gecko-dev/widget/cocoa/nsDragService.mm

/* -*- 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 "mozilla/Logging.h"

#include "gfxContext.h"
#include "nsArrayUtils.h"
#include "nsDragService.h"
#include "nsArrayUtils.h"
#include "nsObjCExceptions.h"
#include "nsITransferable.h"
#include "nsString.h"
#include "nsClipboard.h"
#include "nsXPCOM.h"
#include "nsISupportsPrimitives.h"
#include "nsCOMPtr.h"
#include "nsPrimitiveHelpers.h"
#include "nsLinebreakConverter.h"
#include "nsIMacUtils.h"
#include "nsIDOMNode.h"
#include "nsRect.h"
#include "nsPoint.h"
#include "nsIIOService.h"
#include "nsIDocument.h"
#include "nsIContent.h"
#include "nsView.h"
#include "nsCocoaUtils.h"
#include "mozilla/gfx/2D.h"
#include "gfxPlatform.h"
#include "nsDeviceContext.h"

using namespace mozilla;
using namespace mozilla::gfx;

extern mozilla::LazyLogModule sCocoaLog;

extern void EnsureLogInitialized();

extern NSPasteboard* globalDragPboard;
extern ChildView* gLastDragView;
extern NSEvent* gLastDragMouseDownEvent;
extern bool gUserCancelledDrag;

// This global makes the transferable array available to Cocoa's promised
// file destination callback.
nsIArray *gDraggedTransferables = nullptr;

NSString* const kPublicUrlPboardType      = @"public.url";
NSString* const kPublicUrlNamePboardType  = @"public.url-name";
NSString* const kUrlsWithTitlesPboardType = @"WebURLsWithTitlesPboardType";
NSString* const kMozWildcardPboardType    = @"org.mozilla.MozillaWildcard";
NSString* const kMozCustomTypesPboardType = @"org.mozilla.custom-clipdata";
NSString* const kMozFileUrlsPboardType    = @"org.mozilla.file-urls";

nsDragService::nsDragService()
  : mNativeDragView(nil), mNativeDragEvent(nil), mDragImageChanged(false)
{
  EnsureLogInitialized();
}

nsDragService::~nsDragService()
{
}

NSImage*
nsDragService::ConstructDragImage(nsIDOMNode* aDOMNode,
                                  nsIScriptableRegion* aRegion,
                                  NSPoint* aDragPoint)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;

  CGFloat scaleFactor = nsCocoaUtils::GetBackingScaleFactor(mNativeDragView);

  LayoutDeviceIntRect dragRect(0, 0, 20, 20);
  NSImage* image = ConstructDragImage(mSourceNode, aRegion, mScreenPosition, &dragRect);
  if (!image) {
    // if no image was returned, just draw a rectangle
    NSSize size;
    size.width = nsCocoaUtils::DevPixelsToCocoaPoints(dragRect.width, scaleFactor);
    size.height = nsCocoaUtils::DevPixelsToCocoaPoints(dragRect.height, scaleFactor);
    image = [[NSImage alloc] initWithSize:size];
    [image lockFocus];
    [[NSColor grayColor] set];
    NSBezierPath* path = [NSBezierPath bezierPath];
    [path setLineWidth:2.0];
    [path moveToPoint:NSMakePoint(0, 0)];
    [path lineToPoint:NSMakePoint(0, size.height)];
    [path lineToPoint:NSMakePoint(size.width, size.height)];
    [path lineToPoint:NSMakePoint(size.width, 0)];
    [path lineToPoint:NSMakePoint(0, 0)];
    [path stroke];
    [image unlockFocus];
  }

  LayoutDeviceIntPoint pt(dragRect.x, dragRect.YMost());
  NSPoint point = nsCocoaUtils::DevPixelsToCocoaPoints(pt, scaleFactor);
  point.y = nsCocoaUtils::FlippedScreenY(point.y);

  point = nsCocoaUtils::ConvertPointFromScreen([mNativeDragView window], point);
  *aDragPoint = [mNativeDragView convertPoint:point fromView:nil];

  return image;

  NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
}

NSImage*
nsDragService::ConstructDragImage(nsIDOMNode* aDOMNode,
                                  nsIScriptableRegion* aRegion,
                                  CSSIntPoint aPoint,
                                  LayoutDeviceIntRect* aDragRect)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;

  CGFloat scaleFactor = nsCocoaUtils::GetBackingScaleFactor(mNativeDragView);

  RefPtr<SourceSurface> surface;
  nsPresContext* pc;
  nsresult rv = DrawDrag(aDOMNode, aRegion, aPoint,
                         aDragRect, &surface, &pc);
  if (pc && (!aDragRect->width || !aDragRect->height)) {
    // just use some suitable defaults
    int32_t size = nsCocoaUtils::CocoaPointsToDevPixels(20, scaleFactor);
    aDragRect->SetRect(pc->CSSPixelsToDevPixels(aPoint.x),
                       pc->CSSPixelsToDevPixels(aPoint.y), size, size);
  }

  if (NS_FAILED(rv) || !surface)
    return nil;

  uint32_t width = aDragRect->width;
  uint32_t height = aDragRect->height;

  RefPtr<DataSourceSurface> dataSurface =
    Factory::CreateDataSourceSurface(IntSize(width, height),
                                     SurfaceFormat::B8G8R8A8);
  DataSourceSurface::MappedSurface map;
  if (!dataSurface->Map(DataSourceSurface::MapType::READ_WRITE, &map)) {
    return nil;
  }

  RefPtr<DrawTarget> dt =
    Factory::CreateDrawTargetForData(BackendType::CAIRO,
                                     map.mData,
                                     dataSurface->GetSize(),
                                     map.mStride,
                                     dataSurface->GetFormat());
  if (!dt) {
    dataSurface->Unmap();
    return nil;
  }

  dt->FillRect(gfx::Rect(0, 0, width, height),
               SurfacePattern(surface, ExtendMode::CLAMP),
               DrawOptions(1.0f, CompositionOp::OP_SOURCE));

  NSBitmapImageRep* imageRep =
    [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
                                            pixelsWide:width
                                            pixelsHigh:height
                                         bitsPerSample:8
                                       samplesPerPixel:4
                                              hasAlpha:YES
                                              isPlanar:NO
                                        colorSpaceName:NSDeviceRGBColorSpace
                                           bytesPerRow:width * 4
                                          bitsPerPixel:32];

  uint8_t* dest = [imageRep bitmapData];
  for (uint32_t i = 0; i < height; ++i) {
    uint8_t* src = map.mData + i * map.mStride;
    for (uint32_t j = 0; j < width; ++j) {
      // Reduce transparency overall by multipying by a factor. Remember, Alpha
      // is premultipled here. Also, Quartz likes RGBA, so do that translation as well.
#ifdef IS_BIG_ENDIAN
      dest[0] = uint8_t(src[1] * DRAG_TRANSLUCENCY);
      dest[1] = uint8_t(src[2] * DRAG_TRANSLUCENCY);
      dest[2] = uint8_t(src[3] * DRAG_TRANSLUCENCY);
      dest[3] = uint8_t(src[0] * DRAG_TRANSLUCENCY);
#else
      dest[0] = uint8_t(src[2] * DRAG_TRANSLUCENCY);
      dest[1] = uint8_t(src[1] * DRAG_TRANSLUCENCY);
      dest[2] = uint8_t(src[0] * DRAG_TRANSLUCENCY);
      dest[3] = uint8_t(src[3] * DRAG_TRANSLUCENCY);
#endif
      src += 4;
      dest += 4;
    }
  }
  dataSurface->Unmap();

  NSImage* image =
    [[NSImage alloc] initWithSize:NSMakeSize(width / scaleFactor,
                                             height / scaleFactor)];
  [image addRepresentation:imageRep];
  [imageRep release];

  return [image autorelease];

  NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
}

bool
nsDragService::IsValidType(NSString* availableType, bool allowFileURL)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_RETURN;

