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

15 files changed, 469 insertions, 428 deletions

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index a262ded..09ecfd1 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -124,9 +124,6 @@ public:
 };
 Q_GLOBAL_STATIC(QGLDefaultOverlayFormat, defaultOverlayFormatInstance)
 
-QGLExtensions::Extensions QGLExtensions::glExtensions = 0;
-bool QGLExtensions::nvidiaFboNeedsFinish = false;
-
 Q_GLOBAL_STATIC(QGLSignalProxy, theSignalProxy)
 QGLSignalProxy *QGLSignalProxy::instance()
 {
@@ -154,11 +151,9 @@ public:
         // falling back to the GL 1 engine..
         static bool mac_x1600_check_done = false;
         if (!mac_x1600_check_done) {
-            QGLWidget *tmp = 0;
-            if (!QGLContext::currentContext()) {
-                tmp = new QGLWidget();
-                tmp->makeCurrent();
-            }
+            QGLTemporaryContext *tmp = 0;
+            if (!QGLContext::currentContext())
+                tmp = new QGLTemporaryContext();
             if (strstr((char *) glGetString(GL_RENDERER), "X1600"))
                 engineType = QPaintEngine::OpenGL;
             if (tmp)
@@ -178,7 +173,7 @@ public:
             // from an old GL 1.1 server to a GL 2.x client. In that case we can't
             // use GL 2.0.
             if ((QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_2_0)
-                && (QGLExtensions::glExtensions & QGLExtensions::FragmentShader)
+                && (QGLExtensions::glExtensions() & QGLExtensions::FragmentShader)
                 && qgetenv("QT_GL_USE_OPENGL1ENGINE").isEmpty())
                 engineType = QPaintEngine::OpenGL2;
             else
@@ -1250,7 +1245,7 @@ QGLFormat::OpenGLVersionFlags QGLFormat::openGLVersionFlags()
     static bool cachedDefault = false;
     static OpenGLVersionFlags defaultVersionFlags = OpenGL_Version_None;
     QGLContext *currentCtx = const_cast<QGLContext *>(QGLContext::currentContext());
-    QGLWidget *dummy = 0;
+    QGLTemporaryContext *tmpContext = 0;
 
     if (currentCtx && currentCtx->d_func()->version_flags_cached)
         return currentCtx->d_func()->version_flags;
@@ -1261,8 +1256,7 @@ QGLFormat::OpenGLVersionFlags QGLFormat::openGLVersionFlags()
         } else {
             if (!hasOpenGL())
                 return defaultVersionFlags;
-            dummy = new QGLWidget;
-            dummy->makeCurrent(); // glGetString() needs a current context
+            tmpContext = new QGLTemporaryContext;
             cachedDefault = true;
         }
     }
@@ -1273,9 +1267,9 @@ QGLFormat::OpenGLVersionFlags QGLFormat::openGLVersionFlags()
         currentCtx->d_func()->version_flags_cached = true;
         currentCtx->d_func()->version_flags = versionFlags;
     }
-    if (dummy) {
+    if (tmpContext) {
         defaultVersionFlags = versionFlags;
-        delete dummy;
+        delete tmpContext;
     }
 
     return versionFlags;
@@ -1493,6 +1487,8 @@ void QGLContextPrivate::init(QPaintDevice *dev, const QGLFormat &format)
     max_texture_size = -1;
     version_flags_cached = false;
     version_flags = QGLFormat::OpenGL_Version_None;
+    extension_flags_cached = false;
+    extension_flags = 0;
     current_fbo = 0;
     default_fbo = 0;
     active_engine = 0;
@@ -2147,7 +2143,7 @@ QGLTexture* QGLContextPrivate::bindTexture(const QImage &image, GLenum target, G
     int tx_h = qt_next_power_of_two(image.height());
 
     QImage img = image;
-    if (!(QGLExtensions::glExtensions & QGLExtensions::NPOTTextures)
+    if (!(QGLExtensions::glExtensions() & QGLExtensions::NPOTTextures)
         && !(QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_ES_Version_2_0)
         && (target == GL_TEXTURE_2D && (tx_w != image.width() || tx_h != image.height())))
     {
@@ -2169,7 +2165,7 @@ QGLTexture* QGLContextPrivate::bindTexture(const QImage &image, GLenum target, G
     bool genMipmap = false;
 #endif
     if (glFormat.directRendering()
-        && (QGLExtensions::glExtensions & QGLExtensions::GenerateMipmap)
+        && (QGLExtensions::glExtensions() & QGLExtensions::GenerateMipmap)
         && target == GL_TEXTURE_2D
         && (options & QGLContext::MipmapBindOption))
     {
@@ -2197,7 +2193,7 @@ QGLTexture* QGLContextPrivate::bindTexture(const QImage &image, GLenum target, G
     bool premul = options & QGLContext::PremultipliedAlphaBindOption;
     GLenum externalFormat;
     GLuint pixel_type;
-    if (QGLExtensions::glExtensions & QGLExtensions::BGRATextureFormat) {
+    if (QGLExtensions::glExtensions() & QGLExtensions::BGRATextureFormat) {
         externalFormat = GL_BGRA;
         pixel_type = GL_UNSIGNED_INT_8_8_8_8_REV;
     } else {
@@ -4868,9 +4864,13 @@ QGLWidget::QGLWidget(QGLContext *context, QWidget *parent,
 
