Make QQuickWidget update inside a proxy widget

Performance will be bad but this allows having simple scenes in a
QQuickWidget embedded into a QGraphicsView (ouch).

This kind of setup is strongly discouraged but QWidget already has the
readback-based fallback for render(), so we only need to add the
update re-routing to the proxy widget.

Task-number: QTBUG-49724
Change-Id: I1c80cb0a7b401327304ec7b92c77dc654d843b33
Reviewed-by: Paul Olav Tvete <paul.tvete@theqtcompany.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/src/quickwidgets/qquickwidget.cpp b/src/quickwidgets/qquickwidget.cpp
index 1703ba1199..c97d747189 100644
--- a/src/quickwidgets/qquickwidget.cpp
+++ b/src/quickwidgets/qquickwidget.cpp
@@ -252,8 +252,15 @@ void QQuickWidgetPrivate::renderSceneGraph()
     }
 
     Q_ASSERT(offscreenSurface);
+
     render(true);
-    q->update(); // schedule composition
+
+#ifndef QT_NO_GRAPHICSVIEW
+    if (q->window()->graphicsProxyWidget())
+        QWidgetPrivate::nearestGraphicsProxyWidget(q)->update();
+    else
+#endif
+        q->update(); // schedule composition
 }
 
 QImage QQuickWidgetPrivate::grabFramebuffer()