  // Prevent exposing fileURL for non-fileURL type.
  // We need URL provided by dropped webloc file, but don't need file's URL.
  // kUTTypeFileURL is returned by [NSPasteboard availableTypeFromArray:] for
  // kPublicUrlPboardType, since it conforms to kPublicUrlPboardType.
  bool isValid = true;
  if (!allowFileURL &&
      [availableType isEqualToString:
        [UTIHelper stringFromPboardType:(NSString*)kUTTypeFileURL]]) {
    isValid = false;
  }

  return isValid;

  NS_OBJC_END_TRY_ABORT_BLOCK_RETURN(false);
}

NSString*
nsDragService::GetStringForType(NSPasteboardItem* item, const NSString* type,
                                bool allowFileURL)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;

  NSString* availableType = [item availableTypeFromArray:[NSArray arrayWithObjects:(id)type, nil]];
  if (availableType && IsValidType(availableType, allowFileURL)) {
    return [item stringForType:(id)availableType];
  }

  return nil;

  NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
}

NSString*
nsDragService::GetTitleForURL(NSPasteboardItem* item)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;

  NSString* name =
    GetStringForType(item,
                     [UTIHelper stringFromPboardType:kPublicUrlNamePboardType]);
  if (name) {
    return name;
  }

  NSString* filePath = GetFilePath(item);
  if (filePath) {
    return [filePath lastPathComponent];
  }

  return nil;

  NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
}

NSString*
nsDragService::GetFilePath(NSPasteboardItem* item)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;

  NSString* urlString =
    GetStringForType(item,
                     [UTIHelper stringFromPboardType:(NSString*)kUTTypeFileURL],
                     true);
  if (urlString) {
    NSURL* url = [NSURL URLWithString:urlString];
    if (url) {
      return [url path];
    }
  }

  return nil;

  NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
}

nsresult
nsDragService::InvokeDragSessionImpl(nsIArray* aTransferableArray,
                                     nsIScriptableRegion* aDragRgn,
                                     uint32_t aActionType)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;

  if (!gLastDragView) {
    // gLastDragView is only set during -[ChildView mouseDragged:].
    // InvokeDragSessionImpl is only called while Gecko processes a mouse move
    // event. So if we get here with gLastDragView being null, that means that
    // the mouse button has already been released, and mouseMoved is on the
    // stack instead of mouseDragged. In that case we need to abort the drag
    // because the OS won't know where to drop whatever's being dragged, and we
    // might end up with a stuck drag & drop session.
    return NS_ERROR_FAILURE;
  }

  mDataItems = aTransferableArray;

  // Save the transferables away in case a promised file callback is invoked.
  gDraggedTransferables = aTransferableArray;

  // We need to retain the view and the event during the drag in case either
  // gets destroyed.
  mNativeDragView = [gLastDragView retain];
  mNativeDragEvent = [gLastDragMouseDownEvent retain];

  gUserCancelledDrag = false;

  NSPasteboardItem* pbItem = [NSPasteboardItem new];
  NSMutableArray* types = [NSMutableArray arrayWithCapacity:5];

  if (gDraggedTransferables) {
    uint32_t count = 0;
    gDraggedTransferables->GetLength(&count);

    for (uint32_t j = 0; j < count; j++) {
      nsCOMPtr<nsITransferable> currentTransferable =
        do_QueryElementAt(aTransferableArray, j);
      if (!currentTransferable) {
        return NS_ERROR_FAILURE;
      }

      // Transform the transferable to an NSDictionary
      NSDictionary* pasteboardOutputDict =
        nsClipboard::PasteboardDictFromTransferable(currentTransferable);
      if (!pasteboardOutputDict) {
        return NS_ERROR_FAILURE;
      }

      // write everything out to the general pasteboard
      [types addObjectsFromArray:[pasteboardOutputDict allKeys]];
      // Gecko is initiating this drag so we always want its own views to
      // consider it. Add our wildcard type to the pasteboard to accomplish
      // this.
      [types addObject:[UTIHelper stringFromPboardType:kMozWildcardPboardType]];
    }
  }
  [pbItem setDataProvider:mNativeDragView forTypes:types];