 #endif // QT3_SUPPORT
 
-void QGLExtensions::init_extensions()
+/*
+    Returns the GL extensions for the current context.
+*/
+QGLExtensions::Extensions QGLExtensions::currentContextExtensions()
 {
     QGLExtensionMatcher extensions(reinterpret_cast<const char *>(glGetString(GL_EXTENSIONS)));
+    Extensions glExtensions;
 
     if (extensions.match("GL_ARB_texture_rectangle"))
         glExtensions |= TextureRectangle;
@@ -4931,6 +4931,46 @@ void QGLExtensions::init_extensions()
 
     if (extensions.match("GL_EXT_bgra"))
         glExtensions |= BGRATextureFormat;
+
+    return glExtensions;
+}
+
+/*
+    Returns the GL extensions for the current QGLContext. If there is no
+    current QGLContext, a default context will be created and the extensions
+    for that context will be returned instead.
+*/
+QGLExtensions::Extensions QGLExtensions::glExtensions()
+{
+    QGLTemporaryContext *tmpContext = 0;
+    static bool cachedDefault = false;
+    static Extensions defaultExtensions = 0;
+    QGLContext *currentCtx = const_cast<QGLContext *>(QGLContext::currentContext());
+
+    if (currentCtx && currentCtx->d_func()->extension_flags_cached)
+        return currentCtx->d_func()->extension_flags;
+
+    if (!currentCtx) {
+        if (cachedDefault) {
+            return defaultExtensions;
+        } else {
+            tmpContext = new QGLTemporaryContext;
+            cachedDefault = true;
+        }
+    }
+
+    Extensions extensionFlags = currentContextExtensions();
+    if (currentCtx) {
+        currentCtx->d_func()->extension_flags_cached = true;
+        currentCtx->d_func()->extension_flags = extensionFlags;
+    } else {
+        defaultExtensions = extensionFlags;
+    }
+
+    if (tmpContext)
+        delete tmpContext;
+
+    return extensionFlags;
 }
 
 /*
@@ -4942,7 +4982,6 @@ void QGLWidgetPrivate::initContext(QGLContext *context, const QGLWidget* shareWi
 
     glDevice.setWidget(q);
 
-    QGLExtensions::init();
     glcx = 0;
     autoSwap = true;
 
@@ -5191,7 +5230,7 @@ QSize QGLTexture::bindCompressedTexture
     }
 #if !defined(QT_OPENGL_ES)
     if (!glCompressedTexImage2D) {
-        if (!(QGLExtensions::glExtensions & QGLExtensions::TextureCompression)) {
+        if (!(QGLExtensions::glExtensions() & QGLExtensions::TextureCompression)) {
             qWarning("QGLContext::bindTexture(): The GL implementation does "
                      "not support texture compression extensions.");
             return QSize();
@@ -5230,7 +5269,7 @@ QSize QGLTexture::bindCompressedTextureDDS(const char *buf, int len)
         return QSize();
 
     // Bail out if the necessary extension is not present.
-    if (!(QGLExtensions::glExtensions & QGLExtensions::DDSTextureCompression)) {
+    if (!(QGLExtensions::glExtensions() & QGLExtensions::DDSTextureCompression)) {
         qWarning("QGLContext::bindTexture(): DDS texture compression is not supported.");
         return QSize();
     }
@@ -5340,13 +5379,13 @@ QSize QGLTexture::bindCompressedTexturePVR(const char *buf, int len)
 
