULL);
+            return g_aContexts[i].pCtx;
+        }
+    }
+
+    return NULL;
+}
+
+/**
+ * Converts an atom name string to an X11 atom, looking it up in a cache before asking the server.
+ *
+ * @returns Found X11 atom.
+ * @param   pCtx                The X11 clipboard context to use.
+ * @param   pcszName            Name of atom to return atom for.
+ */
+SHCL_X11_DECL(Atom) clipGetAtom(PSHCLX11CTX pCtx, const char *pcszName)
+{
+    AssertPtrReturn(pcszName, None);
+    return XInternAtom(XtDisplay(pCtx->pWidget), pcszName, False);
+}
+
+/** String written to the wakeup pipe. */
+#define WAKE_UP_STRING      "WakeUp!"
+/** Length of the string written. */
+#define WAKE_UP_STRING_LEN  ( sizeof(WAKE_UP_STRING) - 1 )
+
+/**
+ * Schedules a function call to run on the Xt event thread by passing it to
+ * the application context as a 0ms timeout and waking up the event loop by
+ * writing to the wakeup pipe which it monitors.
+ */
+static int clipThreadScheduleCall(PSHCLX11CTX pCtx,
+                                  void (*proc)(void *, void *),
+                                  void *client_data)
+{
+    LogFlowFunc(("proc=%p, client_data=%p\n", proc, client_data));
+
+#ifndef TESTCASE
+    AssertReturn(pCtx, VERR_INVALID_POINTER);
+    AssertReturn(pCtx->pAppContext, VERR_INVALID_POINTER);
+
+    XtAppAddTimeOut(pCtx->pAppContext, 0, (XtTimerCallbackProc)proc,
+                    (XtPointer)client_data);
+    ssize_t cbWritten = write(pCtx->wakeupPipeWrite, WAKE_UP_STRING, WAKE_UP_STRING_LEN);
+    Assert(cbWritten == WAKE_UP_STRING_LEN);
+    RT_NOREF(cbWritten);
+#else
+    RT_NOREF(pCtx);
+    tstThreadScheduleCall(proc, client_data);
+#endif
+
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+    return VINF_SUCCESS;
+}
+
+/**
+ * Reports the formats currently supported by the X11 clipboard to VBox.
+ *
+ * @note    Runs in Xt event thread.
+ *
+ * @param   pCtx                The X11 clipboard context to use.
+ */
+static void clipReportFormatsToVBox(PSHCLX11CTX pCtx)
+{
+    SHCLFORMATS vboxFmt  = clipVBoxFormatForX11Format(pCtx->idxFmtText);
+                vboxFmt |= clipVBoxFormatForX11Format(pCtx->idxFmtBmp);
+                vboxFmt |= clipVBoxFormatForX11Format(pCtx->idxFmtHTML);
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+                vboxFmt |= clipVBoxFormatForX11Format(pCtx->idxFmtURI);
+#endif
+
+    LogFlowFunc(("idxFmtText=%u ('%s'), idxFmtBmp=%u ('%s'), idxFmtHTML=%u ('%s')",
+                 pCtx->idxFmtText, g_aFormats[pCtx->idxFmtText].pcszAtom,
+                 pCtx->idxFmtBmp,  g_aFormats[pCtx->idxFmtBmp].pcszAtom,
+                 pCtx->idxFmtHTML, g_aFormats[pCtx->idxFmtHTML].pcszAtom));
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    LogFlowFunc((", idxFmtURI=%u ('%s')", pCtx->idxFmtURI, g_aFormats[pCtx->idxFmtURI].pcszAtom));
+#endif
+    LogFlow((" -> vboxFmt=%#x\n", vboxFmt));
+
+#ifdef LOG_ENABLED
+    char *pszFmts = ShClFormatsToStrA(vboxFmt);
+    AssertPtrReturnVoid(pszFmts);
+    LogRel2(("Shared Clipboard: X11 reported available VBox formats '%s'\n", pszFmts));
+    RTStrFree(pszFmts);
+#endif
+
+    pCtx->Callbacks.pfnReportFormats(pCtx->pFrontend, vboxFmt, NULL /* pvUser */);
+}
+
+/**
+ * Forgets which formats were previously in the X11 clipboard.  Called when we
+ * grab the clipboard.
+ *
+ * @param   pCtx                The X11 clipboard context to use.
+ */
+static void clipResetX11Formats(PSHCLX11CTX pCtx)
+{
+    LogFlowFuncEnter();
+
+    pCtx->idxFmtText = 0;
+    pCtx->idxFmtBmp  = 0;
+    pCtx->idxFmtHTML = 0;
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    pCtx->idxFmtURI  = 0;
+#endif
+}
+
+/**
+ * Tells VBox that X11 currently has nothing in its clipboard.
+ *
+ * @param  pCtx                 The X11 clipboard context to use.
+ */
+SHCL_X11_DECL(void) clipReportEmpty(PSHCLX11CTX pCtx)
+{
+    clipResetX11Formats(pCtx);
+    clipReportFormatsToVBox(pCtx);
+}
+
+/**
+ * Go through an array of X11 clipboard targets to see if they contain a text
+ * format we can support, and if so choose the ones we prefer (e.g. we like
+ * UTF-8 better than plain text).
+ *
+ * @return Index to supported X clipboard format.
+ * @param  pCtx                 The X11 clipboard context to use.
+ * @param  paIdxFmtTargets      The list of targets.
+ * @param  cTargets             The size of the list in @a pTargets.
+ */
+SHCL_X11_DECL(SHCLX11FMTIDX) clipGetTextFormatFromTargets(PSHCLX11CTX pCtx,
+                                                          SHCLX11FMTIDX *paIdxFmtTargets,
+                                                          size_t cTargets)
+{
+    AssertPtrReturn(pCtx, NIL_CLIPX11FORMAT);
+    AssertReturn(RT_VALID_PTR(paIdxFmtTargets) || cTargets == 0, NIL_CLIPX11FORMAT);
+
+    SHCLX11FMTIDX idxFmtText = NIL_CLIPX11FORMAT;
+    SHCLX11FMT    fmtTextX11 = SHCLX11FMT_INVALID;
+    for (unsigned i = 0; i < cTargets; ++i)
+    {
+        SHCLX11FMTIDX idxFmt = paIdxFmtTargets[i];
+        if (idxFmt != NIL_CLIPX11FORMAT)
+        {
+            if (   (clipVBoxFormatForX11Format(idxFmt) == VBOX_SHCL_FMT_UNICODETEXT)
+                && fmtTextX11 < clipRealFormatForX11Format(idxFmt))
+            {
+                fmtTextX11 = clipRealFormatForX11Format(idxFmt);
+                idxFmtText = idxFmt;
+            }
+        }
+    }
+    return idxFmtText;
+}
+
+/**
+ * Goes through an array of X11 clipboard targets to see if they contain a bitmap
+ * format we can support, and if so choose the ones we prefer (e.g. we like
+ * BMP better than PNG because we don't have to convert).
+ *
+ * @return Supported X clipboard format.
+ * @param  pCtx                 The X11 clipboard context to use.
+ * @param  paIdxFmtTargets      The list of targets.
+ * @param  cTargets             The size of the list in @a pTargets.
+ */
+static SHCLX11FMTIDX clipGetBitmapFormatFromTargets(PSHCLX11CTX pCtx,
+                                                    SHCLX11FMTIDX *paIdxFmtTargets,
+                                                    size_t cTargets)
+{
+    AssertPtrReturn(pCtx, NIL_CLIPX11FORMAT);
+    AssertReturn(RT_VALID_PTR(paIdxFmtTargets) || cTargets == 0, NIL_CLIPX11FORMAT);
+
+    SHCLX11FMTIDX idxFmtBmp = NIL_CLIPX11FORMAT;
+    SHCLX11FMT    fmtBmpX11 = SHCLX11FMT_INVALID;
+    for (unsigned i = 0; i < cTargets; ++i)
+    {
+        SHCLX11FMTIDX idxFmt = paIdxFmtTargets[i];
+        if (idxFmt != NIL_CLIPX11FORMAT)
+        {
+            if (   (clipVBoxFormatForX11Format(idxFmt) == VBOX_SHCL_FMT_BITMAP)
+                && fmtBmpX11 < clipRealFormatForX11Format(idxFmt))
+            {
+                fmtBmpX11 = clipRealFormatForX11Format(idxFmt);
+                idxFmtBmp = idxFmt;
+            }
+        }
+    }
+    return idxFmtBmp;
+}
+
+/**
+ * Goes through an array of X11 clipboard targets to see if they contain a HTML
+ * format we can support, and if so choose the ones we prefer.
+ *
+ * @return Supported X clipboard format.
+ * @param  pCtx                 The X11 clipboard context to use.
+ * @param  paIdxFmtTargets      The list of targets.
+ * @param  cTargets             The size of the list in @a pTargets.
+ */
+static SHCLX11FMTIDX clipGetHtmlFormatFromTargets(PSHCLX11CTX pCtx,
+                                                  SHCLX11FMTIDX *paIdxFmtTargets,
+                                                  size_t cTargets)
+{
+    AssertPtrReturn(pCtx, NIL_CLIPX11FORMAT);
+    AssertReturn(RT_VALID_PTR(paIdxFmtTargets) || cTargets == 0, NIL_CLIPX11FORMAT);
+
+    SHCLX11FMTIDX idxFmtHTML = NIL_CLIPX11FORMAT;
+    SHCLX11FMT    fmxHTMLX11 = SHCLX11FMT_INVALID;
+    for (unsigned i = 0; i < cTargets; ++i)
+    {
+        SHCLX11FMTIDX idxFmt = paIdxFmtTargets[i];
+        if (idxFmt != NIL_CLIPX11FORMAT)
+        {
+            if (   (clipVBoxFormatForX11Format(idxFmt) == VBOX_SHCL_FMT_HTML)
+                && fmxHTMLX11 < clipRealFormatForX11Format(idxFmt))
+            {
+                fmxHTMLX11 = clipRealFormatForX11Format(idxFmt);
+                idxFmtHTML = idxFmt;
+            }
+        }
+    }
+    return idxFmtHTML;
+}
+
+# ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+/**
+ * Goes through an array of X11 clipboard targets to see if they contain an URI list
+ * format we can support, and if so choose the ones we prefer.
+ *
+ * @return Supported X clipboard format.
+ * @param  pCtx                 The X11 clipboard context to use.
+ * @param  paIdxFmtTargets      The list of targets.
+ * @param  cTargets             The size of the list in @a pTargets.
+ */
+static SHCLX11FMTIDX clipGetURIListFormatFromTargets(PSHCLX11CTX pCtx,
+                                                     SHCLX11FMTIDX *paIdxFmtTargets,
+                                                     size_t cTargets)
+{
+    AssertPtrReturn(pCtx, NIL_CLIPX11FORMAT);
+    AssertReturn(RT_VALID_PTR(paIdxFmtTargets) || cTargets == 0, NIL_CLIPX11FORMAT);
+
+    SHCLX11FMTIDX idxFmtURI = NIL_CLIPX11FORMAT;
+    SHCLX11FMT    fmtURIX11 = SHCLX11FMT_INVALID;
+    for (unsigned i = 0; i < cTargets; ++i)
+    {
+        SHCLX11FMTIDX idxFmt = paIdxFmtTargets[i];
+        if (idxFmt != NIL_CLIPX11FORMAT)
+        {
+            if (   (clipVBoxFormatForX11Format(idxFmt) == VBOX_SHCL_FMT_URI_LIST)
+                && fmtURIX11 < clipRealFormatForX11Format(idxFmt))
+            {
+                fmtURIX11 = clipRealFormatForX11Format(idxFmt);
+                idxFmtURI = idxFmt;
+            }
+        }
+    }
+    return idxFmtURI;
+}
+# endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
+/**
+ * Goes through an array of X11 clipboard targets to see if we can support any
+ * of them and if relevant to choose the ones we prefer (e.g. we like Utf8
+ * better than plain text).
+ *
+ * @param  pCtx                 The X11 clipboard context to use.
+ * @param  paIdxFmtTargets      The list of targets.
+ * @param  cTargets             The size of the list in @a pTargets.
+ */
+static void clipGetFormatsFromTargets(PSHCLX11CTX pCtx,
+                                      SHCLX11FMTIDX *paIdxFmtTargets, size_t cTargets)
+{
+    AssertPtrReturnVoid(pCtx);
+    AssertPtrReturnVoid(paIdxFmtTargets);
+
+    SHCLX11FMTIDX idxFmtText = clipGetTextFormatFromTargets(pCtx, paIdxFmtTargets, cTargets);
+    if (pCtx->idxFmtText != idxFmtText)
+        pCtx->idxFmtText = idxFmtText;
+
+    pCtx->idxFmtBmp = SHCLX11FMT_INVALID; /* not yet supported */ /** @todo r=andy Check this. */
+    SHCLX11FMTIDX idxFmtBmp = clipGetBitmapFormatFromTargets(pCtx, paIdxFmtTargets, cTargets);
+    if (pCtx->idxFmtBmp != idxFmtBmp)
+        pCtx->idxFmtBmp = idxFmtBmp;
+
+    SHCLX11FMTIDX idxFmtHTML = clipGetHtmlFormatFromTargets(pCtx, paIdxFmtTargets, cTargets);
+    if (pCtx->idxFmtHTML != idxFmtHTML)
+        pCtx->idxFmtHTML = idxFmtHTML;
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    SHCLX11FMTIDX idxFmtURI = clipGetURIListFormatFromTargets(pCtx, paIdxFmtTargets, cTargets);
+    if (pCtx->idxFmtURI != idxFmtURI)
+        pCtx->idxFmtURI = idxFmtURI;
+#endif
+}
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_XT_BUSY
+DECLINLINE(bool) clipGetXtBusy(PSHCLX11CTX pCtx)
+{
+    LogFlowFunc(("fXtBusy=%RTbool, fXtNeedsUpdate=%RTbool\n", pCtx->fXtBusy, pCtx->fXtNeedsUpdate));
+    return pCtx->fXtBusy;
+}
+
+DECLINLINE(bool) clipGetXtNeedsUpdate(PSHCLX11CTX pCtx)
+{
+    LogFlowFunc(("fXtBusy=%RTbool, fXtNeedsUpdate=%RTbool\n", pCtx->fXtBusy, pCtx->fXtNeedsUpdate));
+    return pCtx->fXtNeedsUpdate;
+}
+
+DECLINLINE(bool) clipSetXtBusy(PSHCLX11CTX pCtx, bool fBusy)
+{
+    pCtx->fXtBusy = fBusy;
+    LogFlowFunc(("fXtBusy=%RTbool, fXtNeedsUpdate=%RTbool\n", pCtx->fXtBusy, pCtx->fXtNeedsUpdate));
+    return pCtx->fXtBusy;
+}
+
+DECLINLINE(bool) clipSetXtNeedsUpdate(PSHCLX11CTX pCtx, bool fNeedsUpdate)
+{
+    pCtx->fXtNeedsUpdate = fNeedsUpdate;
+    LogFlowFunc(("fXtBusy=%RTbool, fXtNeedsUpdate=%RTbool\n", pCtx->fXtBusy, pCtx->fXtNeedsUpdate));
+    return pCtx->fXtNeedsUpdate;
+}
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_XT_BUSY */
+
+/**
+ * Updates the context's information about targets currently supported by X11,
+ * based on an array of X11 atoms.
+ *
+ * @param  pCtx                 The X11 clipboard context to use.
+ * @param  pTargets             The array of atoms describing the targets supported.
+ * @param  cTargets             The size of the array @a pTargets.
+ */
+SHCL_X11_DECL(void) clipUpdateX11Targets(PSHCLX11CTX pCtx, SHCLX11FMTIDX *paIdxFmtTargets, size_t cTargets)
+{
+    LogFlowFuncEnter();
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_XT_BUSY
+    clipSetXtBusy(pCtx, false);
+    if (clipGetXtNeedsUpdate(pCtx))
+    {
+        /* We may already be out of date. */
+        clipSetXtNeedsUpdate(pCtx, false);
+        clipQueryX11Targets(pCtx);
+        return;
+    }
+#endif
+
+    if (paIdxFmtTargets == NULL)
+    {
+        /* No data available */
+        clipReportEmpty(pCtx);
+        return;
+    }
+
+    clipGetFormatsFromTargets(pCtx, paIdxFmtTargets, cTargets);
+    clipReportFormatsToVBox(pCtx);
+}
+
+/**
+ * Notifies the VBox clipboard about available data formats ("targets" on X11),
+ * based on the information obtained from the X11 clipboard.
