Fixed QtGui's GL paint engine getting out of sync when using QtOpenGL

We need to reset the active_engine belonging to QOpenGLContext whenever
we make the QtOpenGL paint engine active, to give the OpenGL paint
engine in QtGui a chance to sync its state if we've used the QtOpenGL
paint engine inbetween.

Change-Id: I445ce2f99bfbacf55650c881c4fdf07f2ff85069
Reviewed-by: Jørgen Lind <jorgen.lind@digia.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/tests/auto/opengl/qgl/tst_qgl.cpp b/tests/auto/opengl/qgl/tst_qgl.cpp
index d8ad3e1470..56198ceb65 100644
--- a/tests/auto/opengl/qgl/tst_qgl.cpp
+++ b/tests/auto/opengl/qgl/tst_qgl.cpp
@@ -1200,6 +1200,33 @@ void tst_QGL::currentFboSync()
 
         QCOMPARE(fbo1.toImage(), fbo2Image);
     }
+
+    {
+        QGLFramebufferObject fbo1(512, 512, QGLFramebufferObject::CombinedDepthStencil);
+
+        QOpenGLFramebufferObjectPaintDevice fbo2(256, 256);
+
+        QImage sourceImage(256, 256, QImage::Format_ARGB32_Premultiplied);
+        QPainter sourcePainter(&sourceImage);
+        qt_opengl_draw_test_pattern(&sourcePainter, 256, 256);
+
+        QPainter fbo2Painter(&fbo2);
+        fbo2Painter.drawImage(0, 0, sourceImage);
+        QImage fbo2Image1 = fbo2.toImage();
+        fbo2Painter.fillRect(0, 0, 256, 256, Qt::white);
+
+        QPainter fbo1Painter(&fbo1);
+        fbo1Painter.drawImage(0, 0, sourceImage);
+        fbo1Painter.end();
+
+        // check that the OpenGL paint engine now knows it needs to sync
+        fbo2Painter.drawImage(0, 0, sourceImage);
+        QImage fbo2Image2 = fbo2.toImage();
+
+        fbo2Painter.end();
+
+        QCOMPARE(fbo2Image1, fbo2Image2);
+    }
 }
 
 // Tests multiple QPainters active on different FBOs at the same time, with