  NSPoint draggingPoint;
  NSImage* image = ConstructDragImage(mSourceNode, aDragRgn, &draggingPoint);

  NSRect localDragRect = image.alignmentRect;
  localDragRect.origin.x = draggingPoint.x;
  localDragRect.origin.y = draggingPoint.y - localDragRect.size.height;

  NSDraggingItem* dragItem =
    [[NSDraggingItem alloc] initWithPasteboardWriter:pbItem];
  [pbItem release];
  [dragItem setDraggingFrame:localDragRect contents:image];

  nsBaseDragService::StartDragSession();
  nsBaseDragService::OpenDragPopup();

  NSDraggingSession* draggingSession =
    [mNativeDragView beginDraggingSessionWithItems:
        [NSArray arrayWithObject:[dragItem autorelease]]
                                             event:mNativeDragEvent
                                            source:mNativeDragView];
  draggingSession.animatesToStartingPositionsOnCancelOrFail = YES;

  return NS_OK;

  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
}

NS_IMETHODIMP
nsDragService::GetData(nsITransferable* aTransferable, uint32_t aItemIndex)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;

  if (!aTransferable)
    return NS_ERROR_FAILURE;

  // get flavor list that includes all acceptable flavors (including ones obtained through conversion)
  nsCOMPtr<nsIArray> flavorList;
  nsresult rv = aTransferable->FlavorsTransferableCanImport(getter_AddRefs(flavorList));
  if (NS_FAILED(rv))
    return NS_ERROR_FAILURE;

  uint32_t acceptableFlavorCount;
  flavorList->GetLength(&acceptableFlavorCount);

  // if this drag originated within Mozilla we should just use the cached data from
  // when the drag started if possible
  if (mDataItems) {
    nsCOMPtr<nsITransferable> currentTransferable = do_QueryElementAt(mDataItems, aItemIndex);
    if (currentTransferable) {
      for (uint32_t i = 0; i < acceptableFlavorCount; i++) {
        nsCOMPtr<nsISupportsCString> currentFlavor = do_QueryElementAt(flavorList, i);
        if (!currentFlavor)
          continue;
        nsXPIDLCString flavorStr;
        currentFlavor->ToString(getter_Copies(flavorStr));

        nsCOMPtr<nsISupports> dataSupports;
        uint32_t dataSize = 0;
        rv = currentTransferable->GetTransferData(flavorStr, getter_AddRefs(dataSupports), &dataSize);
        if (NS_SUCCEEDED(rv)) {
          aTransferable->SetTransferData(flavorStr, dataSupports, dataSize);
          return NS_OK; // maybe try to fill in more types? Is there a point?
        }
      }
    }
  }

  // now check the actual clipboard for data
  for (uint32_t i = 0; i < acceptableFlavorCount; i++) {
    nsCOMPtr<nsISupportsCString> currentFlavor = do_QueryElementAt(flavorList, i);
    if (!currentFlavor)
      continue;

    nsXPIDLCString flavorStr;
    currentFlavor->ToString(getter_Copies(flavorStr));

    MOZ_LOG(sCocoaLog, LogLevel::Info, ("nsDragService::GetData: looking for clipboard data of type %s\n", flavorStr.get()));

    NSArray* droppedItems = [globalDragPboard pasteboardItems];
    if (!droppedItems) {
      continue;
    }

    uint32_t itemCount = [droppedItems count];
    if (aItemIndex >= itemCount) {
      continue;
    }

    NSPasteboardItem* item = [droppedItems objectAtIndex:aItemIndex];
    if (!item) {
      continue;
    }

    if (flavorStr.EqualsLiteral(kFileMime)) {
      NSString* filePath = GetFilePath(item);
      if (!filePath)
        continue;

      unsigned int stringLength = [filePath length];
      unsigned int dataLength = (stringLength + 1) * sizeof(char16_t); // in bytes
      char16_t* clipboardDataPtr = (char16_t*)malloc(dataLength);
      if (!clipboardDataPtr)
        return NS_ERROR_OUT_OF_MEMORY;
      [filePath getCharacters:reinterpret_cast<unichar*>(clipboardDataPtr)];
      clipboardDataPtr[stringLength] = 0; // null terminate