     // Bail out if the necessary extension is not present.
     if (textureFormat == GL_ETC1_RGB8_OES) {
-        if (!(QGLExtensions::glExtensions &
+        if (!(QGLExtensions::glExtensions() &
                     QGLExtensions::ETC1TextureCompression)) {
             qWarning("QGLContext::bindTexture(): ETC1 texture compression is not supported.");
             return QSize();
         }
     } else {
-        if (!(QGLExtensions::glExtensions &
+        if (!(QGLExtensions::glExtensions() &
                     QGLExtensions::PVRTCTextureCompression)) {
             qWarning("QGLContext::bindTexture(): PVRTC texture compression is not supported.");
             return QSize();
diff --git a/src/opengl/qgl.h b/src/opengl/qgl.h
index 374c6d6..1a04ff9 100644
--- a/src/opengl/qgl.h
+++ b/src/opengl/qgl.h
@@ -401,6 +401,7 @@ private:
     friend class QGLContextGroup;
     friend class QGLSharedResourceGuard;
     friend class QGLPixmapBlurFilter;
+    friend class QGLExtensions;
     friend QGLFormat::OpenGLVersionFlags QGLFormat::openGLVersionFlags();
 #ifdef Q_WS_MAC
 public:
diff --git a/src/opengl/qgl_mac.mm b/src/opengl/qgl_mac.mm
index 6ed07e5..c01575b 100644
--- a/src/opengl/qgl_mac.mm
+++ b/src/opengl/qgl_mac.mm
@@ -116,6 +116,68 @@ extern void qt_mac_dispose_rgn(RgnHandle); //qregion_mac.cpp
 extern QRegion qt_mac_convert_mac_region(RgnHandle); //qregion_mac.cpp
 extern void qt_mac_to_pascal_string(QString s, Str255 str, TextEncoding encoding=0, int len=-1);  //qglobal.cpp
 
+/*
+    QGLTemporaryContext implementation
+*/
+
+class QGLTemporaryContextPrivate
+{
+public:
+#ifndef QT_MAC_USE_COCOA
+    AGLContext ctx;
+#else
+    NSOpenGLContext *ctx;
+#endif
+};
+
+QGLTemporaryContext::QGLTemporaryContext(bool, QWidget *)
+    : d(new QGLTemporaryContextPrivate)
+{
+    d->ctx = 0;
+#ifndef QT_MAC_USE_COCOA
+    GLint attribs[] = {AGL_RGBA, AGL_NONE};
+    AGLPixelFormat fmt = aglChoosePixelFormat(0, 0, attribs);
+    if (!fmt) {
+        qDebug("QGLTemporaryContext: Couldn't find any RGB visuals");
+        return;
+    }
+    d->ctx = aglCreateContext(fmt, 0);
+    if (!d->ctx)
+        qDebug("QGLTemporaryContext: Unable to create context");
+    else
+        aglSetCurrentContext(d->ctx);
+    aglDestroyPixelFormat(fmt);
+#else
+    QMacCocoaAutoReleasePool pool;
+    NSOpenGLPixelFormatAttribute attribs[] = { 0 };
+    NSOpenGLPixelFormat *fmt = [[NSOpenGLPixelFormat alloc] initWithAttributes:attribs];
+    if (!fmt) {
+        qWarning("QGLTemporaryContext: Cannot find any visuals");
+        return;
+    }
+
+    d->ctx = [[NSOpenGLContext alloc] initWithFormat:fmt shareContext:0];
+    if (!d->ctx)
+        qWarning("QGLTemporaryContext: Cannot create context");
+    else
+        [d->ctx makeCurrentContext];
+    [fmt release];
+#endif
+}
+
+QGLTemporaryContext::~QGLTemporaryContext()
+{
+    if (d->ctx) {
+#ifndef QT_MAC_USE_COCOA
+        aglSetCurrentContext(0);
+        aglDestroyContext(d->ctx);
+#else
+        [NSOpenGLContext clearCurrentContext];
+        [d->ctx release];
+#endif
+    }
+}
+
 bool QGLFormat::hasOpenGL()
 {
     return true;
@@ -918,54 +980,6 @@ void QGLWidgetPrivate::updatePaintDevice()
     q->update();
 }
 
-
-void QGLExtensions::init()
-{
-    static bool init_done = false;
-
-    if (init_done)
-        return;
-    init_done = true;
-
-#ifndef QT_MAC_USE_COCOA
-    GLint attribs[] = { AGL_RGBA, AGL_NONE };
-    AGLPixelFormat fmt = aglChoosePixelFormat(0, 0, attribs);
-    if (!fmt) {
-        qDebug("QGLExtensions: Couldn't find any RGB visuals");
-        return;
-    }
-    AGLContext ctx = aglCreateContext(fmt, 0);
-    if (!ctx) {
-        qDebug("QGLExtensions: Unable to create context");
-    } else {
-        aglSetCurrentContext(ctx);
-        init_extensions();
-        aglSetCurrentContext(0);
-        aglDestroyContext(ctx);
-    }
-    aglDestroyPixelFormat(fmt);
-#else
-    QMacCocoaAutoReleasePool pool;
-    NSOpenGLPixelFormatAttribute attribs[] = { 0 };
-    NSOpenGLPixelFormat *fmt = [[NSOpenGLPixelFormat alloc] initWithAttributes:attribs];
-    if (!fmt) {
-        qWarning("QGLExtensions: Cannot find any visuals");
-        return;
-    }
-
-    NSOpenGLContext *ctx = [[NSOpenGLContext alloc] initWithFormat:fmt shareContext:0];
-    if (!ctx) {
-        qWarning("QGLExtensions: Cannot create context");
-    } else {
-        [ctx makeCurrentContext];
-        init_extensions();
-        [NSOpenGLContext clearCurrentContext];
-        [ctx release];
-    }
-    [fmt release];
-#endif
-}
-
 #endif
 
