widget/src/xpwidgets/nsBaseDragService.cpp
author Vivien Nicolas <21@vingtetun.org>
Wed, 14 Dec 2011 11:34:33 +0100
changeset 83341 7c621c7bfea34f5a9ec5eb09b23c5ae7be1c8294
parent 81380 7e2695c9d94e2f652122fd8374e62ae881373e49
child 108942 7ceaa303896bae686f83081212fec143d3dfd21d
permissions -rw-r--r--
Bug 709010 - Add a empty components directory to b2g/. r=cjones

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Mats Palmgren <mats.palmgren@bredband.net>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "nsBaseDragService.h"
#include "nsITransferable.h"

#include "nsIServiceManager.h"
#include "nsITransferable.h"
#include "nsISupportsArray.h"
#include "nsSize.h"
#include "nsXPCOM.h"
#include "nsISupportsPrimitives.h"
#include "nsCOMPtr.h"
#include "nsIInterfaceRequestorUtils.h"
#include "nsIFrame.h"
#include "nsIDocument.h"
#include "nsIContent.h"
#include "nsIPresShell.h"
#include "nsIViewManager.h"
#include "nsIDOMNode.h"
#include "nsIDOMDragEvent.h"
#include "nsISelection.h"
#include "nsISelectionPrivate.h"
#include "nsPresContext.h"
#include "nsIDOMDataTransfer.h"
#include "nsICanvasElementExternal.h"
#include "nsIImageLoadingContent.h"
#include "imgIContainer.h"
#include "imgIRequest.h"
#include "nsRegion.h"
#include "nsGUIEvent.h"
#include "nsXULPopupManager.h"
#include "nsMenuPopupFrame.h"
#include "mozilla/Preferences.h"

#include "gfxContext.h"
#include "gfxPlatform.h"

using namespace mozilla;

#define DRAGIMAGES_PREF "nglayout.enable_drag_images"

nsBaseDragService::nsBaseDragService()
  : mCanDrop(false), mOnlyChromeDrop(false), mDoingDrag(false),
    mHasImage(false), mUserCancelled(false),
    mDragAction(DRAGDROP_ACTION_NONE), mTargetSize(0,0),
    mImageX(0), mImageY(0), mScreenX(-1), mScreenY(-1), mSuppressLevel(0),
    mInputSource(nsIDOMMouseEvent::MOZ_SOURCE_MOUSE)
{
}

nsBaseDragService::~nsBaseDragService()
{
}

NS_IMPL_ISUPPORTS2(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(PRUint32 anAction)
{
  mDragAction = anAction;
  return NS_OK;
}

//---------------------------------------------------------
NS_IMETHODIMP
nsBaseDragService::GetDragAction(PRUint32 * anAction)
{
  *anAction = mDragAction;
  return NS_OK;
}

//---------------------------------------------------------
NS_IMETHODIMP
nsBaseDragService::SetTargetSize(nsSize aDragTargetSize)
{
  mTargetSize = aDragTargetSize;
  return NS_OK;
}

//---------------------------------------------------------
NS_IMETHODIMP
nsBaseDragService::GetTargetSize(nsSize * aDragTargetSize)
{
  *aDragTargetSize = mTargetSize;
  return NS_OK;
}

//-------------------------------------------------------------------------

NS_IMETHODIMP
nsBaseDragService::GetNumDropItems(PRUint32 * aNumItems)
{
  *aNumItems = 0;
  return NS_ERROR_FAILURE;
}


//
// GetSourceDocument
//
// Returns the DOM document where the drag was initiated. This will be
// nsnull if the drag began outside of our application.
//
NS_IMETHODIMP
nsBaseDragService::GetSourceDocument(nsIDOMDocument** aSourceDocument)
{
  *aSourceDocument = mSourceDocument.get();
  NS_IF_ADDREF(*aSourceDocument);

  return NS_OK;
}

//
// GetSourceNode
//
// Returns the DOM node where the drag was initiated. This will be
// nsnull if the drag began outside of our application.
//
NS_IMETHODIMP
nsBaseDragService::GetSourceNode(nsIDOMNode** aSourceNode)
{
  *aSourceNode = mSourceNode.get();
  NS_IF_ADDREF(*aSourceNode);

  return NS_OK;
}


//-------------------------------------------------------------------------

NS_IMETHODIMP
nsBaseDragService::GetData(nsITransferable * aTransferable,
                           PRUint32 aItemIndex)
{
  return NS_ERROR_FAILURE;
}