+ *
+ * @note  Callback installed by clipQueryX11Targets() for XtGetSelectionValue().
+ * @note  This function is treated as API glue, and as such is not part of any
+ *        unit test.  So keep it simple, be paranoid and log everything.
+ */
+SHCL_X11_DECL(void) clipQueryX11TargetsCallback(Widget widget, XtPointer pClient,
+                                                Atom * /* selection */, Atom *atomType,
+                                                XtPointer pValue, long unsigned int *pcLen,
+                                                int *piFormat)
+{
+    RT_NOREF(piFormat);
+
+    PSHCLX11CTX pCtx = reinterpret_cast<SHCLX11CTX *>(pClient);
+
+    LogFlowFunc(("pValue=%p, *pcLen=%u, *atomType=%d%s\n",
+                 pValue, *pcLen, *atomType, *atomType == XT_CONVERT_FAIL ? " (XT_CONVERT_FAIL)" : ""));
+
+    Atom *pAtoms = (Atom *)pValue;
+
+    unsigned cFormats = *pcLen;
+
+    LogRel2(("Shared Clipboard: Querying X11 formats ...\n"));
+    LogRel2(("Shared Clipboard: %u X11 formats were found\n", cFormats));
+
+    SHCLX11FMTIDX *paIdxFmt = NULL;
+    if (   cFormats
+        && pValue
+        && (*atomType != XT_CONVERT_FAIL /* time out */))
+    {
+        /* Allocated array to hold the format indices. */
+        paIdxFmt = (SHCLX11FMTIDX *)RTMemAllocZ(cFormats * sizeof(SHCLX11FMTIDX));
+    }
+
+#if !defined(TESTCASE)
+    if (pValue)
+    {
+        for (unsigned i = 0; i < cFormats; ++i)
+        {
+            if (pAtoms[i])
+            {
+                char *pszName = XGetAtomName(XtDisplay(widget), pAtoms[i]);
+                LogRel2(("Shared Clipboard: Found X11 format '%s'\n", pszName));
+                XFree(pszName);
+            }
+            else
+                LogFunc(("Found empty target\n"));
+        }
+    }
+#endif
+
+    if (paIdxFmt)
+    {
+        for (unsigned i = 0; i < cFormats; ++i)
+        {
+            for (unsigned j = 0; j < RT_ELEMENTS(g_aFormats); ++j)
+            {
+                Atom target = XInternAtom(XtDisplay(widget),
+                                          g_aFormats[j].pcszAtom, False);
+                if (*(pAtoms + i) == target)
+                    paIdxFmt[i] = j;
+            }
+#if !defined(TESTCASE)
+            if (paIdxFmt[i] != SHCLX11FMT_INVALID)
+                LogRel2(("Shared Clipboard: Reporting X11 format '%s'\n", g_aFormats[paIdxFmt[i]].pcszAtom));
+#endif
+        }
+    }
+    else
+        LogFunc(("Reporting empty targets (none reported or allocation failure)\n"));
+
+    clipUpdateX11Targets(pCtx, paIdxFmt, cFormats);
+    RTMemFree(paIdxFmt);
+
+    XtFree(reinterpret_cast<char *>(pValue));
+}
+
+/**
+ * Queries the current formats ("targets") of the X11 clipboard ("CLIPBOARD").
+ *
+ * @param   pCtx                The X11 clipboard context to use.
+ */
+SHCL_X11_DECL(void) clipQueryX11Targets(PSHCLX11CTX pCtx)
+{
+#ifndef TESTCASE
+
+# ifdef VBOX_WITH_SHARED_CLIPBOARD_XT_BUSY
+    if (clipGetXtBusy(pCtx))
+    {
+        clipSetXtNeedsUpdate(pCtx, true);
+        return;
+    }
+    clipSetXtBusy(pCtx, true);
+# endif
+
+    XtGetSelectionValue(pCtx->pWidget,
+                        clipGetAtom(pCtx, "CLIPBOARD"),
+                        clipGetAtom(pCtx, "TARGETS"),
+                        clipQueryX11TargetsCallback, pCtx,
+                        CurrentTime);
+#else
+    tstRequestTargets(pCtx);
+#endif
+}
+
+typedef struct
+{
+    int type;                   /* event base */
+    unsigned long serial;
+    Bool send_event;
+    Display *display;
+    Window window;
+    int subtype;
+    Window owner;
+    Atom selection;
+    Time timestamp;
+    Time selection_timestamp;
+} XFixesSelectionNotifyEvent;
+
+#ifndef TESTCASE
+/**
+ * Waits until an event arrives and handle it if it is an XFIXES selection
+ * event, which Xt doesn't know about.
+ *
+ * @param   pCtx                The X11 clipboard context to use.
+ */
+static void clipPeekEventAndDoXFixesHandling(PSHCLX11CTX pCtx)
+{
+    union
+    {
+        XEvent event;
+        XFixesSelectionNotifyEvent fixes;
+    } event = { { 0 } };
+
+    if (XtAppPeekEvent(pCtx->pAppContext, &event.event))
+    {
+        if (   (event.event.type == pCtx->fixesEventBase)
+            && (event.fixes.owner != XtWindow(pCtx->pWidget)))
+        {
+            if (   (event.fixes.subtype == 0  /* XFixesSetSelectionOwnerNotify */)
+                && (event.fixes.owner != 0))
+                clipQueryX11Targets(pCtx);
+            else
+                clipReportEmpty(pCtx);
+        }
+    }
+}
+
+/**
+ * The main loop of our X11 event thread.
+ *
+ * @returns VBox status code.
+ * @param   hThreadSelf             Associated thread handle.
+ * @param   pvUser                  Pointer to the X11 clipboard context to use.
+ */
+static DECLCALLBACK(int) clipThreadMain(RTTHREAD hThreadSelf, void *pvUser)
+{
+    PSHCLX11CTX pCtx = (PSHCLX11CTX)pvUser;
+    AssertPtr(pCtx);
+
+    LogFlowFunc(("pCtx=%p\n", pCtx));
+
+    bool fSignalled = false; /* Whether we have signalled the parent already or not. */
+
+    int rc = clipInitInternal(pCtx);
+    if (RT_SUCCESS(rc))
+    {
+        rc = clipRegisterContext(pCtx);
+        if (RT_SUCCESS(rc))
+        {
+            if (pCtx->fGrabClipboardOnStart)
+                clipQueryX11Targets(pCtx);
+
+            pCtx->fThreadStarted = true;
+
+            /* We're now ready to run, tell parent. */
+            int rc2 = RTThreadUserSignal(hThreadSelf);
+            AssertRC(rc2);
+
+            fSignalled = true;
+
+            while (XtAppGetExitFlag(pCtx->pAppContext) == FALSE)
+            {
+                clipPeekEventAndDoXFixesHandling(pCtx);
+                XtAppProcessEvent(pCtx->pAppContext, XtIMAll);
+            }
+
+            LogRel(("Shared Clipboard: X11 event thread exiting\n"));
+
+            clipUnregisterContext(pCtx);
+        }
+        else
+        {
+            LogRel(("Shared Clipboard: unable to register clip context: %Rrc\n", rc));
+        }
+
+        clipUninitInternal(pCtx);
+    }
+
+    if (!fSignalled) /* Signal parent if we didn't do so yet. */
+    {
+        int rc2 = RTThreadUserSignal(hThreadSelf);
+        AssertRC(rc2);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Worker function for stopping the clipboard which runs on the event
+ * thread.
+ *
+ * @param   pvUserData          Pointer to the X11 clipboard context to use.
+ */
+static void clipThreadSignalStop(void *pvUserData, void *)
+{
+    PSHCLX11CTX pCtx = (PSHCLX11CTX)pvUserData;
+
+    /* This might mean that we are getting stopped twice. */
+    Assert(pCtx->pWidget != NULL);
+
+    /* Set the termination flag to tell the Xt event loop to exit.  We
+     * reiterate that any outstanding requests from the X11 event loop to
+     * the VBox part *must* have returned before we do this. */
+    XtAppSetExitFlag(pCtx->pAppContext);
+}
+
+/**
+ * Sets up the XFixes library and load the XFixesSelectSelectionInput symbol.
+ */
+static int clipLoadXFixes(Display *pDisplay, PSHCLX11CTX pCtx)
+{
+    int rc;
+
+    void *hFixesLib = dlopen("libXfixes.so.1", RTLD_LAZY);
+    if (!hFixesLib)
+        hFixesLib = dlopen("libXfixes.so.2", RTLD_LAZY);
+    if (!hFixesLib)
+        hFixesLib = dlopen("libXfixes.so.3", RTLD_LAZY);
+    if (!hFixesLib)
+        hFixesLib = dlopen("libXfixes.so.4", RTLD_LAZY);
+    if (hFixesLib)
+    {
+        /* For us, a NULL function pointer is a failure */
+        pCtx->fixesSelectInput = (void (*)(Display *, Window, Atom, long unsigned int))
+                                 (uintptr_t)dlsym(hFixesLib, "XFixesSelectSelectionInput");
+        if (pCtx->fixesSelectInput)
+        {
+            int dummy1 = 0;
+            int dummy2 = 0;
+            if (XQueryExtension(pDisplay, "XFIXES", &dummy1, &pCtx->fixesEventBase, &dummy2) != 0)
+            {
+                if (pCtx->fixesEventBase >= 0)
+                {
+                    rc = VINF_SUCCESS;
+                }
+                else
+                {
+                    LogRel(("Shared Clipboard: fixesEventBase is less than zero: %d\n", pCtx->fixesEventBase));
+                    rc = VERR_NOT_SUPPORTED;
+                }
+            }
+            else
+            {
+                LogRel(("Shared Clipboard: XQueryExtension failed\n"));
+                rc = VERR_NOT_SUPPORTED;
+            }
+        }
+        else
+        {
+            LogRel(("Shared Clipboard: Symbol XFixesSelectSelectionInput not found!\n"));
+            rc = VERR_NOT_SUPPORTED;
+        }
+    }
+    else
+    {
+        LogRel(("Shared Clipboard: libxFixes.so.* not found!\n"));
+        rc = VERR_NOT_SUPPORTED;
+    }
+    return rc;
+}
+
+/**
+ * This is the callback which is scheduled when data is available on the
+ * wakeup pipe.  It simply reads all data from the pipe.
+ *
+ * @param   pvUserData          Pointer to the X11 clipboard context to use.
+ */
+static void clipThreadDrainWakeupPipe(XtPointer pvUserData, int *, XtInputId *)
+{
+    LogFlowFuncEnter();
+
+    PSHCLX11CTX pCtx = (PSHCLX11CTX)pvUserData;
+    char acBuf[WAKE_UP_STRING_LEN];
+
+    while (read(pCtx->wakeupPipeRead, acBuf, sizeof(acBuf)) > 0) {}
+}
+#endif /* !TESTCASE */
+
+/**
+ * X11-specific initialisation for the Shared Clipboard.
+ *
+ * Note: Must be called from the thread serving the Xt stuff.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                The X11 clipboard context to init.
+ */
+static int clipInitInternal(PSHCLX11CTX pCtx)
+{
+    LogFlowFunc(("pCtx=%p\n", pCtx));
+
+    /* Make sure we are thread safe. */
+    XtToolkitThreadInitialize();
+
+    /*
+     * Set up the Clipboard application context and main window.  We call all
+     * these functions directly instead of calling XtOpenApplication() so
+     * that we can fail gracefully if we can't get an X11 display.
+     */
+    XtToolkitInitialize();
+
+    int rc = VINF_SUCCESS;
+
+    Assert(pCtx->pAppContext == NULL); /* No nested initialization. */
+    pCtx->pAppContext = XtCreateApplicationContext();
+    if (pCtx->pAppContext == NULL)
+    {
+        LogRel(("Shared Clipboard: Failed to create Xt application context\n"));
+        return VERR_NOT_SUPPORTED; /** @todo Fudge! */
+    }
+
+    /* Create a window and make it a clipboard viewer. */
+    int      cArgc  = 0;
+    char    *pcArgv = 0;
+    Display *pDisplay = XtOpenDisplay(pCtx->pAppContext, 0, 0, "VBoxShCl", 0, 0, &cArgc, &pcArgv);
+    if (pDisplay == NULL)
+    {
+        LogRel(("Shared Clipboard: Failed to connect to the X11 clipboard - the window system may not be running\n"));
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+#ifndef TESTCASE
+    if (RT_SUCCESS(rc))
+    {
+        rc = clipLoadXFixes(pDisplay, pCtx);
+        if (RT_FAILURE(rc))
+           LogRel(("Shared Clipboard: Failed to load the XFIXES extension\n"));
+    }
+#endif
+
+    if (RT_SUCCESS(rc))
+    {
+        pCtx->pWidget = XtVaAppCreateShell(0, "VBoxShCl",
+                                           applicationShellWidgetClass,
+                                           pDisplay, XtNwidth, 1, XtNheight,
+                                           1, NULL);
+        if (pCtx->pWidget == NULL)
+        {
+            LogRel(("Shared Clipboard: Failed to create Xt app shell\n"));
+            rc = VERR_NO_MEMORY; /** @todo r=andy Improve this. */
+        }
+        else
+        {
+#ifndef TESTCASE
+            if (!XtAppAddInput(pCtx->pAppContext, pCtx->wakeupPipeRead,
+                               (XtPointer) XtInputReadMask,
+                               clipThreadDrainWakeupPipe, (XtPointer) pCtx))
+            {
+                LogRel(("Shared Clipboard: Failed to add input to Xt app context\n"));
+                rc = VERR_ACCESS_DENIED; /** @todo r=andy Improve this. */
+            }
+#endif
+        }
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        XtSetMappedWhenManaged(pCtx->pWidget, false);
+        XtRealizeWidget(pCtx->pWidget);
+
+#ifndef TESTCASE
+        /* Enable clipboard update notification. */
+        pCtx->fixesSelectInput(pDisplay, XtWindow(pCtx->pWidget),
+                               clipGetAtom(pCtx, "CLIPBOARD"),
+                               7 /* All XFixes*Selection*NotifyMask flags */);
+#endif
+    }
+
+    if (RT_FAILURE(rc))
+    {
+        LogRel(("Shared Clipboard: Initialisation failed: %Rrc\n", rc));
+        clipUninitInternal(pCtx);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * X11-specific uninitialisation for the Shared Clipboard.
+ *
+ * Note: Must be called from the thread serving the Xt stuff.
+ *
+ * @param   pCtx                The X11 clipboard context to uninit.
+ */
+static void clipUninitInternal(PSHCLX11CTX pCtx)
+{
+    AssertPtrReturnVoid(pCtx);
+
+    LogFlowFunc(("pCtx=%p\n", pCtx));
+
+    if (pCtx->pWidget)
+    {
+        /* Valid widget + invalid appcontext = bug.  But don't return yet. */
+        AssertPtr(pCtx->pAppContext);
+
+        XtDestroyWidget(pCtx->pWidget);
+        pCtx->pWidget = NULL;
+    }
+
+    if (pCtx->pAppContext)
+    {
+        XtDestroyApplicationContext(pCtx->pAppContext);
+        pCtx->pAppContext = NULL;
+    }
+
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+}
+
+/**
+ * Sets the callback table, internal version.
+ *
+ * @param   pCtx                The clipboard context.
+ * @param   pCallbacks          Callback table to set. If NULL, the current callback table will be cleared.
+ */
+static void shClX11SetCallbacksInternal(PSHCLX11CTX pCtx, PSHCLCALLBACKS pCallbacks)
+{
+    if (pCallbacks)
+    {
+        memcpy(&pCtx->Callbacks, pCallbacks, sizeof(SHCLCALLBACKS));
+    }
+    else
+        RT_ZERO(pCtx->Callbacks);
+}
+
+/**
+ * Sets the callback table.
+ *
+ * @param   pCtx                The clipboard context.
+ * @param   pCallbacks          Callback table to set. If NULL, the current callback table will be cleared.
+ */
+void ShClX11SetCallbacks(PSHCLX11CTX pCtx, PSHCLCALLBACKS pCallbacks)
+{
+    shClX11SetCallbacksInternal(pCtx, pCallbacks);
+}
+
+/**
+ * Initializes a X11 context of the Shared Clipboard.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                The clipboard context to initialize.
+ * @param   pCallbacks          Callback table to use.
+ * @param   pParent             Parent context to use.
+ * @param   fHeadless           Whether the code runs in a headless environment or not.
