Rework how Qt handles GL extensions.

Qt used to store the GL extensions a particular implementation supported
in a global cache, which was initialized once and never updated.
This could cause problems because different types of context might
support different kinds of extensions (e.g. the difference between
sw and hw contexts). With this patch, the GL extensions are cached
and updated within each QGLContext. It also makes the extension
initialization lazy, which saves application initialization costs for
embedded platforms.
The patch introduces a internal cross platform QGLTemporaryContext
class that is used to create a light-weight GL context without going
via QGLWidget and friends (QWS and WinCE still have QGLWidget fallbacks
for now).

Reviewed-by: Kim
Reviewed-by: Samuel

1 files changed, 3 insertions, 4 deletions

diff --git a/src/opengl/qwindowsurface_gl.cpp b/src/opengl/qwindowsurface_gl.cpp
index 8ee4361..7a565e6 100644
--- a/src/opengl/qwindowsurface_gl.cpp
+++ b/src/opengl/qwindowsurface_gl.cpp
@@ -295,7 +295,6 @@ QGLWindowSurface::QGLWindowSurface(QWidget *window)
     : QWindowSurface(window), d_ptr(new QGLWindowSurfacePrivate)
 {
     Q_ASSERT(window->isTopLevel());
-    QGLExtensions::init();
     d_ptr->pb = 0;
     d_ptr->fbo = 0;
     d_ptr->ctx = 0;
@@ -520,7 +519,7 @@ void QGLWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoint &
 
     glDisable(GL_SCISSOR_TEST);
 
-    if (d_ptr->fbo && (QGLExtensions::glExtensions & QGLExtensions::FramebufferBlit)) {
+    if (d_ptr->fbo && (QGLExtensions::glExtensions() & QGLExtensions::FramebufferBlit)) {
         const int h = d_ptr->fbo->height();
 
         const int sx0 = br.left();
@@ -698,7 +697,7 @@ void QGLWindowSurface::updateGeometry() {
     }
 
     if (d_ptr->destructive_swap_buffers
-        && (QGLExtensions::glExtensions & QGLExtensions::FramebufferObject)
+        && (QGLExtensions::glExtensions() & QGLExtensions::FramebufferObject)
         && (d_ptr->fbo || !d_ptr->tried_fbo)
         && qt_gl_preferGL2Engine())
     {
@@ -712,7 +711,7 @@ void QGLWindowSurface::updateGeometry() {
         format.setInternalTextureFormat(GLenum(GL_RGBA));
         format.setTextureTarget(target);
 
-        if (QGLExtensions::glExtensions & QGLExtensions::FramebufferBlit)
+        if (QGLExtensions::glExtensions() & QGLExtensions::FramebufferBlit)
             format.setSamples(8);
 
         d_ptr->fbo = new QGLFramebufferObject(rect.size(), format);