      nsCOMPtr<nsIFile> file;
      rv = NS_NewLocalFile(nsDependentString(clipboardDataPtr), true, getter_AddRefs(file));
      free(clipboardDataPtr);
      if (NS_FAILED(rv))
        continue;

      aTransferable->SetTransferData(flavorStr, file, dataLength);
      
      break;
    }
    else if (flavorStr.EqualsLiteral(kCustomTypesMime)) {
      NSString* availableType =
        [item availableTypeFromArray:
          [NSArray arrayWithObject:kMozCustomTypesPboardType]];
      if (!availableType || !IsValidType(availableType, false)) {
          continue;
      }
      NSData *pasteboardData = [item dataForType:availableType];
      if (!pasteboardData) {
        continue;
      }

      unsigned int dataLength = [pasteboardData length];
      void* clipboardDataPtr = malloc(dataLength);
      if (!clipboardDataPtr) {
        return NS_ERROR_OUT_OF_MEMORY;
      }
      [pasteboardData getBytes:clipboardDataPtr];

      nsCOMPtr<nsISupports> genericDataWrapper;
      nsPrimitiveHelpers::CreatePrimitiveForData(flavorStr, clipboardDataPtr, dataLength,
                                                 getter_AddRefs(genericDataWrapper));

      aTransferable->SetTransferData(flavorStr, genericDataWrapper, sizeof(nsIInputStream*));
      free(clipboardDataPtr);
      break;
    }

    NSString* pString = nil;
    if (flavorStr.EqualsLiteral(kUnicodeMime)) {
      pString =
        GetStringForType(
          item, [UTIHelper stringFromPboardType:NSPasteboardTypeString]);
    } else if (flavorStr.EqualsLiteral(kHTMLMime)) {
      pString =
        GetStringForType(item,
                         [UTIHelper stringFromPboardType:NSPasteboardTypeHTML]);
    } else if (flavorStr.EqualsLiteral(kURLMime)) {
      pString =
        GetStringForType(item,
                         [UTIHelper stringFromPboardType:kPublicUrlPboardType]);
      if (pString) {
        NSString* title = GetTitleForURL(item);
        if (!title) {
          title = pString;
        }
        pString = [NSString stringWithFormat:@"%@\n%@", pString, title];
      }
    } else if (flavorStr.EqualsLiteral(kURLDataMime)) {
      pString =
        GetStringForType(item,
                         [UTIHelper stringFromPboardType:kPublicUrlPboardType]);
    } else if (flavorStr.EqualsLiteral(kURLDescriptionMime)) {
      pString = GetTitleForURL(item);
    } else if (flavorStr.EqualsLiteral(kRTFMime)) {
      pString =
        GetStringForType(item,
                         [UTIHelper stringFromPboardType:NSPasteboardTypeRTF]);
    }
    if (pString) {
      NSData* stringData;
      if (flavorStr.EqualsLiteral(kRTFMime)) {
        stringData = [pString dataUsingEncoding:NSASCIIStringEncoding];
      } else {
        stringData = [pString dataUsingEncoding:NSUnicodeStringEncoding];
      }
      unsigned int dataLength = [stringData length];
      void* clipboardDataPtr = malloc(dataLength);
      if (!clipboardDataPtr)
        return NS_ERROR_OUT_OF_MEMORY;
      [stringData getBytes:clipboardDataPtr];

      // The DOM only wants LF, so convert from MacOS line endings to DOM line endings.
      int32_t signedDataLength = dataLength;
      nsLinebreakHelpers::ConvertPlatformToDOMLinebreaks(flavorStr, &clipboardDataPtr, &signedDataLength);
      dataLength = signedDataLength;