+ */
+int ShClX11Init(PSHCLX11CTX pCtx, PSHCLCALLBACKS pCallbacks, PSHCLCONTEXT pParent, bool fHeadless)
+{
+    AssertPtrReturn(pCtx, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("pCtx=%p\n", pCtx));
+
+    int rc = VINF_SUCCESS;
+
+    RT_BZERO(pCtx, sizeof(SHCLX11CTX));
+
+    if (fHeadless)
+    {
+        /*
+         * If we don't find the DISPLAY environment variable we assume that
+         * we are not connected to an X11 server. Don't actually try to do
+         * this then, just fail silently and report success on every call.
+         * This is important for VBoxHeadless.
+         */
+        LogRel(("Shared Clipboard: X11 DISPLAY variable not set -- disabling clipboard sharing\n"));
+    }
+
+    /* Install given callbacks. */
+    shClX11SetCallbacksInternal(pCtx, pCallbacks);
+
+    pCtx->fHaveX11       = !fHeadless;
+    pCtx->pFrontend      = pParent;
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_XT_BUSY
+    pCtx->fXtBusy        = false;
+    pCtx->fXtNeedsUpdate = false;
+#endif
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS_HTTP
+    ShClTransferHttpServerInit(&pCtx->HttpCtx.HttpServer);
+#endif
+
+#ifdef TESTCASE
+    if (RT_SUCCESS(rc))
+    {
+        /** @todo The testcases currently do not utilize the threading code. So init stuff here. */
+        rc = clipInitInternal(pCtx);
+        if (RT_SUCCESS(rc))
+            rc = clipRegisterContext(pCtx);
+    }
+#endif
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Destroys a Shared Clipboard X11 context.
+ *
+ * @param   pCtx                The X11 clipboard context to destroy.
+ */
+void ShClX11Destroy(PSHCLX11CTX pCtx)
+{
+    if (!pCtx)
+        return;
+
+    LogFlowFunc(("pCtx=%p\n", pCtx));
+
+#ifdef TESTCASE
+    /** @todo The testcases currently do not utilize the threading code. So uninit stuff here. */
+    clipUnregisterContext(pCtx);
+    clipUninitInternal(pCtx);
+#endif
+
+    if (pCtx->fHaveX11)
+    {
+        /* We set this to NULL when the event thread exits.  It really should
+         * have exited at this point, when we are about to unload the code from
+         * memory. */
+        Assert(pCtx->pWidget == NULL);
+    }
+}
+
+#ifndef TESTCASE
+/**
+ * Starts our own Xt even thread for handling Shared Clipboard messages, extended version.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                The X11 clipboard context to use.
+ * @param   pszName             Thread name to use.
+ * @param   fGrab               Whether we should try to grab the shared clipboard at once.
+ */
+int ShClX11ThreadStartEx(PSHCLX11CTX pCtx, const char *pszName, bool fGrab)
+{
+    AssertPtrReturn(pCtx, VERR_INVALID_POINTER);
+
+    /*
+     * Immediately return if we are not connected to the X server.
+     */
+    if (!pCtx->fHaveX11)
+        return VINF_SUCCESS;
+
+    pCtx->fGrabClipboardOnStart = fGrab;
+
+    clipResetX11Formats(pCtx);
+
+    int rc;
+
+    /*
+     * Create the pipes.
+     ** @todo r=andy Replace this with RTPipe API.
+     */
+    int pipes[2];
+    if (!pipe(pipes))
+    {
+        pCtx->wakeupPipeRead  = pipes[0];
+        pCtx->wakeupPipeWrite = pipes[1];
+
+        if (!fcntl(pCtx->wakeupPipeRead, F_SETFL, O_NONBLOCK))
+        {
+            rc = VINF_SUCCESS;
+        }
+        else
+            rc = RTErrConvertFromErrno(errno);
+    }
+    else
+        rc = RTErrConvertFromErrno(errno);
+
+    if (RT_SUCCESS(rc))
+    {
+        LogRel2(("Shared Clipboard: Starting X11 event thread ...\n"));
+
+        rc = RTThreadCreate(&pCtx->Thread, clipThreadMain, pCtx, 0,
+                            RTTHREADTYPE_IO, RTTHREADFLAGS_WAITABLE, pszName);
+        if (RT_SUCCESS(rc))
+            rc = RTThreadUserWait(pCtx->Thread, RT_MS_30SEC /* msTimeout */);
+
+        if (RT_FAILURE(rc))
+        {
+            LogRel(("Shared Clipboard: Failed to start the X11 event thread with %Rrc\n", rc));
+            clipUninitInternal(pCtx);
+        }
+        else
+        {
+            if (!pCtx->fThreadStarted)
+            {
+                LogRel(("Shared Clipboard: X11 event thread reported an error while starting\n"));
+            }
+            else
+                LogRel2(("Shared Clipboard: X11 event thread started\n"));
+        }
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Starts our own Xt even thread for handling Shared Clipboard messages.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                The X11 clipboard context to use.
+ * @param   fGrab               Whether we should try to grab the shared clipboard at once.
+ */
+int ShClX11ThreadStart(PSHCLX11CTX pCtx, bool fGrab)
+{
+    return ShClX11ThreadStartEx(pCtx, "SHCLX11", fGrab);
+}
+
+/**
+ * Stops the Shared Clipboard Xt even thread.
+ *
+ * @note  Any requests from this object to get clipboard data from VBox
+ *        *must* have completed or aborted before we are called, as
+ *        otherwise the X11 event loop will still be waiting for the request
+ *        to return and will not be able to terminate.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                The X11 clipboard context to use.
+ */
+int ShClX11ThreadStop(PSHCLX11CTX pCtx)
+{
+    int rc;
+    /*
+     * Immediately return if we are not connected to the X server.
+     */
+    if (!pCtx->fHaveX11)
+        return VINF_SUCCESS;
+
+    LogRel2(("Shared Clipboard: Signalling the X11 event thread to stop\n"));
+
+    /* Write to the "stop" pipe. */
+    rc = clipThreadScheduleCall(pCtx, clipThreadSignalStop, (XtPointer)pCtx);
+    if (RT_FAILURE(rc))
+    {
+        LogRel(("Shared Clipboard: cannot notify X11 event thread on shutdown with %Rrc\n", rc));
+        return rc;
+    }
+
+    LogRel2(("Shared Clipboard: Waiting for X11 event thread to stop ...\n"));
+
+    int rcThread;
+    rc = RTThreadWait(pCtx->Thread, RT_MS_30SEC /* msTimeout */, &rcThread);
+    if (RT_SUCCESS(rc))
+        rc = rcThread;
+    if (RT_SUCCESS(rc))
+    {
+        if (pCtx->wakeupPipeRead != 0)
+        {
+            close(pCtx->wakeupPipeRead);
+            pCtx->wakeupPipeRead = 0;
+        }
+
+        if (pCtx->wakeupPipeWrite != 0)
+        {
+            close(pCtx->wakeupPipeWrite);
+            pCtx->wakeupPipeWrite = 0;
+        }
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        LogRel2(("Shared Clipboard: X11 event thread stopped successfully\n"));
+    }
+    else
+        LogRel(("Shared Clipboard: Stopping X11 event thread failed with %Rrc\n", rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+#endif /* !TESTCASE */
+
+/**
+ * Returns the targets supported by VBox.
+ *
+ * This will return a list of atoms which tells the caller
+ * what kind of clipboard formats we support.
+ *
+ * @returns VBox status code.
+ * @param  pCtx                 The X11 clipboard context to use.
+ * @param  atomTypeReturn       The type of the data we are returning.
+ * @param  pValReturn           A pointer to the data we are returning. This
+ *                              should be set to memory allocated by XtMalloc,
+ *                              which will be freed later by the Xt toolkit.
+ * @param  pcLenReturn          The length of the data we are returning.
+ * @param  piFormatReturn       The format (8bit, 16bit, 32bit) of the data we are
+ *                              returning.
+ * @note  X11 backend code, called by the XtOwnSelection callback.
+ */
+static int clipCreateX11Targets(PSHCLX11CTX pCtx, Atom *atomTypeReturn,
+                                XtPointer *pValReturn,
+                                unsigned long *pcLenReturn,
+                                int *piFormatReturn)
+{
+    const unsigned cFixedTargets = 3; /* See below. */
+
+    Atom *pAtomTargets = (Atom *)XtMalloc((SHCL_MAX_X11_FORMATS + cFixedTargets) * sizeof(Atom));
+    if (!pAtomTargets)
+        return VERR_NO_MEMORY;
+
+    unsigned cTargets = 0;
+    SHCLX11FMTIDX idxFmt = NIL_CLIPX11FORMAT;
+    do
+    {
+        idxFmt = clipEnumX11Formats(pCtx->vboxFormats, idxFmt);
+        if (idxFmt != NIL_CLIPX11FORMAT)
+        {
+            pAtomTargets[cTargets] = clipAtomForX11Format(pCtx, idxFmt);
+            ++cTargets;
+        }
+    } while (idxFmt != NIL_CLIPX11FORMAT);
+
+    /* We always offer these fixed targets. */
+    pAtomTargets[cTargets]     = clipGetAtom(pCtx, "TARGETS");
+    pAtomTargets[cTargets + 1] = clipGetAtom(pCtx, "MULTIPLE");
+    pAtomTargets[cTargets + 2] = clipGetAtom(pCtx, "TIMESTAMP");
+
+    *atomTypeReturn = XA_ATOM;
+    *pValReturn = (XtPointer)pAtomTargets;
+    *pcLenReturn = cTargets + cFixedTargets;
+    *piFormatReturn = 32;
+
+    LogFlowFunc(("cTargets=%u\n", cTargets + cFixedTargets));
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Helper for ShClX11RequestDataForX11Callback() that will cache the data returned.
+ *
+ * @returns VBox status code. VERR_NO_DATA if no data available.
+ * @param   pCtx                The X11 clipboard context to use.
+ * @param   uFmt                Clipboard format to read data in.
+ * @param   ppv                 Returns an allocated buffer with data read on success.
+ *                              Needs to be free'd with RTMemFree() by the caller.
+ * @param   pcb                 Returns the amount of data read (in bytes) on success.
+ */
+static int shClX11RequestDataForX11CallbackHelper(PSHCLX11CTX pCtx, SHCLFORMAT uFmt,
+                                                  void **ppv, uint32_t *pcb)
+{
+    AssertPtrReturn(pCtx, VERR_INVALID_POINTER);
+    AssertPtrReturn(ppv,  VERR_INVALID_POINTER);
+    AssertPtrReturn(pcb,  VERR_INVALID_POINTER);
+
+    LogFlowFunc(("pCtx=%p, uFmt=%#x\n", pCtx, uFmt));
+
+    int rc = VINF_SUCCESS;
+
+    void    *pv = NULL;
+    uint32_t cb = 0;
+
+    if (uFmt == VBOX_SHCL_FMT_UNICODETEXT)
+    {
+        if (pCtx->pvUnicodeCache == NULL) /** @todo r=andy Using string cache here? */
+            rc = pCtx->Callbacks.pfnOnRequestDataFromSource(pCtx->pFrontend, uFmt, &pCtx->pvUnicodeCache, &pCtx->cbUnicodeCache,
+                                                            NULL /* pvUser */);
+        if (   RT_SUCCESS(rc)
+            /* Catch misbehaving callbacks. */
+            && pCtx->pvUnicodeCache
+            && pCtx->cbUnicodeCache)
+        {
+            pv = RTMemDup(pCtx->pvUnicodeCache, pCtx->cbUnicodeCache);
+            if (pv)
+                cb = pCtx->cbUnicodeCache;
+            else
+                rc = VERR_NO_MEMORY;
+        }
+    }
+    else
+        rc = pCtx->Callbacks.pfnOnRequestDataFromSource(pCtx->pFrontend, uFmt, &pv, &cb, NULL /* pvUser */);
+
+
+    /* Safey net in case the callbacks above misbehave
+     * (must return VERR_NO_DATA if no data available). */
+    if (   RT_SUCCESS(rc)
+        && (pv == NULL || cb == 0))
+        rc = VERR_NO_DATA;
+
+    if (RT_SUCCESS(rc))
+    {
+        *ppv = pv;
+        *pcb = cb;
+    }
+
+    LogFlowFunc(("Returning pv=%p, cb=%RU32, rc=%Rrc\n", pv, cb, rc));
+    return rc;
+}
+
+/**
+ * Satisfies a request from X11 to convert the clipboard text to UTF-8 LF.
+ *
+ * @returns VBox status code. VERR_NO_DATA if no data was converted.
+ * @param  pDisplay             An X11 display structure, needed for conversions
+ *                              performed by Xlib.
+ * @param  pv                   The text to be converted (UCS-2 with Windows EOLs).
+ * @param  cb                   The length of the text in @cb in bytes.
+ * @param  atomTypeReturn       Where to store the atom for the type of the data
+ *                              we are returning.
+ * @param  pValReturn           Where to store the pointer to the data we are
+ *                              returning.  This should be to memory allocated by
+ *                              XtMalloc, which will be freed by the Xt toolkit
+ *                              later.
+ * @param  pcLenReturn          Where to store the length of the data we are
+ *                              returning.
+ * @param  piFormatReturn       Where to store the bit width (8, 16, 32) of the
+ *                              data we are returning.
+ */
+static int clipConvertUtf16ToX11Data(Display *pDisplay, PRTUTF16 pwszSrc,
+                                     size_t cbSrc, Atom *atomTarget,
+                                     Atom *atomTypeReturn,
+                                     XtPointer *pValReturn,
+                                     unsigned long *pcLenReturn,
+                                     int *piFormatReturn)
+{
+    RT_NOREF(pDisplay);
+    AssertReturn(cbSrc % sizeof(RTUTF16) == 0, VERR_INVALID_PARAMETER);
+
+    const size_t cwcSrc = cbSrc / sizeof(RTUTF16);
+    if (!cwcSrc)
+        return VERR_NO_DATA;
+
+    /* This may slightly overestimate the space needed. */
+    size_t chDst = 0;
+    int rc = ShClUtf16LenUtf8(pwszSrc, cwcSrc, &chDst);
+    if (RT_SUCCESS(rc))
+    {
+        chDst++; /* Add space for terminator. */
+
+        char *pszDst = (char *)XtMalloc(chDst);
+        if (pszDst)
+        {
+            size_t cbActual = 0;
+            rc = ShClConvUtf16CRLFToUtf8LF(pwszSrc, cwcSrc, pszDst, chDst, &cbActual);
+            if (RT_SUCCESS(rc))
+            {
+                *atomTypeReturn = *atomTarget;
+                *pValReturn     = (XtPointer)pszDst;
+                *pcLenReturn    = cbActual + 1 /* Include terminator */;
+                *piFormatReturn = 8;
+            }
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Satisfies a request from X11 to convert the clipboard HTML fragment to UTF-8.  We
+ * return null-terminated text, but can cope with non-null-terminated input.
+ *
+ * @returns VBox status code.
+ * @param  pDisplay             An X11 display structure, needed for conversions
+ *                              performed by Xlib.
+ * @param  pv                   The text to be converted (UTF8 with Windows EOLs).
+ * @param  cb                   The length of the text in @cb in bytes.
+ * @param  atomTypeReturn       Where to store the atom for the type of the data
+ *                              we are returning.
+ * @param  pValReturn           Where to store the pointer to the data we are
+ *                              returning.  This should be to memory allocated by
+ *                              XtMalloc, which will be freed by the Xt toolkit later.
+ * @param  pcLenReturn          Where to store the length of the data we are returning.
+ * @param  piFormatReturn       Where to store the bit width (8, 16, 32) of the
+ *                              data we are returning.
+ */
+static int clipConvertHtmlToX11Data(Display *pDisplay, const char *pszSrc,
+                                    size_t cbSrc, Atom *atomTarget,
+                                    Atom *atomTypeReturn,
+                                    XtPointer *pValReturn,
+                                    unsigned long *pcLenReturn,
+                                    int *piFormatReturn)
+{
+    RT_NOREF(pDisplay, pValReturn);
+
+    /* This may slightly overestimate the space needed. */
+    LogFlowFunc(("Source: %s", pszSrc));
+
+    char *pszDest = (char *)XtMalloc(cbSrc);
+    if (pszDest == NULL)
+        return VERR_NO_MEMORY;
+
+    memcpy(pszDest, pszSrc, cbSrc);
+
+    *atomTypeReturn = *atomTarget;
+    *pValReturn = (XtPointer)pszDest;
+    *pcLenReturn = cbSrc;
+    *piFormatReturn = 8;
+
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * Does this atom correspond to one of the two selection types we support?
+ *
+ * @param  pCtx                 The X11 clipboard context to use.
+ * @param  selType              The atom in question.
