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

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

1 files changed, 1625 insertions, 0 deletions

diff --git a/src/VBox/Main/src-client/GuestDnDPrivate.cpp b/src/VBox/Main/src-client/GuestDnDPrivate.cpp
new file mode 100644
index 00000000..3007e181
--- /dev/null
+++ b/src/VBox/Main/src-client/GuestDnDPrivate.cpp
@@ -0,0 +1,1625 @@
+/* $Id: GuestDnDPrivate.cpp $ */
+/** @file
+ * Private guest drag and drop code, used by GuestDnDTarget + GuestDnDSource.
+ */
+
+/*
+ * 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
+ */
+
+#define LOG_GROUP LOG_GROUP_GUEST_DND
+#include "LoggingNew.h"
+
+#include "GuestImpl.h"
+#include "AutoCaller.h"
+
+#ifdef VBOX_WITH_DRAG_AND_DROP
+# include "ConsoleImpl.h"
+# include "ProgressImpl.h"
+# include "GuestDnDPrivate.h"
+
+# include <algorithm>
+
+# include <iprt/dir.h>
+# include <iprt/path.h>
+# include <iprt/stream.h>
+# include <iprt/semaphore.h>
+# include <iprt/cpp/utils.h>
+
+# include <VMMDev.h>
+
+# include <VBox/GuestHost/DragAndDrop.h>
+# include <VBox/HostServices/DragAndDropSvc.h>
+# include <VBox/version.h>
+
+/** @page pg_main_dnd  Dungeons & Dragons - Overview
+ * Overview:
+ *
+ * Drag and Drop is handled over the internal HGCM service for the host <->
+ * guest communication. Beside that we need to map the Drag and Drop protocols
+ * of the various OS's we support to our internal channels, this is also highly
+ * communicative in both directions. Unfortunately HGCM isn't really designed
+ * for that. Next we have to foul some of the components. This includes to
+ * trick X11 on the guest side, but also Qt needs to be tricked on the host
+ * side a little bit.
+ *
+ * The following components are involved:
+ *
+ * 1. GUI: Uses the Qt classes for Drag and Drop and mainly forward the content
+ *    of it to the Main IGuest / IGuestDnDSource / IGuestDnDTarget interfaces.
+ * 2. Main: Public interface for doing Drag and Drop. Also manage the IProgress
+ *    interfaces for blocking the caller by showing a progress dialog (see
+ *    this file).
+ * 3. HGCM service: Handle all messages from the host to the guest at once and
+ *    encapsulate the internal communication details (see dndmanager.cpp and
+ *    friends).
+ * 4. Guest Additions: Split into the platform neutral part (see
+ *    VBoxGuestR3LibDragAndDrop.cpp) and the guest OS specific parts.
+ *    Receive/send message from/to the HGCM service and does all guest specific
+ *    operations. For Windows guests VBoxTray is in charge, whereas on UNIX-y guests
+ *    VBoxClient will be used.
+ *
+ * Terminology:
+ *
+ * All transfers contain a MIME format and according meta data. This meta data then can
+ * be interpreted either as raw meta data or something else. When raw meta data is
+ * being handled, this gets passed through to the destination (guest / host) without
+ * modification. Other meta data (like URI lists) can and will be modified by the
+ * receiving side before passing to OS. How and when modifications will be applied
+ * depends on the MIME format.
+ *
+ * Host -> Guest:
+ * 1. There are DnD Enter, Move, Leave events which are send exactly like this
+ *    to the guest. The info includes the position, MIME types and allowed actions.
+ *    The guest has to respond with an action it would accept, so the GUI could
+ *    change the cursor accordingly.
+ * 2. On drop, first a drop event is sent. If this is accepted a drop data
+ *    event follows. This blocks the GUI and shows some progress indicator.
+ *
+ * Guest -> Host:
+ * 1. The GUI is asking the guest if a DnD event is pending when the user moves
+ *    the cursor out of the view window. If so, this returns the mimetypes and
+ *    allowed actions.
+ * (2. On every mouse move this is asked again, to make sure the DnD event is
+ *     still valid.)
+ * 3. On drop the host request the data from the guest. This blocks the GUI and
+ *    shows some progress indicator.
+ *
+ * Implementation hints:
+ * m_strSupportedFormats here in this file defines the allowed mime-types.
+ * This is necessary because we need special handling for some of the
+ * mime-types. E.g. for URI lists we need to transfer the actual dirs and
+ * files. Text EOL may to be changed. Also unknown mime-types may need special
+ * handling as well, which may lead to undefined behavior in the host/guest, if
+ * not done.
+ *
+ * Dropping of a directory, means recursively transferring _all_ the content.
+ *
+ * Directories and files are placed into the user's temporary directory on the
+ * guest (e.g. /tmp/VirtualBox Dropped Files). We can't delete them after the
+ * DnD operation, because we didn't know what the DnD target does with it. E.g.
+ * it could just be opened in place. This could lead ofc to filling up the disk
+ * within the guest. To inform the user about this, a small app could be
+ * developed which scans this directory regularly and inform the user with a
+ * tray icon hint (and maybe the possibility to clean this up instantly). The
+ * same has to be done in the G->H direction when it is implemented.
+ *
+ * Only regular files are supported; symlinks are not allowed.
+ *
+ * Transfers currently are an all-succeed or all-fail operation (see todos).
+ *
+ * On MacOS hosts we had to implement own DnD "promises" support for file transfers,
+ * as Qt does not support this out-of-the-box.
+ *
+ * The code tries to preserve the file modes of the transfered directories / files.
+ * This is useful (and maybe necessary) for two things:
+ * 1. If a file is executable, it should be also after the transfer, so the
+ *    user can just execute it, without manually tweaking the modes first.
+ * 2. If a dir/file is not accessible by group/others in the host, it shouldn't
+ *    be in the guest.
+ * In any case, the user mode is always set to rwx (so that we can access it
+ * ourself, in e.g. for a cleanup case after cancel).
+ *
+ * ACEs / ACLs currently are not supported.
+ *
+ * Cancelling ongoing transfers is supported in both directions by the guest
+ * and/or host side and cleans up all previous steps. This also involves
+ * removing partially transferred directories / files in the temporary directory.
+ *
+ ** @todo
+ * - ESC doesn't really work (on Windows guests it's already implemented)
+ *   ... in any case it seems a little bit difficult to handle from the Qt side.
+ * - Transfers currently do not have any interactive (UI) callbacks / hooks which
+ *   e.g. would allow to skip / replace / rename and entry, or abort the operation on failure.
+ * - Add support for more MIME types (especially images, csv)
+ * - Test unusual behavior:
+ *   - DnD service crash in the guest during a DnD op (e.g. crash of VBoxClient or X11)
+ *   - Not expected order of the events between HGCM and the guest
+ * - Security considerations: We transfer a lot of memory between the guest and
+ *   the host and even allow the creation of dirs/files. Maybe there should be
+ *   limits introduced to preventing DoS attacks or filling up all the memory
+ *   (both in the host and the guest).
+ */
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+
+/** Tries locking the GuestDnD object and returns on failure. */
+#define GUESTDND_LOCK() do { \
+        int const vrcLock = RTCritSectEnter(&m_CritSect); \
+        if (RT_SUCCESS(vrcLock)) { /* likely */ } else return vrcLock; \
+    } while (0)
+
+/** Tries locking the GuestDnD object and returns a_Ret failure. */
+#define GUESTDND_LOCK_RET(a_Ret) do { \
+        int const vrcLock = RTCritSectEnter(&m_CritSect); \
+        if (RT_SUCCESS(vrcLock)) { /* likely */ } else return vrcLock; \
+    } while (0)
+
+/** Unlocks a formerly locked GuestDnD object. */
+#define GUESTDND_UNLOCK() do { \
+        int const vrcUnlock = RTCritSectLeave(&m_CritSect); \
+        AssertRC(vrcUnlock); \
+    } while (0)
+
+
+/*********************************************************************************************************************************
+*   GuestDnDSendCtx implementation.                                                                                              *
+*********************************************************************************************************************************/
+
+GuestDnDSendCtx::GuestDnDSendCtx(void)
+    : pTarget(NULL)
+    , pState(NULL)
+{
+    reset();
+}
+
+/**
+ * Resets a GuestDnDSendCtx object.
