Adding upstream version 86.0.1.upstream/86.0.1upstream

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

1 files changed, 951 insertions, 0 deletions

diff --git a/widget/nsBaseDragService.cpp b/widget/nsBaseDragService.cpp
new file mode 100644
index 0000000000..cfe09dc2f2
--- /dev/null
+++ b/widget/nsBaseDragService.cpp
@@ -0,0 +1,951 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsBaseDragService.h"
+#include "nsITransferable.h"
+
+#include "nsArrayUtils.h"
+#include "nsITransferable.h"
+#include "nsSize.h"
+#include "nsXPCOM.h"
+#include "nsCOMPtr.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIFrame.h"
+#include "nsFrameLoaderOwner.h"
+#include "nsIContent.h"
+#include "nsViewManager.h"
+#include "nsINode.h"
+#include "nsPresContext.h"
+#include "nsIImageLoadingContent.h"
+#include "imgIContainer.h"
+#include "imgIRequest.h"
+#include "ImageRegion.h"
+#include "nsQueryObject.h"
+#include "nsRegion.h"
+#include "nsXULPopupManager.h"
+#include "nsMenuPopupFrame.h"
+#ifdef MOZ_XUL
+#  include "nsTreeBodyFrame.h"
+#endif
+#include "mozilla/MouseEvents.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/SVGImageContext.h"
+#include "mozilla/Unused.h"
+#include "mozilla/ViewportUtils.h"
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/DataTransferItemList.h"
+#include "mozilla/dom/DataTransfer.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "mozilla/dom/DragEvent.h"
+#include "mozilla/dom/MouseEventBinding.h"
+#include "mozilla/dom/Selection.h"
+#include "mozilla/gfx/2D.h"
+#include "nsFrameLoader.h"
+#include "BrowserParent.h"
+#include "GeckoProfiler.h"
+#include "nsIMutableArray.h"
+#include "gfxContext.h"
+#include "gfxPlatform.h"
+#include <algorithm>
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::gfx;
+using namespace mozilla::image;
+
+#define DRAGIMAGES_PREF "nglayout.enable_drag_images"
+
+nsBaseDragService::nsBaseDragService()
+    : mCanDrop(false),
+      mOnlyChromeDrop(false),
+      mDoingDrag(false),
+      mSessionIsSynthesizedForTests(false),
+      mEndingSession(false),
+      mHasImage(false),
+      mUserCancelled(false),
+      mDragEventDispatchedToChildProcess(false),
+      mDragAction(DRAGDROP_ACTION_NONE),
+      mDragActionFromChildProcess(DRAGDROP_ACTION_UNINITIALIZED),
+      mEffectAllowedForTests(DRAGDROP_ACTION_UNINITIALIZED),
+      mContentPolicyType(nsIContentPolicy::TYPE_OTHER),
+      mSuppressLevel(0),
+      mInputSource(MouseEvent_Binding::MOZ_SOURCE_MOUSE) {}
+
+nsBaseDragService::~nsBaseDragService() = default;
+
+NS_IMPL_ISUPPORTS(nsBaseDragService, nsIDragService, nsIDragSession)
+
+//---------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::SetCanDrop(bool aCanDrop) {
+  mCanDrop = aCanDrop;
+  return NS_OK;
+}
+
+//---------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::GetCanDrop(bool* aCanDrop) {
+  *aCanDrop = mCanDrop;
+  return NS_OK;
+}
+//---------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::SetOnlyChromeDrop(bool aOnlyChrome) {
+  mOnlyChromeDrop = aOnlyChrome;
+  return NS_OK;
+}
+
+//---------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::GetOnlyChromeDrop(bool* aOnlyChrome) {
+  *aOnlyChrome = mOnlyChromeDrop;
+  return NS_OK;
+}
+
+//---------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::SetDragAction(uint32_t anAction) {
+  mDragAction = anAction;
+  return NS_OK;
+}
+
+//---------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::GetDragAction(uint32_t* anAction) {
+  *anAction = mDragAction;
+  return NS_OK;
+}
+
+//-------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsBaseDragService::GetNumDropItems(uint32_t* aNumItems) {
+  *aNumItems = 0;
+  return NS_ERROR_FAILURE;
+}
+
+//
+// GetSourceDocument
+//
+// Returns the DOM document where the drag was initiated. This will be
+// nullptr if the drag began outside of our application.
+//
+NS_IMETHODIMP
+nsBaseDragService::GetSourceDocument(Document** aSourceDocument) {
+  *aSourceDocument = mSourceDocument.get();
+  NS_IF_ADDREF(*aSourceDocument);
+
+  return NS_OK;
+}
+
+//
+// GetSourceNode
+//
+// Returns the DOM node where the drag was initiated. This will be
+// nullptr if the drag began outside of our application.