+ */
+static bool clipIsSupportedSelectionType(PSHCLX11CTX pCtx, Atom selType)
+{
+    return(   (selType == clipGetAtom(pCtx, "CLIPBOARD"))
+           || (selType == clipGetAtom(pCtx, "PRIMARY")));
+}
+
+/**
+ * Removes a trailing nul character from a string by adjusting the string
+ * length.  Some X11 applications don't like zero-terminated text...
+ *
+ * @param  pText                The text in question.
+ * @param  pcText               The length of the text, adjusted on return.
+ * @param  format               The format of the text.
+ */
+static void clipTrimTrailingNul(XtPointer pText, unsigned long *pcText,
+                                SHCLX11FMT format)
+{
+    AssertPtrReturnVoid(pText);
+    AssertPtrReturnVoid(pcText);
+    AssertReturnVoid((format == SHCLX11FMT_UTF8) || (format == SHCLX11FMT_TEXT) || (format == SHCLX11FMT_HTML));
+
+    if (((char *)pText)[*pcText - 1] == '\0')
+       --(*pcText);
+}
+
+static int clipConvertToX11Data(PSHCLX11CTX pCtx, Atom *atomTarget,
+                                Atom *atomTypeReturn,
+                                XtPointer *pValReturn,
+                                unsigned long *pcLenReturn,
+                                int *piFormatReturn)
+{
+    int rc = VERR_NOT_SUPPORTED; /* Play safe by default. */
+
+    SHCLX11FMTIDX idxFmtX11 = clipFindX11FormatByAtom(pCtx, *atomTarget);
+    SHCLX11FMT    fmtX11    = clipRealFormatForX11Format(idxFmtX11);
+
+    LogFlowFunc(("vboxFormats=0x%x, idxFmtX11=%u ('%s'), fmtX11=%u\n",
+                 pCtx->vboxFormats, idxFmtX11, g_aFormats[idxFmtX11].pcszAtom, fmtX11));
+
+#ifdef LOG_ENABLED
+    char *pszFmts = ShClFormatsToStrA(pCtx->vboxFormats);
+    AssertPtrReturn(pszFmts, VERR_NO_MEMORY);
+    LogRel2(("Shared Clipboard: Converting VBox formats '%s' to '%s' for X11\n",
+             pszFmts, g_aFormats[idxFmtX11].pcszAtom));
+    RTStrFree(pszFmts);
+#endif
+
+    void    *pv = NULL;
+    uint32_t cb = 0;
+
+    if (   (   (fmtX11 == SHCLX11FMT_UTF8)
+            || (fmtX11 == SHCLX11FMT_TEXT)
+           )
+        && (pCtx->vboxFormats & VBOX_SHCL_FMT_UNICODETEXT))
+    {
+        rc = shClX11RequestDataForX11CallbackHelper(pCtx, VBOX_SHCL_FMT_UNICODETEXT, &pv, &cb);
+        if (   RT_SUCCESS(rc)
+            && (   (fmtX11 == SHCLX11FMT_UTF8)
+                || (fmtX11 == SHCLX11FMT_TEXT)))
+        {
+            rc = clipConvertUtf16ToX11Data(XtDisplay(pCtx->pWidget),
+                                           (PRTUTF16)pv, cb, atomTarget,
+                                           atomTypeReturn, pValReturn,
+                                           pcLenReturn, piFormatReturn);
+        }
+
+        if (RT_SUCCESS(rc))
+            clipTrimTrailingNul(*(XtPointer *)pValReturn, pcLenReturn, fmtX11);
+
+        RTMemFree(pv);
+    }
+    else if (   (fmtX11 == SHCLX11FMT_BMP)
+             && (pCtx->vboxFormats & VBOX_SHCL_FMT_BITMAP))
+    {
+        rc = shClX11RequestDataForX11CallbackHelper(pCtx, VBOX_SHCL_FMT_BITMAP, &pv, &cb);
+        if (   RT_SUCCESS(rc)
+            && (fmtX11 == SHCLX11FMT_BMP))
+        {
+            /* Create a full BMP from it. */
+            rc = ShClDibToBmp(pv, cb, (void **)pValReturn,
+                              (size_t *)pcLenReturn);
+        }
+
+        if (RT_SUCCESS(rc))
+        {
+            *atomTypeReturn = *atomTarget;
+            *piFormatReturn = 8;
+        }
+
+        RTMemFree(pv);
+    }
+    else if (  (fmtX11 == SHCLX11FMT_HTML)
+            && (pCtx->vboxFormats & VBOX_SHCL_FMT_HTML))
+    {
+        rc = shClX11RequestDataForX11CallbackHelper(pCtx, VBOX_SHCL_FMT_HTML, &pv, &cb);
+        if (RT_SUCCESS(rc))
+        {
+            /**
+             * The common VBox HTML encoding will be UTF-8.
+             * Before sending it to the X11 clipboard we have to convert it to UTF-8 first.
+             *
+             * Strange that we get UTF-16 from the X11 clipboard, but
+             * in same time we send UTF-8 to X11 clipboard and it works.
+             ** @todo r=andy Verify this.
+             */
+            rc = clipConvertHtmlToX11Data(XtDisplay(pCtx->pWidget),
+                                          (const char*)pv, cb, atomTarget,
+                                          atomTypeReturn, pValReturn,
+                                          pcLenReturn, piFormatReturn);
+            if (RT_SUCCESS(rc))
+                clipTrimTrailingNul(*(XtPointer *)pValReturn, pcLenReturn, fmtX11);
+
+            RTMemFree(pv);
+        }
+    }
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    else if (fmtX11 == SHCLX11FMT_URI_LIST)
+    {
+        if (pCtx->vboxFormats & VBOX_SHCL_FMT_URI_LIST)
+        {
+            rc = shClX11RequestDataForX11CallbackHelper(pCtx, VBOX_SHCL_FMT_URI_LIST, &pv, &cb);
+            if (RT_SUCCESS(rc))
+            {
+                void *pvDst = (void *)XtMalloc(cb);
+                if (pvDst)
+                {
+                    memcpy(pvDst, pv, cb);
+
+                    *atomTypeReturn = *atomTarget;
+                    *pValReturn     = (XtPointer)pvDst;
+                    *pcLenReturn    = cb;
+                    *piFormatReturn = 8;
+                }
+                else
+                    rc = VERR_NO_MEMORY;
+            }
+        }
+        /* else not supported yet. */
+    }
+#endif
+    else
+    {
+        *atomTypeReturn = XT_CONVERT_FAIL;
+        *pValReturn     = (XtPointer)NULL;
+        *pcLenReturn    = 0;
+        *piFormatReturn = 0;
+    }
+
+    if (RT_FAILURE(rc))
+    {
+        char *pszFmts2 = ShClFormatsToStrA(pCtx->vboxFormats);
+        char *pszAtomName = XGetAtomName(XtDisplay(pCtx->pWidget), *atomTarget);
+
+        LogRel(("Shared Clipboard: Converting VBox formats '%s' to '%s' for X11 (idxFmtX11=%u, fmtX11=%u, atomTarget='%s') failed, rc=%Rrc\n",
+                pszFmts2 ? pszFmts2 : "unknown", g_aFormats[idxFmtX11].pcszAtom, idxFmtX11, fmtX11, pszAtomName ? pszAtomName : "unknown", rc));
+
+        if (pszFmts2)
+            RTStrFree(pszFmts2);
+        if (pszAtomName)
+            XFree(pszAtomName);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Returns VBox's clipboard data for an X11 client.
+ *
+ * @note Callback for XtOwnSelection.
+ */
+static Boolean clipXtConvertSelectionProc(Widget widget, Atom *atomSelection,
+                                          Atom *atomTarget,
+                                          Atom *atomTypeReturn,
+                                          XtPointer *pValReturn,
+                                          unsigned long *pcLenReturn,
+                                          int *piFormatReturn)
+{
+    LogFlowFuncEnter();
+
+    PSHCLX11CTX pCtx = clipLookupContext(widget);
+    if (!pCtx)
+        return False;
+
+    /* Is this the rigt selection (clipboard) we were asked for? */
+    if (!clipIsSupportedSelectionType(pCtx, *atomSelection))
+        return False;
+
+    int rc;
+    if (*atomTarget == clipGetAtom(pCtx, "TARGETS"))
+        rc = clipCreateX11Targets(pCtx, atomTypeReturn, pValReturn,
+                                  pcLenReturn, piFormatReturn);
+    else
+        rc = clipConvertToX11Data(pCtx, atomTarget, atomTypeReturn,
+                                  pValReturn, pcLenReturn, piFormatReturn);
+
+#if 0 /** @todo Disabled -- crashes when running with tstClipboardGH-X11. */
+    XSelectionRequestEvent* pReq =
+        XtGetSelectionRequest(widget, *atomSelection, (XtRequestId)NULL);
+    LogFlowFunc(("returning pVBoxWnd=%#x, ownerWnd=%#x, reqWnd=%#x, %RTbool, rc=%Rrc\n",
+                 XtWindow(pCtx->pWidget), pReq->owner, pReq->requestor, RT_SUCCESS(rc), rc));
+#endif
+    return RT_SUCCESS(rc) ? True : False;
+}
+
+static void clipXtConvertSelectionProcLose(Widget widget, Atom *atomSelection)
+{
+    RT_NOREF(widget, atomSelection);
+    LogFlowFuncEnter();
+}
+
+static void clipXtConvertSelectionProcDone(Widget widget, Atom *atomSelection, Atom *atomTarget)
+{
+    RT_NOREF(widget, atomSelection, atomTarget);
+    LogFlowFuncEnter();
+}
+
+/**
+ * Structure used to pass information about formats that VBox supports.
+ */
+typedef struct _CLIPNEWVBOXFORMATS
+{
+    /** Context information for the X11 clipboard. */
+    PSHCLX11CTX pCtx;
+    /** Formats supported by VBox. */
+    SHCLFORMATS  Formats;
+} CLIPNEWVBOXFORMATS, *PCLIPNEWVBOXFORMATS;
+
+
+
+/**
+ * Invalidates the local cache of the data in the VBox clipboard.
+ *
+ * @param   pCtx                The X11 clipboard context to use.
+ */
+static void clipInvalidateClipboardCache(PSHCLX11CTX pCtx)
+{
+    if (pCtx->pvUnicodeCache != NULL)
+    {
+        RTMemFree(pCtx->pvUnicodeCache);
+        pCtx->pvUnicodeCache = NULL;
+    }
+}
+
+/**
+ * Takes possession of the X11 clipboard (and middle-button selection).
+ *
+ * @param   pCtx                The X11 clipboard context to use.
+ * @param   uFormats            Clipboard formats to set.
+ */
+static void clipGrabX11Clipboard(PSHCLX11CTX pCtx, SHCLFORMATS uFormats)
+{
+    LogFlowFuncEnter();
+
+    /** @ŧodo r=andy The docs say: "the value CurrentTime is not acceptable" here!? */
+    if (XtOwnSelection(pCtx->pWidget, clipGetAtom(pCtx, "CLIPBOARD"),
+                       CurrentTime,
+                       clipXtConvertSelectionProc, clipXtConvertSelectionProcLose, clipXtConvertSelectionProcDone))
+    {
+        pCtx->vboxFormats = uFormats;
+
+        /* Grab the middle-button paste selection too. */
+        XtOwnSelection(pCtx->pWidget, clipGetAtom(pCtx, "PRIMARY"),
+                       CurrentTime, clipXtConvertSelectionProc, NULL, 0);
+#ifndef TESTCASE
+        /* Xt suppresses these if we already own the clipboard, so send them
+         * ourselves. */
+        XSetSelectionOwner(XtDisplay(pCtx->pWidget),
+                           clipGetAtom(pCtx, "CLIPBOARD"),
+                           XtWindow(pCtx->pWidget), CurrentTime);
+        XSetSelectionOwner(XtDisplay(pCtx->pWidget),
+                           clipGetAtom(pCtx, "PRIMARY"),
+                           XtWindow(pCtx->pWidget), CurrentTime);
+#endif
+    }
+}
+
+/**
+ * Worker function for ShClX11ReportFormatsToX11 which runs on the
+ * event thread.
+ *
+ * @param pvUserData            Pointer to a CLIPNEWVBOXFORMATS structure containing
+ *                              information about the VBox formats available and the
+ *                              clipboard context data.  Must be freed by the worker.
+ */
+static void ShClX11ReportFormatsToX11Worker(void *pvUserData, void * /* interval */)
+{
+    AssertPtrReturnVoid(pvUserData);
+
+    CLIPNEWVBOXFORMATS *pFormats = (CLIPNEWVBOXFORMATS *)pvUserData;
+
+    PSHCLX11CTX pCtx     = pFormats->pCtx;
+    SHCLFORMATS fFormats = pFormats->Formats;
+
+    RTMemFree(pFormats);
+
+#ifdef LOG_ENABLED
+    char *pszFmts = ShClFormatsToStrA(fFormats);
+    AssertPtrReturnVoid(pszFmts);
+    LogRel2(("Shared Clipboard: Reported available VBox formats %s to X11\n", pszFmts));
+    RTStrFree(pszFmts);
+#endif
+
+    clipInvalidateClipboardCache(pCtx);
+    clipGrabX11Clipboard(pCtx, fFormats);
+    clipResetX11Formats(pCtx);
+
+    LogFlowFuncLeave();
+}
+
+/**
+ * Announces new clipboard formats to the X11 clipboard.
+ *
+ * @returns VBox status code.
+ * @param   pCtx                Context data for the clipboard backend.
+ * @param   uFormats            Clipboard formats offered.
+ */
+int ShClX11ReportFormatsToX11(PSHCLX11CTX pCtx, SHCLFORMATS uFormats)
+{
+    /*
+     * Immediately return if we are not connected to the X server.
+     */
+    if (!pCtx->fHaveX11)
+        return VINF_SUCCESS;
+
+    int rc;
+
+    /* This must be free'd by the worker callback. */
+    PCLIPNEWVBOXFORMATS pFormats = (PCLIPNEWVBOXFORMATS)RTMemAlloc(sizeof(CLIPNEWVBOXFORMATS));
+    if (pFormats)
+    {
+        pFormats->pCtx    = pCtx;
+        pFormats->Formats = uFormats;
+        rc = clipThreadScheduleCall(pCtx, ShClX11ReportFormatsToX11Worker,
+                                    (XtPointer)pFormats);
+        if (RT_FAILURE(rc))
+            RTMemFree(pFormats);
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Converts the data obtained from the X11 clipboard to the required format,
+ * place it in the buffer supplied and signal that data has arrived.
+ *
+ * Converts the text obtained UTF-16LE with Windows EOLs.
+ * Converts full BMP data to DIB format.