+ */
+void GuestDnDSendCtx::reset(void)
+{
+    uScreenID  = 0;
+
+    Transfer.reset();
+
+    int vrc2 = EventCallback.Reset();
+    AssertRC(vrc2);
+
+    GuestDnDData::reset();
+}
+
+
+/*********************************************************************************************************************************
+*   GuestDnDRecvCtx implementation.                                                                                              *
+*********************************************************************************************************************************/
+
+GuestDnDRecvCtx::GuestDnDRecvCtx(void)
+    : pSource(NULL)
+    , pState(NULL)
+{
+    reset();
+}
+
+/**
+ * Resets a GuestDnDRecvCtx object.
+ */
+void GuestDnDRecvCtx::reset(void)
+{
+    lstFmtOffered.clear();
+    strFmtReq  = "";
+    strFmtRecv = "";
+    enmAction  = 0;
+
+    Transfer.reset();
+
+    int vrc2 = EventCallback.Reset();
+    AssertRC(vrc2);
+
+    GuestDnDData::reset();
+}
+
+
+/*********************************************************************************************************************************
+*   GuestDnDCallbackEvent implementation.                                                                                        *
+*********************************************************************************************************************************/
+
+GuestDnDCallbackEvent::~GuestDnDCallbackEvent(void)
+{
+    if (NIL_RTSEMEVENT != m_SemEvent)
+        RTSemEventDestroy(m_SemEvent);
+}
+
+/**
+ * Resets a GuestDnDCallbackEvent object.
+ */
+int GuestDnDCallbackEvent::Reset(void)
+{
+    int vrc = VINF_SUCCESS;
+
+    if (m_SemEvent == NIL_RTSEMEVENT)
+        vrc = RTSemEventCreate(&m_SemEvent);
+
+    m_vrc = VINF_SUCCESS;
+    return vrc;
+}
+
+/**
+ * Completes a callback event by notifying the waiting side.
+ *
+ * @returns VBox status code.
+ * @param   vrc                 Result code to use for the event completion.
+ */
+int GuestDnDCallbackEvent::Notify(int vrc /* = VINF_SUCCESS */)
+{
+    m_vrc = vrc;
+    return RTSemEventSignal(m_SemEvent);
+}
+
+/**
+ * Waits on a callback event for being notified.
+ *
+ * @returns VBox status code.
+ * @param   msTimeout           Timeout (in ms) to wait for callback event.
+ */
+int GuestDnDCallbackEvent::Wait(RTMSINTERVAL msTimeout)
+{
+    return RTSemEventWait(m_SemEvent, msTimeout);
+}
+
+
+/*********************************************************************************************************************************
+*   GuestDnDState implementation                                                                                                 *
+*********************************************************************************************************************************/
+
+GuestDnDState::GuestDnDState(const ComObjPtr<Guest>& pGuest)
+    : m_uProtocolVersion(0)
+    , m_fGuestFeatures0(VBOX_DND_GF_NONE)
+    , m_EventSem(NIL_RTSEMEVENT)
+    , m_pParent(pGuest)
+{
+    reset();
+
+    int vrc = RTCritSectInit(&m_CritSect);
+    if (RT_FAILURE(vrc))
+        throw vrc;
+    vrc = RTSemEventCreate(&m_EventSem);
+    if (RT_FAILURE(vrc))
+        throw vrc;
+}
+
+GuestDnDState::~GuestDnDState(void)
+{
+    int vrc = RTSemEventDestroy(m_EventSem);
+    AssertRC(vrc);
+    vrc = RTCritSectDelete(&m_CritSect);
+    AssertRC(vrc);
+}
+
+/**
+ * Notifies the waiting side about a guest notification response.
+ *
+ * @returns VBox status code.
+ * @param   vrcGuest    Guest VBox status code to set for the response.
+ *                      Defaults to VINF_SUCCESS (for success).
+ */
+int GuestDnDState::notifyAboutGuestResponse(int vrcGuest /* = VINF_SUCCESS */)
+{
+    m_vrcGuest = vrcGuest;
+    return RTSemEventSignal(m_EventSem);
+}
+
+/**
+ * Resets a guest drag'n drop state.
+ */
+void GuestDnDState::reset(void)
+{
+    LogRel2(("DnD: Reset\n"));
+
+    m_enmState =  VBOXDNDSTATE_UNKNOWN;
+
+    m_dndActionDefault     = VBOX_DND_ACTION_IGNORE;
+    m_dndLstActionsAllowed = VBOX_DND_ACTION_IGNORE;
+
+    m_lstFormats.clear();
+    m_mapCallbacks.clear();
+
+    m_vrcGuest = VERR_IPE_UNINITIALIZED_STATUS;
+}
+
+/**
+ * Default callback handler for guest callbacks.
+ *
+ * This handler acts as a fallback in case important callback messages are not being handled
+ * by the specific callers.
+ *
+ * @returns VBox status code. Will get sent back to the host service.
+ * @retval  VERR_NO_DATA if no new messages from the host side are available at the moment.
+ * @retval  VERR_CANCELLED for indicating that the current operation was cancelled.
+ * @param   uMsg                HGCM message ID (function number).
+ * @param   pvParms             Pointer to additional message data. Optional and can be NULL.
+ * @param   cbParms             Size (in bytes) additional message data. Optional and can be 0.
+ * @param   pvUser              User-supplied pointer on callback registration.
+ */
+/* static */
+DECLCALLBACK(int) GuestDnDState::i_defaultCallback(uint32_t uMsg, void *pvParms, size_t cbParms, void *pvUser)
+{
+    GuestDnDState *pThis = (GuestDnDState *)pvUser;
+    AssertPtrReturn(pThis, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("uMsg=%RU32 (%#x)\n", uMsg, uMsg));
+
+    int vrc = VERR_IPE_UNINITIALIZED_STATUS;
+
+    switch (uMsg)
+    {
+        case GUEST_DND_FN_EVT_ERROR:
+        {
+            PVBOXDNDCBEVTERRORDATA pCBData = reinterpret_cast<PVBOXDNDCBEVTERRORDATA>(pvParms);
+            AssertPtr(pCBData);
+            AssertReturn(sizeof(VBOXDNDCBEVTERRORDATA) == cbParms, VERR_INVALID_PARAMETER);
+            AssertReturn(CB_MAGIC_DND_EVT_ERROR == pCBData->hdr.uMagic, VERR_INVALID_PARAMETER);
+
+            if (RT_SUCCESS(pCBData->rc))
+            {
+                AssertMsgFailed(("Guest has sent an error event but did not specify an actual error code\n"));
+                pCBData->rc = VERR_GENERAL_FAILURE; /* Make sure some error is set. */
+            }
+
+            vrc = pThis->setProgress(100, DND_PROGRESS_ERROR, pCBData->rc,
+                                     Utf8StrFmt("Received error from guest: %Rrc", pCBData->rc));
+            AssertRCBreak(vrc);
+            vrc = pThis->notifyAboutGuestResponse(pCBData->rc);
+            AssertRCBreak(vrc);
+            break;
+        }
+
+        case GUEST_DND_FN_GET_NEXT_HOST_MSG:
+            vrc = VERR_NO_DATA; /* Indicate back to the host service that there are no new messages. */
+            break;
+
+        default:
+            AssertMsgBreakStmt(pThis->isProgressRunning() == false,
+                               ("Progress object not completed / canceld yet! State is '%s' (%#x)\n",
+                                DnDStateToStr(pThis->m_enmState), pThis->m_enmState),
+                               vrc = VERR_INVALID_STATE); /* Please report this! */
+            vrc = VERR_CANCELLED;
+            break;
+    }
+
+    LogFlowFunc(("Returning vrc=%Rrc\n", vrc));
+    return vrc;
+}
+
+/**
+ * Resets the progress object.