 QT_END_NAMESPACE
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 30f5591..0104f07 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -261,6 +261,60 @@ private:
 // "ctx" is destroyed.  Returns null if nothing is sharing with ctx.
 Q_OPENGL_EXPORT const QGLContext *qt_gl_transfer_context(const QGLContext *);
 
+// GL extension definitions
+class QGLExtensions {
+public:
+    enum Extension {
+        TextureRectangle        = 0x00000001,
+        SampleBuffers           = 0x00000002,
+        GenerateMipmap          = 0x00000004,
+        TextureCompression      = 0x00000008,
+        FragmentProgram         = 0x00000010,
+        MirroredRepeat          = 0x00000020,
+        FramebufferObject       = 0x00000040,
+        StencilTwoSide          = 0x00000080,
+        StencilWrap             = 0x00000100,
+        PackedDepthStencil      = 0x00000200,
+        NVFloatBuffer           = 0x00000400,
+        PixelBufferObject       = 0x00000800,
+        FramebufferBlit         = 0x00001000,
+        NPOTTextures            = 0x00002000,
+        BGRATextureFormat       = 0x00004000,
+        DDSTextureCompression   = 0x00008000,
+        ETC1TextureCompression  = 0x00010000,
+        PVRTCTextureCompression = 0x00020000,
+        FragmentShader          = 0x00040000
+    };
+    Q_DECLARE_FLAGS(Extensions, Extension)
+
+    static Extensions glExtensions();
+
+private:
+    static Extensions currentContextExtensions();
+};
+
+/*
+    QGLTemporaryContext - the main objective of this class is to have a way of
+    creating a GL context and making it current, without going via QGLWidget
+    and friends. At certain points during GL initialization we need a current
+    context in order decide what GL features are available, and to resolve GL
+    extensions. Having a light-weight way of creating such a context saves
+    initial application startup time, and it doesn't wind up creating recursive
+    conflicts.
+    The class currently uses a private d pointer to hide the platform specific
+    types. This could possibly been done inline with #ifdef'ery, but it causes
+    major headaches on e.g. X11 due to namespace pollution.
+*/
+class QGLTemporaryContextPrivate;
+class QGLTemporaryContext {
+public:
+    QGLTemporaryContext(bool directRendering = true, QWidget *parent = 0);
+    ~QGLTemporaryContext();
+
+private:
+    QScopedPointer<QGLTemporaryContextPrivate> d;
+};
+
 class QGLTexture;
 
 // This probably needs to grow to GL_MAX_VERTEX_ATTRIBS, but 3 is ok for now as that's
@@ -333,10 +387,12 @@ public:
     uint crWin : 1;
     uint internal_context : 1;
     uint version_flags_cached : 1;
+    uint extension_flags_cached : 1;
     QPaintDevice *paintDevice;
     QColor transpColor;
     QGLContext *q_ptr;
     QGLFormat::OpenGLVersionFlags version_flags;
+    QGLExtensions::Extensions extension_flags;
 
     QGLContextGroup *group;
     GLint max_texture_size;
@@ -375,41 +431,8 @@ Q_SIGNALS:
     void aboutToDestroyContext(const QGLContext *context);
 };
 
-// GL extension definitions
-class QGLExtensions {
-public:
-    enum Extension {
-        TextureRectangle        = 0x00000001,
-        SampleBuffers           = 0x00000002,
-        GenerateMipmap          = 0x00000004,
-        TextureCompression      = 0x00000008,
-        FragmentProgram         = 0x00000010,
-        MirroredRepeat          = 0x00000020,
-        FramebufferObject       = 0x00000040,
-        StencilTwoSide          = 0x00000080,
-        StencilWrap             = 0x00000100,
-        PackedDepthStencil      = 0x00000200,
-        NVFloatBuffer           = 0x00000400,
-        PixelBufferObject       = 0x00000800,
-        FramebufferBlit         = 0x00001000,
-        NPOTTextures            = 0x00002000,
-        BGRATextureFormat       = 0x00004000,
-        DDSTextureCompression   = 0x00008000,
-        ETC1TextureCompression  = 0x00010000,
-        PVRTCTextureCompression = 0x00020000,
-        FragmentShader          = 0x00040000
-    };
-    Q_DECLARE_FLAGS(Extensions, Extension)
-
-    static Extensions glExtensions;
-    static bool nvidiaFboNeedsFinish;
-    static void init(); // sys dependent
-    static void init_extensions(); // general: called by init()
-};
-
 Q_DECLARE_OPERATORS_FOR_FLAGS(QGLExtensions::Extensions)
 