+//
+NS_IMETHODIMP
+nsBaseDragService::GetSourceNode(nsINode** aSourceNode) {
+  *aSourceNode = do_AddRef(mSourceNode).take();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::GetTriggeringPrincipal(nsIPrincipal** aPrincipal) {
+  NS_IF_ADDREF(*aPrincipal = mTriggeringPrincipal);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::SetTriggeringPrincipal(nsIPrincipal* aPrincipal) {
+  mTriggeringPrincipal = aPrincipal;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::GetCsp(nsIContentSecurityPolicy** aCsp) {
+  NS_IF_ADDREF(*aCsp = mCsp);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::SetCsp(nsIContentSecurityPolicy* aCsp) {
+  mCsp = aCsp;
+  return NS_OK;
+}
+
+//-------------------------------------------------------------------------
+
+NS_IMETHODIMP
+nsBaseDragService::GetData(nsITransferable* aTransferable,
+                           uint32_t aItemIndex) {
+  return NS_ERROR_FAILURE;
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::IsDataFlavorSupported(const char* aDataFlavor,
+                                         bool* _retval) {
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::GetDataTransferXPCOM(DataTransfer** aDataTransfer) {
+  *aDataTransfer = mDataTransfer;
+  NS_IF_ADDREF(*aDataTransfer);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::SetDataTransferXPCOM(DataTransfer* aDataTransfer) {
+  NS_ENSURE_STATE(aDataTransfer);
+  mDataTransfer = aDataTransfer;
+  return NS_OK;
+}
+
+DataTransfer* nsBaseDragService::GetDataTransfer() { return mDataTransfer; }
+
+void nsBaseDragService::SetDataTransfer(DataTransfer* aDataTransfer) {
+  mDataTransfer = aDataTransfer;
+}
+
+bool nsBaseDragService::IsSynthesizedForTests() {
+  return mSessionIsSynthesizedForTests;
+}
+
+uint32_t nsBaseDragService::GetEffectAllowedForTests() {
+  MOZ_ASSERT(mSessionIsSynthesizedForTests);
+  return mEffectAllowedForTests;
+}
+
+NS_IMETHODIMP nsBaseDragService::SetDragEndPointForTests(int32_t aScreenX,
+                                                         int32_t aScreenY) {
+  MOZ_ASSERT(mDoingDrag);
+  MOZ_ASSERT(mSourceDocument);
+  MOZ_ASSERT(mSessionIsSynthesizedForTests);
+  if (!mDoingDrag || !mSourceDocument || !mSessionIsSynthesizedForTests) {
+    return NS_ERROR_FAILURE;
+  }
+  nsPresContext* presContext = mSourceDocument->GetPresContext();
+  if (NS_WARN_IF(!presContext)) {
+    return NS_ERROR_FAILURE;
+  }
+  SetDragEndPoint(
+      LayoutDeviceIntPoint(presContext->CSSPixelsToDevPixels(aScreenX),
+                           presContext->CSSPixelsToDevPixels(aScreenY)));
+  return NS_OK;
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::InvokeDragSession(
+    nsINode* aDOMNode, nsIPrincipal* aPrincipal, nsIContentSecurityPolicy* aCsp,
+    nsICookieJarSettings* aCookieJarSettings, nsIArray* aTransferableArray,
+    uint32_t aActionType,
+    nsContentPolicyType aContentPolicyType = nsIContentPolicy::TYPE_OTHER) {
+  AUTO_PROFILER_LABEL("nsBaseDragService::InvokeDragSession", OTHER);
+
+  NS_ENSURE_TRUE(aDOMNode, NS_ERROR_INVALID_ARG);
+  NS_ENSURE_TRUE(mSuppressLevel == 0, NS_ERROR_FAILURE);
+
+  // stash the document of the dom node
+  mSourceDocument = aDOMNode->OwnerDoc();
+  mTriggeringPrincipal = aPrincipal;
+  mCsp = aCsp;
+  mSourceNode = aDOMNode;
+  mContentPolicyType = aContentPolicyType;
+  mEndDragPoint = LayoutDeviceIntPoint(0, 0);
+
+  // When the mouse goes down, the selection code starts a mouse
+  // capture. However, this gets in the way of determining drag
+  // feedback for things like trees because the event coordinates
+  // are in the wrong coord system, so turn off mouse capture.