+ *
+ * @returns HRESULT
+ * @param   pParent             Parent to set for the progress object.
+ * @param   strDesc             Description of the progress.
+ */
+HRESULT GuestDnDState::resetProgress(const ComObjPtr<Guest>& pParent, const Utf8Str &strDesc)
+{
+    AssertReturn(strDesc.isNotEmpty(), E_INVALIDARG);
+
+    m_pProgress.setNull();
+
+    HRESULT hrc = m_pProgress.createObject();
+    if (SUCCEEDED(hrc))
+        hrc = m_pProgress->init(static_cast<IGuest *>(pParent), Bstr(strDesc).raw(), TRUE /* aCancelable */);
+
+    return hrc;
+}
+
+/**
+ * Returns whether the progress object has been canceled or not.
+ *
+ * @returns \c true if canceled or progress does not exist, \c false if not.
+ */
+bool GuestDnDState::isProgressCanceled(void) const
+{
+    if (m_pProgress.isNull())
+        return true;
+
+    BOOL fCanceled;
+    HRESULT hrc = m_pProgress->COMGETTER(Canceled)(&fCanceled);
+    AssertComRCReturn(hrc, false);
+    return RT_BOOL(fCanceled);
+}
+
+/**
+ * Returns whether the progress object still is in a running state or not.
+ *
+ * @returns \c true if running, \c false if not.
+ */
+bool GuestDnDState::isProgressRunning(void) const
+{
+    if (m_pProgress.isNull())
+        return false;
+
+    BOOL fCompleted;
+    HRESULT const hrc = m_pProgress->COMGETTER(Completed)(&fCompleted);
+    AssertComRCReturn(hrc, false);
+    return !RT_BOOL(fCompleted);
+}
+
+/**
+ * Sets (registers or unregisters) a callback for a specific HGCM message.
+ *
+ * @returns VBox status code.
+ * @param   uMsg                HGCM message ID to set callback for.
+ * @param   pfnCallback         Callback function pointer to use. Pass NULL to unregister.
+ * @param   pvUser              User-provided arguments for the callback function. Optional and can be NULL.
+ */
+int GuestDnDState::setCallback(uint32_t uMsg, PFNGUESTDNDCALLBACK pfnCallback, void *pvUser /* = NULL */)
+{
+    GuestDnDCallbackMap::iterator it = m_mapCallbacks.find(uMsg);
+
+    /* Register. */
+    if (pfnCallback)
+    {
+        try
+        {
+            m_mapCallbacks[uMsg] = GuestDnDCallback(pfnCallback, uMsg, pvUser);
+        }
+        catch (std::bad_alloc &)
+        {
+            return VERR_NO_MEMORY;
+        }
+        return VINF_SUCCESS;
+    }
+
+    /* Unregister. */
+    if (it != m_mapCallbacks.end())
+        m_mapCallbacks.erase(it);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Sets the progress object to a new state.
+ *
+ * @returns VBox status code.
+ * @param   uPercentage         Percentage (0-100) to set.
+ * @param   uStatus             Status (of type DND_PROGRESS_XXX) to set.
+ * @param   vrcOp               VBox status code to set. Optional.
+ * @param   strMsg              Message to set. Optional.
+ */
+int GuestDnDState::setProgress(unsigned uPercentage, uint32_t uStatus,
+                               int vrcOp /* = VINF_SUCCESS */, const Utf8Str &strMsg /* = Utf8Str::Empty */)
+{
+    LogFlowFunc(("uPercentage=%u, uStatus=%RU32, , vrcOp=%Rrc, strMsg=%s\n",
+                 uPercentage, uStatus, vrcOp, strMsg.c_str()));
+
+    if (m_pProgress.isNull())
+        return VINF_SUCCESS;
+
+    BOOL fCompleted = FALSE;
+    HRESULT hrc = m_pProgress->COMGETTER(Completed)(&fCompleted);
+    AssertComRCReturn(hrc, VERR_COM_UNEXPECTED);
+
+    BOOL fCanceled  = FALSE;
+    hrc = m_pProgress->COMGETTER(Canceled)(&fCanceled);
+    AssertComRCReturn(hrc, VERR_COM_UNEXPECTED);
+
+    LogFlowFunc(("Progress fCompleted=%RTbool, fCanceled=%RTbool\n", fCompleted, fCanceled));
+
+    int vrc = VINF_SUCCESS;
+
+    switch (uStatus)
+    {
+        case DragAndDropSvc::DND_PROGRESS_ERROR:
+        {
+            LogRel(("DnD: Guest reported error %Rrc\n", vrcOp));
+
+            if (!fCompleted)
+                hrc = m_pProgress->i_notifyComplete(VBOX_E_DND_ERROR, COM_IIDOF(IGuest),
+                                                    m_pParent->getComponentName(), strMsg.c_str());
+            break;
+        }
+
+        case DragAndDropSvc::DND_PROGRESS_CANCELLED:
+        {
+            LogRel2(("DnD: Guest cancelled operation\n"));
+
+            if (!fCanceled)
+            {
+                hrc = m_pProgress->Cancel();
+                AssertComRC(hrc);
+            }
+
+            if (!fCompleted)
+            {
+                hrc = m_pProgress->i_notifyComplete(S_OK);
+                AssertComRC(hrc);
+            }
+            break;
+        }
+
+        case DragAndDropSvc::DND_PROGRESS_RUNNING:
+            RT_FALL_THROUGH();
+        case DragAndDropSvc::DND_PROGRESS_COMPLETE:
+        {
+            LogRel2(("DnD: Guest reporting running/completion status with %u%%\n", uPercentage));
+
+            if (   !fCompleted
+                && !fCanceled)
+            {
+                hrc = m_pProgress->SetCurrentOperationProgress(uPercentage);
+                AssertComRCReturn(hrc, VERR_COM_UNEXPECTED);
+                if (   uStatus     == DragAndDropSvc::DND_PROGRESS_COMPLETE
+                    || uPercentage >= 100)
+                {
+                    hrc = m_pProgress->i_notifyComplete(S_OK);
+                    AssertComRCReturn(hrc, VERR_COM_UNEXPECTED);
+                }
+            }
+            break;
+        }
+
+        default:
+            break;
+    }
+
+    LogFlowFuncLeaveRC(vrc);
+    return vrc;
+}
+
+/**
+ * Dispatching function for handling the host service service callback.
+ *
+ * @returns VBox status code.
+ * @param   u32Function         HGCM message ID to handle.
+ * @param   pvParms             Pointer to optional data provided for a particular message. Optional.
+ * @param   cbParms             Size (in bytes) of \a pvParms.
