Bug 1826778 [Linux] Lock cursor type set by widget code r=emilio

If we set resize cursor on widget level keep it locked and prevent layout
to switch it back to default (by synthetic mouse events for instance)
until resize is finished.

Differential Revision: https://phabricator.services.mozilla.com/D179049

widget/gtk/nsWindow.cpp

@@ -415,6 +415,7 @@ nsWindow::nsWindow()
       mNoAutoHide(false),
       mIsTransparent(false),
       mHasReceivedSizeAllocate(false),
+      mWidgetCursorLocked(false),
       mPopupTrackInHierarchy(false),
       mPopupTrackInHierarchyConfigured(false),
       mHiddenPopupPositioned(false),
@@ -3328,6 +3329,10 @@ void nsWindow::SetCursor(const Cursor& aCursor) {
     return;
   }
 
+  if (mWidgetCursorLocked) {
+    return;
+  }
+
   // Only change cursor if it's actually been changed
   if (!mUpdateCursor && mCursor == aCursor) {
     return;
@@ -4433,6 +4438,7 @@ void nsWindow::OnMotionNotifyEvent(GdkEventMotion* aEvent) {
     }
   }
 
+  mWidgetCursorLocked = false;
   const auto refPoint = GetRefPoint(this, aEvent);
   if (auto edge = CheckResizerEdge(refPoint)) {
     nsCursor cursor = eCursor_none;
@@ -4455,6 +4461,10 @@ void nsWindow::OnMotionNotifyEvent(GdkEventMotion* aEvent) {
         break;
     }
     SetCursor(Cursor{cursor});
+    // If we set resize cursor on widget level keep it locked and prevent layout
+    // to switch it back to default (by synthetic mouse events for instance)
+    // until resize is finished.
+    mWidgetCursorLocked = true;
     return;
   }
 

widget/gtk/nsWindow.h

@@ -672,6 +672,7 @@ class nsWindow final : public nsBaseWidget {
   bool mIsTransparent : 1;
   // We can expect at least one size-allocate event after early resizes.
   bool mHasReceivedSizeAllocate : 1;
+  bool mWidgetCursorLocked : 1;
 
   /*  Gkt creates popup in two incarnations - wl_subsurface and xdg_popup.
    *  Kind of popup is choosen before GdkWindow is mapped so we can change