Fixed a crash in the boxes demo when using -graphicssystem opengl.

Several problems:
1. The demo leaked the scene contents, which caused cleanup problems.
2. The QGLContext::currentContext() could be changed behind Qt's back
   under Windows (the temp contexts never reset the current context).
3. QGLFormat::openGLVersionFlags() function would return uninitialized
   flags if the QGLWidget constructor happened to call
   qt_gl_preferGL2Engine().

Reviewed-by: Kim

1 files changed, 4 insertions, 3 deletions

diff --git a/demos/boxes/main.cpp b/demos/boxes/main.cpp
index 557afc9..957f183 100644
--- a/demos/boxes/main.cpp
+++ b/demos/boxes/main.cpp
@@ -68,7 +68,7 @@ protected:
 inline bool matchString(const char *extensionString, const char *subString)
 {
     int subStringLength = strlen(subString);
-    return (strncmp(extensionString, subString, subStringLength) == 0) 
+    return (strncmp(extensionString, subString, subStringLength) == 0)
         && ((extensionString[subStringLength] == ' ') || (extensionString[subStringLength] == '\0'));
 }
 
@@ -137,11 +137,12 @@ int main(int argc, char **argv)
         "This demo can be GPU and CPU intensive and may\n"
         "work poorly or not at all on your system.");
 
+    widget->makeCurrent(); // The current context must be set before calling Scene's constructor
+    Scene scene(1024, 768, maxTextureSize);
     GraphicsView view;
     view.setViewport(widget);
     view.setViewportUpdateMode(QGraphicsView::FullViewportUpdate);
-    widget->makeCurrent(); // The current context must be set before calling Scene's constructor
-    view.setScene(new Scene(1024, 768, maxTextureSize));
+    view.setScene(&scene);
     view.show();
 
     return app.exec();