+ */
+int GuestDnDState::onDispatch(uint32_t u32Function, void *pvParms, uint32_t cbParms)
+{
+    LogFlowFunc(("u32Function=%RU32, pvParms=%p, cbParms=%RU32\n", u32Function, pvParms, cbParms));
+
+    int vrc = VERR_WRONG_ORDER; /* Play safe. */
+
+    /* Whether or not to try calling host-installed callbacks after successfully processing the message. */
+    bool fTryCallbacks = false;
+
+    switch (u32Function)
+    {
+        case DragAndDropSvc::GUEST_DND_FN_CONNECT:
+        {
+            DragAndDropSvc::PVBOXDNDCBCONNECTDATA pCBData = reinterpret_cast<DragAndDropSvc::PVBOXDNDCBCONNECTDATA>(pvParms);
+            AssertPtr(pCBData);
+            AssertReturn(sizeof(DragAndDropSvc::VBOXDNDCBCONNECTDATA) == cbParms, VERR_INVALID_PARAMETER);
+            AssertReturn(DragAndDropSvc::CB_MAGIC_DND_CONNECT == pCBData->hdr.uMagic, VERR_INVALID_PARAMETER);
+
+            m_uProtocolVersion = pCBData->uProtocolVersion;
+            /** @todo Handle flags. */
+
+            LogThisFunc(("Client connected, using protocol v%RU32\n", m_uProtocolVersion));
+
+            vrc = VINF_SUCCESS;
+            break;
+        }
+
+        case DragAndDropSvc::GUEST_DND_FN_REPORT_FEATURES:
+        {
+            DragAndDropSvc::PVBOXDNDCBREPORTFEATURESDATA pCBData = reinterpret_cast<DragAndDropSvc::PVBOXDNDCBREPORTFEATURESDATA>(pvParms);
+            AssertPtr(pCBData);
+            AssertReturn(sizeof(DragAndDropSvc::VBOXDNDCBREPORTFEATURESDATA) == cbParms, VERR_INVALID_PARAMETER);
+            AssertReturn(DragAndDropSvc::CB_MAGIC_DND_REPORT_FEATURES == pCBData->hdr.uMagic, VERR_INVALID_PARAMETER);
+
+            m_fGuestFeatures0 = pCBData->fGuestFeatures0;
+
+            LogThisFunc(("Client reported features: %#RX64\n", m_fGuestFeatures0));
+
+            vrc = VINF_SUCCESS;
+            break;
+        }
+
+        /* Note: GUEST_DND_FN_EVT_ERROR is handled in either the state's default callback or in specific
+         *       (overriden) callbacks (e.g. GuestDnDSendCtx / GuestDnDRecvCtx). */
+
+        case DragAndDropSvc::GUEST_DND_FN_DISCONNECT:
+        {
+            LogThisFunc(("Client disconnected\n"));
+            vrc = setProgress(100, DND_PROGRESS_CANCELLED, VINF_SUCCESS);
+            break;
+        }
+
+        case DragAndDropSvc::GUEST_DND_FN_HG_ACK_OP:
+        {
+            DragAndDropSvc::PVBOXDNDCBHGACKOPDATA pCBData = reinterpret_cast<DragAndDropSvc::PVBOXDNDCBHGACKOPDATA>(pvParms);
+            AssertPtr(pCBData);
+            AssertReturn(sizeof(DragAndDropSvc::VBOXDNDCBHGACKOPDATA) == cbParms, VERR_INVALID_PARAMETER);
+            AssertReturn(DragAndDropSvc::CB_MAGIC_DND_HG_ACK_OP == pCBData->hdr.uMagic, VERR_INVALID_PARAMETER);
+
+            LogRel2(("DnD: Guest responded with action '%s' for host->guest drag event\n", DnDActionToStr(pCBData->uAction)));
+
+            setActionDefault(pCBData->uAction);
+            vrc = notifyAboutGuestResponse();
+            break;
+        }
+
+        case DragAndDropSvc::GUEST_DND_FN_HG_REQ_DATA:
+        {
+            DragAndDropSvc::PVBOXDNDCBHGREQDATADATA pCBData = reinterpret_cast<DragAndDropSvc::PVBOXDNDCBHGREQDATADATA>(pvParms);
+            AssertPtr(pCBData);
+            AssertReturn(sizeof(DragAndDropSvc::VBOXDNDCBHGREQDATADATA) == cbParms, VERR_INVALID_PARAMETER);
+            AssertReturn(DragAndDropSvc::CB_MAGIC_DND_HG_REQ_DATA == pCBData->hdr.uMagic, VERR_INVALID_PARAMETER);
+
+            if (   pCBData->cbFormat  == 0
+                || pCBData->cbFormat  > _64K /** @todo Make this configurable? */
+                || pCBData->pszFormat == NULL)
+                vrc = VERR_INVALID_PARAMETER;
+            else if (!RTStrIsValidEncoding(pCBData->pszFormat))
+                vrc = VERR_INVALID_PARAMETER;
+            else
+            {
+                setFormats(GuestDnD::toFormatList(pCBData->pszFormat));
+                vrc = VINF_SUCCESS;
+            }
+
+            int vrc2 = notifyAboutGuestResponse();
+            if (RT_SUCCESS(vrc))
+                vrc = vrc2;
+            break;
+        }
+
+        case DragAndDropSvc::GUEST_DND_FN_HG_EVT_PROGRESS:
+        {
+            DragAndDropSvc::PVBOXDNDCBHGEVTPROGRESSDATA pCBData =
+               reinterpret_cast<DragAndDropSvc::PVBOXDNDCBHGEVTPROGRESSDATA>(pvParms);
+            AssertPtr(pCBData);
+            AssertReturn(sizeof(DragAndDropSvc::VBOXDNDCBHGEVTPROGRESSDATA) == cbParms, VERR_INVALID_PARAMETER);
+            AssertReturn(DragAndDropSvc::CB_MAGIC_DND_HG_EVT_PROGRESS == pCBData->hdr.uMagic, VERR_INVALID_PARAMETER);
+
+            vrc = setProgress(pCBData->uPercentage, pCBData->uStatus, pCBData->rc);
+            if (RT_SUCCESS(vrc))
+                vrc = notifyAboutGuestResponse(pCBData->rc);
+            break;
+        }
+#ifdef VBOX_WITH_DRAG_AND_DROP_GH
+        case DragAndDropSvc::GUEST_DND_FN_GH_ACK_PENDING:
+        {
+            DragAndDropSvc::PVBOXDNDCBGHACKPENDINGDATA pCBData =
+               reinterpret_cast<DragAndDropSvc::PVBOXDNDCBGHACKPENDINGDATA>(pvParms);
+            AssertPtr(pCBData);
+            AssertReturn(sizeof(DragAndDropSvc::VBOXDNDCBGHACKPENDINGDATA) == cbParms, VERR_INVALID_PARAMETER);
+            AssertReturn(DragAndDropSvc::CB_MAGIC_DND_GH_ACK_PENDING == pCBData->hdr.uMagic, VERR_INVALID_PARAMETER);
+
+            LogRel2(("DnD: Guest responded with pending action '%s' (%RU32 bytes format data) to guest->host drag event\n",
+                     DnDActionToStr(pCBData->uDefAction), pCBData->cbFormat));
+
+            if (   pCBData->cbFormat  == 0
+                || pCBData->cbFormat  > _64K /** @todo Make the maximum size configurable? */
+                || pCBData->pszFormat == NULL)
+                vrc = VERR_INVALID_PARAMETER;
+            else if (!RTStrIsValidEncoding(pCBData->pszFormat))
+                vrc = VERR_INVALID_PARAMETER;
+            else
+            {
+                setFormats   (GuestDnD::toFormatList(pCBData->pszFormat));
+                setActionDefault (pCBData->uDefAction);
+                setActionsAllowed(pCBData->uAllActions);
+
+                vrc = VINF_SUCCESS;
+            }
+
+            int vrc2 = notifyAboutGuestResponse();
+            if (RT_SUCCESS(vrc))
+                vrc = vrc2;
+            break;
+        }
+#endif /* VBOX_WITH_DRAG_AND_DROP_GH */
+        default:
+            /* * Try if the event is covered by a registered callback. */
+            fTryCallbacks = true;
+            break;
+    }
+
+    /*
+     * Try the host's installed callbacks (if any).
+     */
+    if (fTryCallbacks)
+    {
+        GuestDnDCallbackMap::const_iterator it = m_mapCallbacks.find(u32Function);
+        if (it != m_mapCallbacks.end())
+        {
+            AssertPtr(it->second.pfnCallback);
+            vrc = it->second.pfnCallback(u32Function, pvParms, cbParms, it->second.pvUser);
+        }
+        else
+        {
+            /* Invoke the default callback handler in case we don't have any registered callback above. */
+            vrc = i_defaultCallback(u32Function, pvParms, cbParms, this /* pvUser */);
+        }
+    }
+
+    LogFlowFunc(("Returning vrc=%Rrc\n", vrc));
+    return vrc;
+}
+
+/**
+ * Helper function to query the internal progress object to an IProgress interface.
+ *
+ * @returns HRESULT
+ * @param   ppProgress          Where to query the progress object to.
+ */
+HRESULT GuestDnDState::queryProgressTo(IProgress **ppProgress)
+{
+    return m_pProgress.queryInterfaceTo(ppProgress);
+}
+
+/**
+ * Waits for a guest response to happen, extended version.
+ *
+ * @returns VBox status code.