-
 // Temporarily make a context current if not already current or
 // shared with the current contex.  The previous context is made
 // current when the object goes out of scope.
@@ -533,7 +556,7 @@ bool qt_gl_preferGL2Engine();
 
 inline GLenum qt_gl_preferredTextureFormat()
 {
-    return (QGLExtensions::glExtensions & QGLExtensions::BGRATextureFormat) && QSysInfo::ByteOrder == QSysInfo::LittleEndian
+    return (QGLExtensions::glExtensions() & QGLExtensions::BGRATextureFormat) && QSysInfo::ByteOrder == QSysInfo::LittleEndian
         ? GL_BGRA : GL_RGBA;
 }
 
@@ -542,7 +565,7 @@ inline GLenum qt_gl_preferredTextureTarget()
 #if defined(QT_OPENGL_ES_2)
     return GL_TEXTURE_2D;
 #else
-    return (QGLExtensions::glExtensions & QGLExtensions::TextureRectangle)
+    return (QGLExtensions::glExtensions() & QGLExtensions::TextureRectangle)
            && !qt_gl_preferGL2Engine()
            ? GL_TEXTURE_RECTANGLE_NV
            : GL_TEXTURE_2D;
@@ -614,7 +637,7 @@ private:
 };
 
 
-// This class can be used to match GL extensions with doing any mallocs. The
+// This class can be used to match GL extensions without doing any mallocs. The
 // class assumes that the GL extension string ends with a space character,
 // which it should do on all conformant platforms. Create the object and pass
 // in a pointer to the extension string, then call match() on each extension
diff --git a/src/opengl/qgl_qws.cpp b/src/opengl/qgl_qws.cpp
index f69ad7b..d4adc8b 100644
--- a/src/opengl/qgl_qws.cpp
+++ b/src/opengl/qgl_qws.cpp
@@ -83,6 +83,28 @@ static QGLScreen *glScreenForDevice(QPaintDevice *device)
         return 0;
 }
 
+/*
+    QGLTemporaryContext implementation
+*/
+
+class QGLTemporaryContextPrivate
+{
+public:
+    QGLWidget *widget;
+};
+
+QGLTemporaryContext::QGLTemporaryContext(bool, QWidget *)
+    : d(new QGLTemporaryContextPrivate)
+{
+    d->widget = new QGLWidget;
+    d->widget->makeCurrent();
+}
+
+QGLTemporaryContext::~QGLTemporaryContext()
+{
+    delete d->widget;
+}
+
 /*****************************************************************************
   QOpenGL debug facilities
  *****************************************************************************/
@@ -311,36 +333,4 @@ void QGLWidget::setColormap(const QGLColormap &)
 {
 }
 
-void QGLExtensions::init()
-{
-    static bool init_done = false;
-
-    if (init_done)
-        return;
-    init_done = true;
-
-    // We need a context current to initialize the extensions,
-    // but getting a valid EGLNativeWindowType this early can be
-    // problematic under QWS.  So use a pbuffer instead.
-    //
-    // Unfortunately OpenGL/ES 2.0 systems don't normally
-    // support pbuffers, so we have no choice but to try
-    // our luck with a window on those systems.
-#if defined(QT_OPENGL_ES_2)
-    QGLWidget tmpWidget;
-    tmpWidget.makeCurrent();
-
-    init_extensions();
-
-    tmpWidget.doneCurrent();
-#else
-    QGLPixelBuffer pbuffer(16, 16);
-    pbuffer.makeCurrent();
-
-    init_extensions();
-
-    pbuffer.doneCurrent();
-#endif
-}
-
 QT_END_NAMESPACE
diff --git a/src/opengl/qgl_win.cpp b/src/opengl/qgl_win.cpp
index 443fbf2..ed4814f 100644
--- a/src/opengl/qgl_win.cpp
+++ b/src/opengl/qgl_win.cpp
@@ -551,7 +551,7 @@ QGLFormat pfiToQGLFormat(HDC hdc, int pfi)
     QVarLengthArray<int> iAttributes(40);
     QVarLengthArray<int> iValues(40);
     int i = 0;
-    bool has_sample_buffers = QGLExtensions::glExtensions & QGLExtensions::SampleBuffers;
+    bool has_sample_buffers = QGLExtensions::glExtensions() & QGLExtensions::SampleBuffers;
 
     iAttributes[i++] = WGL_DOUBLE_BUFFER_ARB; // 0
     iAttributes[i++] = WGL_DEPTH_BITS_ARB; // 1
@@ -628,52 +628,14 @@ QGLFormat pfiToQGLFormat(HDC hdc, int pfi)
 