      // skip BOM (Byte Order Mark to distinguish little or big endian)      
      char16_t* clipboardDataPtrNoBOM = (char16_t*)clipboardDataPtr;
      if ((dataLength > 2) &&
          ((clipboardDataPtrNoBOM[0] == 0xFEFF) ||
           (clipboardDataPtrNoBOM[0] == 0xFFFE))) {
        dataLength -= sizeof(char16_t);
        clipboardDataPtrNoBOM += 1;
      }

      nsCOMPtr<nsISupports> genericDataWrapper;
      nsPrimitiveHelpers::CreatePrimitiveForData(flavorStr, clipboardDataPtrNoBOM, dataLength,
                                                 getter_AddRefs(genericDataWrapper));
      aTransferable->SetTransferData(flavorStr, genericDataWrapper, dataLength);
      free(clipboardDataPtr);
      break;
    }

    // We have never supported this on Mac OS X, we should someday. Normally dragging images
    // in is accomplished with a file path drag instead of the image data itself.
    /*
    if (flavorStr.EqualsLiteral(kPNGImageMime) || flavorStr.EqualsLiteral(kJPEGImageMime) ||
        flavorStr.EqualsLiteral(kJPGImageMime) || flavorStr.EqualsLiteral(kGIFImageMime)) {

    }
    */
  }
  return NS_OK;

  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
}

NS_IMETHODIMP
nsDragService::IsDataFlavorSupported(const char *aDataFlavor, bool *_retval)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;

  *_retval = false;

  if (!globalDragPboard)
    return NS_ERROR_FAILURE;

  nsDependentCString dataFlavor(aDataFlavor);

  // first see if we have data for this in our cached transferable
  if (mDataItems) {
    uint32_t dataItemsCount;
    mDataItems->GetLength(&dataItemsCount);
    for (unsigned int i = 0; i < dataItemsCount; i++) {
      nsCOMPtr<nsITransferable> currentTransferable = do_QueryElementAt(mDataItems, i);
      if (!currentTransferable)
        continue;

      nsCOMPtr<nsIArray> flavorList;
      nsresult rv = currentTransferable->FlavorsTransferableCanImport(getter_AddRefs(flavorList));
      if (NS_FAILED(rv))
        continue;

      uint32_t flavorCount;
      flavorList->GetLength(&flavorCount);
      for (uint32_t j = 0; j < flavorCount; j++) {
        nsCOMPtr<nsISupportsCString> currentFlavor = do_QueryElementAt(flavorList, j);
        if (!currentFlavor)
          continue;
        nsXPIDLCString flavorStr;
        currentFlavor->ToString(getter_Copies(flavorStr));
        if (dataFlavor.Equals(flavorStr)) {
          *_retval = true;
          return NS_OK;
        }
      }
    }
  }

  const NSString* type = nil;
  bool allowFileURL = false;
  if (dataFlavor.EqualsLiteral(kFileMime)) {
    type = [UTIHelper stringFromPboardType:(NSString*)kUTTypeFileURL];
    allowFileURL = true;
  } else if (dataFlavor.EqualsLiteral(kUnicodeMime)) {
    type = [UTIHelper stringFromPboardType:NSPasteboardTypeString];
  } else if (dataFlavor.EqualsLiteral(kHTMLMime)) {
    type = [UTIHelper stringFromPboardType:NSPasteboardTypeHTML];
  } else if (dataFlavor.EqualsLiteral(kURLMime) ||
             dataFlavor.EqualsLiteral(kURLDataMime)) {
    type = [UTIHelper stringFromPboardType:kPublicUrlPboardType];
  } else if (dataFlavor.EqualsLiteral(kURLDescriptionMime)) {
    type = [UTIHelper stringFromPboardType:kPublicUrlNamePboardType];
  } else if (dataFlavor.EqualsLiteral(kRTFMime)) {
    type = [UTIHelper stringFromPboardType:NSPasteboardTypeRTF];
  } else if (dataFlavor.EqualsLiteral(kCustomTypesMime)) {
    type = [UTIHelper stringFromPboardType:kMozCustomTypesPboardType];
  }

  NSString* availableType =
    [globalDragPboard availableTypeFromArray:[NSArray arrayWithObjects:(id)type,
                                                                       nil]];
  if (availableType && IsValidType(availableType, allowFileURL)) {
    *_retval = true;
  }

  return NS_OK;