+ * @retval  VERR_TIMEOUT when waiting has timed out.
+ * @retval  VERR_DND_GUEST_ERROR on an error reported back from the guest.
+ * @param   msTimeout           Timeout (in ms) for waiting. Optional, waits 3000 ms if not specified.
+ * @param   pvrcGuest           Where to return the guest error when
+ *                              VERR_DND_GUEST_ERROR is returned. Optional.
+ */
+int GuestDnDState::waitForGuestResponseEx(RTMSINTERVAL msTimeout /* = 3000 */, int *pvrcGuest /* = NULL */)
+{
+    int vrc = RTSemEventWait(m_EventSem, msTimeout);
+    if (RT_SUCCESS(vrc))
+    {
+        if (RT_FAILURE(m_vrcGuest))
+            vrc = VERR_DND_GUEST_ERROR;
+        if (pvrcGuest)
+            *pvrcGuest = m_vrcGuest;
+    }
+    return vrc;
+}
+
+/**
+ * Waits for a guest response to happen.
+ *
+ * @returns VBox status code.
+ * @retval  VERR_TIMEOUT when waiting has timed out.
+ * @retval  VERR_DND_GUEST_ERROR on an error reported back from the guest.
+ * @param   pvrcGuest            Where to return the guest error when
+ *                               VERR_DND_GUEST_ERROR is returned. Optional.
+ *
+ * @note    Uses the default timeout of 3000 ms.
+ */
+int GuestDnDState::waitForGuestResponse(int *pvrcGuest /* = NULL */)
+{
+    return waitForGuestResponseEx(3000 /* ms */, pvrcGuest);
+}
+
+/*********************************************************************************************************************************
+ * GuestDnD implementation.                                                                                                      *
+ ********************************************************************************************************************************/
+
+/** Static (Singleton) instance of the GuestDnD object. */
+GuestDnD* GuestDnD::s_pInstance = NULL;
+
+GuestDnD::GuestDnD(const ComObjPtr<Guest> &pGuest)
+    : m_pGuest(pGuest)
+    , m_cTransfersPending(0)
+{
+    LogFlowFuncEnter();
+
+    try
+    {
+        m_pState = new GuestDnDState(pGuest);
+    }
+    catch (std::bad_alloc &)
+    {
+        throw VERR_NO_MEMORY;
+    }
+
+    int vrc = RTCritSectInit(&m_CritSect);
+    if (RT_FAILURE(vrc))
+        throw vrc;
+
+    /* List of supported default MIME types. */
+    LogRel2(("DnD: Supported default host formats:\n"));
+    const com::Utf8Str arrEntries[] = { VBOX_DND_FORMATS_DEFAULT };
+    for (size_t i = 0; i < RT_ELEMENTS(arrEntries); i++)
+    {
+        m_strDefaultFormats.push_back(arrEntries[i]);
+        LogRel2(("DnD: \t%s\n", arrEntries[i].c_str()));
+    }
+}
+
+GuestDnD::~GuestDnD(void)
+{
+    LogFlowFuncEnter();
+
+    Assert(m_cTransfersPending == 0); /* Sanity. */
+
+    RTCritSectDelete(&m_CritSect);
+
+    if (m_pState)
+        delete m_pState;
+}
+
+/**
+ * Adjusts coordinations to a given screen.
+ *
+ * @returns HRESULT
+ * @param   uScreenId           ID of screen to adjust coordinates to.
+ * @param   puX                 Pointer to X coordinate to adjust. Will return the adjusted value on success.
+ * @param   puY                 Pointer to Y coordinate to adjust. Will return the adjusted value on success.
+ */
+HRESULT GuestDnD::adjustScreenCoordinates(ULONG uScreenId, ULONG *puX, ULONG *puY) const
+{
+    /** @todo r=andy Save the current screen's shifting coordinates to speed things up.
+     *               Only query for new offsets when the screen ID or the screen's resolution has changed. */
+
+    /* For multi-monitor support we need to add shift values to the coordinates
+     * (depending on the screen number). */
+    ComObjPtr<Console> pConsole = m_pGuest->i_getConsole();
+    ComPtr<IDisplay> pDisplay;
+    HRESULT hrc = pConsole->COMGETTER(Display)(pDisplay.asOutParam());
+    if (FAILED(hrc))
+        return hrc;
+
+    ULONG dummy;
+    LONG xShift, yShift;
+    GuestMonitorStatus_T monitorStatus;
+    hrc = pDisplay->GetScreenResolution(uScreenId, &dummy, &dummy, &dummy, &xShift, &yShift, &monitorStatus);
+    if (FAILED(hrc))
+        return hrc;
+
+    if (puX)
+        *puX += xShift;
+    if (puY)
+        *puY += yShift;
+
+    LogFlowFunc(("uScreenId=%RU32, x=%RU32, y=%RU32\n", uScreenId, puX ? *puX : 0, puY ? *puY : 0));
+    return S_OK;
+}
+
+/**
+ * Returns a DnD guest state.
+ *
+ * @returns Pointer to DnD guest state, or NULL if not found / invalid.
+ * @param   uID                 ID of DnD guest state to return.
+ */
+GuestDnDState *GuestDnD::getState(uint32_t uID /* = 0 */) const
+{
+    AssertMsgReturn(uID == 0, ("Only one state (0) is supported at the moment\n"), NULL);
+
+    return m_pState;
+}
+
+/**
+ * Sends a (blocking) message to the host side of the host service.
+ *
+ * @returns VBox status code.
+ * @param   u32Function         HGCM message ID to send.
+ * @param   cParms              Number of parameters to send.
+ * @param   paParms             Array of parameters to send. Must match \c cParms.
+ */
+int GuestDnD::hostCall(uint32_t u32Function, uint32_t cParms, PVBOXHGCMSVCPARM paParms) const
+{
+    Assert(!m_pGuest.isNull());
+    ComObjPtr<Console> pConsole = m_pGuest->i_getConsole();
+
+    /* Forward the information to the VMM device. */
+    Assert(!pConsole.isNull());
+    VMMDev *pVMMDev = pConsole->i_getVMMDev();
+    if (!pVMMDev)
+        return VERR_COM_OBJECT_NOT_FOUND;
+
+    return pVMMDev->hgcmHostCall("VBoxDragAndDropSvc", u32Function, cParms, paParms);
+}
+
+/**
+ * Registers a GuestDnDSource object with the GuestDnD manager.
+ *
+ * Currently only one source is supported at a time.
+ *
+ * @returns VBox status code.
+ * @param   Source              Source to register.
+ */
+int GuestDnD::registerSource(const ComObjPtr<GuestDnDSource> &Source)
+{
+    GUESTDND_LOCK();
+
+    Assert(m_lstSrc.size() == 0); /* We only support one source at a time at the moment. */
+    m_lstSrc.push_back(Source);
+
+    GUESTDND_UNLOCK();
+    return VINF_SUCCESS;
+}
+
+/**
+ * Unregisters a GuestDnDSource object from the GuestDnD manager.
+ *
+ * @returns VBox status code.
+ * @param   Source              Source to unregister.
+ */
+int GuestDnD::unregisterSource(const ComObjPtr<GuestDnDSource> &Source)
+{
+    GUESTDND_LOCK();
+
+    GuestDnDSrcList::iterator itSrc = std::find(m_lstSrc.begin(), m_lstSrc.end(), Source);
+    if (itSrc != m_lstSrc.end())
+        m_lstSrc.erase(itSrc);
+
+    GUESTDND_UNLOCK();
+    return VINF_SUCCESS;
+}
+
+/**
+ * Returns the current number of registered sources.
+ *
+ * @returns Current number of registered sources.
+ */
+size_t GuestDnD::getSourceCount(void)
+{
+    GUESTDND_LOCK_RET(0);
+
+    size_t cSources = m_lstSrc.size();
+
+    GUESTDND_UNLOCK();
+    return cSources;
+}
+
+/**
+ * Registers a GuestDnDTarget object with the GuestDnD manager.
+ *
+ * Currently only one target is supported at a time.
+ *
+ * @returns VBox status code.