+  PresShell::ClearMouseCapture(nullptr);
+
+  if (mSessionIsSynthesizedForTests) {
+    mDoingDrag = true;
+    mDragAction = aActionType;
+    mEffectAllowedForTests = aActionType;
+    return NS_OK;
+  }
+
+  // If you're hitting this, a test is causing the browser to attempt to enter
+  // the drag-drop native nested event loop, which will put the browser in a
+  // state that won't run tests properly until there's manual intervention
+  // to exit the drag-drop loop (either by moving the mouse or hitting escape),
+  // which can't be done from script since we're in the nested loop.
+  //
+  // The best way to avoid this is to catch the dragstart event on the item
+  // being dragged, and then to call preventDefault() and stopPropagating() on
+  // it.
+  if (XRE_IsParentProcess()) {
+    MOZ_ASSERT(
+        !xpc::IsInAutomation(),
+        "About to start drag-drop native loop on which will prevent later "
+        "tests from running properly.");
+  }
+
+  uint32_t length = 0;
+  mozilla::Unused << aTransferableArray->GetLength(&length);
+  if (!length) {
+    nsCOMPtr<nsIMutableArray> mutableArray =
+        do_QueryInterface(aTransferableArray);
+    if (mutableArray) {
+      // In order to be able trigger dnd, we need to have some transferable
+      // object.
+      nsCOMPtr<nsITransferable> trans =
+          do_CreateInstance("@mozilla.org/widget/transferable;1");
+      trans->Init(nullptr);
+      trans->SetRequestingPrincipal(mSourceNode->NodePrincipal());
+      trans->SetContentPolicyType(mContentPolicyType);
+      trans->SetCookieJarSettings(aCookieJarSettings);
+      mutableArray->AppendElement(trans);
+    }
+  } else {
+    for (uint32_t i = 0; i < length; ++i) {
+      nsCOMPtr<nsITransferable> trans =
+          do_QueryElementAt(aTransferableArray, i);
+      if (trans) {
+        // Set the requestingPrincipal on the transferable.
+        trans->SetRequestingPrincipal(mSourceNode->NodePrincipal());
+        trans->SetContentPolicyType(mContentPolicyType);
+        trans->SetCookieJarSettings(aCookieJarSettings);
+      }
+    }
+  }
+
+  nsresult rv = InvokeDragSessionImpl(aTransferableArray, mRegion, aActionType);
+
+  if (NS_FAILED(rv)) {
+    // Set mDoingDrag so that EndDragSession cleans up and sends the dragend
+    // event after the aborted drag.
+    mDoingDrag = true;
+    EndDragSession(true, 0);
+  }
+
+  return rv;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::InvokeDragSessionWithImage(
+    nsINode* aDOMNode, nsIPrincipal* aPrincipal, nsIContentSecurityPolicy* aCsp,
+    nsICookieJarSettings* aCookieJarSettings, nsIArray* aTransferableArray,
+    uint32_t aActionType, nsINode* aImage, int32_t aImageX, int32_t aImageY,
+    DragEvent* aDragEvent, DataTransfer* aDataTransfer) {
+  NS_ENSURE_TRUE(aDragEvent, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(aDataTransfer, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(mSuppressLevel == 0, NS_ERROR_FAILURE);
+
+  mSessionIsSynthesizedForTests =
+      aDragEvent->WidgetEventPtr()->mFlags.mIsSynthesizedForTests;
+  mDataTransfer = aDataTransfer;
+  mSelection = nullptr;
+  mHasImage = true;
+  mDragPopup = nullptr;
+  mImage = aImage;
+  mImageOffset = CSSIntPoint(aImageX, aImageY);
+  mDragStartData = nullptr;
+
+  mScreenPosition.x = aDragEvent->ScreenX(CallerType::System);
+  mScreenPosition.y = aDragEvent->ScreenY(CallerType::System);
+  mInputSource = aDragEvent->MozInputSource();
+
+  // If dragging within a XUL tree and no custom drag image was
+  // set, the region argument to InvokeDragSessionWithImage needs
+  // to be set to the area encompassing the selected rows of the
+  // tree to ensure that the drag feedback gets clipped to those
+  // rows. For other content, region should be null.