 
 /*
-   Creates a temporary GL context and makes it current
-   - cleans up when the object is destructed.
+    QGLTemporaryContext implementation
 */
 
 Q_GUI_EXPORT const QString qt_getRegisteredWndClass();
 
-class QGLTempContext
+class QGLTemporaryContextPrivate
 {
 public:
-    QGLTempContext(bool directRendering, QWidget *parent = 0)
-    {
-        QString windowClassName = qt_getRegisteredWndClass();
-        if (parent && !parent->internalWinId())
-            parent = parent->nativeParentWidget();
-
-        dmy_id = CreateWindow((const wchar_t *)windowClassName.utf16(),
-                              0, 0, 0, 0, 1, 1,
-                              parent ? parent->winId() : 0, 0, qWinAppInst(), 0);
-
-        dmy_pdc = GetDC(dmy_id);
-        PIXELFORMATDESCRIPTOR dmy_pfd;
-        memset(&dmy_pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
-        dmy_pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
-        dmy_pfd.nVersion = 1;
-        dmy_pfd.dwFlags = PFD_SUPPORT_OPENGL | PFD_DRAW_TO_WINDOW;
-        dmy_pfd.iPixelType = PFD_TYPE_RGBA;
-        if (!directRendering)
-            dmy_pfd.dwFlags |= PFD_GENERIC_FORMAT;
-
-        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);
-    }
-
-    ~QGLTempContext() {
-        wglMakeCurrent(dmy_pdc, 0);
-        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;
@@ -681,6 +643,45 @@ public:
     WId dmy_id;
 };
 
+QGLTemporaryContext::QGLTemporaryContext(bool directRendering, QWidget *parent)
+    : d(new QGLTemporaryContextPrivate)
+{
+    QString windowClassName = qt_getRegisteredWndClass();
+    if (parent && !parent->internalWinId())
+        parent = parent->nativeParentWidget();
+
+    d->dmy_id = CreateWindow((const wchar_t *)windowClassName.utf16(),
+                             0, 0, 0, 0, 1, 1,
+                             parent ? parent->winId() : 0, 0, qWinAppInst(), 0);
+
+    d->dmy_pdc = GetDC(d->dmy_id);
+    PIXELFORMATDESCRIPTOR dmy_pfd;
+    memset(&dmy_pfd, 0, sizeof(PIXELFORMATDESCRIPTOR));
+    dmy_pfd.nSize = sizeof(PIXELFORMATDESCRIPTOR);
+    dmy_pfd.nVersion = 1;
+    dmy_pfd.dwFlags = PFD_SUPPORT_OPENGL | PFD_DRAW_TO_WINDOW;
+    dmy_pfd.iPixelType = PFD_TYPE_RGBA;
+    if (!directRendering)
+        dmy_pfd.dwFlags |= PFD_GENERIC_FORMAT;
+
+    int dmy_pf = ChoosePixelFormat(d->dmy_pdc, &dmy_pfd);
+    SetPixelFormat(d->dmy_pdc, dmy_pf, &dmy_pfd);
+    d->dmy_rc = wglCreateContext(d->dmy_pdc);
+    d->old_dc = wglGetCurrentDC();
+    d->old_context = wglGetCurrentContext();
+    wglMakeCurrent(d->dmy_pdc, d->dmy_rc);
+}
+
+QGLTemporaryContext::~QGLTemporaryContext()
+{
+    wglMakeCurrent(d->dmy_pdc, 0);
+    wglDeleteContext(d->dmy_rc);
+    ReleaseDC(d->dmy_id, d->dmy_pdc);
+    DestroyWindow(d->dmy_id);
+    if (d->old_dc && d->old_context)
+        wglMakeCurrent(d->old_dc, d->old_context);
+}
+
 bool QGLContext::chooseContext(const QGLContext* shareContext)
 {
     Q_D(QGLContext);
@@ -721,10 +722,10 @@ bool QGLContext::chooseContext(const QGLContext* shareContext)
         myDc = GetDC(d->win);
     }
 
