QQuickWidget: Clean up if RHI goes away under our feet

The QQuickWidget doesn't normally own the RHI; the QWidgetRepaintManager
does, via QBackingStoreRhiSupport. If the top level widget is destroyed,
so is its QBackingStore, and the corresponding RHI. But the QQuickWidget
may outlive its top level parent, in which case it needs to update its
cached reference to the RHI, and do proper cleanup before it goes away.

QRhiWidget already does the same thing, for the same use-case.

This was observed when recreating the top level QWidget via destroy/create
as part of the RHI widget compositor logic.

Fixes: QTBUG-119760
Pick-to: 6.7 6.6 6.5
Change-Id: Ic44449abcfe4271660a3ac4e132d0c4a71a21b65
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp b/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
index fde6945ede..0c88c71582 100644
--- a/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
+++ b/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
@@ -138,6 +138,7 @@ private slots:
 #endif
     void focusPreserved();
     void accessibilityHandlesViewChange();
+    void cleanupRhi();
 
 private:
     QPointingDevice *device = QTest::createTouchDevice();
@@ -1027,6 +1028,24 @@ void tst_qquickwidget::accessibilityHandlesViewChange()
     (void)iface->child(0);
 }
 
+class CreateDestroyWidget : public QWidget
+{
+public:
+    using QWidget::create;
+    using QWidget::destroy;
+};
+
+void tst_qquickwidget::cleanupRhi()
+{
+    CreateDestroyWidget topLevel;
+    QQuickWidget quickWidget(&topLevel);
+    quickWidget.setSource(testFileUrl("rectangle.qml"));
+    topLevel.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&topLevel));
+
+    topLevel.destroy();
+    topLevel.create();
+}
 
 QTEST_MAIN(tst_qquickwidget)