+ */
+SHCL_X11_DECL(void) clipConvertDataFromX11Worker(void *pClient, void *pvSrc, unsigned cbSrc)
+{
+    CLIPREADX11CBREQ *pReq = (CLIPREADX11CBREQ *)pClient;
+    AssertPtrReturnVoid(pReq);
+
+    LogFlowFunc(("pReq->uFmtVBox=%#x, pReq->idxFmtX11=%u, pReq->pCtx=%p\n", pReq->uFmtVBox, pReq->idxFmtX11, pReq->pCtx));
+
+    LogRel2(("Shared Clipboard: Converting X11 format '%s' to VBox format %#x\n",
+             g_aFormats[pReq->idxFmtX11].pcszAtom, pReq->uFmtVBox));
+
+    AssertPtr(pReq->pCtx);
+    Assert(pReq->uFmtVBox != VBOX_SHCL_FMT_NONE); /* Sanity. */
+
+    int rc = VINF_SUCCESS;
+
+    void  *pvDst = NULL;
+    size_t cbDst = 0;
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_XT_BUSY
+    PSHCLX11CTX pCtx = pReq->pCtx;
+    AssertPtr(pReq->pCtx);
+    clipSetXtBusy(pCtx, false);
+    if (clipGetXtNeedsUpdate(pCtx))
+        clipQueryX11Targets(pCtx);
+#endif
+
+    /* If X11 clipboard buffer has no data, libXt can pass to XtGetSelectionValue()
+     * callback an empty string, in this case cbSrc is 0. */
+    if (pvSrc == NULL || cbSrc == 0)
+    {
+        /* The clipboard selection may have changed before we could get it. */
+        rc = VERR_NO_DATA;
+    }
+    else if (pReq->uFmtVBox == VBOX_SHCL_FMT_UNICODETEXT)
+    {
+        /* In which format is the clipboard data? */
+        switch (clipRealFormatForX11Format(pReq->idxFmtX11))
+        {
+            case SHCLX11FMT_UTF8:
+                RT_FALL_THROUGH();
+            case SHCLX11FMT_TEXT:
+            {
+                size_t cwDst;
+                /* If we are given broken UTF-8, we treat it as Latin1. */ /** @todo BUGBUG Is this acceptable? */
+                if (RT_SUCCESS(RTStrValidateEncodingEx((char *)pvSrc, cbSrc, 0)))
+                    rc = ShClConvUtf8LFToUtf16CRLF((const char *)pvSrc, cbSrc,
+                                                   (PRTUTF16 *)&pvDst, &cwDst);
+                else
+                    rc = ShClConvLatin1LFToUtf16CRLF((char *)pvSrc, cbSrc,
+                                                     (PRTUTF16 *)&pvDst, &cwDst);
+                if (RT_SUCCESS(rc))
+                {
+                    cwDst += 1                        /* Include terminator */;
+                    cbDst  = cwDst * sizeof(RTUTF16); /* Convert RTUTF16 units to bytes. */
+                }
+                break;
+            }
+
+            default:
+            {
+                rc = VERR_INVALID_PARAMETER;
+                break;
+            }
+        }
+    }
+    else if (pReq->uFmtVBox == VBOX_SHCL_FMT_BITMAP)
+    {
+        /* In which format is the clipboard data? */
+        switch (clipRealFormatForX11Format(pReq->idxFmtX11))
+        {
+            case SHCLX11FMT_BMP:
+            {
+                const void *pDib;
+                size_t cbDibSize;
+                rc = ShClBmpGetDib((const void *)pvSrc, cbSrc,
+                                   &pDib, &cbDibSize);
+                if (RT_SUCCESS(rc))
+                {
+                    pvDst = RTMemAlloc(cbDibSize);
+                    if (!pvDst)
+                        rc = VERR_NO_MEMORY;
+                    else
+                    {
+                        memcpy(pvDst, pDib, cbDibSize);
+                        cbDst = cbDibSize;
+                    }
+                }
+                break;
+            }
+
+            default:
+            {
+                rc = VERR_INVALID_PARAMETER;
+                break;
+            }
+        }
+    }
+    else if (pReq->uFmtVBox == VBOX_SHCL_FMT_HTML)
+    {
+        /* In which format is the clipboard data? */
+        switch (clipRealFormatForX11Format(pReq->idxFmtX11))
+        {
+            case SHCLX11FMT_HTML:
+            {
+                /*
+                 * The common VBox HTML encoding will be - UTF-8
+                 * because it more general for HTML formats then UTF-16
+                 * X11 clipboard returns UTF-16, so before sending it we should
+                 * convert it to UTF-8.
+                 */
+                pvDst = NULL;
+                cbDst = 0;
+
+                /*
+                 * Some applications sends data in UTF-16, some in UTF-8,
+                 * without indication it in MIME.
+                 *
+                 * In case of UTF-16, at least [Open|Libre] Office adds an byte order mark (0xfeff)
+                 * at the start of the clipboard data.
+                 */
+                if (   cbSrc >= sizeof(RTUTF16)
+                    && *(PRTUTF16)pvSrc == VBOX_SHCL_UTF16LEMARKER)
+                {
+                    rc = ShClConvUtf16ToUtf8HTML((PRTUTF16)pvSrc, cbSrc / sizeof(RTUTF16), (char**)&pvDst, &cbDst);
+                    if (RT_SUCCESS(rc))
+                    {
+                        LogFlowFunc(("UTF-16 Unicode source (%u bytes):\n%ls\n\n", cbSrc, pvSrc));
+                        LogFlowFunc(("Byte Order Mark = %hx", ((PRTUTF16)pvSrc)[0]));
+                        LogFlowFunc(("UTF-8 Unicode dest (%u bytes):\n%s\n\n", cbDst, pvDst));
+                    }
+                    else
+                        LogRel(("Shared Clipboard: Converting UTF-16 Unicode failed with %Rrc\n", rc));
+                }
+                else /* Raw data. */
+                {
+                    pvDst = RTMemAllocZ(cbSrc + 1 /* '\0' */);
+                    if(pvDst)
+                    {
+                         memcpy(pvDst, pvSrc, cbSrc);
+                         cbDst = cbSrc + 1 /* '\0' */;
+                    }
+                    else
+                    {
+                         rc = VERR_NO_MEMORY;
+                         break;
+                    }
+                }
+
+                rc = VINF_SUCCESS;
+                break;
+            }
+
+            default:
+            {
+                rc = VERR_INVALID_PARAMETER;
+                break;
+            }
+        }
+    }
+# ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    else if (pReq->uFmtVBox == VBOX_SHCL_FMT_URI_LIST)
+    {
+        /* In which format is the clipboard data? */
+        switch (clipRealFormatForX11Format(pReq->idxFmtX11))
+        {
+            case SHCLX11FMT_URI_LIST:
+            {
+                /* For URI lists we only accept valid UTF-8 encodings. */
+                if (RT_SUCCESS(RTStrValidateEncodingEx((char *)pvSrc, cbSrc, 0)))
+                {
+                    /* URI lists on X are strings separated with "\r\n". */
+                    RTCList<RTCString> lstRootEntries = RTCString((char *)pvSrc, cbSrc).split("\r\n");
+                    for (size_t i = 0; i < lstRootEntries.size(); ++i)
+                    {
+                        char *pszEntry = RTUriFilePath(lstRootEntries.at(i).c_str());
+                        AssertPtrBreakStmt(pszEntry, VERR_INVALID_PARAMETER);
+
+                        rc = RTStrAAppend((char **)&pvDst, "http://localhost");
+                        AssertRCBreakStmt(rc, VERR_NO_MEMORY);
+                        cbDst += (uint32_t)strlen(pszEntry);
+
+
+
+                        /** @todo BUGBUG Fix port! */
+                        /** @todo Add port + UUID (virtual path). */
+
+                        rc = RTStrAAppend((char **)&pvDst, pszEntry);
+                        AssertRCBreakStmt(rc, VERR_NO_MEMORY);
+                        cbDst += (uint32_t)strlen(pszEntry);
+
+                        LogFlowFunc(("URI list entry '%s'\n", (char *)pvDst));
+
+                        rc = RTStrAAppend((char **)&pvDst, "\r\n");
+                        AssertRCBreakStmt(rc, VERR_NO_MEMORY);
+                        cbDst += (uint32_t)strlen("\r\n");
+
+                        RTStrFree(pszEntry);
+                    }
+
+                    if (cbDst)
+                        cbDst++; /* Include final (zero) termination. */
+
+                    LogFlowFunc(("URI list: cbDst=%RU32\n", cbDst));
+                }
+                else
+                    rc = VERR_INVALID_PARAMETER;
+                break;
+            }
+
+            default:
+            {
+                rc = VERR_INVALID_PARAMETER;
+                break;
+            }
+        }
+    }
+# endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+    else
+        rc = VERR_NOT_SUPPORTED;
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Converting X11 format '%s' (idxFmtX11=%u) to VBox format %#x failed, rc=%Rrc\n",
+                g_aFormats[pReq->idxFmtX11].pcszAtom, pReq->idxFmtX11, pReq->uFmtVBox, rc));
+
+    SHCLX11READDATAREQ SendData;
+    RT_ZERO(SendData);
+    SendData.pReq         = pReq->pReq;
+    SendData.rcCompletion = rc;
+
+    pCtx->Callbacks.pfnOnSendDataToDest(pReq->pCtx->pFrontend, pvDst, cbDst, &SendData);
+
+    RTMemFree(pvDst);
+    RTMemFree(pReq);
+
+    LogFlowFuncLeaveRC(rc);
+}
+
+/**
+ * Converts the data obtained from the X11 clipboard to the required format,
+ * place it in the buffer supplied and signal that data has arrived.
+ *
+ * Converts the text obtained UTF-16LE with Windows EOLs.
+ * Converts full BMP data to DIB format.
+ */
+SHCL_X11_DECL(void) clipConvertDataFromX11(Widget widget, XtPointer pClient,
+                                           Atom * /* selection */, Atom *atomType,
+                                           XtPointer pvSrc, long unsigned int *pcLen,
+                                           int *piFormat)
+{
+    RT_NOREF(widget);
+    if (*atomType == XT_CONVERT_FAIL) /* Xt timeout */
+        clipConvertDataFromX11Worker(pClient, NULL, 0);
+    else
+    {
+        CLIPREADX11CBREQ *pReq = (CLIPREADX11CBREQ *)pClient;
+        if (pReq->pCtx->Callbacks.pfnOnClipboardRead)
+        {
+            void  *pvData = NULL;
+            size_t cbData = 0;
+            int rc = pReq->pCtx->Callbacks.pfnOnClipboardRead(pReq->pCtx->pFrontend, pReq->uFmtVBox, &pvData, &cbData, NULL);
+            if (RT_SUCCESS(rc))
+            {
+                /* Feed to conversion worker. */
+                clipConvertDataFromX11Worker(pClient, pvData, cbData);
+                RTMemFree(pvData);
+            }
+            else
+                clipConvertDataFromX11Worker(pClient, NULL, 0);
+        }
+        else /* Call with current data provided by X (default). */
+            clipConvertDataFromX11Worker(pClient, pvSrc, (*pcLen) * (*piFormat) / 8);
+    }
+
+    XtFree((char *)pvSrc);
+}
+
+static int clipGetSelectionValue(PSHCLX11CTX pCtx, SHCLX11FMTIDX idxFmt,
+                                 CLIPREADX11CBREQ *pReq)
+{
+#ifndef TESTCASE
+    XtGetSelectionValue(pCtx->pWidget, clipGetAtom(pCtx, "CLIPBOARD"),
+                        clipAtomForX11Format(pCtx, idxFmt),
+                        clipConvertDataFromX11,
+                        reinterpret_cast<XtPointer>(pReq),
+                        CurrentTime);
+#else
+    tstClipRequestData(pCtx, idxFmt, (void *)pReq);
+#endif
+
+    return VINF_SUCCESS; /** @todo Return real rc. */
+}
+
+/**
+ * Worker function for ShClX11ReadDataFromX11 which runs on the event thread.
+ *
+ * @param pvUserData            Pointer to a CLIPREADX11CBREQ structure containing
+ *                              information about the clipboard read request.
+ *                              Must be free'd by the worker.
+ */
+static void ShClX11ReadDataFromX11Worker(void *pvUserData, void * /* interval */)
+{
+    AssertPtrReturnVoid(pvUserData);
+
+    CLIPREADX11CBREQ *pReq = (CLIPREADX11CBREQ *)pvUserData;
+    SHCLX11CTX       *pCtx = pReq->pCtx;
+    AssertPtrReturnVoid(pCtx);
+
+    LogFlowFunc(("pReq->uFmtVBox=%#x, idxFmtX11=%#x\n", pReq->uFmtVBox, pReq->idxFmtX11));
+
+    int rc = VERR_NO_DATA; /* VBox thinks we have data and we don't. */
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_XT_BUSY
+    const bool fXtBusy = clipGetXtBusy(pCtx);
+    clipSetXtBusy(pCtx, true);
+    if (fXtBusy)
+    {
+        /* If the clipboard is busy just fend off the request. */
+        rc = VERR_TRY_AGAIN;
+    }
+    else
+#endif
+    if (pReq->uFmtVBox & VBOX_SHCL_FMT_UNICODETEXT)
+    {
+        pReq->idxFmtX11 = pCtx->idxFmtText;
+        if (pReq->idxFmtX11 != SHCLX11FMT_INVALID)
+        {
+            /* Send out a request for the data to the current clipboard owner. */
+            rc = clipGetSelectionValue(pCtx, pCtx->idxFmtText, pReq);
+        }
+    }
+    else if (pReq->uFmtVBox & VBOX_SHCL_FMT_BITMAP)
+    {
+        pReq->idxFmtX11 = pCtx->idxFmtBmp;
+        if (pReq->idxFmtX11 != SHCLX11FMT_INVALID)
+        {
+            /* Send out a request for the data to the current clipboard owner. */
+            rc = clipGetSelectionValue(pCtx, pCtx->idxFmtBmp, pReq);
+        }
+    }
+    else if (pReq->uFmtVBox & VBOX_SHCL_FMT_HTML)
+    {
+        pReq->idxFmtX11 = pCtx->idxFmtHTML;
+        if (pReq->idxFmtX11 != SHCLX11FMT_INVALID)
+        {
+            /* Send out a request for the data to the current clipboard owner. */
+            rc = clipGetSelectionValue(pCtx, pCtx->idxFmtHTML, pReq);
+        }
+    }
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    else if (pReq->uFmtVBox & VBOX_SHCL_FMT_URI_LIST)
+    {
+        pReq->idxFmtX11 = pCtx->idxFmtURI;
+        if (pReq->idxFmtX11 != SHCLX11FMT_INVALID)
+        {
+            /* Send out a request for the data to the current clipboard owner. */
+            rc = clipGetSelectionValue(pCtx, pCtx->idxFmtURI, pReq);
+        }
+    }
+#endif
+    else
+    {
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_XT_BUSY
+        clipSetXtBusy(pCtx, false);
+#endif
+        rc = VERR_NOT_IMPLEMENTED;
+    }
+
+    if (RT_FAILURE(rc))
+    {
+        /* The clipboard callback was never scheduled, so we must signal
+         * that the request processing is finished and clean up ourselves. */
+        SHCLX11READDATAREQ SendData;
+        RT_ZERO(SendData);
+        SendData.pReq         = pReq->pReq;
+        SendData.rcCompletion = rc;
+
+        pCtx->Callbacks.pfnOnSendDataToDest(pReq->pCtx->pFrontend, NULL /* pv */ ,0 /* cb */, &SendData);
+        RTMemFree(pReq);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+}
+
+/**
+ * Called when VBox wants to read the X11 clipboard.
+ *
+ * @returns VBox status code.
+ * @retval  VERR_NO_DATA if format is supported but no data is available currently.
+ * @retval  VERR_NOT_IMPLEMENTED if the format is not implemented.
+ * @param   pCtx                Context data for the clipboard backend.
+ * @param   uFmt                The format that the VBox would like to receive the data in.
+ * @param   pReq                Read callback request to use. Will be free'd in the callback on success.
+ *                              Otherwise the caller has to free this again on error.
+ *
+ * @note   We allocate a request structure which must be freed by the worker.
+ */
+int ShClX11ReadDataFromX11(PSHCLX11CTX pCtx, SHCLFORMAT uFmt, CLIPREADCBREQ *pReq)
+{
+    AssertPtrReturn(pReq, VERR_INVALID_POINTER);
+    /*
+     * Immediately return if we are not connected to the X server.
+     */
+    if (!pCtx->fHaveX11)
+        return VERR_NO_DATA;
+
+    int rc = VINF_SUCCESS;
+
+    CLIPREADX11CBREQ *pX11Req = (CLIPREADX11CBREQ *)RTMemAllocZ(sizeof(CLIPREADX11CBREQ));
+    if (pX11Req)
+    {
+        pX11Req->pCtx     = pCtx;
+        pX11Req->uFmtVBox = uFmt;
+        pX11Req->pReq     = pReq;
+
+        /* We use this to schedule a worker function on the event thread. */
+        rc = clipThreadScheduleCall(pCtx, ShClX11ReadDataFromX11Worker, (XtPointer)pX11Req);
+        if (RT_FAILURE(rc))
+            RTMemFree(pX11Req);
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
diff --git a/src/VBox/GuestHost/SharedClipboard/testcase/Makefile.kmk b/src/VBox/GuestHost/SharedClipboard/testcase/Makefile.kmk
new file mode 100644
index 00000000..5b073ea1
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/testcase/Makefile.kmk
@@ -0,0 +1,76 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Shared Clipboard Guest/Host testcases.