-    // NB! the QGLTempContext object is needed for the
+    // NB! the QGLTemporaryContext object is needed for the
     // wglGetProcAddress() calls to succeed and are absolutely
     // necessary - don't remove!
-    QGLTempContext tmp_ctx(d->glFormat.directRendering(), widget);
+    QGLTemporaryContext tmp_ctx(d->glFormat.directRendering(), widget);
 
     if (!myDc) {
         qWarning("QGLContext::chooseContext(): Paint device cannot be null");
@@ -965,7 +966,7 @@ int QGLContext::choosePixelFormat(void* dummyPfd, HDC pdc)
             iAttributes[i++] = 1;
         }
         int si = 0;
-        bool trySampleBuffers = QGLExtensions::glExtensions & QGLExtensions::SampleBuffers;
+        bool trySampleBuffers = QGLExtensions::glExtensions() & QGLExtensions::SampleBuffers;
         if (trySampleBuffers && d->glFormat.sampleBuffers()) {
             iAttributes[i++] = WGL_SAMPLE_BUFFERS_ARB;
             iAttributes[i++] = TRUE;
@@ -1471,15 +1472,4 @@ void QGLWidget::setColormap(const QGLColormap & c)
     }
 }
 
-void QGLExtensions::init()
-{
-    static bool init_done = false;
-
-    if (init_done)
-        return;
-    init_done = true;
-    QGLTempContext temp_ctx(QGLFormat::defaultFormat().directRendering());
-    init_extensions();
-}
-
 QT_END_NAMESPACE
diff --git a/src/opengl/qgl_wince.cpp b/src/opengl/qgl_wince.cpp
index 460f10d..00a125a 100644
--- a/src/opengl/qgl_wince.cpp
+++ b/src/opengl/qgl_wince.cpp
@@ -95,8 +95,27 @@ public:
 
 #include <qcolor.h>
 
+/*
+    QGLTemporaryContext implementation
+*/
 
+class QGLTemporaryContextPrivate
+{
+public:
+    QGLWidget *widget;
+};
 
+QGLTemporaryContext::QGLTemporaryContext(bool, QWidget *)
+    : d(new QGLTemporaryContextPrivate)
+{
+    d->widget = new QGLWidget;
+    d->widget->makeCurrent();
+}
+
+QGLTemporaryContext::~QGLTemporaryContext()
+{
+    delete d->widget;
+}
 
 /*****************************************************************************
   QGLFormat Win32/WGL-specific code
@@ -627,21 +646,4 @@ void QGLWidget::setColormap(const QGLColormap & c)
     }
 }
 
-void QGLExtensions::init()
-{
-    static bool init_done = false;
-
-    if (init_done)
-        return;
-    init_done = true;
-
-    // We need a context current to initialize the extensions.
-    QGLWidget tmpWidget;
-    tmpWidget.makeCurrent();
-
-    init_extensions();
-
-    tmpWidget.doneCurrent();
-}
-
 QT_END_NAMESPACE
diff --git a/src/opengl/qgl_x11.cpp b/src/opengl/qgl_x11.cpp
index e883ddc..f4cc7c7 100644
--- a/src/opengl/qgl_x11.cpp
+++ b/src/opengl/qgl_x11.cpp
@@ -549,7 +549,7 @@ void *QGLContext::chooseVisual()
     bool triedDouble = false;
     bool triedSample = false;
     if (fmt.sampleBuffers())
-        fmt.setSampleBuffers(QGLExtensions::glExtensions & QGLExtensions::SampleBuffers);
+        fmt.setSampleBuffers(QGLExtensions::glExtensions() & QGLExtensions::SampleBuffers);
     while(!fail && !(vis = tryVisual(fmt, bufDepths[i]))) {
         if (!fmt.rgba() && bufDepths[i] > 1) {
             i++;
@@ -1132,71 +1132,70 @@ void *QGLContext::getProcAddress(const QString &proc) const
     return glXGetProcAddressARB(reinterpret_cast<const GLubyte *>(proc.toLatin1().data()));
 }
 
-//
-// This class is used to create a temporary, minimal GL context, which is used
-// to retrive GL version and extension info. It's significantly faster to
-// construct than a QGLWidget, and it doesn't have the recursive creation
-// problem that QGLWidget would have. E.g. creating a temporary QGLWidget to
-// retrieve GL info as part of the QGLWidget initialization.
-//
-class QGLTempContext
-{
+/*
+    QGLTemporaryContext implementation
+*/
+
+class QGLTemporaryContextPrivate {
 public:
-    QGLTempContext(int screen = 0) :
-            initialized(false),
-            old_drawable(0),
-            old_context(0)
-    {
-        int attribs[] = {GLX_RGBA, XNone};
-        XVisualInfo *vi = glXChooseVisual(X11->display, screen, attribs);
-        if (!vi) {
-            qWarning("QGLTempContext: No GL capable X visuals available.");
-            return;
-        }
+    bool initialized;
+    Window drawable;
+    GLXContext context;
+    GLXDrawable oldDrawable;
+    GLXContext oldContext;
+};
 