//-------------------------------------------------------------------------
NS_IMETHODIMP
nsBaseDragService::IsDataFlavorSupported(const char *aDataFlavor,
                                         bool *_retval)
{
  return NS_ERROR_FAILURE;
}

NS_IMETHODIMP
nsBaseDragService::GetDataTransfer(nsIDOMDataTransfer** aDataTransfer)
{
  *aDataTransfer = mDataTransfer;
  NS_IF_ADDREF(*aDataTransfer);
  return NS_OK;
}

NS_IMETHODIMP
nsBaseDragService::SetDataTransfer(nsIDOMDataTransfer* aDataTransfer)
{
  mDataTransfer = aDataTransfer;
  return NS_OK;
}

//-------------------------------------------------------------------------
NS_IMETHODIMP
nsBaseDragService::InvokeDragSession(nsIDOMNode *aDOMNode,
                                     nsISupportsArray* aTransferableArray,
                                     nsIScriptableRegion* aDragRgn,
                                     PRUint32 aActionType)
{
  NS_ENSURE_TRUE(aDOMNode, NS_ERROR_INVALID_ARG);
  NS_ENSURE_TRUE(mSuppressLevel == 0, NS_ERROR_FAILURE);

  // stash the document of the dom node
  aDOMNode->GetOwnerDocument(getter_AddRefs(mSourceDocument));
  mSourceNode = aDOMNode;
  mEndDragPoint = nsIntPoint(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(nsnull);

  return NS_OK;
}

NS_IMETHODIMP
nsBaseDragService::InvokeDragSessionWithImage(nsIDOMNode* aDOMNode,
                                              nsISupportsArray* aTransferableArray,
                                              nsIScriptableRegion* aRegion,
                                              PRUint32 aActionType,
                                              nsIDOMNode* aImage,
                                              PRInt32 aImageX, PRInt32 aImageY,
                                              nsIDOMDragEvent* aDragEvent,
                                              nsIDOMDataTransfer* 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 = nsnull;
  mHasImage = true;
  mDragPopup = nsnull;
  mImage = aImage;
  mImageX = aImageX;
  mImageY = aImageY;

  aDragEvent->GetScreenX(&mScreenX);
  aDragEvent->GetScreenY(&mScreenY);
  aDragEvent->GetMozInputSource(&mInputSource);

  return InvokeDragSession(aDOMNode, aTransferableArray, aRegion, aActionType);
}

NS_IMETHODIMP
nsBaseDragService::InvokeDragSessionWithSelection(nsISelection* aSelection,
                                                  nsISupportsArray* aTransferableArray,
                                                  PRUint32 aActionType,
                                                  nsIDOMDragEvent* aDragEvent,
                                                  nsIDOMDataTransfer* 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 = nsnull;
  mImage = nsnull;
  mImageX = 0;
  mImageY = 0;

  aDragEvent->GetScreenX(&mScreenX);
  aDragEvent->GetScreenY(&mScreenY);
  aDragEvent->GetMozInputSource(&mInputSource);

  // just get the focused node from the selection
  // XXXndeakin this should actually be the deepest node that contains both
  // endpoints of the selection
  nsCOMPtr<nsIDOMNode> node;
  aSelection->GetFocusNode(getter_AddRefs(node));

  return InvokeDragSession(node, aTransferableArray, nsnull, aActionType);
}

//-------------------------------------------------------------------------
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 = nsnull;

  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, mScreenX - mImageX, mScreenY - mImageY, false, nsnull);
    }
  }
}

//-------------------------------------------------------------------------
NS_IMETHODIMP
nsBaseDragService::EndDragSession(bool aDoneDrag)
{
  if (!mDoingDrag) {
    return NS_ERROR_FAILURE;
  }

  if (aDoneDrag && !mSuppressLevel)
    FireDragEventAtSource(NS_DRAGDROP_END);

  if (mDragPopup) {
    nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
    if (pm) {
      pm->HidePopup(mDragPopup, false, true, false);
    }
  }

  mDoingDrag = false;

  // release the source we've been holding on to.
  mSourceDocument = nsnull;
  mSourceNode = nsnull;
  mSelection = nsnull;
  mDataTransfer = nsnull;
  mHasImage = false;
  mUserCancelled = false;
  mDragPopup = nsnull;
  mImage = nsnull;
  mImageX = 0;
  mImageY = 0;
  mScreenX = -1;
  mScreenY = -1;
  mInputSource = nsIDOMMouseEvent::MOZ_SOURCE_MOUSE;

  return NS_OK;
}

NS_IMETHODIMP
nsBaseDragService::FireDragEventAtSource(PRUint32 aMsg)
{
  if (mSourceNode && !mSuppressLevel) {
    nsCOMPtr<nsIDocument> doc = do_QueryInterface(mSourceDocument);
    if (doc) {
      nsCOMPtr<nsIPresShell> presShell = doc->GetShell();
      if (presShell) {
        nsEventStatus status = nsEventStatus_eIgnore;
        nsDragEvent event(true, aMsg, nsnull);
        event.inputSource = mInputSource;
        if (aMsg == NS_DRAGDROP_END) {
          event.refPoint.x = mEndDragPoint.x;
          event.refPoint.y = mEndDragPoint.y;
          event.userCancelled = mUserCancelled;
        }

