Make QGLFramebufferObject crash-proof if QGLContext destroyed first

Sometimes it isn't possible to arrange for the QGLFramebufferObject
to be destroyed before the QGLContext group in which it was created.
Especially during application shutdown or in applications with
multiple shared contexts.

This change modifies QGLFramebufferObject to use QGLSharedResourceGuard,
which ensures that when the last QGLContext in a sharing group is
destroyed, any remaining FBO's will revert to !isValid().  It is now
safe to destroy the context before the FBO, or the FBO before the context.

Unit test included.

Reviewed-by: Sarah Smith

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/auto/qgl/tst_qgl.cpp b/tests/auto/qgl/tst_qgl.cpp
index 999d119a24..8027e9b021 100644
--- a/tests/auto/qgl/tst_qgl.cpp
+++ b/tests/auto/qgl/tst_qgl.cpp
@@ -84,6 +84,7 @@ private slots:
     void testDontCrashOnDanglingResources();
     void replaceClipping();
     void clipTest();
+    void destroyFBOAfterContext();
 };
 
 tst_QGL::tst_QGL()
@@ -1720,6 +1721,33 @@ void tst_QGL::clipTest()
     QCOMPARE(widgetFB, reference);
 }
 
+void tst_QGL::destroyFBOAfterContext()
+{
+    if (!QGLFramebufferObject::hasOpenGLFramebufferObjects())
+        QSKIP("QGLFramebufferObject not supported on this platform", SkipSingle);
+
+    QGLWidget *glw = new QGLWidget();
+    glw->makeCurrent();
+
+    // No multisample with combined depth/stencil attachment:
+    QGLFramebufferObjectFormat fboFormat;
+    fboFormat.setAttachment(QGLFramebufferObject::CombinedDepthStencil);
+
+    // Don't complicate things by using NPOT:
+    QGLFramebufferObject *fbo = new QGLFramebufferObject(256, 128, fboFormat);
+
+    // The handle should be valid until the context is destroyed.
+    QVERIFY(fbo->handle() != 0);
+    QVERIFY(fbo->isValid());
+
+    delete glw;
+
+    // The handle should now be zero.
+    QVERIFY(fbo->handle() == 0);
+    QVERIFY(!fbo->isValid());
+
+    delete fbo;
+}
 
 QTEST_MAIN(tst_QGL)
 #include "tst_qgl.moc"