Merge branch '4.7' of scm.dev.nokia.troll.no:qt/oslo-staging-2 into 4.7-integration

* '4.7' of scm.dev.nokia.troll.no:qt/oslo-staging-2:
  Make tst_image a little bit more tollerent to rounding errors
  Clear the QGLWindowSurface in ::beginPaint when needed.
  Made QT_GL_SWAPBUFFER_PRESERVE=1 with the GL graphics system work.
  Fix QStaticText with OpenGL1 engine
  tst_qimage: backport fix of commit 0d7e683 into 4.7
  qdrawhelper: backport the optimisations in fetchTransformBilinear from master to 4.7

2 files changed, 16 insertions, 5 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 943a195..c49dba4 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -2103,11 +2103,8 @@ void QGLContextPrivate::syncGlState()
 #ifdef QT_NO_EGL
 void QGLContextPrivate::swapRegion(const QRegion *)
 {
-    static bool firstWarning = true;
-    if (firstWarning) {
-        qWarning() << "::swapRegion called but not supported!";
-        firstWarning = false;
-    }
+    Q_Q(QGLContext);
+    q->swapBuffers();
 }
 #endif
 
diff --git a/src/opengl/qwindowsurface_gl.cpp b/src/opengl/qwindowsurface_gl.cpp
index b86fb78..d602000 100644
--- a/src/opengl/qwindowsurface_gl.cpp
+++ b/src/opengl/qwindowsurface_gl.cpp
@@ -426,6 +426,20 @@ static void drawTexture(const QRectF &rect, GLuint tex_id, const QSize &texSize,
 
 void QGLWindowSurface::beginPaint(const QRegion &)
 {
+    if (! context())
+        return;
+
+    int clearFlags = 0;
+
+    if (context()->d_func()->workaround_needsFullClearOnEveryFrame)
+        clearFlags = GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT;
+    else if (context()->format().alpha())
+        clearFlags = GL_COLOR_BUFFER_BIT;
+
+    if (clearFlags) {
+        glClearColor(0.0, 0.0, 0.0, 0.0);
+        glClear(clearFlags);
+    }
 }
 
 void QGLWindowSurface::endPaint(const QRegion &rgn)