  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
}

NS_IMETHODIMP
nsDragService::GetNumDropItems(uint32_t* aNumItems)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;

  *aNumItems = 0;

  // first check to see if we have a number of items cached
  if (mDataItems) {
    mDataItems->GetLength(aNumItems);
    return NS_OK;
  }

  NSArray* droppedItems = [globalDragPboard pasteboardItems];
  if (droppedItems) {
    *aNumItems = [droppedItems count];
  }

  return NS_OK;

  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
}

NS_IMETHODIMP
nsDragService::UpdateDragImage(nsIDOMNode* aImage, int32_t aImageX, int32_t aImageY)
{
  nsBaseDragService::UpdateDragImage(aImage, aImageX, aImageY);
  mDragImageChanged = true;
  return NS_OK;
}

void
nsDragService::DragMovedWithView(NSDraggingSession* aSession, NSPoint aPoint)
{
  aPoint.y = nsCocoaUtils::FlippedScreenY(aPoint.y);

  // XXX It feels like we should be using the backing scale factor at aPoint
  // rather than the initial drag view, but I've seen no ill effects of this.
  CGFloat scaleFactor = nsCocoaUtils::GetBackingScaleFactor(mNativeDragView);
  LayoutDeviceIntPoint devPoint = nsCocoaUtils::CocoaPointsToDevPixels(aPoint, scaleFactor);

  // If the image has changed, call enumerateDraggingItemsWithOptions to get
  // the item being dragged and update its image.
  if (mDragImageChanged && mNativeDragView) {
    mDragImageChanged = false;

    nsPresContext* pc = nullptr;
    nsCOMPtr<nsIContent> content = do_QueryInterface(mImage);
    if (content) {
      nsCOMPtr<nsIDocument> document = content->OwnerDoc();
      if (document) {
        nsIPresShell* shell = document->GetShell();
        pc = shell ? shell->GetPresContext() : nullptr;
      }
    }

    if (pc) {
      void (^changeImageBlock) (NSDraggingItem*, NSInteger, BOOL*) =
                              ^(NSDraggingItem* draggingItem, NSInteger idx, BOOL* stop) {
        // We never add more than one item right now, but check just in case.
        if (idx > 0) {
          return;
        }

        nsPoint pt = LayoutDevicePixel::ToAppUnits(devPoint,
                       pc->DeviceContext()->AppUnitsPerDevPixelAtUnitFullZoom());
        CSSIntPoint screenPoint = CSSIntPoint(nsPresContext::AppUnitsToIntCSSPixels(pt.x),
                                              nsPresContext::AppUnitsToIntCSSPixels(pt.y));

        // Create a new image; if one isn't returned don't change the current one.
        LayoutDeviceIntRect newRect;
        NSImage* image = ConstructDragImage(mSourceNode, nullptr, screenPoint, &newRect);
        if (image) {
          NSRect draggingRect = nsCocoaUtils::GeckoRectToCocoaRectDevPix(newRect, scaleFactor);
          [draggingItem setDraggingFrame:draggingRect contents:image];
        }
      };

      [aSession enumerateDraggingItemsWithOptions:NSDraggingItemEnumerationConcurrent
                                          forView:nil
                                          classes:[NSArray arrayWithObject:[NSPasteboardItem class]]
                                    searchOptions:@{}
                                       usingBlock:changeImageBlock];
    }
  }

  DragMoved(devPoint.x, devPoint.y);
}

NS_IMETHODIMP
nsDragService::EndDragSession(bool aDoneDrag, uint32_t aKeyModifiers)
{
  NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;

  if (mNativeDragView) {
    [mNativeDragView release];
    mNativeDragView = nil;
  }
  if (mNativeDragEvent) {
    [mNativeDragEvent release];
    mNativeDragEvent = nil;
  }

  mUserCancelled = gUserCancelledDrag;

  nsresult rv = nsBaseDragService::EndDragSession(aDoneDrag, aKeyModifiers);
  mDataItems = nullptr;
  return rv;

  NS_OBJC_END_TRY_ABORT_BLOCK_NSRESULT;
}