        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(PRInt32 aX, PRInt32 aY)
{
  if (mDragPopup) {
    nsIFrame* frame = mDragPopup->GetPrimaryFrame();
    if (frame && frame->GetType() == nsGkAtoms::menuPopupFrame) {
      (static_cast<nsMenuPopupFrame *>(frame))->MoveTo(aX - mImageX, aY - mImageY, true);
    }
  }

  return NS_OK;
}

static nsIPresShell*
GetPresShellForContent(nsIDOMNode* aDOMNode)
{
  nsCOMPtr<nsIContent> content = do_QueryInterface(aDOMNode);
  if (!content)
    return nsnull;

  nsCOMPtr<nsIDocument> document = content->GetCurrentDoc();
  if (document) {
    document->FlushPendingNotifications(Flush_Display);

    return document->GetShell();
  }

  return nsnull;
}

nsresult
nsBaseDragService::DrawDrag(nsIDOMNode* aDOMNode,
                            nsIScriptableRegion* aRegion,
                            PRInt32 aScreenX, PRInt32 aScreenY,
                            nsIntRect* aScreenDragRect,
                            gfxASurface** aSurface,
                            nsPresContext** aPresContext)
{
  *aSurface = nsnull;
  *aPresContext = nsnull;

  // use a default size, in case of an error.
  aScreenDragRect->x = aScreenX - mImageX;
  aScreenDragRect->y = aScreenY - mImageY;
  aScreenDragRect->width = 1;
  aScreenDragRect->height = 1;

  // if a drag image was specified, use that, otherwise, use the source node
  nsCOMPtr<nsIDOMNode> 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();

  // 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
    if (aRegion) {
      // the region's coordinates are relative to the root frame
      nsIFrame* rootFrame = presShell->GetRootFrame();
      if (rootFrame && *aPresContext) {
        nsIntRect dragRect;
        aRegion->GetBoundingBox(&dragRect.x, &dragRect.y, &dragRect.width, &dragRect.height);
        dragRect = dragRect.ToAppUnits(nsPresContext::AppUnitsPerCSSPixel()).
                            ToOutsidePixels((*aPresContext)->AppUnitsPerDevPixel());

        nsIntRect screenRect = rootFrame->GetScreenRectExternal();
        aScreenDragRect->SetRect(screenRect.x + dragRect.x, screenRect.y + dragRect.y,
                                 dragRect.width, dragRect.height);
      }
    }
    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) {
        nsIntRect screenRect = frame->GetScreenRectExternal();
        aScreenDragRect->SetRect(screenRect.x, screenRect.y,
                                 screenRect.width, screenRect.height);
      }
    }

    return NS_OK;
  }

  // draw the image for selections
  if (mSelection) {
    nsIntPoint pnt(aScreenDragRect->x, aScreenDragRect->y);
    nsRefPtr<gfxASurface> surface = presShell->RenderSelection(mSelection, pnt, aScreenDragRect);
    *aSurface = surface;
    NS_IF_ADDREF(*aSurface);
    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<nsICanvasElementExternal> canvas = do_QueryInterface(dragNode);
    if (canvas) {
      return DrawDragForImage(*aPresContext, nsnull, canvas, aScreenX,
                              aScreenY, 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, nsnull, aScreenX,
                              aScreenY, 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

    nsCOMPtr<nsIContent> content = do_QueryInterface(dragNode);
    nsIFrame* frame = content->GetPrimaryFrame();
    if (frame && frame->GetType() == nsGkAtoms::menuPopupFrame) {
      mDragPopup = content;
    }
  }

  nsRefPtr<gfxASurface> surface;
  if (!mDragPopup) {
    // otherwise, just draw the node
    nsIntRegion clipRegion;
    if (aRegion) {
      aRegion->GetRegion(&clipRegion);
    }

    nsIntPoint pnt(aScreenDragRect->x, aScreenDragRect->y);
    surface = presShell->RenderNode(dragNode, aRegion ? &clipRegion : nsnull,
                                    pnt, aScreenDragRect);
  }

