Avoid calling requestUpdate from wrong thread

In certain circumstances, we can get to createDecoration()
from the render thread (from QWaylandGLContext::makeCurrent)

Calling requestUpdate() from this secondary thread would
cause an assert, so we queue the call on the appropriate
thread instead.

This amends 1a2e499e0e05a03460f4335d5266be485f97d3fa.

Pick-to: 5.15 6.2 6.3 6.3.2 6.4
Fixes: QTBUG-105308
Change-Id: I4805265f39e24eb1464897532be2025bc3c27728
Reviewed-by: Inho Lee <inho.lee@qt.io>

src/plugins/platforms/wayland/qwaylandwindow.cpp

@@ -932,7 +932,11 @@ bool QWaylandWindow::createDecoration()
         // size and are not redrawn, leaving the new buffer empty. As a simple
         // work-around, we trigger a full extra update whenever the client-side
         // window decorations are toggled while the window is showing.
-        window()->requestUpdate();
+        // Note: createDecoration() is sometimes called from the render thread
+        // of Qt Quick. This is essentially wrong and could potentially cause problems,
+        // but until the underlying issue has been fixed, we have to use invokeMethod()
+        // here to avoid asserts.
+        QMetaObject::invokeMethod(window(), &QWindow::requestUpdate);
     }
 
     return mWindowDecoration;