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

3 files changed, 8 insertions, 2 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 119c89d..7e45fd9 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -129,7 +129,7 @@ public Q_SLOTS:
                 // since the context holding the texture is shared, and
                 // about to be destroyed, we have to transfer ownership
                 // of the texture to one of the share contexts
-                ctx = const_cast<QGLContext *>(shares.at(0));
+                ctx = const_cast<QGLContext *>((ctx == shares.at(0)) ? shares.at(1) : shares.at(0));
             }
         }
     }
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 97a4a73..0ad6772 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -1245,11 +1245,11 @@ QGLFormat::OpenGLVersionFlags QGLFormat::openGLVersionFlags()
         if (cachedDefault) {
             return defaultVersionFlags;
         } else {
-            cachedDefault = true;
             if (!hasOpenGL())
                 return defaultVersionFlags;
             dummy = new QGLWidget;
             dummy->makeCurrent(); // glGetString() needs a current context
+            cachedDefault = true;
         }
     }
 
diff --git a/src/opengl/qgl_win.cpp b/src/opengl/qgl_win.cpp
index 2f9e225..5b5820a 100644
--- a/src/opengl/qgl_win.cpp
+++ b/src/opengl/qgl_win.cpp
@@ -660,6 +660,8 @@ public:
         int dmy_pf = ChoosePixelFormat(dmy_pdc, &dmy_pfd);
         SetPixelFormat(dmy_pdc, dmy_pf, &dmy_pfd);
         dmy_rc = wglCreateContext(dmy_pdc);
+        old_dc = wglGetCurrentDC();
+        old_context = wglGetCurrentContext();
         wglMakeCurrent(dmy_pdc, dmy_rc);
     }
 
@@ -668,10 +670,14 @@ public:
         wglDeleteContext(dmy_rc);
         ReleaseDC(dmy_id, dmy_pdc);
         DestroyWindow(dmy_id);
+        if (old_dc && old_context)
+            wglMakeCurrent(old_dc, old_context);
     }
 
     HDC dmy_pdc;
     HGLRC dmy_rc;
+    HDC old_dc;
+    HGLRC old_context;
     WId dmy_id;
 };