+  mRegion = Nothing();
+#ifdef MOZ_XUL
+  if (aDOMNode && aDOMNode->IsContent() && !aImage) {
+    if (aDOMNode->NodeInfo()->Equals(nsGkAtoms::treechildren,
+                                     kNameSpaceID_XUL)) {
+      nsTreeBodyFrame* treeBody =
+          do_QueryFrame(aDOMNode->AsContent()->GetPrimaryFrame());
+      if (treeBody) {
+        mRegion = treeBody->GetSelectionRegion();
+      }
+    }
+  }
+#endif
+
+  nsresult rv = InvokeDragSession(
+      aDOMNode, aPrincipal, aCsp, aCookieJarSettings, aTransferableArray,
+      aActionType, nsIContentPolicy::TYPE_INTERNAL_IMAGE);
+  mRegion = Nothing();
+  return rv;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::InvokeDragSessionWithRemoteImage(
+    nsINode* aDOMNode, nsIPrincipal* aPrincipal, nsIContentSecurityPolicy* aCsp,
+    nsICookieJarSettings* aCookieJarSettings, nsIArray* aTransferableArray,
+    uint32_t aActionType, RemoteDragStartData* aDragStartData,
+    DragEvent* aDragEvent, DataTransfer* aDataTransfer) {
+  NS_ENSURE_TRUE(aDragEvent, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(aDataTransfer, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(mSuppressLevel == 0, NS_ERROR_FAILURE);
+
+  mSessionIsSynthesizedForTests =
+      aDragEvent->WidgetEventPtr()->mFlags.mIsSynthesizedForTests;
+  mDataTransfer = aDataTransfer;
+  mSelection = nullptr;
+  mHasImage = true;
+  mDragPopup = nullptr;
+  mImage = nullptr;
+  mDragStartData = aDragStartData;
+  mImageOffset = CSSIntPoint(0, 0);
+
+  mScreenPosition.x = aDragEvent->ScreenX(CallerType::System);
+  mScreenPosition.y = aDragEvent->ScreenY(CallerType::System);
+  mInputSource = aDragEvent->MozInputSource();
+
+  nsresult rv = InvokeDragSession(
+      aDOMNode, aPrincipal, aCsp, aCookieJarSettings, aTransferableArray,
+      aActionType, nsIContentPolicy::TYPE_INTERNAL_IMAGE);
+  mRegion = Nothing();
+  return rv;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::InvokeDragSessionWithSelection(
+    Selection* aSelection, nsIPrincipal* aPrincipal,
+    nsIContentSecurityPolicy* aCsp, nsICookieJarSettings* aCookieJarSettings,
+    nsIArray* aTransferableArray, uint32_t aActionType, DragEvent* aDragEvent,
+    DataTransfer* aDataTransfer) {
+  NS_ENSURE_TRUE(aSelection, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(aDragEvent, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(mSuppressLevel == 0, NS_ERROR_FAILURE);
+
+  mSessionIsSynthesizedForTests =
+      aDragEvent->WidgetEventPtr()->mFlags.mIsSynthesizedForTests;
+  mDataTransfer = aDataTransfer;
+  mSelection = aSelection;
+  mHasImage = true;
+  mDragPopup = nullptr;
+  mImage = nullptr;
+  mImageOffset = CSSIntPoint();
+  mDragStartData = nullptr;
+  mRegion = Nothing();
+
+  mScreenPosition.x = aDragEvent->ScreenX(CallerType::System);
+  mScreenPosition.y = aDragEvent->ScreenY(CallerType::System);
+  mInputSource = aDragEvent->MozInputSource();
+
+  // just get the focused node from the selection
+  // XXXndeakin this should actually be the deepest node that contains both
+  // endpoints of the selection
+  nsCOMPtr<nsINode> node = aSelection->GetFocusNode();
+
+  return InvokeDragSession(node, aPrincipal, aCsp, aCookieJarSettings,
+                           aTransferableArray, aActionType,
+                           nsIContentPolicy::TYPE_OTHER);
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::GetCurrentSession(nsIDragSession** aSession) {
+  if (!aSession) return NS_ERROR_INVALID_ARG;
+
+  // "this" also implements a drag session, so say we are one but only
+  // if there is currently a drag going on.
+  if (!mSuppressLevel && mDoingDrag) {
+    *aSession = this;
+    NS_ADDREF(*aSession);  // addRef because we're a "getter"
+  } else
+    *aSession = nullptr;
+
+  return NS_OK;
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::StartDragSession() {
+  if (mDoingDrag) {
+    return NS_ERROR_FAILURE;
+  }
+  mDoingDrag = true;
+  // By default dispatch drop also to content.
+  mOnlyChromeDrop = false;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsBaseDragService::StartDragSessionForTests(
+    uint32_t aAllowedEffect) {
+  if (NS_WARN_IF(NS_FAILED(StartDragSession()))) {
+    return NS_ERROR_FAILURE;
+  }
+  mDragAction = aAllowedEffect;
+  mEffectAllowedForTests = aAllowedEffect;
+  mSessionIsSynthesizedForTests = true;
+  return NS_OK;
+}
+
+void nsBaseDragService::OpenDragPopup() {
+  if (mDragPopup) {
+    nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
+    if (pm) {
+      pm->ShowPopupAtScreen(mDragPopup, mScreenPosition.x - mImageOffset.x,
+                            mScreenPosition.y - mImageOffset.y, false, nullptr);
+    }
+  }
+}
+
+int32_t nsBaseDragService::TakeChildProcessDragAction() {
+  // If the last event was dispatched to the child process, use the drag action
+  // assigned from it instead and return it. DRAGDROP_ACTION_UNINITIALIZED is
+  // returned otherwise.
