Bug 1121947, Implement e10 cursor drag feedback on Mac, r=smaug

dom/events/EventStateManager.cpp

@@ -3281,12 +3281,13 @@ EventStateManager::PostHandleEvent(nsPresContext* aPresContext,
       }
       if (dispatchedToContentProcess) {
         dragSession->SetCanDrop(true);
-      }
-
-      // now set the drop effect in the initial dataTransfer. This ensures
-      // that we can get the desired drop effect in the drop event.
-      if (initialDataTransfer)
+      } else if (initialDataTransfer) {
+        // Now set the drop effect in the initial dataTransfer. This ensures
+        // that we can get the desired drop effect in the drop event. For events
+        // dispatched to content, the content process will take care of setting
+        // this.
         initialDataTransfer->SetDropEffectInt(dropEffect);
+      }
     }
     break;
 

widget/cocoa/nsChildView.mm

@@ -5586,15 +5586,13 @@ static int32_t RoundUp(double aDouble)
 // drag'n'drop stuff
 #define kDragServiceContractID "@mozilla.org/widget/dragservice;1"
 
-- (NSDragOperation)dragOperationForSession:(nsIDragSession*)aDragSession
+- (NSDragOperation)dragOperationFromDragAction:(int32_t)aDragAction
 {
-  uint32_t dragAction;
-  aDragSession->GetDragAction(&dragAction);
-  if (nsIDragService::DRAGDROP_ACTION_LINK & dragAction)
+  if (nsIDragService::DRAGDROP_ACTION_LINK & aDragAction)
     return NSDragOperationLink;
-  if (nsIDragService::DRAGDROP_ACTION_COPY & dragAction)
+  if (nsIDragService::DRAGDROP_ACTION_COPY & aDragAction)
     return NSDragOperationCopy;
-  if (nsIDragService::DRAGDROP_ACTION_MOVE & dragAction)
+  if (nsIDragService::DRAGDROP_ACTION_MOVE & aDragAction)
     return NSDragOperationGeneric;
   return NSDragOperationNone;
 }
@@ -5693,7 +5691,22 @@ static int32_t RoundUp(double aDouble)
     switch (aMessage) {
       case NS_DRAGDROP_ENTER:
       case NS_DRAGDROP_OVER:
-        return [self dragOperationForSession:dragSession];
+      {
+        uint32_t dragAction;
+        dragSession->GetDragAction(&dragAction);
+
+        // If TakeChildProcessDragAction returns something other than
+        // DRAGDROP_ACTION_UNINITIALIZED, it means that the last event was sent
+        // to the child process and this event is also being sent to the child
+        // process. In this case, use the last event's action instead.
+        nsDragService* dragService = static_cast<nsDragService *>(mDragService);
+        int32_t childDragAction = dragService->TakeChildProcessDragAction();
+        if (childDragAction != nsIDragService::DRAGDROP_ACTION_UNINITIALIZED) {
+          dragAction = childDragAction;
+        }
+
+        return [self dragOperationFromDragAction:dragAction];
+      }
       case NS_DRAGDROP_EXIT:
       case NS_DRAGDROP_DROP: {
         nsCOMPtr<nsIDOMNode> sourceNode;

widget/nsBaseDragService.cpp

@@ -55,7 +55,8 @@ nsBaseDragService::nsBaseDragService()
   : mCanDrop(false), mOnlyChromeDrop(false), mDoingDrag(false),
     mHasImage(false), mUserCancelled(false),
     mDragEventDispatchedToChildProcess(false),
-    mDragAction(DRAGDROP_ACTION_NONE), mTargetSize(0,0),
+    mDragAction(DRAGDROP_ACTION_NONE),
+    mDragActionFromChildProcess(DRAGDROP_ACTION_UNINITIALIZED), mTargetSize(0,0),
     mImageX(0), mImageY(0), mScreenX(-1), mScreenY(-1), mSuppressLevel(0),
     mInputSource(nsIDOMMouseEvent::MOZ_SOURCE_MOUSE)
 {
@@ -332,6 +333,21 @@ nsBaseDragService::OpenDragPopup()
   }
 }
 
+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)
@@ -720,6 +736,7 @@ nsBaseDragService::UserCancelled()
 NS_IMETHODIMP
 nsBaseDragService::UpdateDragEffect()
 {
+  mDragActionFromChildProcess = mDragAction;
   return NS_OK;
 }
 

widget/nsBaseDragService.h

@@ -57,6 +57,8 @@ public:
 
   uint16_t GetInputSource() { return mInputSource; }
 
+  int32_t TakeChildProcessDragAction();
+
 protected:
   virtual ~nsBaseDragService();
 
@@ -132,6 +134,8 @@ protected:
   bool mDragEventDispatchedToChildProcess;
 
   uint32_t mDragAction;
+  uint32_t mDragActionFromChildProcess;
+
   nsSize mTargetSize;
   nsCOMPtr<nsIDOMNode> mSourceNode;
   nsCOMPtr<nsIDOMDocument> mSourceDocument;       // the document at the drag source. will be null