+#
+
+#
+# Copyright (C) 2011-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+if defined(VBOX_WITH_TESTCASES) && !defined(VBOX_ONLY_ADDITIONS) && !defined(VBOX_ONLY_SDK)
+ if1of ($(KBUILD_TARGET), freebsd linux netbsd openbsd solaris)
+
+  PROGRAMS += tstClipboardGH-X11 tstClipboardGH-X11Smoke
+  TESTING  += \
+  	$(tstClipboardGH-X11_0_OUTDIR)/tstClipboardGH-X11.run \
+  	$(tstClipboardGH-X11_0_OUTDIR)/tstClipboardGH-X11Smoke.run
+
+  tstClipboardGH-X11_TEMPLATE  = VBoxR3TstExe
+  tstClipboardGH-X11_DEFS      = VBOX_WITH_HGCM UNIT_TEST TESTCASE
+  tstClipboardGH-X11_SOURCES   = \
+  	tstClipboardGH-X11.cpp \
+  	../clipboard-x11.cpp \
+  	../clipboard-common.cpp
+  tstClipboardGH-X11_CXXFLAGS += -Wno-array-bounds
+  tstClipboardGH-X11_LIBS      = X11 Xt
+  tstClipboardGH-X11_CLEAN     = $(tstClipboardGH-X11_0_OUTDIR)/tstClipboardGH-X11.run
+
+  tstClipboardGH-X11Smoke_TEMPLATE = VBoxR3TstExe
+  tstClipboardGH-X11Smoke_DEFS     = VBOX_WITH_HGCM SMOKETEST
+  tstClipboardGH-X11Smoke_SOURCES  = \
+  	tstClipboardGH-X11Smoke.cpp \
+  	../clipboard-x11.cpp \
+  	../clipboard-common.cpp
+  tstClipboardGH-X11Smoke_LIBPATH  = $(VBOX_LIBPATH_X11)
+  tstClipboardGH-X11Smoke_LIBS     = X11 Xt
+  tstClipboardGH-X11Smoke_CLEAN    = $(tstClipboardGH-X11Smoke_0_OUTDIR)/tstClipboardGH-X11Smoke.run
+
+  $$(tstClipboardGH-X11_0_OUTDIR)/tstClipboardGH-X11.run: $$(tstClipboardGH-X11_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstClipboardGH-X11_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+
+  $$(tstClipboardGH-X11Smoke_0_OUTDIR)/tstClipboardGH-X11Smoke.run: $$(tstClipboardGH-X11Smoke_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstClipboardGH-X11Smoke_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+
+  if defined(VBOX_WITH_QTGUI)
+   include $(PATH_SUB_CURRENT)/tstClipboardQt/Makefile.kmk
+  endif
+
+
+ endif
+endif
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardGH-X11.cpp b/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardGH-X11.cpp
new file mode 100644
index 00000000..f9bc19c1
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardGH-X11.cpp
@@ -0,0 +1,941 @@
+/* $Id: tstClipboardGH-X11.cpp $ */
+/** @file
+ * Shared Clipboard guest/host X11 code test cases.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <VBox/GuestHost/SharedClipboard.h>
+#include <VBox/GuestHost/SharedClipboard-x11.h>
+#include <VBox/GuestHost/clipboard-helper.h>
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+
+#include <iprt/assert.h>
+#include <iprt/string.h>
+#include <iprt/test.h>
+#include <iprt/utf16.h>
+
+#include <poll.h>
+#include <X11/Xatom.h>
+
+
+/*********************************************************************************************************************************
+*   Externals                                                                                                                    *
+*********************************************************************************************************************************/
+extern SHCLX11FMTTABLE g_aFormats[];
+
+extern void clipUpdateX11Targets(PSHCLX11CTX pCtx, SHCLX11FMTIDX *pTargets, size_t cTargets);
+extern void clipReportEmpty(PSHCLX11CTX pCtx);
+extern void clipConvertDataFromX11Worker(void *pClient, void *pvSrc, unsigned cbSrc);
+extern SHCLX11FMTIDX clipGetTextFormatFromTargets(PSHCLX11CTX pCtx, SHCLX11FMTIDX *pTargets, size_t cTargets);
+extern SHCLX11FMT clipRealFormatForX11Format(SHCLX11FMTIDX uFmtIdx);
+extern Atom clipGetAtom(PSHCLX11CTX pCtx, const char *pcszName);
+extern void clipQueryX11Targets(PSHCLX11CTX pCtx);
+extern size_t clipReportMaxX11Formats(void);
+
+
+/*********************************************************************************************************************************
+*   Internal prototypes                                                                                                          *
+*********************************************************************************************************************************/
+static SHCLX11FMTIDX tstClipFindX11FormatByAtomText(const char *pcszAtom);
+
+
+/*********************************************************************************************************************************
+*   Prototypes, used for testcases by clipboard-x11.cpp                                                                          *
+*********************************************************************************************************************************/
+void tstRequestTargets(SHCLX11CTX* pCtx);
+void tstClipRequestData(PSHCLX11CTX pCtx, SHCLX11FMTIDX target, void *closure);
+void tstThreadScheduleCall(void (*proc)(void *, void *), void *client_data);
+
+
+/*********************************************************************************************************************************
+*   Own callback implementations                                                                                                 *
+*********************************************************************************************************************************/
+extern DECLCALLBACK(void) clipQueryX11TargetsCallback(Widget widget, XtPointer pClient,
+                                                      Atom * /* selection */, Atom *atomType,
+                                                      XtPointer pValue, long unsigned int *pcLen,
+                                                      int *piFormat);
+
+
+/*********************************************************************************************************************************
+*   Defines                                                                                                                      *
+*********************************************************************************************************************************/
+#define TESTCASE_WIDGET_ID (Widget)0xffff
+
+
+/* For the purpose of the test case, we just execute the procedure to be
+ * scheduled, as we are running single threaded. */
+void tstThreadScheduleCall(void (*proc)(void *, void *), void *client_data)
+{
+    proc(client_data, NULL);
+}
+
+/* The data in the simulated VBox clipboard. */
+static int g_tst_rcDataVBox = VINF_SUCCESS;
+static void *g_tst_pvDataVBox = NULL;
+static uint32_t g_tst_cbDataVBox = 0;
+
+/* Set empty data in the simulated VBox clipboard. */
+static void tstClipEmptyVBox(PSHCLX11CTX pCtx, int retval)
+{
+    g_tst_rcDataVBox = retval;
+    RTMemFree(g_tst_pvDataVBox);
+    g_tst_pvDataVBox = NULL;
+    g_tst_cbDataVBox = 0;
+    ShClX11ReportFormatsToX11(pCtx, 0);
+}
+
+/* Set the data in the simulated VBox clipboard. */
+static int tstClipSetVBoxUtf16(PSHCLX11CTX pCtx, int retval,
+                               const char *pcszData, size_t cb)
+{
+    PRTUTF16 pwszData = NULL;
+    size_t cwData = 0;
+    int rc = RTStrToUtf16Ex(pcszData, RTSTR_MAX, &pwszData, 0, &cwData);
+    if (RT_FAILURE(rc))
+        return rc;
+    AssertReturn(cb <= cwData * 2 + 2, VERR_BUFFER_OVERFLOW);
+    void *pv = RTMemDup(pwszData, cb);
+    RTUtf16Free(pwszData);
+    if (pv == NULL)
+        return VERR_NO_MEMORY;
+    if (g_tst_pvDataVBox)
+        RTMemFree(g_tst_pvDataVBox);
+    g_tst_rcDataVBox = retval;
+    g_tst_pvDataVBox = pv;
+    g_tst_cbDataVBox = cb;
+    ShClX11ReportFormatsToX11(pCtx, VBOX_SHCL_FMT_UNICODETEXT);
+    return VINF_SUCCESS;
+}
+
+Display *XtDisplay(Widget w) { NOREF(w); return (Display *) 0xffff; }
+
+void XtAppSetExitFlag(XtAppContext app_context) { NOREF(app_context); }
+
+void XtDestroyWidget(Widget w) { NOREF(w); }
+
+XtAppContext XtCreateApplicationContext(void) { return (XtAppContext)0xffff; }
+
+void XtDestroyApplicationContext(XtAppContext app_context) { NOREF(app_context); }
+
+void XtToolkitInitialize(void) {}
+
+Boolean XtToolkitThreadInitialize(void) { return True; }
+
+Display *XtOpenDisplay(XtAppContext app_context,
+                       _Xconst _XtString display_string,
+                       _Xconst _XtString application_name,
+                       _Xconst _XtString application_class,
+                       XrmOptionDescRec *options, Cardinal num_options,
+                       int *argc, char **argv)
+{
+    RT_NOREF8(app_context, display_string, application_name, application_class, options, num_options, argc, argv);
+    return (Display *)0xffff;
+}
+
+Widget XtVaAppCreateShell(_Xconst _XtString application_name,  _Xconst _XtString application_class,
+                          WidgetClass widget_class, Display *display, ...)
+{
+    RT_NOREF(application_name, application_class, widget_class, display);
+    return TESTCASE_WIDGET_ID;
+}
+
+void XtSetMappedWhenManaged(Widget widget, _XtBoolean mapped_when_managed) { RT_NOREF(widget, mapped_when_managed); }
+
+void XtRealizeWidget(Widget widget) { NOREF(widget); }
+
+XtInputId XtAppAddInput(XtAppContext app_context, int source, XtPointer condition, XtInputCallbackProc proc, XtPointer closure)
+{
+    RT_NOREF(app_context, source, condition, proc, closure);
+    return 0xffff;
+}
+
+/* Atoms we need other than the formats we support. */
+static const char *g_tst_apszSupAtoms[] =
+{
+    "PRIMARY", "CLIPBOARD", "TARGETS", "MULTIPLE", "TIMESTAMP"
+};
+
+/* This just looks for the atom names in a couple of tables and returns an
+ * index with an offset added. */
+Atom XInternAtom(Display *, const char *pcsz, int)
+{
+    Atom atom = 0;
+    size_t const cFormats = clipReportMaxX11Formats();
+    size_t i;
+    for (i = 0; i < cFormats; ++i)
+    {
+        if (!strcmp(pcsz, g_aFormats[i].pcszAtom))
+            atom = (Atom) (i + 0x1000);
+    }
+    for (i = 0; i < RT_ELEMENTS(g_tst_apszSupAtoms); ++i)
+        if (!strcmp(pcsz, g_tst_apszSupAtoms[i]))
+            atom = (Atom) (i + 0x2000);
+    Assert(atom);  /* Have we missed any atoms? */
+    return atom;
+}
+
+/* Take a request for the targets we are currently offering. */
+static SHCLX11FMTIDX g_tst_aSelTargetsIdx[10] = { 0 };
+static size_t g_tst_cTargets = 0;
+
+void tstRequestTargets(SHCLX11CTX* pCtx)
+{
+    clipUpdateX11Targets(pCtx, g_tst_aSelTargetsIdx, g_tst_cTargets);
+}
+
+/* The current values of the X selection, which will be returned to the
+ * XtGetSelectionValue callback. */
+static Atom g_tst_atmSelType = 0;
+static const void *g_tst_pSelData = NULL;
+static unsigned long g_tst_cSelData = 0;
+static int g_tst_selFormat = 0;
+
+void tstClipRequestData(PSHCLX11CTX pCtx, SHCLX11FMTIDX target, void *closure)
+{
+    RT_NOREF(pCtx);
+    unsigned long count = 0;
+    int format = 0;
+    if (target != g_tst_aSelTargetsIdx[0])
+    {
+        clipConvertDataFromX11Worker(closure, NULL, 0); /* Could not convert to target. */
+        return;
+    }
+    void *pValue = NULL;
+    pValue = g_tst_pSelData ? RTMemDup(g_tst_pSelData, g_tst_cSelData) : NULL;
+    count = g_tst_pSelData ? g_tst_cSelData : 0;
+    format = g_tst_selFormat;
+    if (!pValue)
+    {
+        count = 0;
+        format = 0;
+    }
+    clipConvertDataFromX11Worker(closure, pValue, count * format / 8);
+    if (pValue)
+        RTMemFree(pValue);
+}
+
+/* The formats currently on offer from X11 via the shared clipboard. */
+static uint32_t g_tst_uX11Formats = 0;
+
+static uint32_t tstClipQueryFormats(void)
+{
+    return g_tst_uX11Formats;
+}
+
+static void tstClipInvalidateFormats(void)
+{
+    g_tst_uX11Formats = ~0;
+}
+
+/* Does our clipboard code currently own the selection? */
+static bool g_tst_fOwnsSel = false;
+/* The procedure that is called when we should convert the selection to a
+ * given format. */
+static XtConvertSelectionProc g_tst_pfnSelConvert = NULL;
+/* The procedure which is called when we lose the selection. */
+static XtLoseSelectionProc g_tst_pfnSelLose = NULL;
+/* The procedure which is called when the selection transfer has completed. */
+static XtSelectionDoneProc g_tst_pfnSelDone = NULL;
+
+Boolean XtOwnSelection(Widget widget, Atom selection, Time time,
+                       XtConvertSelectionProc convert,
+                       XtLoseSelectionProc lose,
+                       XtSelectionDoneProc done)
+{
+    RT_NOREF(widget, time);
+    if (selection != XInternAtom(NULL, "CLIPBOARD", 0))
+        return True;  /* We don't really care about this. */
+    g_tst_fOwnsSel = true;  /* Always succeed. */
+    g_tst_pfnSelConvert = convert;
+    g_tst_pfnSelLose = lose;
+    g_tst_pfnSelDone = done;
+    return True;
+}
+
+void XtDisownSelection(Widget widget, Atom selection, Time time)
+{
+    RT_NOREF(widget, time, selection);
+    g_tst_fOwnsSel = false;
+    g_tst_pfnSelConvert = NULL;
+    g_tst_pfnSelLose = NULL;
+    g_tst_pfnSelDone = NULL;
+}
+
+/* Request the shared clipboard to convert its data to a given format. */
+static bool tstClipConvertSelection(const char *pcszTarget, Atom *type,
+                                    XtPointer *value, unsigned long *length,
+                                    int *format)
+{
+    Atom target = XInternAtom(NULL, pcszTarget, 0);
+    if (target == 0)
+        return false;
+    /* Initialise all return values in case we make a quick exit. */
+    *type = XA_STRING;
+    *value = NULL;
+    *length = 0;
+    *format = 0;
+    if (!g_tst_fOwnsSel)
+        return false;
+    if (!g_tst_pfnSelConvert)
+        return false;
+    Atom clipAtom = XInternAtom(NULL, "CLIPBOARD", 0);
+    if (!g_tst_pfnSelConvert(TESTCASE_WIDGET_ID, &clipAtom, &target, type,
+                             value, length, format))
+        return false;
+    if (g_tst_pfnSelDone)
+        g_tst_pfnSelDone(TESTCASE_WIDGET_ID, &clipAtom, &target);
+    return true;
+}
+
+/* Set the current X selection data */
+static void tstClipSetSelectionValues(const char *pcszTarget, Atom type,
+                                      const void *data,
+                                      unsigned long count, int format)
+{
+    Atom clipAtom = XInternAtom(NULL, "CLIPBOARD", 0);
+    g_tst_aSelTargetsIdx[0] = tstClipFindX11FormatByAtomText(pcszTarget);
+    g_tst_cTargets = 1;
+    g_tst_atmSelType = type;
+    g_tst_pSelData = data;
+    g_tst_cSelData = count;
+    g_tst_selFormat = format;
+    if (g_tst_pfnSelLose)
+        g_tst_pfnSelLose(TESTCASE_WIDGET_ID, &clipAtom);
+    g_tst_fOwnsSel = false;
+}
+
+static void tstClipSendTargetUpdate(PSHCLX11CTX pCtx)
+{
+    clipQueryX11Targets(pCtx);
+}
+
+/* Configure if and how the X11 TARGETS clipboard target will fail. */
+static void tstClipSetTargetsFailure(void)
+{
+    g_tst_cTargets = 0;
+}
+
+char *XtMalloc(Cardinal size)
+{
+    return (char *) RTMemAlloc(size);
+}
+
+void XtFree(char *ptr)
+{
+    RTMemFree((void *)ptr);
+}
+
+char *XGetAtomName(Display *display, Atom atom)
+{
+    RT_NOREF(display);
+    const char *pcszName = NULL;
+    if (atom < 0x1000)
+        return NULL;
+    if (0x1000 <= atom && atom < 0x2000)
+    {
+        unsigned index = atom - 0x1000;
+        AssertReturn(index < clipReportMaxX11Formats(), NULL);
+        pcszName = g_aFormats[index].pcszAtom;
+    }
+    else
+    {
+        unsigned index = atom - 0x2000;
+        AssertReturn(index < RT_ELEMENTS(g_tst_apszSupAtoms), NULL);
+        pcszName = g_tst_apszSupAtoms[index];
+    }
+    return (char *)RTMemDup(pcszName, sizeof(pcszName) + 1);
+}
+
+int XFree(void *data)
+{
+    RTMemFree(data);
+    return 0;
+}
+
+void XFreeStringList(char **list)
+{
+    if (list)
+        RTMemFree(*list);
+    RTMemFree(list);
+}
+
+#define TESTCASE_MAX_BUF_SIZE 256
+
+static int g_tst_rcCompleted = VINF_SUCCESS;
+static int g_tst_cbCompleted = 0;
+static CLIPREADCBREQ *g_tst_pCompletedReq = NULL;
+static char g_tst_abCompletedBuf[TESTCASE_MAX_BUF_SIZE];
+
+static DECLCALLBACK(int) tstShClReportFormatsCallback(PSHCLCONTEXT pCtx, uint32_t fFormats, void *pvUser)
+{
+    RT_NOREF(pCtx, pvUser);
+    g_tst_uX11Formats = fFormats;
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) tstShClOnRequestDataFromSourceCallback(PSHCLCONTEXT pCtx, SHCLFORMAT uFmt, void **ppv, uint32_t *pcb, void *pvUser)
+{
+    RT_NOREF(pCtx, uFmt, pvUser);
+    *pcb = g_tst_cbDataVBox;
+    if (g_tst_pvDataVBox != NULL)
+    {
+        void *pv = RTMemDup(g_tst_pvDataVBox, g_tst_cbDataVBox);
+        *ppv = pv;
+        return pv != NULL ? g_tst_rcDataVBox : VERR_NO_MEMORY;
+    }
+    *ppv = NULL;
+    return g_tst_rcDataVBox;
+}
+
+static DECLCALLBACK(int) tstShClOnSendDataToDestCallback(PSHCLCONTEXT pCtx, void *pv, uint32_t cb, void *pvUser)
+{
+    RT_NOREF(pCtx);
+
+    PSHCLX11READDATAREQ pData = (PSHCLX11READDATAREQ)pvUser;
+
+    if (cb <= TESTCASE_MAX_BUF_SIZE)
+    {
+        g_tst_rcCompleted = pData->rcCompletion;
+        if (cb != 0)
+            memcpy(g_tst_abCompletedBuf, pv, cb);
+    }
+    else
+        g_tst_rcCompleted = VERR_BUFFER_OVERFLOW;
+    g_tst_cbCompleted = cb;
+    g_tst_pCompletedReq = pData->pReq;
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Looks up the X11 format matching a given X11 atom text.