+  int32_t retval = DRAGDROP_ACTION_UNINITIALIZED;
+  if (TakeDragEventDispatchedToChildProcess() &&
+      mDragActionFromChildProcess != DRAGDROP_ACTION_UNINITIALIZED) {
+    retval = mDragActionFromChildProcess;
+  }
+
+  return retval;
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsBaseDragService::EndDragSession(bool aDoneDrag, uint32_t aKeyModifiers) {
+  if (!mDoingDrag || mEndingSession) {
+    return NS_ERROR_FAILURE;
+  }
+
+  mEndingSession = true;
+
+  if (aDoneDrag && !mSuppressLevel) {
+    FireDragEventAtSource(eDragEnd, aKeyModifiers);
+  }
+
+  if (mDragPopup) {
+    nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
+    if (pm) {
+      pm->HidePopup(mDragPopup, false, true, false, false);
+    }
+  }
+
+  for (uint32_t i = 0; i < mChildProcesses.Length(); ++i) {
+    mozilla::Unused << mChildProcesses[i]->SendEndDragSession(
+        aDoneDrag, mUserCancelled, mEndDragPoint, aKeyModifiers);
+    // Continue sending input events with input priority when stopping the dnd
+    // session.
+    mChildProcesses[i]->SetInputPriorityEventEnabled(true);
+  }
+  mChildProcesses.Clear();
+
+  // mDataTransfer and the items it owns are going to die anyway, but we
+  // explicitly deref the contained data here so that we don't have to wait for
+  // CC to reclaim the memory.
+  if (XRE_IsParentProcess()) {
+    DiscardInternalTransferData();
+  }
+
+  mDoingDrag = false;
+  mSessionIsSynthesizedForTests = false;
+  mEffectAllowedForTests = nsIDragService::DRAGDROP_ACTION_UNINITIALIZED;
+  mEndingSession = false;
+  mCanDrop = false;
+
+  // release the source we've been holding on to.
+  mSourceDocument = nullptr;
+  mSourceNode = nullptr;
+  mTriggeringPrincipal = nullptr;
+  mCsp = nullptr;
+  mSelection = nullptr;
+  mDataTransfer = nullptr;
+  mHasImage = false;
+  mUserCancelled = false;
+  mDragPopup = nullptr;
+  mDragStartData = nullptr;
+  mImage = nullptr;
+  mImageOffset = CSSIntPoint();
+  mScreenPosition = CSSIntPoint();
+  mEndDragPoint = LayoutDeviceIntPoint(0, 0);
+  mInputSource = MouseEvent_Binding::MOZ_SOURCE_MOUSE;
+  mRegion = Nothing();
+
+  return NS_OK;
+}
+
+void nsBaseDragService::DiscardInternalTransferData() {
+  if (mDataTransfer && mSourceNode) {
+    MOZ_ASSERT(mDataTransfer);
+
+    DataTransferItemList* items = mDataTransfer->Items();
+    for (size_t i = 0; i < items->Length(); i++) {
+      bool found;
+      DataTransferItem* item = items->IndexedGetter(i, found);
+
+      // Non-OTHER items may still be needed by JS. Skip them.
+      if (!found || item->Kind() != DataTransferItem::KIND_OTHER) {
+        continue;
+      }
+
+      nsCOMPtr<nsIVariant> variant = item->DataNoSecurityCheck();
+      nsCOMPtr<nsIWritableVariant> writable = do_QueryInterface(variant);
+
+      if (writable) {
+        writable->SetAsEmpty();
+      }
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsBaseDragService::FireDragEventAtSource(EventMessage aEventMessage,
+                                         uint32_t aKeyModifiers) {
+  if (mSourceNode && mSourceDocument && !mSuppressLevel) {
+    RefPtr<PresShell> presShell = mSourceDocument->GetPresShell();
+    if (presShell) {
+      nsEventStatus status = nsEventStatus_eIgnore;
+      WidgetDragEvent event(true, aEventMessage, nullptr);
+      event.mFlags.mIsSynthesizedForTests = mSessionIsSynthesizedForTests;
+      event.mInputSource = mInputSource;
+      if (aEventMessage == eDragEnd) {
+        event.mRefPoint = mEndDragPoint;
+        event.mUserCancelled = mUserCancelled;
+      }
+      event.mModifiers = aKeyModifiers;
+      // Send the drag event to APZ, which needs to know about them to be
+      // able to accurately detect the end of a drag gesture.
