Bug 1212733, cache dnd window state instead of using gtk_window_get_type_hint, r=karlt

widget/gtk/nsWindow.cpp

@@ -423,6 +423,7 @@ nsWindow::nsWindow()
 #if GTK_CHECK_VERSION(3,4,0)
     mHandleTouchEvent    = false;
 #endif
+    mIsDragPopup         = false;
 
     mContainer           = nullptr;
     mGdkWindow           = nullptr;
@@ -1895,16 +1896,11 @@ nsWindow::CaptureRollupEvents(nsIRollupListener *aListener,
 
     if (aDoCapture) {
         gRollupListener = aListener;
-        // real grab is only done when there is no dragging
-        if (!nsWindow::DragInProgress()) {
-            // Maybe the dnd flag is not yet set at this point, but dnd has already started
-            // so let's be extra careful and skip this operation for dnd popup panels always
-            // (panels with type="drag").
-            GdkWindowTypeHint gdkTypeHint = gtk_window_get_type_hint(GTK_WINDOW(mShell));
-            if (gdkTypeHint != GDK_WINDOW_TYPE_HINT_DND) {
-              gtk_grab_add(GTK_WIDGET(mContainer));
-              GrabPointer(GetLastUserInputTime());
-            }
+        // Don't add a grab if a drag is in progress, or if the widget is a drag
+        // feedback popup. (panels with type="drag").
+        if (!mIsDragPopup && !nsWindow::DragInProgress()) {
+            gtk_grab_add(GTK_WIDGET(mContainer));
+            GrabPointer(GetLastUserInputTime());
         }
     }
     else {
@@ -3670,6 +3666,7 @@ nsWindow::Create(nsIWidget        *aParent,
             GdkWindowTypeHint gtkTypeHint;
             if (aInitData->mIsDragPopup) {
                 gtkTypeHint = GDK_WINDOW_TYPE_HINT_DND;
+                mIsDragPopup = true;
             }
             else {
                 switch (aInitData->mPopupHint) {

widget/gtk/nsWindow.h

@@ -389,6 +389,8 @@ protected:
     // whether we handle touch event
     bool                mHandleTouchEvent;
 #endif
+    // true if this is a drag and drop feedback popup
+    bool               mIsDragPopup;
 
 private:
     void               DestroyChildWindows();