Added a public function to enforce usage og the old GL engine.

Some applications that uses a mix of OpenGL and QPainter code may
not work correctly with the new GL 2 engine (e.g. the composition demo).
The same is most likely also true for user apps, therefore we need
a way to enforce the usage of the old GL 1 engine for the sake of
compatibility.

Task-number: 260872
Reviewed-by: Samuel

1 files changed, 9 insertions, 2 deletions

diff --git a/dist/changes-4.6.0 b/dist/changes-4.6.0
index ca984ac..f9984d3 100644
--- a/dist/changes-4.6.0
+++ b/dist/changes-4.6.0
@@ -54,8 +54,15 @@ information about a particular change.
    this is that Nokia focuses on OpenGL for desktop hardware accelerated
    rendering.
 
- - When mixing OpenGL and QPainter calls you need to surround your custom
-   OpenGL calls with QPainter::beginNativePainting() and
+ - The default engine used to draw onto OpenGL buffers has changed in
+   Qt 4.6. The QPaintEngine::OpenGL2 engine is now used as the default
+   engine. This *may* cause compatibility problems for applications
+   that use a mix of QPainter and native OpenGL calls to draw into a GL
+   buffer. Use the QGL::setPreferredPaintEngine() function to enforce
+   usage of the old GL paint engine.
+
+ - When mixing OpenGL and QPainter calls you need to surround your
+   custom OpenGL calls with QPainter::beginNativePainting() and
    QPainter::endNativePainting().
    This is to ensure that the paint engine flushes any pending drawing and sets
    up the GL modelview/projection matrices properly before you can issue custom