+      if (nsPresContext* presContext = presShell->GetPresContext()) {
+        if (nsCOMPtr<nsIWidget> widget = presContext->GetRootWidget()) {
+          widget->DispatchEventToAPZOnly(&event);
+        }
+      }
+
+      nsCOMPtr<nsIContent> content = do_QueryInterface(mSourceNode);
+      return presShell->HandleDOMEventWithTarget(content, &event, &status);
+    }
+  }
+
+  return NS_OK;
+}
+
+/* This is used by Windows and Mac to update the position of a popup being
+ * used as a drag image during the drag. This isn't used on GTK as it manages
+ * the drag popup itself.
+ */
+NS_IMETHODIMP
+nsBaseDragService::DragMoved(int32_t aX, int32_t aY) {
+  if (mDragPopup) {
+    nsIFrame* frame = mDragPopup->GetPrimaryFrame();
+    if (frame && frame->IsMenuPopupFrame()) {
+      CSSIntPoint cssPos =
+          RoundedToInt(LayoutDeviceIntPoint(aX, aY) /
+                       frame->PresContext()->CSSToDevPixelScale()) -
+          mImageOffset;
+      (static_cast<nsMenuPopupFrame*>(frame))->MoveTo(cssPos, true);
+    }
+  }
+
+  return NS_OK;
+}
+
+static PresShell* GetPresShellForContent(nsINode* aDOMNode) {
+  nsCOMPtr<nsIContent> content = do_QueryInterface(aDOMNode);
+  if (!content) return nullptr;
+
+  RefPtr<Document> document = content->GetComposedDoc();
+  if (document) {
+    document->FlushPendingNotifications(FlushType::Display);
+    return document->GetPresShell();
+  }
+
+  return nullptr;
+}
+
+nsresult nsBaseDragService::DrawDrag(nsINode* aDOMNode,
+                                     const Maybe<CSSIntRegion>& aRegion,
+                                     CSSIntPoint aScreenPosition,
+                                     LayoutDeviceIntRect* aScreenDragRect,
+                                     RefPtr<SourceSurface>* aSurface,
+                                     nsPresContext** aPresContext) {
+  *aSurface = nullptr;
+  *aPresContext = nullptr;
+
+  // use a default size, in case of an error.
+  aScreenDragRect->SetRect(aScreenPosition.x - mImageOffset.x,
+                           aScreenPosition.y - mImageOffset.y, 1, 1);
+
+  // if a drag image was specified, use that, otherwise, use the source node
+  nsCOMPtr<nsINode> dragNode = mImage ? mImage.get() : aDOMNode;
+
+  // get the presshell for the node being dragged. If the drag image is not in
+  // a document or has no frame, get the presshell from the source drag node
+  PresShell* presShell = GetPresShellForContent(dragNode);
+  if (!presShell && mImage) {
+    presShell = GetPresShellForContent(aDOMNode);
+  }
+  if (!presShell) {
+    return NS_ERROR_FAILURE;
+  }
+
+  *aPresContext = presShell->GetPresContext();
+
+  if (mDragStartData) {
+    if (mImage) {
+      // Just clear the surface if chrome has overridden it with an image.
+      *aSurface = nullptr;
+    } else {
+      *aSurface = mDragStartData->TakeVisualization(aScreenDragRect);
+    }
+
+    mDragStartData = nullptr;
+    return NS_OK;
+  }
+
+  // convert mouse position to dev pixels of the prescontext
+  CSSIntPoint screenPosition(aScreenPosition);
+  screenPosition.x -= mImageOffset.x;
+  screenPosition.y -= mImageOffset.y;
+  LayoutDeviceIntPoint screenPoint =
+      ConvertToUnscaledDevPixels(*aPresContext, screenPosition);
+  aScreenDragRect->MoveTo(screenPoint.x, screenPoint.y);
+
+  // check if drag images are disabled
+  bool enableDragImages = Preferences::GetBool(DRAGIMAGES_PREF, true);
+
+  // didn't want an image, so just set the screen rectangle to the frame size
+  if (!enableDragImages || !mHasImage) {
+    // This holds a quantity in RelativeTo{presShell->GetRootFrame(),
+    // ViewportType::Layout} space.
