Bug 1622107 [Wayland] Reset Drag and Drop operation when compositor f…

…ails to cancel it, r=jhorak

This is a workaround for https://gitlab.gnome.org/GNOME/mutter/-/issues/1658

Wayland compositor sometimes fails to send wl_data_source::cancelled() so we don't get info that the D&D is finished
and it's still marked as active internally which preverts Firefox to do any further D&D operation.

In the patch we detect such scenario and reset internal D&D state.

Differential Revision: https://phabricator.services.mozilla.com/D106266

widget/gtk/nsWindow.cpp

@@ -3699,6 +3699,10 @@ void nsWindow::OnButtonPressEvent(GdkEventButton* aEvent) {
   if (!StaticPrefs::ui_context_menus_after_mouseup()) {
     DispatchContextMenuEventFromMouseEvent(domButton, aEvent);
   }
+
+  if (!mIsX11Display) {
+    WaylandDragWorkaround(aEvent);
+  }
 }
 
 void nsWindow::OnButtonReleaseEvent(GdkEventButton* aEvent) {
@@ -6453,15 +6457,48 @@ bool nsWindow::CheckForRollup(gdouble aMouseX, gdouble aMouseY, bool aIsWheel,
 /* static */
 bool nsWindow::DragInProgress(void) {
   nsCOMPtr<nsIDragService> dragService = do_GetService(kCDragServiceCID);
-
-  if (!dragService) return false;
+  if (!dragService) {
+    return false;
+  }
 
   nsCOMPtr<nsIDragSession> currentDragSession;
   dragService->GetCurrentSession(getter_AddRefs(currentDragSession));
 
   return currentDragSession != nullptr;
 }
 
+// This is an ugly workaround for
+// https://bugzilla.mozilla.org/show_bug.cgi?id=1622107
+// We try to detect when Wayland compositor / gtk fails to deliver
+// info about finished D&D operations and cancel it on our own.
+void nsWindow::WaylandDragWorkaround(GdkEventButton* aEvent) {
+  static int buttonPressCountWithDrag = 0;
+
+  // We track only left button state as Firefox performs D&D on left
+  // button only.
+  if (aEvent->button != 1 || aEvent->type != GDK_BUTTON_PRESS) {
+    return;
+  }
+
+  nsCOMPtr<nsIDragService> dragService = do_GetService(kCDragServiceCID);
+  if (!dragService) {
+    return;
+  }
+  nsCOMPtr<nsIDragSession> currentDragSession;
+  dragService->GetCurrentSession(getter_AddRefs(currentDragSession));
+
+  if (currentDragSession != nullptr) {
+    buttonPressCountWithDrag++;
+    if (buttonPressCountWithDrag > 1) {
+      NS_WARNING(
+          "Quit unfinished Wayland Drag and Drop operation. Buggy Wayland "
+          "compositor?");
+      buttonPressCountWithDrag = 0;
+      dragService->EndDragSession(false, 0);
+    }
+  }
+}
+
 static bool is_mouse_in_window(GdkWindow* aWindow, gdouble aMouseX,
                                gdouble aMouseY) {
   gint x = 0;

widget/gtk/nsWindow.h

@@ -241,6 +241,7 @@ class nsWindow final : public nsBaseWidget {
   bool GetCSDDecorationOffset(int* aDx, int* aDy);
   void SetEGLNativeWindowSize(const LayoutDeviceIntSize& aEGLWindowSize);
   static nsWindow* GetFocusedWindow();
+  void WaylandDragWorkaround(GdkEventButton* aEvent);
 #endif
 
   RefPtr<mozilla::gfx::VsyncSource> GetVsyncSource() override;