  // if an image was specified, reposition the drag rectangle to
  // the supplied offset in mImageX and mImageY.
  if (mImage) {
    aScreenDragRect->x = aScreenX - mImageX;
    aScreenDragRect->y = aScreenY - mImageY;
  }

  *aSurface = surface;
  NS_IF_ADDREF(*aSurface);

  return NS_OK;
}

nsresult
nsBaseDragService::DrawDragForImage(nsPresContext* aPresContext,
                                    nsIImageLoadingContent* aImageLoader,
                                    nsICanvasElementExternal* aCanvas,
                                    PRInt32 aScreenX, PRInt32 aScreenY,
                                    nsIntRect* aScreenDragRect,
                                    gfxASurface** 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
    imgContainer->GetWidth(&aScreenDragRect->width);
    imgContainer->GetHeight(&aScreenDragRect->height);
  }
  else {
    NS_ASSERTION(aCanvas, "both image and canvas are null");
    nsIntSize sz = aCanvas->GetSizeExternal();
    aScreenDragRect->width = sz.width;
    aScreenDragRect->height = sz.height;
  }

  nsIntSize srcSize = aScreenDragRect->Size();
  nsIntSize destSize = srcSize;

  if (destSize.width == 0 || destSize.height == 0)
    return NS_ERROR_FAILURE;

  // if the image is larger than half the screen size, scale it down. This
  // scaling algorithm is the same as is used in nsPresShell::PaintRangePaintInfo
  nsDeviceContext* deviceContext = aPresContext->DeviceContext();
  nsRect maxSize;
  deviceContext->GetClientRect(maxSize);
  nscoord maxWidth = aPresContext->AppUnitsToDevPixels(maxSize.width >> 1);
  nscoord maxHeight = aPresContext->AppUnitsToDevPixels(maxSize.height >> 1);
  if (destSize.width > maxWidth || destSize.height > maxHeight) {
    float scale = 1.0;
    if (destSize.width > maxWidth)
      scale = NS_MIN(scale, float(maxWidth) / destSize.width);
    if (destSize.height > maxHeight)
      scale = NS_MIN(scale, float(maxHeight) / destSize.height);

    destSize.width = NSToIntFloor(float(destSize.width) * scale);
    destSize.height = NSToIntFloor(float(destSize.height) * scale);

    aScreenDragRect->x = NSToIntFloor(aScreenX - float(mImageX) * scale);
    aScreenDragRect->y = NSToIntFloor(aScreenY - float(mImageY) * scale);
    aScreenDragRect->width = destSize.width;
    aScreenDragRect->height = destSize.height;
  }

  nsRefPtr<gfxASurface> surface =
    gfxPlatform::GetPlatform()->CreateOffscreenSurface(gfxIntSize(destSize.width, destSize.height),
                                                       gfxASurface::CONTENT_COLOR_ALPHA);
  if (!surface)
    return NS_ERROR_FAILURE;

  nsRefPtr<gfxContext> ctx = new gfxContext(surface);
  if (!ctx)
    return NS_ERROR_FAILURE;

  *aSurface = surface;
  NS_ADDREF(*aSurface);

  if (aImageLoader) {
    gfxRect outRect(0, 0, destSize.width, destSize.height);
    gfxMatrix scale =
      gfxMatrix().Scale(srcSize.width/outRect.Width(), srcSize.height/outRect.Height());
    nsIntRect imgSize(0, 0, srcSize.width, srcSize.height);
    imgContainer->Draw(ctx, gfxPattern::FILTER_GOOD, scale, outRect, imgSize,
                       destSize, imgIContainer::FLAG_SYNC_DECODE);
    return NS_OK;
  } else {
    return aCanvas->RenderContextsExternal(ctx, gfxPattern::FILTER_GOOD);
  }
}

void
nsBaseDragService::ConvertToUnscaledDevPixels(nsPresContext* aPresContext,
                                              PRInt32* aScreenX, PRInt32* aScreenY)
{
  PRInt32 adj = aPresContext->DeviceContext()->UnscaledAppUnitsPerDevPixel();
  *aScreenX = nsPresContext::CSSPixelsToAppUnits(*aScreenX) / adj;
  *aScreenY = nsPresContext::CSSPixelsToAppUnits(*aScreenY) / adj;
}

NS_IMETHODIMP
nsBaseDragService::Suppress()
{
  EndDragSession(false);
  ++mSuppressLevel;
  return NS_OK;
}

NS_IMETHODIMP
nsBaseDragService::Unsuppress()
{
  --mSuppressLevel;
  return NS_OK;
}