+    nsRect presLayoutRect;
+    if (aRegion) {
+      // if a region was specified, set the screen rectangle to the area that
+      // the region occupies
+      presLayoutRect = ToAppUnits(aRegion->GetBounds(), AppUnitsPerCSSPixel());
+    } else {
+      // otherwise, there was no region so just set the rectangle to
+      // the size of the primary frame of the content.
+      nsCOMPtr<nsIContent> content = do_QueryInterface(dragNode);
+      nsIFrame* frame = content->GetPrimaryFrame();
+      if (frame) {
+        presLayoutRect = frame->GetRect();
+      }
+    }
+
+    LayoutDeviceRect screenVisualRect = ViewportUtils::ToScreenRelativeVisual(
+        LayoutDeviceRect::FromAppUnits(presLayoutRect,
+                                       (*aPresContext)->AppUnitsPerDevPixel()),
+        *aPresContext);
+    aScreenDragRect->SizeTo(screenVisualRect.Width(),
+                            screenVisualRect.Height());
+    return NS_OK;
+  }
+
+  // draw the image for selections
+  if (mSelection) {
+    LayoutDeviceIntPoint pnt(aScreenDragRect->TopLeft());
+    *aSurface = presShell->RenderSelection(
+        mSelection, pnt, aScreenDragRect,
+        mImage ? RenderImageFlags::None : RenderImageFlags::AutoScale);
+    return NS_OK;
+  }
+
+  // if a custom image was specified, check if it is an image node and draw
+  // using the source rather than the displayed image. But if mImage isn't
+  // an image or canvas, fall through to RenderNode below.
+  if (mImage) {
+    nsCOMPtr<nsIContent> content = do_QueryInterface(dragNode);
+    HTMLCanvasElement* canvas = HTMLCanvasElement::FromNodeOrNull(content);
+    if (canvas) {
+      return DrawDragForImage(*aPresContext, nullptr, canvas, aScreenDragRect,
+                              aSurface);
+    }
+
+    nsCOMPtr<nsIImageLoadingContent> imageLoader = do_QueryInterface(dragNode);
+    // for image nodes, create the drag image from the actual image data
+    if (imageLoader) {
+      return DrawDragForImage(*aPresContext, imageLoader, nullptr,
+                              aScreenDragRect, aSurface);
+    }
+
+    // If the image is a popup, use that as the image. This allows custom drag
+    // images that can change during the drag, but means that any platform
+    // default image handling won't occur.
+    // XXXndeakin this should be chrome-only
+
+    nsIFrame* frame = content->GetPrimaryFrame();
+    if (frame && frame->IsMenuPopupFrame()) {
+      mDragPopup = content;
+    }
+  }
+
+  if (!mDragPopup) {
+    // otherwise, just draw the node
+    RenderImageFlags renderFlags =
+        mImage ? RenderImageFlags::None : RenderImageFlags::AutoScale;
+    if (renderFlags != RenderImageFlags::None) {
+      // check if the dragged node itself is an img element
+      if (dragNode->NodeName().LowerCaseEqualsLiteral("img")) {
+        renderFlags = renderFlags | RenderImageFlags::IsImage;
+      } else {
+        nsINodeList* childList = dragNode->ChildNodes();
+        uint32_t length = childList->Length();
+        // check every childnode for being an img element
+        // XXXbz why don't we need to check descendants recursively?
+        for (uint32_t count = 0; count < length; ++count) {
+          if (childList->Item(count)->NodeName().LowerCaseEqualsLiteral(
+                  "img")) {
+            // if the dragnode contains an image, set RenderImageFlags::IsImage
+            // flag
+            renderFlags = renderFlags | RenderImageFlags::IsImage;
+            break;
+          }
+        }
+      }
+    }
+    LayoutDeviceIntPoint pnt(aScreenDragRect->TopLeft());
+    *aSurface = presShell->RenderNode(dragNode, aRegion, pnt, aScreenDragRect,
+                                      renderFlags);
+  }
+
+  // If an image was specified, reset the position from the offset that was
+  // supplied.