+ * @param   Target              Target to register.
+ */
+int GuestDnD::registerTarget(const ComObjPtr<GuestDnDTarget> &Target)
+{
+    GUESTDND_LOCK();
+
+    Assert(m_lstTgt.size() == 0); /* We only support one target at a time at the moment. */
+    m_lstTgt.push_back(Target);
+
+    GUESTDND_UNLOCK();
+    return VINF_SUCCESS;
+}
+
+/**
+ * Unregisters a GuestDnDTarget object from the GuestDnD manager.
+ *
+ * @returns VBox status code.
+ * @param   Target              Target to unregister.
+ */
+int GuestDnD::unregisterTarget(const ComObjPtr<GuestDnDTarget> &Target)
+{
+    GUESTDND_LOCK();
+
+    GuestDnDTgtList::iterator itTgt = std::find(m_lstTgt.begin(), m_lstTgt.end(), Target);
+    if (itTgt != m_lstTgt.end())
+        m_lstTgt.erase(itTgt);
+
+    GUESTDND_UNLOCK();
+    return VINF_SUCCESS;
+}
+
+/**
+ * Returns the current number of registered targets.
+ *
+ * @returns Current number of registered targets.
+ */
+size_t GuestDnD::getTargetCount(void)
+{
+    GUESTDND_LOCK_RET(0);
+
+    size_t cTargets = m_lstTgt.size();
+
+    GUESTDND_UNLOCK();
+    return cTargets;
+}
+
+/**
+ * Static main dispatcher function to handle callbacks from the DnD host service.
+ *
+ * @returns VBox status code.
+ * @param   pvExtension         Pointer to service extension.
+ * @param   u32Function         Callback HGCM message ID.
+ * @param   pvParms             Pointer to optional data provided for a particular message. Optional.
+ * @param   cbParms             Size (in bytes) of \a pvParms.
+ */
+/* static */
+DECLCALLBACK(int) GuestDnD::notifyDnDDispatcher(void *pvExtension, uint32_t u32Function,
+                                                void *pvParms, uint32_t cbParms)
+{
+    LogFlowFunc(("pvExtension=%p, u32Function=%RU32, pvParms=%p, cbParms=%RU32\n",
+                 pvExtension, u32Function, pvParms, cbParms));
+
+    GuestDnD *pGuestDnD = reinterpret_cast<GuestDnD*>(pvExtension);
+    AssertPtrReturn(pGuestDnD, VERR_INVALID_POINTER);
+
+    /** @todo In case we need to handle multiple guest DnD responses at a time this
+     *        would be the place to lookup and dispatch to those. For the moment we
+     *        only have one response -- simple. */
+    if (pGuestDnD->m_pState)
+        return pGuestDnD->m_pState->onDispatch(u32Function, pvParms, cbParms);
+
+    return VERR_NOT_SUPPORTED;
+}
+
+/**
+ * Static helper function to determine whether a format is part of a given MIME list.
+ *
+ * @returns \c true if found, \c false if not.
+ * @param   strFormat           Format to search for.
+ * @param   lstFormats          MIME list to search in.
+ */
+/* static */
+bool GuestDnD::isFormatInFormatList(const com::Utf8Str &strFormat, const GuestDnDMIMEList &lstFormats)
+{
+    return std::find(lstFormats.begin(), lstFormats.end(), strFormat) != lstFormats.end();
+}
+
+/**
+ * Static helper function to create a GuestDnDMIMEList out of a format list string.
+ *
+ * @returns MIME list object.
+ * @param   strFormats          List of formats to convert.
+ * @param   strSep              Separator to use. If not specified, DND_FORMATS_SEPARATOR_STR will be used.
+ */
+/* static */
+GuestDnDMIMEList GuestDnD::toFormatList(const com::Utf8Str &strFormats, const com::Utf8Str &strSep /* = DND_FORMATS_SEPARATOR_STR */)
+{
+    GuestDnDMIMEList lstFormats;
+    RTCList<RTCString> lstFormatsTmp = strFormats.split(strSep);
+
+    for (size_t i = 0; i < lstFormatsTmp.size(); i++)
+        lstFormats.push_back(com::Utf8Str(lstFormatsTmp.at(i)));
+
+    return lstFormats;
+}
+
+/**
+ * Static helper function to create a format list string from a given GuestDnDMIMEList object.
+ *
+ * @returns Format list string.
+ * @param   lstFormats          GuestDnDMIMEList to convert.
+ * @param   strSep              Separator to use between formats.
+ *                              Uses DND_FORMATS_SEPARATOR_STR as default.
+ */
+/* static */
+com::Utf8Str GuestDnD::toFormatString(const GuestDnDMIMEList &lstFormats, const com::Utf8Str &strSep /* = DND_FORMATS_SEPARATOR_STR */)
+{
+    com::Utf8Str strFormat;
+    for (size_t i = 0; i < lstFormats.size(); i++)
+    {
+        const com::Utf8Str &f = lstFormats.at(i);
+        strFormat += f + strSep;
+    }
+
+    return strFormat;
+}
+
+/**
+ * Static helper function to create a filtered GuestDnDMIMEList object from supported and wanted formats.
+ *
+ * @returns Filtered MIME list object.
+ * @param   lstFormatsSupported     MIME list of supported formats.
+ * @param   lstFormatsWanted        MIME list of wanted formats in returned object.
+ */
+/* static */
+GuestDnDMIMEList GuestDnD::toFilteredFormatList(const GuestDnDMIMEList &lstFormatsSupported, const GuestDnDMIMEList &lstFormatsWanted)
+{
+    GuestDnDMIMEList lstFormats;
+
+    for (size_t i = 0; i < lstFormatsWanted.size(); i++)
+    {
+        /* Only keep supported format types. */
+        if (std::find(lstFormatsSupported.begin(),
+                      lstFormatsSupported.end(), lstFormatsWanted.at(i)) != lstFormatsSupported.end())
+        {
+            lstFormats.push_back(lstFormatsWanted[i]);
+        }
+    }
+
+    return lstFormats;
+}
+
+/**
+ * Static helper function to create a filtered GuestDnDMIMEList object from supported and wanted formats.
+ *
+ * @returns Filtered MIME list object.
+ * @param   lstFormatsSupported     MIME list of supported formats.
+ * @param   strFormatsWanted        Format list string of wanted formats in returned object.
+ */
+/* static */
+GuestDnDMIMEList GuestDnD::toFilteredFormatList(const GuestDnDMIMEList &lstFormatsSupported, const com::Utf8Str &strFormatsWanted)
+{
+    GuestDnDMIMEList lstFmt;
+
+    RTCList<RTCString> lstFormats = strFormatsWanted.split(DND_FORMATS_SEPARATOR_STR);
+    size_t i = 0;
+    while (i < lstFormats.size())
+    {
+        /* Only keep allowed format types. */
+        if (std::find(lstFormatsSupported.begin(),
+                      lstFormatsSupported.end(), lstFormats.at(i)) != lstFormatsSupported.end())
+        {
+            lstFmt.push_back(lstFormats[i]);
+        }
+        i++;
+    }
+
+    return lstFmt;
+}
+
+/**
+ * Static helper function to convert a Main DnD action an internal DnD action.
+ *
+ * @returns Internal DnD action, or VBOX_DND_ACTION_IGNORE if not found / supported.
+ * @param   enmAction               Main DnD action to convert.
+ */
+/* static */
+VBOXDNDACTION GuestDnD::toHGCMAction(DnDAction_T enmAction)
+{
+    VBOXDNDACTION dndAction = VBOX_DND_ACTION_IGNORE;
+    switch (enmAction)
+    {
+        case DnDAction_Copy:
+            dndAction = VBOX_DND_ACTION_COPY;
+            break;
+        case DnDAction_Move:
+            dndAction = VBOX_DND_ACTION_MOVE;
+            break;
+        case DnDAction_Link:
+            /* For now it doesn't seems useful to allow a link
+               action between host & guest. Later? */
+        case DnDAction_Ignore:
+            /* Ignored. */
+            break;
+        default:
+            AssertMsgFailed(("Action %RU32 not recognized!\n", enmAction));
+            break;
+    }
+
+    return dndAction;
+}
+
+/**
+ * Static helper function to convert a Main DnD default action and allowed Main actions to their
+ * corresponding internal representations.
