2 files changed, 48 insertions, 0 deletions
diff --git a/src/quickwidgets/qquickwidget.cpp b/src/quickwidgets/qquickwidget.cpp
index 4a98122fea..9dba007540 100644
--- a/src/quickwidgets/qquickwidget.cpp
+++ b/src/quickwidgets/qquickwidget.cpp
@@ -154,7 +154,18 @@ void QQuickWidgetPrivate::invalidateRenderControl()
 
 void QQuickWidgetPrivate::handleWindowChange()
 {
+    if (offscreenWindow->isPersistentSceneGraph() && qGuiApp->testAttribute(Qt::AA_ShareOpenGLContexts))
+        return;
+
+    // In case of !isPersistentSceneGraph or when we need a new context due to
+    // the need to share resources with the new window's context, we must both
+    // invalidate the scenegraph and destroy the context. With
+    // QQuickRenderControl destroying the context must be preceded by an
+    // invalidate to prevent being left with dangling context references in the
+    // rendercontrol.
+
     invalidateRenderControl();
+
     if (!useSoftwareRenderer)
         destroyContext();
 }
@@ -417,6 +428,20 @@ QObject *QQuickWidgetPrivate::focusObject()
     persistent. The OpenGL context is thus not destroyed when hiding the
     widget. The context is destroyed only when the widget is destroyed or when
     the widget gets reparented into another top-level widget's child hierarchy.
+    However, some applications, in particular those that have their own
+    graphics resources due to performing custom OpenGL rendering in the Qt
+    Quick scene, may wish to disable the latter since they may not be prepared
+    to handle the loss of the context when moving a QQuickWidget into another
+    window. Such applications can set the
+    QCoreApplication::AA_ShareOpenGLContexts attribute. For a discussion on the
+    details of resource initialization and cleanup, refer to the QOpenGLWidget
+    documentation.
+
+    \note QQuickWidget offers less fine-grained control over its internal
+    OpenGL context than QOpenGLWidget, and there are subtle differences, most
+    notably that disabling the persistent scene graph will lead to destroying
+    the context on a window change regardless of the presence of
+    QCoreApplication::AA_ShareOpenGLContexts.
 
     \section1 Limitations
 
diff --git a/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp b/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
index 09359060f6..7676bd6c31 100644
--- a/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
+++ b/tests/auto/quickwidgets/qquickwidget/tst_qquickwidget.cpp
@@ -34,6 +34,7 @@
 #include <QtQuick/qquickitem.h>
 #include "../../shared/util.h"
 #include <QtGui/QWindow>
+#include <QtGui/QImage>
 #include <QtCore/QDebug>
 #include <QtQml/qqmlengine.h>
 
@@ -55,6 +56,7 @@ private slots:
     void readback();
     void renderingSignals();
     void grabBeforeShow();
+    void reparentToNewWindow();
 };
 
 
@@ -301,6 +303,27 @@ void tst_qquickwidget::grabBeforeShow()
     QVERIFY(!widget.grab().isNull());
 }
 
+void tst_qquickwidget::reparentToNewWindow()
+{
+    QWidget window1;
+    QWidget window2;
+
+    QQuickWidget *qqw = new QQuickWidget(&window1);
+    qqw->setSource(testFileUrl("rectangle.qml"));
+    window1.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&window1, 5000));
+    window2.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&window2, 5000));
+
+    QSignalSpy afterRenderingSpy(qqw->quickWindow(), &QQuickWindow::afterRendering);
+    qqw->setParent(&window2);
+    qqw->show();
+    QTRY_VERIFY(afterRenderingSpy.size() > 0);
+
+    QImage img = qqw->grabFramebuffer();
+    QCOMPARE(img.pixel(5, 5), qRgb(255, 0, 0));
+}
+
 QTEST_MAIN(tst_qquickwidget)
 
 #include "tst_qquickwidget.moc"