+ *
+ * @returns the format on success, NIL_CLIPX11FORMAT on failure
+ * @param   pcszAtom                Atom text to look up format for.
+ */
+static SHCLX11FMTIDX tstClipFindX11FormatByAtomText(const char *pcszAtom)
+{
+    const size_t j = clipReportMaxX11Formats();
+
+    for (unsigned i = 0; i < j; ++i)
+    {
+        if (!strcmp(g_aFormats[i].pcszAtom, pcszAtom))
+            return i;
+    }
+    return NIL_CLIPX11FORMAT;
+}
+
+static bool tstClipTextFormatConversion(PSHCLX11CTX pCtx)
+{
+    bool fSuccess = true;
+    SHCLX11FMTIDX targets[2];
+    SHCLX11FMTIDX x11Format;
+    targets[0] = tstClipFindX11FormatByAtomText("text/plain");
+    targets[1] = tstClipFindX11FormatByAtomText("image/bmp");
+    x11Format = clipGetTextFormatFromTargets(pCtx, targets, 2);
+    if (clipRealFormatForX11Format(x11Format) != SHCLX11FMT_TEXT)
+        fSuccess = false;
+    targets[0] = tstClipFindX11FormatByAtomText("UTF8_STRING");
+    targets[1] = tstClipFindX11FormatByAtomText("text/plain");
+    x11Format = clipGetTextFormatFromTargets(pCtx, targets, 2);
+    if (clipRealFormatForX11Format(x11Format) != SHCLX11FMT_UTF8)
+        fSuccess = false;
+    return fSuccess;
+}
+
+static void tstClipGetCompletedRequest(int *prc, char ** ppc, uint32_t *pcb, CLIPREADCBREQ **ppReq)
+{
+    *prc = g_tst_rcCompleted;
+    *ppc = g_tst_abCompletedBuf;
+    *pcb = g_tst_cbCompleted;
+    *ppReq = g_tst_pCompletedReq;
+}
+
+static void tstStringFromX11(RTTEST hTest, PSHCLX11CTX pCtx,
+                             const char *pcszExp, int rcExp)
+{
+    bool retval = true;
+    tstClipSendTargetUpdate(pCtx);
+    if (tstClipQueryFormats() != VBOX_SHCL_FMT_UNICODETEXT)
+    {
+        RTTestFailed(hTest, "Wrong targets reported: %02X\n", tstClipQueryFormats());
+    }
+    else
+    {
+        char *pc;
+        CLIPREADCBREQ *pReq = (CLIPREADCBREQ *)&pReq, *pReqRet = NULL;
+        ShClX11ReadDataFromX11(pCtx, VBOX_SHCL_FMT_UNICODETEXT, pReq);
+        int rc = VINF_SUCCESS;
+        uint32_t cbActual = 0;
+        tstClipGetCompletedRequest(&rc, &pc, &cbActual, &pReqRet);
+        if (rc != rcExp)
+            RTTestFailed(hTest, "Wrong return code, expected %Rrc, got %Rrc\n",
+                         rcExp, rc);
+        else if (pReqRet != pReq)
+            RTTestFailed(hTest, "Wrong returned request data, expected %p, got %p\n",
+                         pReq, pReqRet);
+        else if (RT_FAILURE(rcExp))
+            retval = true;
+        else
+        {
+            RTUTF16 wcExp[TESTCASE_MAX_BUF_SIZE / 2];
+            RTUTF16 *pwcExp = wcExp;
+            size_t cwc = 0;
+            rc = RTStrToUtf16Ex(pcszExp, RTSTR_MAX, &pwcExp,
+                                RT_ELEMENTS(wcExp), &cwc);
+            size_t cbExp = cwc * 2 + 2;
+            AssertRC(rc);
+            if (RT_SUCCESS(rc))
+            {
+                if (cbActual != cbExp)
+                {
+                    RTTestFailed(hTest, "Returned string is the wrong size, string \"%.*ls\", size %u, expected \"%s\", size %u\n",
+                                 RT_MIN(TESTCASE_MAX_BUF_SIZE, cbActual), pc, cbActual,
+                                 pcszExp, cbExp);
+                }
+                else
+                {
+                    if (memcmp(pc, wcExp, cbExp) == 0)
+                        retval = true;
+                    else
+                        RTTestFailed(hTest, "Returned string \"%.*ls\" does not match expected string \"%s\"\n",
+                                     TESTCASE_MAX_BUF_SIZE, pc, pcszExp);
+                }
+            }
+        }
+    }
+    if (!retval)
+        RTTestFailureDetails(hTest, "Expected: string \"%s\", rc %Rrc\n",
+                             pcszExp, rcExp);
+}
+
+static void tstLatin1FromX11(RTTEST hTest, PSHCLX11CTX pCtx,
+                             const char *pcszExp, int rcExp)
+{
+    bool retval = false;
+    tstClipSendTargetUpdate(pCtx);
+    if (tstClipQueryFormats() != VBOX_SHCL_FMT_UNICODETEXT)
+        RTTestFailed(hTest, "Wrong targets reported: %02X\n",
+                     tstClipQueryFormats());
+    else
+    {
+        char *pc;
+        CLIPREADCBREQ *pReq = (CLIPREADCBREQ *)&pReq, *pReqRet = NULL;
+        ShClX11ReadDataFromX11(pCtx, VBOX_SHCL_FMT_UNICODETEXT, pReq);
+        int rc = VINF_SUCCESS;
+        uint32_t cbActual = 0;
+        tstClipGetCompletedRequest(&rc, &pc, &cbActual, &pReqRet);
+        if (rc != rcExp)
+            RTTestFailed(hTest, "Wrong return code, expected %Rrc, got %Rrc\n",
+                         rcExp, rc);
+        else if (pReqRet != pReq)
+            RTTestFailed(hTest, "Wrong returned request data, expected %p, got %p\n",
+                         pReq, pReqRet);
+        else if (RT_FAILURE(rcExp))
+            retval = true;
+        else
+        {
+            RTUTF16 wcExp[TESTCASE_MAX_BUF_SIZE / 2];
+            //RTUTF16 *pwcExp = wcExp; - unused
+            size_t cwc;
+            for (cwc = 0; cwc == 0 || pcszExp[cwc - 1] != '\0'; ++cwc)
+                wcExp[cwc] = pcszExp[cwc];
+            size_t cbExp = cwc * 2;
+            if (cbActual != cbExp)
+            {
+                RTTestFailed(hTest, "Returned string is the wrong size, string \"%.*ls\", size %u, expected \"%s\", size %u\n",
+                             RT_MIN(TESTCASE_MAX_BUF_SIZE, cbActual), pc, cbActual,
+                             pcszExp, cbExp);
+            }
+            else
+            {
+                if (memcmp(pc, wcExp, cbExp) == 0)
+                    retval = true;
+                else
+                    RTTestFailed(hTest, "Returned string \"%.*ls\" does not match expected string \"%s\"\n",
+                                 TESTCASE_MAX_BUF_SIZE, pc, pcszExp);
+            }
+        }
+    }
+    if (!retval)
+        RTTestFailureDetails(hTest, "Expected: string \"%s\", rc %Rrc\n",
+                             pcszExp, rcExp);
+}
+
+static void tstStringFromVBox(RTTEST hTest, PSHCLX11CTX pCtx, const char *pcszTarget, Atom typeExp,  const char *valueExp)
+{
+    RT_NOREF(pCtx);
+    bool retval = false;
+    Atom type;
+    XtPointer value = NULL;
+    unsigned long length;
+    int format;
+    size_t lenExp = strlen(valueExp);
+    if (tstClipConvertSelection(pcszTarget, &type, &value, &length, &format))
+    {
+        if (   type != typeExp
+            || length != lenExp
+            || format != 8
+            || memcmp((const void *) value, (const void *)valueExp,
+                      lenExp))
+        {
+            RTTestFailed(hTest, "Bad data: type %d, (expected %d), length %u, (expected %u), format %d (expected %d), value \"%.*s\" (expected \"%.*s\")\n",
+                     type, typeExp, length, lenExp, format, 8,
+                     RT_MIN(length, 20), value, RT_MIN(lenExp, 20), valueExp);
+        }
+        else
+            retval = true;
+    }
+    else
+        RTTestFailed(hTest, "Conversion failed\n");
+    XtFree((char *)value);
+    if (!retval)
+        RTTestFailureDetails(hTest, "Conversion to %s, expected \"%s\"\n",
+                             pcszTarget, valueExp);
+}
+
+static void tstNoX11(PSHCLX11CTX pCtx, const char *pcszTestCtx)
+{
+    CLIPREADCBREQ *pReq = (CLIPREADCBREQ *)&pReq;
+    int rc = ShClX11ReadDataFromX11(pCtx, VBOX_SHCL_FMT_UNICODETEXT, pReq);
+    RTTESTI_CHECK_MSG(rc == VERR_NO_DATA, ("context: %s\n", pcszTestCtx));
+}
+
+static void tstStringFromVBoxFailed(RTTEST hTest, PSHCLX11CTX pCtx, const char *pcszTarget)
+{
+    RT_NOREF(pCtx);
+    Atom type;
+    XtPointer value = NULL;
+    unsigned long length;
+    int format;
+    RTTEST_CHECK_MSG(hTest, !tstClipConvertSelection(pcszTarget, &type, &value,
+                                                     &length, &format),
+                     (hTest, "Conversion to target %s, should have failed but didn't, returned type %d, length %u, format %d, value \"%.*s\"\n",
+                      pcszTarget, type, length, format, RT_MIN(length, 20),
+                      value));
+    XtFree((char *)value);
+}
+
+static void tstNoSelectionOwnership(PSHCLX11CTX pCtx, const char *pcszTestCtx)
+{
+    RT_NOREF(pCtx);
+    RTTESTI_CHECK_MSG(!g_tst_fOwnsSel, ("context: %s\n", pcszTestCtx));
+}
+
+static void tstBadFormatRequestFromHost(RTTEST hTest, PSHCLX11CTX pCtx)
+{
+    tstClipSetSelectionValues("UTF8_STRING", XA_STRING, "hello world",
+                           sizeof("hello world"), 8);
+    tstClipSendTargetUpdate(pCtx);
+    if (tstClipQueryFormats() != VBOX_SHCL_FMT_UNICODETEXT)
+        RTTestFailed(hTest, "Wrong targets reported: %02X\n",
+                     tstClipQueryFormats());
+    else
+    {
+        char *pc;
+        CLIPREADCBREQ *pReq = (CLIPREADCBREQ *)&pReq, *pReqRet = NULL;
+        ShClX11ReadDataFromX11(pCtx, 0xF000 /* vboxFormat */, pReq);  /* Bad format. */
+        int rc = VINF_SUCCESS;
+        uint32_t cbActual = 0;
+        tstClipGetCompletedRequest(&rc, &pc, &cbActual, &pReqRet);
+        if (rc != VERR_NOT_IMPLEMENTED)
+            RTTestFailed(hTest, "Wrong return code, expected VERR_NOT_IMPLEMENTED, got %Rrc\n",
+                         rc);
+        tstClipSetSelectionValues("", XA_STRING, "", sizeof(""), 8);
+        tstClipSendTargetUpdate(pCtx);
+        if (tstClipQueryFormats() == VBOX_SHCL_FMT_UNICODETEXT)
+            RTTestFailed(hTest, "Failed to report targets after bad host request.\n");
+    }
+}
+
+int main()
+{
+    /*
+     * Init the runtime, test and say hello.
+     */
+    RTTEST hTest;
+    int rc = RTTestInitAndCreate("tstClipboardGH-X11", &hTest);
+    if (RT_FAILURE(rc))
+        return RTEXITCODE_FAILURE;
+    RTTestBanner(hTest);
+
+    /*
+     * Run the tests.