+  if (mImage) {
+    aScreenDragRect->MoveTo(screenPoint.x, screenPoint.y);
+  }
+
+  return NS_OK;
+}
+
+nsresult nsBaseDragService::DrawDragForImage(
+    nsPresContext* aPresContext, nsIImageLoadingContent* aImageLoader,
+    HTMLCanvasElement* aCanvas, LayoutDeviceIntRect* aScreenDragRect,
+    RefPtr<SourceSurface>* aSurface) {
+  nsCOMPtr<imgIContainer> imgContainer;
+  if (aImageLoader) {
+    nsCOMPtr<imgIRequest> imgRequest;
+    nsresult rv = aImageLoader->GetRequest(
+        nsIImageLoadingContent::CURRENT_REQUEST, getter_AddRefs(imgRequest));
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (!imgRequest) return NS_ERROR_NOT_AVAILABLE;
+
+    rv = imgRequest->GetImage(getter_AddRefs(imgContainer));
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (!imgContainer) return NS_ERROR_NOT_AVAILABLE;
+
+    // use the size of the image as the size of the drag image
+    int32_t imageWidth, imageHeight;
+    rv = imgContainer->GetWidth(&imageWidth);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = imgContainer->GetHeight(&imageHeight);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    aScreenDragRect->SizeTo(aPresContext->CSSPixelsToDevPixels(imageWidth),
+                            aPresContext->CSSPixelsToDevPixels(imageHeight));
+  } else {
+    // XXX The canvas size should be converted to dev pixels.
+    NS_ASSERTION(aCanvas, "both image and canvas are null");
+    nsIntSize sz = aCanvas->GetSize();
+    aScreenDragRect->SizeTo(sz.width, sz.height);
+  }
+
+  nsIntSize destSize;
+  destSize.width = aScreenDragRect->Width();
+  destSize.height = aScreenDragRect->Height();
+  if (destSize.width == 0 || destSize.height == 0) return NS_ERROR_FAILURE;
+
+  nsresult result = NS_OK;
+  if (aImageLoader) {
+    RefPtr<DrawTarget> dt =
+        gfxPlatform::GetPlatform()->CreateOffscreenContentDrawTarget(
+            destSize, SurfaceFormat::B8G8R8A8);
+    if (!dt || !dt->IsValid()) return NS_ERROR_FAILURE;
+
+    RefPtr<gfxContext> ctx = gfxContext::CreateOrNull(dt);
+    if (!ctx) return NS_ERROR_FAILURE;
+
+    ImgDrawResult res =
+        imgContainer->Draw(ctx, destSize, ImageRegion::Create(destSize),
+                           imgIContainer::FRAME_CURRENT, SamplingFilter::GOOD,
+                           /* no SVGImageContext */ Nothing(),
+                           imgIContainer::FLAG_SYNC_DECODE, 1.0);
+    if (res == ImgDrawResult::BAD_IMAGE || res == ImgDrawResult::BAD_ARGS ||
+        res == ImgDrawResult::NOT_SUPPORTED) {
+      return NS_ERROR_FAILURE;
+    }
+    *aSurface = dt->Snapshot();
+  } else {
+    *aSurface = aCanvas->GetSurfaceSnapshot();
+  }
+
+  return result;
+}
+
+LayoutDeviceIntPoint nsBaseDragService::ConvertToUnscaledDevPixels(
+    nsPresContext* aPresContext, CSSIntPoint aScreenPosition) {
+  int32_t adj =
+      aPresContext->DeviceContext()->AppUnitsPerDevPixelAtUnitFullZoom();
+  return LayoutDeviceIntPoint(
+      nsPresContext::CSSPixelsToAppUnits(aScreenPosition.x) / adj,
+      nsPresContext::CSSPixelsToAppUnits(aScreenPosition.y) / adj);
+}
+
+NS_IMETHODIMP
+nsBaseDragService::Suppress() {
+  EndDragSession(false, 0);
+  ++mSuppressLevel;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::Unsuppress() {
+  --mSuppressLevel;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::UserCancelled() {
+  mUserCancelled = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::UpdateDragEffect() {
+  mDragActionFromChildProcess = mDragAction;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::UpdateDragImage(nsINode* aImage, int32_t aImageX,
+                                   int32_t aImageY) {
+  // Don't change the image if this is a drag from another source or if there
+  // is a drag popup.
+  if (!mSourceNode || mDragPopup) return NS_OK;
+
+  mImage = aImage;
+  mImageOffset = CSSIntPoint(aImageX, aImageY);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseDragService::DragEventDispatchedToChildProcess() {
+  mDragEventDispatchedToChildProcess = true;
+  return NS_OK;
+}
+
+bool nsBaseDragService::MaybeAddChildProcess(
+    mozilla::dom::ContentParent* aChild) {
+  if (!mChildProcesses.Contains(aChild)) {
+    mChildProcesses.AppendElement(aChild);
+    return true;
+  }
+  return false;
+}
+
+bool nsBaseDragService::RemoveAllChildProcesses() {
+  for (uint32_t c = 0; c < mChildProcesses.Length(); c++) {
+    mozilla::Unused << mChildProcesses[c]->SendEndDragSession(
+        true, false, LayoutDeviceIntPoint(), 0);
+  }
+  mChildProcesses.Clear();
+  return true;
+}