+ *
+ * @param   enmDnDActionDefault     Default Main action to convert.
+ * @param   pDnDActionDefault       Where to store the converted default action.
+ * @param   vecDnDActionsAllowed    Allowed Main actions to convert.
+ * @param   pDnDLstActionsAllowed   Where to store the converted allowed actions.
+ */
+/* static */
+void GuestDnD::toHGCMActions(DnDAction_T                    enmDnDActionDefault,
+                             VBOXDNDACTION                 *pDnDActionDefault,
+                             const std::vector<DnDAction_T> vecDnDActionsAllowed,
+                             VBOXDNDACTIONLIST             *pDnDLstActionsAllowed)
+{
+    VBOXDNDACTIONLIST dndLstActionsAllowed = VBOX_DND_ACTION_IGNORE;
+    VBOXDNDACTION     dndActionDefault     = toHGCMAction(enmDnDActionDefault);
+
+    if (!vecDnDActionsAllowed.empty())
+    {
+        /* First convert the allowed actions to a bit array. */
+        for (size_t i = 0; i < vecDnDActionsAllowed.size(); i++)
+            dndLstActionsAllowed |= toHGCMAction(vecDnDActionsAllowed[i]);
+
+        /*
+         * If no default action is set (ignoring), try one of the
+         * set allowed actions, preferring copy, move (in that order).
+         */
+        if (isDnDIgnoreAction(dndActionDefault))
+        {
+            if (hasDnDCopyAction(dndLstActionsAllowed))
+                dndActionDefault = VBOX_DND_ACTION_COPY;
+            else if (hasDnDMoveAction(dndLstActionsAllowed))
+                dndActionDefault = VBOX_DND_ACTION_MOVE;
+        }
+    }
+
+    if (pDnDActionDefault)
+        *pDnDActionDefault     = dndActionDefault;
+    if (pDnDLstActionsAllowed)
+        *pDnDLstActionsAllowed = dndLstActionsAllowed;
+}
+
+/**
+ * Static helper function to convert an internal DnD action to its Main representation.
+ *
+ * @returns Converted Main DnD action.
+ * @param   dndAction           DnD action to convert.
+ */
+/* static */
+DnDAction_T GuestDnD::toMainAction(VBOXDNDACTION dndAction)
+{
+    /* For now it doesn't seems useful to allow a
+     * link action between host & guest. Maybe later! */
+    return isDnDCopyAction(dndAction) ? DnDAction_Copy
+         : isDnDMoveAction(dndAction) ? DnDAction_Move
+         :                              DnDAction_Ignore;
+}
+
+/**
+ * Static helper function to convert an internal DnD action list to its Main representation.
+ *
+ * @returns Converted Main DnD action list.
+ * @param   dndActionList       DnD action list to convert.
+ */
+/* static */
+std::vector<DnDAction_T> GuestDnD::toMainActions(VBOXDNDACTIONLIST dndActionList)
+{
+    std::vector<DnDAction_T> vecActions;
+
+    /* For now it doesn't seems useful to allow a
+     * link action between host & guest. Maybe later! */
+    RTCList<DnDAction_T> lstActions;
+    if (hasDnDCopyAction(dndActionList))
+        lstActions.append(DnDAction_Copy);
+    if (hasDnDMoveAction(dndActionList))
+        lstActions.append(DnDAction_Move);
+
+    for (size_t i = 0; i < lstActions.size(); ++i)
+        vecActions.push_back(lstActions.at(i));
+
+    return vecActions;
+}
+
+/*********************************************************************************************************************************
+ * GuestDnDBase implementation.                                                                                                  *
+ ********************************************************************************************************************************/
+
+GuestDnDBase::GuestDnDBase(VirtualBoxBase *pBase)
+    : m_pBase(pBase)
+    , m_fIsPending(false)
+{
+    /* Initialize public attributes. */
+    m_lstFmtSupported = GuestDnDInst()->defaultFormats();
+}
+
+GuestDnDBase::~GuestDnDBase(void)
+{
+}
+
+/**
+ * Checks whether a given DnD format is supported or not.
+ *
+ * @returns \c true if supported, \c false if not.
+ * @param   aFormat             DnD format to check.
+ */
+bool GuestDnDBase::i_isFormatSupported(const com::Utf8Str &aFormat) const
+{
+    return std::find(m_lstFmtSupported.begin(), m_lstFmtSupported.end(), aFormat) != m_lstFmtSupported.end();
+}
+
+/**
+ * Returns the currently supported DnD formats.
+ *
+ * @returns List of the supported DnD formats.
+ */
+const GuestDnDMIMEList &GuestDnDBase::i_getFormats(void) const
+{
+    return m_lstFmtSupported;
+}
+
+/**
+ * Adds DnD formats to the supported formats list.
+ *
+ * @returns HRESULT
+ * @param   aFormats            List of DnD formats to add.
+ */
+HRESULT GuestDnDBase::i_addFormats(const GuestDnDMIMEList &aFormats)
+{
+    for (size_t i = 0; i < aFormats.size(); ++i)
+    {
+        Utf8Str strFormat = aFormats.at(i);
+        if (std::find(m_lstFmtSupported.begin(),
+                      m_lstFmtSupported.end(), strFormat) == m_lstFmtSupported.end())
+        {
+            m_lstFmtSupported.push_back(strFormat);
+        }
+    }
+
+    return S_OK;
+}
+
+/**
+ * Removes DnD formats from tehh supported formats list.
+ *
+ * @returns HRESULT
+ * @param   aFormats            List of DnD formats to remove.
+ */
+HRESULT GuestDnDBase::i_removeFormats(const GuestDnDMIMEList &aFormats)
+{
+    for (size_t i = 0; i < aFormats.size(); ++i)
+    {
+        Utf8Str strFormat = aFormats.at(i);
+        GuestDnDMIMEList::iterator itFormat = std::find(m_lstFmtSupported.begin(),
+                                                        m_lstFmtSupported.end(), strFormat);
+        if (itFormat != m_lstFmtSupported.end())
+            m_lstFmtSupported.erase(itFormat);
+    }
+
+    return S_OK;
+}
+
+/**
+ * Prints an error in the release log and sets the COM error info.
+ *
+ * @returns HRESULT
+ * @param   vrc                 IPRT-style error code to print in addition.
+ *                              Will not be printed if set to a non-error (e.g. VINF _ / VWRN_) code.
+ * @param   pcszMsgFmt          Format string.
+ * @param   va                  Format arguments.
+ * @note
+ */
+HRESULT GuestDnDBase::i_setErrorV(int vrc, const char *pcszMsgFmt, va_list va)
+{
+    char *psz = NULL;
+    if (RTStrAPrintfV(&psz, pcszMsgFmt, va) < 0)
+        return E_OUTOFMEMORY;
+    AssertPtrReturn(psz, E_OUTOFMEMORY);
+
+    HRESULT hrc;
+    if (RT_FAILURE(vrc))
+    {
+        LogRel(("DnD: Error: %s (%Rrc)\n", psz, vrc));
+        hrc = m_pBase->setErrorBoth(VBOX_E_DND_ERROR, vrc, "DnD: Error: %s (%Rrc)", psz, vrc);
+    }
+    else
+    {
+        LogRel(("DnD: Error: %s\n", psz));
+        hrc = m_pBase->setErrorBoth(VBOX_E_DND_ERROR, vrc, "DnD: Error: %s", psz);
+    }
+
+    RTStrFree(psz);
+    return hrc;
+}
+
+/**
+ * Prints an error in the release log and sets the COM error info.
+ *
+ * @returns HRESULT
+ * @param   vrc                 IPRT-style error code to print in addition.
+ *                              Will not be printed if set to a non-error (e.g. VINF _ / VWRN_) code.
+ * @param   pcszMsgFmt          Format string.