+     */
+    SHCLCALLBACKS Callbacks;
+    RT_ZERO(Callbacks);
+    Callbacks.pfnReportFormats           = tstShClReportFormatsCallback;
+    Callbacks.pfnOnRequestDataFromSource = tstShClOnRequestDataFromSourceCallback;
+    Callbacks.pfnOnSendDataToDest        = tstShClOnSendDataToDestCallback;
+
+    SHCLX11CTX X11Ctx;
+    rc = ShClX11Init(&X11Ctx, &Callbacks, NULL /* pParent */, false /* fHeadless */);
+    AssertRCReturn(rc, RTEXITCODE_FAILURE);
+
+    char *pc;
+    uint32_t cbActual;
+    CLIPREADCBREQ *pReq = (CLIPREADCBREQ *)&pReq, *pReqRet = NULL;
+
+    /* UTF-8 from X11 */
+    RTTestSub(hTest, "reading UTF-8 from X11");
+    /* Simple test */
+    tstClipSetSelectionValues("UTF8_STRING", XA_STRING, "hello world",
+                              sizeof("hello world"), 8);
+    tstStringFromX11(hTest, &X11Ctx, "hello world", VINF_SUCCESS);
+    /* With an embedded carriage return */
+    tstClipSetSelectionValues("text/plain;charset=UTF-8", XA_STRING,
+                              "hello\nworld", sizeof("hello\nworld"), 8);
+    tstStringFromX11(hTest, &X11Ctx, "hello\r\nworld", VINF_SUCCESS);
+    /* With an embedded CRLF */
+    tstClipSetSelectionValues("text/plain;charset=UTF-8", XA_STRING,
+                              "hello\r\nworld", sizeof("hello\r\nworld"), 8);
+    tstStringFromX11(hTest, &X11Ctx, "hello\r\r\nworld", VINF_SUCCESS);
+    /* With an embedded LFCR */
+    tstClipSetSelectionValues("text/plain;charset=UTF-8", XA_STRING,
+                              "hello\n\rworld", sizeof("hello\n\rworld"), 8);
+    tstStringFromX11(hTest, &X11Ctx, "hello\r\n\rworld", VINF_SUCCESS);
+    /* An empty string */
+    tstClipSetSelectionValues("text/plain;charset=utf-8", XA_STRING, "",
+                              sizeof(""), 8);
+    tstStringFromX11(hTest, &X11Ctx, "", VINF_SUCCESS);
+    /* With an embedded UTF-8 character. */
+    tstClipSetSelectionValues("STRING", XA_STRING,
+                              "100\xE2\x82\xAC" /* 100 Euro */,
+                              sizeof("100\xE2\x82\xAC"), 8);
+    tstStringFromX11(hTest, &X11Ctx, "100\xE2\x82\xAC", VINF_SUCCESS);
+    /* A non-zero-terminated string */
+    tstClipSetSelectionValues("TEXT", XA_STRING,
+                              "hello world", sizeof("hello world") - 1, 8);
+    tstStringFromX11(hTest, &X11Ctx, "hello world", VINF_SUCCESS);
+
+    /* Latin1 from X11 */
+    RTTestSub(hTest, "reading Latin1 from X11");
+    /* Simple test */
+    tstClipSetSelectionValues("STRING", XA_STRING, "Georges Dupr\xEA",
+                              sizeof("Georges Dupr\xEA"), 8);
+    tstLatin1FromX11(hTest, &X11Ctx, "Georges Dupr\xEA", VINF_SUCCESS);
+    /* With an embedded carriage return */
+    tstClipSetSelectionValues("TEXT", XA_STRING, "Georges\nDupr\xEA",
+                              sizeof("Georges\nDupr\xEA"), 8);
+    tstLatin1FromX11(hTest, &X11Ctx, "Georges\r\nDupr\xEA", VINF_SUCCESS);
+    /* With an embedded CRLF */
+    tstClipSetSelectionValues("TEXT", XA_STRING, "Georges\r\nDupr\xEA",
+                              sizeof("Georges\r\nDupr\xEA"), 8);
+    tstLatin1FromX11(hTest, &X11Ctx, "Georges\r\r\nDupr\xEA", VINF_SUCCESS);
+    /* With an embedded LFCR */
+    tstClipSetSelectionValues("TEXT", XA_STRING, "Georges\n\rDupr\xEA",
+                              sizeof("Georges\n\rDupr\xEA"), 8);
+    tstLatin1FromX11(hTest, &X11Ctx, "Georges\r\n\rDupr\xEA", VINF_SUCCESS);
+    /* A non-zero-terminated string */
+    tstClipSetSelectionValues("text/plain", XA_STRING,
+                              "Georges Dupr\xEA!",
+                              sizeof("Georges Dupr\xEA!") - 1, 8);
+    tstLatin1FromX11(hTest, &X11Ctx, "Georges Dupr\xEA!", VINF_SUCCESS);
+
+    /*
+     * Unknown X11 format
+     */
+    RTTestSub(hTest, "handling of an unknown X11 format");
+    tstClipInvalidateFormats();
+    tstClipSetSelectionValues("CLIPBOARD", XA_STRING, "Test",
+                              sizeof("Test"), 8);
+    tstClipSendTargetUpdate(&X11Ctx);
+    RTTEST_CHECK_MSG(hTest, tstClipQueryFormats() == 0,
+                     (hTest, "Failed to send a format update notification\n"));
+
+    /*
+     * Timeout from X11
+     */
+    RTTestSub(hTest, "X11 timeout");
+    tstClipSetSelectionValues("UTF8_STRING", XT_CONVERT_FAIL, NULL,0, 8);
+    tstStringFromX11(hTest, &X11Ctx, "", VERR_NO_DATA);
+
+    /*
+     * No data in X11 clipboard
+     */
+    RTTestSub(hTest, "a data request from an empty X11 clipboard");
+    tstClipSetSelectionValues("UTF8_STRING", XA_STRING, NULL,
+                              0, 8);
+    ShClX11ReadDataFromX11(&X11Ctx, VBOX_SHCL_FMT_UNICODETEXT, pReq);
+    tstClipGetCompletedRequest(&rc, &pc, &cbActual, &pReqRet);
+    RTTEST_CHECK_MSG(hTest, rc == VERR_NO_DATA,
+                     (hTest, "Returned %Rrc instead of VERR_NO_DATA\n",
+                      rc));
+    RTTEST_CHECK_MSG(hTest, pReqRet == pReq,
+                     (hTest, "Wrong returned request data, expected %p, got %p\n",
+                     pReq, pReqRet));
+
+    /*
+     * Ensure that VBox is notified when we return the CB to X11
+     */
+    RTTestSub(hTest, "notification of switch to X11 clipboard");
+    tstClipInvalidateFormats();
+    clipReportEmpty(&X11Ctx);
+    RTTEST_CHECK_MSG(hTest, tstClipQueryFormats() == 0,
+                     (hTest, "Failed to send a format update (release) notification\n"));
+
+    /*
+     * Request for an invalid VBox format from X11
+     */
+    RTTestSub(hTest, "a request for an invalid VBox format from X11");
+    /* Testing for 0xffff will go into handling VBOX_SHCL_FMT_UNICODETEXT, where we don't have
+     * have any data at the moment so far, so this will return VERR_NO_DATA. */
+    ShClX11ReadDataFromX11(&X11Ctx, 0xffff /* vboxFormat */, pReq);
+    tstClipGetCompletedRequest(&rc, &pc, &cbActual, &pReqRet);
+    RTTEST_CHECK_MSG(hTest, rc == VERR_NO_DATA,
+                     (hTest, "Returned %Rrc instead of VERR_NO_DATA\n",
+                      rc));
+    RTTEST_CHECK_MSG(hTest, pReqRet == pReq,
+                     (hTest, "Wrong returned request data, expected %p, got %p\n",
+                     pReq, pReqRet));
+
+    /*
+     * Targets failure from X11
+     */
+    RTTestSub(hTest, "X11 targets conversion failure");
+    tstClipSetSelectionValues("UTF8_STRING", XA_STRING, "hello world",
+                              sizeof("hello world"), 8);
+    tstClipSetTargetsFailure();
+    Atom atom = XA_STRING;
+    long unsigned int cLen = 0;
+    int format = 8;
+    clipQueryX11TargetsCallback(NULL, (XtPointer) &X11Ctx, NULL, &atom, NULL, &cLen,
+                                &format);
+    RTTEST_CHECK_MSG(hTest, tstClipQueryFormats() == 0,
+                     (hTest, "Wrong targets reported: %02X\n",
+                      tstClipQueryFormats()));
+
+    /*
+     * X11 text format conversion
+     */
+    RTTestSub(hTest, "handling of X11 selection targets");
+    RTTEST_CHECK_MSG(hTest, tstClipTextFormatConversion(&X11Ctx),
+                     (hTest, "failed to select the right X11 text formats\n"));
+    /*
+     * UTF-8 from VBox
+     */
+    RTTestSub(hTest, "reading UTF-8 from VBox");
+    /* Simple test */
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "hello world",
+                        sizeof("hello world") * 2);
+    tstStringFromVBox(hTest, &X11Ctx, "UTF8_STRING",
+                      clipGetAtom(&X11Ctx, "UTF8_STRING"), "hello world");
+    /* With an embedded carriage return */
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "hello\r\nworld",
+                        sizeof("hello\r\nworld") * 2);
+    tstStringFromVBox(hTest, &X11Ctx, "text/plain;charset=UTF-8",
+                      clipGetAtom(&X11Ctx, "text/plain;charset=UTF-8"),
+                      "hello\nworld");
+    /* With an embedded CRCRLF */
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "hello\r\r\nworld",
+                        sizeof("hello\r\r\nworld") * 2);
+    tstStringFromVBox(hTest, &X11Ctx, "text/plain;charset=UTF-8",
+                      clipGetAtom(&X11Ctx, "text/plain;charset=UTF-8"),
+                      "hello\r\nworld");
+    /* With an embedded CRLFCR */
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "hello\r\n\rworld",
+                        sizeof("hello\r\n\rworld") * 2);
+    tstStringFromVBox(hTest, &X11Ctx, "text/plain;charset=UTF-8",
+                      clipGetAtom(&X11Ctx, "text/plain;charset=UTF-8"),
+                      "hello\n\rworld");
+    /* An empty string */
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "", 2);
+    tstStringFromVBox(hTest, &X11Ctx, "text/plain;charset=utf-8",
+                      clipGetAtom(&X11Ctx, "text/plain;charset=utf-8"), "");
+    /* With an embedded UTF-8 character. */
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "100\xE2\x82\xAC" /* 100 Euro */,
+                        10);
+    tstStringFromVBox(hTest, &X11Ctx, "STRING",
+                      clipGetAtom(&X11Ctx, "STRING"), "100\xE2\x82\xAC");
+    /* A non-zero-terminated string */
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "hello world",
+                        sizeof("hello world") * 2 - 2);
+    tstStringFromVBox(hTest, &X11Ctx, "TEXT", clipGetAtom(&X11Ctx, "TEXT"),
+                     "hello world");
+
+    /*
+     * Timeout from VBox
+     */
+    RTTestSub(hTest, "reading from VBox with timeout");
+    tstClipEmptyVBox(&X11Ctx, VERR_TIMEOUT);
+    tstStringFromVBoxFailed(hTest, &X11Ctx, "UTF8_STRING");
+
+    /*
+     * No data in VBox clipboard
+     */
+    RTTestSub(hTest, "an empty VBox clipboard");
+    tstClipSetSelectionValues("TEXT", XA_STRING, "", sizeof(""), 8);
+    tstClipEmptyVBox(&X11Ctx, VINF_SUCCESS);
+    RTTEST_CHECK_MSG(hTest, g_tst_fOwnsSel,
+                     (hTest, "VBox grabbed the clipboard with no data and we ignored it\n"));
+    tstStringFromVBoxFailed(hTest, &X11Ctx, "UTF8_STRING");
+
+    /*
+     * An unknown VBox format
+     */
+    RTTestSub(hTest, "reading an unknown VBox format");
+    tstClipSetSelectionValues("TEXT", XA_STRING, "", sizeof(""), 8);
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "", 2);
+    ShClX11ReportFormatsToX11(&X11Ctx, 0xa0000);
+    RTTEST_CHECK_MSG(hTest, g_tst_fOwnsSel,
+                     (hTest, "VBox grabbed the clipboard with unknown data and we ignored it\n"));
+    tstStringFromVBoxFailed(hTest, &X11Ctx, "UTF8_STRING");
+
+    /*
+     * VBox requests a bad format
+     */
+    RTTestSub(hTest, "recovery from a bad format request");
+    tstBadFormatRequestFromHost(hTest, &X11Ctx);
+
+    ShClX11Destroy(&X11Ctx);
+
+    /*
+     * Headless clipboard tests
+     */
+    rc = ShClX11Init(&X11Ctx, &Callbacks, NULL /* pParent */, true /* fHeadless */);
+    AssertRCReturn(rc, RTEXITCODE_FAILURE);
+
+    /* Read from X11 */
+    RTTestSub(hTest, "reading from X11, headless clipboard");
+    /* Simple test */
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "",
+                        sizeof("") * 2);
+    tstClipSetSelectionValues("UTF8_STRING", XA_STRING, "hello world",
+                              sizeof("hello world"), 8);
+    tstNoX11(&X11Ctx, "reading from X11, headless clipboard");
+
+    /* Read from VBox */
+    RTTestSub(hTest, "reading from VBox, headless clipboard");
+    /* Simple test */
+    tstClipEmptyVBox(&X11Ctx, VERR_WRONG_ORDER);
+    tstClipSetSelectionValues("TEXT", XA_STRING, "", sizeof(""), 8);
+    tstClipSetVBoxUtf16(&X11Ctx, VINF_SUCCESS, "hello world",
+                        sizeof("hello world") * 2);
+    tstNoSelectionOwnership(&X11Ctx, "reading from VBox, headless clipboard");
+
+    ShClX11Destroy(&X11Ctx);
+
+    return RTTestSummaryAndDestroy(hTest);
+}
+
diff --git a/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardGH-X11Smoke.cpp b/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardGH-X11Smoke.cpp
new file mode 100644
index 00000000..226c6fac
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardGH-X11Smoke.cpp
@@ -0,0 +1,103 @@
+/* $Id: tstClipboardGH-X11Smoke.cpp $ */
+/** @file
+ * Shared Clipboard guest/host X11 code smoke tests.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+/* This is a simple test case that just starts a copy of the X11 clipboard
+ * backend, checks the X11 clipboard and exits.  If ever needed I will add an
+ * interactive mode in which the user can read and copy to the clipboard from
+ * the command line. */
+
+#include <iprt/assert.h>
+#include <iprt/env.h>
+#include <iprt/err.h>
+#include <iprt/test.h>
+
+#include <VBox/GuestHost/SharedClipboard.h>
+#include <VBox/GuestHost/SharedClipboard-x11.h>
+#include <VBox/GuestHost/clipboard-helper.h>
+
+
+static DECLCALLBACK(int) tstShClReportFormatsCallback(PSHCLCONTEXT pCtx, uint32_t fFormats, void *pvUser)
+{
+    RT_NOREF(pCtx, fFormats, pvUser);
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) tstShClOnRequestDataFromSourceCallback(PSHCLCONTEXT pCtx, SHCLFORMAT uFmt, void **ppv, uint32_t *pcb, void *pvUser)
+{
+    RT_NOREF(pCtx, uFmt, ppv, pcb, pvUser);
+    return VERR_NO_DATA;
+}
+
+static DECLCALLBACK(int) tstShClOnSendDataToDest(PSHCLCONTEXT pCtx, void *pv, uint32_t cb, void *pvUser)
+{
+    RT_NOREF(pCtx, pv, cb, pvUser);
+    return VINF_SUCCESS;
+}
+
+int main()
+{
+    /*
+     * Init the runtime, test and say hello.
+     */
+    RTTEST hTest;
+    int rc = RTTestInitAndCreate("tstClipboardGH-X11Smoke", &hTest);
+    if (rc)
+        return rc;
+    RTTestBanner(hTest);
+
+    /*
+     * Run the test.
+     */
+    rc = VINF_SUCCESS;
+    /* We can't test anything without an X session, so just return success
+     * in that case. */
+    if (!RTEnvExist("DISPLAY"))
+    {
+        RTTestPrintf(hTest, RTTESTLVL_INFO,
+                     "X11 not available, not running test\n");
+        return RTTestSummaryAndDestroy(hTest);
+    }
+
+    SHCLCALLBACKS Callbacks;
+    RT_ZERO(Callbacks);
+    Callbacks.pfnReportFormats           = tstShClReportFormatsCallback;
+    Callbacks.pfnOnRequestDataFromSource = tstShClOnRequestDataFromSourceCallback;
+    Callbacks.pfnOnSendDataToDest        = tstShClOnSendDataToDest;
+
+    SHCLX11CTX X11Ctx;
+    rc = ShClX11Init(&X11Ctx, &Callbacks, NULL /* pParent */, false);
+    AssertRCReturn(rc, 1);
+    rc = ShClX11ThreadStart(&X11Ctx, false /* fGrab */);
+    AssertRCReturn(rc, 1);
+    /* Give the clipboard time to synchronise. */
+    RTThreadSleep(500);
+    rc = ShClX11ThreadStop(&X11Ctx);
+    AssertRCReturn(rc, 1);
+    ShClX11Destroy(&X11Ctx);
+    return RTTestSummaryAndDestroy(hTest);
+}
+
diff --git a/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardQt/Makefile.kmk b/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardQt/Makefile.kmk
new file mode 100644
index 00000000..bd9401a3
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardQt/Makefile.kmk
@@ -0,0 +1,52 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for tstClipboardQt.
+#
+
+#
+# Copyright (C) 2011-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+#
+# Targets and units.
+#
+USES += qt5
+PROGRAMS += tstClipboardQt
+
+#
+# tstClipboardQt
+#
+tstClipboardQt_TEMPLATE = VBoxQtGuiExe
+tstClipboardQt_NAME = tstClipboardQt
+tstClipboardQt_CXXFLAGS = \
+	$(VBOX_GCC_Wno-implicit-fallthrough) \
+	$(VBOX_GCC_Wno-deprecated-declarations)
+
+tstClipboardQt_SOURCES = \
+	tstClipboardQt.cpp
+
+# The Qt modules we're using.
+tstClipboardQt_QT_MODULES = Core Gui Widgets PrintSupport
+
+include $(FILE_KBUILD_SUB_FOOTER)
diff --git a/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardQt/tstClipboardQt.cpp b/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardQt/tstClipboardQt.cpp
new file mode 100644
index 00000000..ebf3e8fb
--- /dev/null
+++ b/src/VBox/GuestHost/SharedClipboard/testcase/tstClipboardQt/tstClipboardQt.cpp
@@ -0,0 +1,47 @@
+/* $Id: tstClipboardQt.cpp $ */
+/** @file
+ * Shared Clipboard guest/host Qt code test cases.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <QApplication>
+#include <QMainWindow>
+#include <QTextEdit>
+#include <QHBoxLayout>
+int main(int argc, char *argv[])
+{
+    QApplication app(argc, argv);
+    QMainWindow window;
+    QWidget *pWidget = new QWidget;
+    window.setCentralWidget(pWidget);
+    QHBoxLayout *pLayout = new QHBoxLayout(pWidget);
+
+    QTextEdit *pTextEdit = new QTextEdit;
+    pLayout->addWidget(pTextEdit);
+
+
+    window.show();
+
+    app.exec();
+}