widget/nsBaseDragService.cpp
author Noemi Erli <nerli@mozilla.com>
Tue, 26 Feb 2019 03:43:12 +0200
changeset 461110 3c030119c0dcf447dd1afe7165b2d6846a0bc7f0
parent 459622 a11e3f4d19db673bc84fcc386d992139c5354867
child 466751 7b71c9da0214e43368ab5cfb95344ca5ae13d670
permissions -rw-r--r--
Backed out 10 changesets (bug 1505871) for wrench bustages CLOSED TREE Backed out changeset 045ab0ec3613 (bug 1505871) Backed out changeset 6486435a048d (bug 1505871) Backed out changeset 9be871042749 (bug 1505871) Backed out changeset 0007feaf988d (bug 1505871) Backed out changeset 3cb8fb01e77e (bug 1505871) Backed out changeset 2fff213d97e3 (bug 1505871) Backed out changeset 1ad20d485eca (bug 1505871) Backed out changeset 0fd8742fa662 (bug 1505871) Backed out changeset 1899600a7985 (bug 1505871) Backed out changeset f9578d20e54e (bug 1505871)

/* -*- 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 "nsIServiceManager.h"
#include "nsITransferable.h"
#include "nsSize.h"
#include "nsXPCOM.h"
#include "nsISupportsPrimitives.h"
#include "nsCOMPtr.h"
#include "nsIInterfaceRequestorUtils.h"
#include "nsIFrame.h"
#include "nsFrameLoaderOwner.h"
#include "mozilla/dom/Document.h"
#include "nsIContent.h"
#include "nsIPresShell.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"
#include "SVGImageContext.h"
#ifdef MOZ_XUL
#  include "nsTreeBodyFrame.h"
#endif
#include "mozilla/MouseEvents.h"
#include "mozilla/Preferences.h"
#include "mozilla/dom/BindingDeclarations.h"
#include "mozilla/dom/DataTransferItemList.h"
#include "mozilla/dom/DataTransfer.h"
#include "mozilla/dom/DragEvent.h"
#include "mozilla/dom/MouseEventBinding.h"
#include "mozilla/dom/Selection.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/Unused.h"
#include "nsFrameLoader.h"
#include "TabParent.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),
      mHasImage(false),
      mUserCancelled(false),
      mDragEventDispatchedToChildProcess(false),
      mDragAction(DRAGDROP_ACTION_NONE),
      mDragActionFromChildProcess(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::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;
}

//-------------------------------------------------------------------------
NS_IMETHODIMP
nsBaseDragService::InvokeDragSession(
    nsINode* aDOMNode, nsIPrincipal* aPrincipal, 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;
  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.
  nsIPresShell::ClearMouseCapture(nullptr);

  uint32_t length = 0;
  mozilla::Unused << aTransferableArray->GetLength(&length);
  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);
    }
  }

  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, 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);

  mDataTransfer = aDataTransfer;
  mSelection = nullptr;
  mHasImage = true;
  mDragPopup = nullptr;
  mImage = aImage;
  mImageOffset = CSSIntPoint(aImageX, aImageY);

  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, aTransferableArray, aActionType,
                        nsIContentPolicy::TYPE_INTERNAL_IMAGE);
  mRegion = Nothing();
  return rv;
}

NS_IMETHODIMP
nsBaseDragService::InvokeDragSessionWithSelection(Selection* aSelection,
                                                  nsIPrincipal* aPrincipal,
                                                  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);

  mDataTransfer = aDataTransfer;
  mSelection = aSelection;
  mHasImage = true;
  mDragPopup = nullptr;
  mImage = nullptr;
  mImageOffset = CSSIntPoint();
  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, 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;
}

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) {
    return NS_ERROR_FAILURE;
  }

  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;
  mCanDrop = false;

  // release the source we've been holding on to.
  mSourceDocument = nullptr;
  mSourceNode = nullptr;
  mTriggeringPrincipal = nullptr;
  mSelection = nullptr;
  mDataTransfer = nullptr;
  mHasImage = false;
  mUserCancelled = false;
  mDragPopup = 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) {
    nsCOMPtr<nsIPresShell> presShell = mSourceDocument->GetShell();
    if (presShell) {
      nsEventStatus status = nsEventStatus_eIgnore;
      WidgetDragEvent event(true, aEventMessage, nullptr);
      event.inputSource = 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 nsIPresShell* 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->GetShell();
  }

  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
  nsIPresShell* presShell = GetPresShellForContent(dragNode);
  if (!presShell && mImage) presShell = GetPresShellForContent(aDOMNode);
  if (!presShell) return NS_ERROR_FAILURE;

  *aPresContext = presShell->GetPresContext();

  RefPtr<nsFrameLoaderOwner> flo = do_QueryObject(dragNode);
  if (flo) {
    RefPtr<nsFrameLoader> fl = flo->GetFrameLoader();
    if (fl) {
      auto* tp = static_cast<mozilla::dom::TabParent*>(fl->GetRemoteBrowser());
      if (tp && tp->TakeDragVisualization(*aSurface, aScreenDragRect)) {
        if (mImage) {
          // Just clear the surface if chrome has overridden it with an image.
          *aSurface = 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) {
    // if a region was specified, set the screen rectangle to the area that
    // the region occupies
    CSSIntRect dragRect;
    if (aRegion) {
      // the region's coordinates are relative to the root frame
      dragRect = aRegion->GetBounds();

      nsIFrame* rootFrame = presShell->GetRootFrame();
      CSSIntRect screenRect = rootFrame->GetScreenRect();
      dragRect.MoveBy(screenRect.TopLeft());
    } 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) {
        dragRect = frame->GetScreenRect();
      }
    }

    nsIntRect dragRectDev =
        ToAppUnits(dragRect, AppUnitsPerCSSPixel())
            .ToOutsidePixels((*aPresContext)->AppUnitsPerDevPixel());
    aScreenDragRect->SizeTo(dragRectDev.Width(), dragRectDev.Height());
    return NS_OK;
  }

  // draw the image for selections
  if (mSelection) {
    LayoutDeviceIntPoint pnt(aScreenDragRect->TopLeft());
    *aSurface = presShell->RenderSelection(
        mSelection, pnt, aScreenDragRect,
        mImage ? 0 : nsIPresShell::RENDER_AUTO_SCALE);
    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
    uint32_t renderFlags = mImage ? 0 : nsIPresShell::RENDER_AUTO_SCALE;
    if (renderFlags) {
      // check if the dragged node itself is an img element
      if (dragNode->NodeName().LowerCaseEqualsLiteral("img")) {
        renderFlags = renderFlags | nsIPresShell::RENDER_IS_IMAGE;
      } 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 RENDER_IS_IMAGE flag
            renderFlags = renderFlags | nsIPresShell::RENDER_IS_IMAGE;
            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;
}