+ * @param   ...                 Format arguments.
+ * @note
+ */
+HRESULT GuestDnDBase::i_setError(int vrc, const char *pcszMsgFmt, ...)
+{
+    va_list va;
+    va_start(va, pcszMsgFmt);
+    HRESULT const hrc = i_setErrorV(vrc, pcszMsgFmt, va);
+    va_end(va);
+
+    return hrc;
+}
+
+/**
+ * Prints an error in the release log, sets the COM error info and calls the object's reset function.
+ *
+ * @returns HRESULT
+ * @param   pcszMsgFmt          Format string.
+ * @param   va                  Format arguments.
+ * @note
+ */
+HRESULT GuestDnDBase::i_setErrorAndReset(const char *pcszMsgFmt, ...)
+{
+    va_list va;
+    va_start(va, pcszMsgFmt);
+    HRESULT const hrc = i_setErrorV(VINF_SUCCESS, pcszMsgFmt, va);
+    va_end(va);
+
+    i_reset();
+
+    return hrc;
+}
+
+/**
+ * Prints an error in the release log, sets the COM error info and calls the object's reset function.
+ *
+ * @returns HRESULT
+ * @param   vrc                 IPRT-style error code to print in addition.
+ *                              Will not be printed if set to a non-error (e.g. VINF _ / VWRN_) code.
+ * @param   pcszMsgFmt          Format string.
+ * @param   ...                 Format arguments.
+ * @note
+ */
+HRESULT GuestDnDBase::i_setErrorAndReset(int vrc, const char *pcszMsgFmt, ...)
+{
+    va_list va;
+    va_start(va, pcszMsgFmt);
+    HRESULT const hrc = i_setErrorV(vrc, pcszMsgFmt, va);
+    va_end(va);
+
+    i_reset();
+
+    return hrc;
+}
+
+/**
+ * Adds a new guest DnD message to the internal message queue.
+ *
+ * @returns VBox status code.
+ * @param   pMsg                Pointer to message to add.
+ */
+int GuestDnDBase::msgQueueAdd(GuestDnDMsg *pMsg)
+{
+    m_DataBase.lstMsgOut.push_back(pMsg);
+    return VINF_SUCCESS;
+}
+
+/**
+ * Returns the next guest DnD message in the internal message queue (FIFO).
+ *
+ * @returns Pointer to guest DnD message, or NULL if none found.
+ */
+GuestDnDMsg *GuestDnDBase::msgQueueGetNext(void)
+{
+    if (m_DataBase.lstMsgOut.empty())
+        return NULL;
+    return m_DataBase.lstMsgOut.front();
+}
+
+/**
+ * Removes the next guest DnD message from the internal message queue.
+ */
+void GuestDnDBase::msgQueueRemoveNext(void)
+{
+    if (!m_DataBase.lstMsgOut.empty())
+    {
+        GuestDnDMsg *pMsg = m_DataBase.lstMsgOut.front();
+        if (pMsg)
+            delete pMsg;
+        m_DataBase.lstMsgOut.pop_front();
+    }
+}
+
+/**
+ * Clears the internal message queue.
+ */
+void GuestDnDBase::msgQueueClear(void)
+{
+    LogFlowFunc(("cMsg=%zu\n", m_DataBase.lstMsgOut.size()));
+
+    GuestDnDMsgList::iterator itMsg = m_DataBase.lstMsgOut.begin();
+    while (itMsg != m_DataBase.lstMsgOut.end())
+    {
+        GuestDnDMsg *pMsg = *itMsg;
+        if (pMsg)
+            delete pMsg;
+
+        itMsg++;
+    }
+
+    m_DataBase.lstMsgOut.clear();
+}
+
+/**
+ * Sends a request to the guest side to cancel the current DnD operation.
+ *
+ * @returns VBox status code.
+ */
+int GuestDnDBase::sendCancel(void)
+{
+    GuestDnDMsg Msg;
+    Msg.setType(HOST_DND_FN_CANCEL);
+    if (m_pState->m_uProtocolVersion >= 3)
+        Msg.appendUInt32(0); /** @todo ContextID not used yet. */
+
+    LogRel2(("DnD: Cancelling operation on guest ...\n"));
+
+    int vrc = GuestDnDInst()->hostCall(Msg.getType(), Msg.getCount(), Msg.getParms());
+    if (RT_FAILURE(vrc))
+        LogRel(("DnD: Cancelling operation on guest failed with %Rrc\n", vrc));
+
+    return vrc;
+}
+
+/**
+ * Helper function to update the progress based on given a GuestDnDData object.
+ *
+ * @returns VBox status code.
+ * @param   pData               GuestDnDData object to use for accounting.
+ * @param   pState              Guest state to update its progress object for.
+ * @param   cbDataAdd           By how much data (in bytes) to update the progress.
+ */
+int GuestDnDBase::updateProgress(GuestDnDData *pData, GuestDnDState *pState,
+                                 size_t cbDataAdd /* = 0 */)
+{
+    AssertPtrReturn(pData, VERR_INVALID_POINTER);
+    AssertPtrReturn(pState, VERR_INVALID_POINTER);
+    /* cbDataAdd is optional. */
+
+    LogFlowFunc(("cbExtra=%zu, cbProcessed=%zu, cbRemaining=%zu, cbDataAdd=%zu\n",
+                 pData->cbExtra, pData->cbProcessed, pData->getRemaining(), cbDataAdd));
+
+    if (   !pState
+        || !cbDataAdd) /* Only update if something really changes. */
+        return VINF_SUCCESS;
+
+    if (cbDataAdd)
+        pData->addProcessed(cbDataAdd);
+
+    const uint8_t uPercent = pData->getPercentComplete();
+
+    LogRel2(("DnD: Transfer %RU8%% complete\n", uPercent));
+
+    int vrc = pState->setProgress(uPercent, pData->isComplete() ? DND_PROGRESS_COMPLETE : DND_PROGRESS_RUNNING);
+    LogFlowFuncLeaveRC(vrc);
+    return vrc;
+}
+
+/**
+ * Waits for a specific guest callback event to get signalled.
+ *
+ * @returns VBox status code. Will return VERR_CANCELLED if the user has cancelled the progress object.
+ * @param   pEvent                  Callback event to wait for.
+ * @param   pState                  Guest state to update.
+ * @param   msTimeout               Timeout (in ms) to wait.
+ */
+int GuestDnDBase::waitForEvent(GuestDnDCallbackEvent *pEvent, GuestDnDState *pState, RTMSINTERVAL msTimeout)
+{
+    AssertPtrReturn(pEvent, VERR_INVALID_POINTER);
+    AssertPtrReturn(pState, VERR_INVALID_POINTER);
+
+    int vrc;
+
+    LogFlowFunc(("msTimeout=%RU32\n", msTimeout));
+
+    uint64_t tsStart = RTTimeMilliTS();
+    do
+    {
+        /*
+         * Wait until our desired callback triggered the
+         * wait event. As we don't want to block if the guest does not
+         * respond, do busy waiting here.
+         */
+        vrc = pEvent->Wait(500 /* ms */);
+        if (RT_SUCCESS(vrc))
+        {
+            vrc = pEvent->Result();
+            LogFlowFunc(("Callback done, result is %Rrc\n", vrc));
+            break;
+        }
+        if (vrc == VERR_TIMEOUT) /* Continue waiting. */
+            vrc = VINF_SUCCESS;
+
+        if (   msTimeout != RT_INDEFINITE_WAIT
+            && RTTimeMilliTS() - tsStart > msTimeout)
+        {
+            vrc = VERR_TIMEOUT;
+            LogRel2(("DnD: Error: Guest did not respond within time\n"));
+        }
+        else if (pState->isProgressCanceled())
+        {
+            LogRel2(("DnD: Operation was canceled by user\n"));
+            vrc = VERR_CANCELLED;
+        }
+
+    } while (RT_SUCCESS(vrc));
+
+    LogFlowFuncLeaveRC(vrc);
+    return vrc;
+}
+
+#endif /* VBOX_WITH_DRAG_AND_DROP */
+