-        int useGL;
-        glXGetConfig(X11->display, vi, GLX_USE_GL, &useGL);
-        if (!useGL) {
-            XFree(vi);
-            return;
-        }
+QGLTemporaryContext::QGLTemporaryContext(bool, QWidget *)
+    : d(new QGLTemporaryContextPrivate)
+{
+    d->initialized = false;
+    d->oldDrawable = 0;
+    d->oldContext = 0;
+    int screen = 0;
+
+    int attribs[] = {GLX_RGBA, XNone};
+    XVisualInfo *vi = glXChooseVisual(X11->display, screen, attribs);
+    if (!vi) {
+        qWarning("QGLTempContext: No GL capable X visuals available.");
+        return;
+    }
 
-        old_drawable = glXGetCurrentDrawable();
-        old_context = glXGetCurrentContext();
-
-        XSetWindowAttributes a;
-        a.colormap = qt_gl_choose_cmap(X11->display, vi);
-        drawable = XCreateWindow(X11->display, RootWindow(X11->display, screen),
-                                 0, 0, 1, 1, 0,
-                                 vi->depth, InputOutput, vi->visual,
-                                 CWColormap, &a);
-        context = glXCreateContext(X11->display, vi, 0, True);
-        if (context && glXMakeCurrent(X11->display, drawable, context)) {
-            initialized = true;
-        } else {
-            qWarning("QGLTempContext: Unable to create GL context.");
-            XDestroyWindow(X11->display, drawable);
-        }
+    int useGL;
+    glXGetConfig(X11->display, vi, GLX_USE_GL, &useGL);
+    if (!useGL) {
         XFree(vi);
+        return;
     }
 
-    ~QGLTempContext() {
-        if (initialized) {
-            glXMakeCurrent(X11->display, 0, 0);
-            glXDestroyContext(X11->display, context);
-            XDestroyWindow(X11->display, drawable);
-        }
-        if (old_drawable && old_context)
-            glXMakeCurrent(X11->display, old_drawable, old_context);
+    d->oldDrawable = glXGetCurrentDrawable();
+    d->oldContext = glXGetCurrentContext();
+
+    XSetWindowAttributes a;
+    a.colormap = qt_gl_choose_cmap(X11->display, vi);
+    d->drawable = XCreateWindow(X11->display, RootWindow(X11->display, screen),
+                                0, 0, 1, 1, 0,
+                                vi->depth, InputOutput, vi->visual,
+                                CWColormap, &a);
+    d->context = glXCreateContext(X11->display, vi, 0, True);
+    if (d->context && glXMakeCurrent(X11->display, d->drawable, d->context)) {
+        d->initialized = true;
+    } else {
+        qWarning("QGLTempContext: Unable to create GL context.");
+        XDestroyWindow(X11->display, d->drawable);
     }
+    XFree(vi);
+}
 
-private:
-    bool initialized;
-    Window drawable;
-    GLXContext context;
-    GLXDrawable old_drawable;
-    GLXContext old_context;
-};
+QGLTemporaryContext::~QGLTemporaryContext()
+{
+    if (d->initialized) {
+        glXMakeCurrent(X11->display, 0, 0);
+        glXDestroyContext(X11->display, d->context);
+        XDestroyWindow(X11->display, d->drawable);
+    }
+    if (d->oldDrawable && d->oldContext)
+        glXMakeCurrent(X11->display, d->oldDrawable, d->oldContext);
+}
 
 /*****************************************************************************
   QGLOverlayWidget (Internal overlay class for X11)
@@ -1632,27 +1631,6 @@ void QGLWidget::setColormap(const QGLColormap & c)
     delete [] cmw;
 }
 
-void QGLExtensions::init()
-{
-    static bool init_done = false;
-
-    if (init_done)
-        return;
-    init_done = true;
-
-    QGLTempContext context;
-    init_extensions();
-
-    // nvidia 9x.xx unix drivers contain a bug which requires us to call glFinish before releasing an fbo
-    // to avoid painting artifacts
-    const QByteArray versionString(reinterpret_cast<const char*>(glGetString(GL_VERSION)));
-    const int pos = versionString.indexOf("NVIDIA");
-    if (pos >= 0) {
-        const float nvidiaDriverVersion = versionString.mid(pos + strlen("NVIDIA")).toFloat();
-        nvidiaFboNeedsFinish = nvidiaDriverVersion >= 90.0 && nvidiaDriverVersion < 100.0;
-    }
-}
-
 // Solaris defines glXBindTexImageEXT as part of the GL library
 #if defined(GLX_VERSION_1_3) && !defined(Q_OS_HPUX)
 typedef void (*qt_glXBindTexImageEXT)(Display*, GLXDrawable, int, const int*);
@@ -1668,7 +1646,7 @@ static bool qt_resolveTextureFromPixmap(QPaintDevice *paintDevice)
         resolvedTextureFromPixmap = true;
 
         // Check to see if we have NPOT texture support
-        if ( !(QGLExtensions::glExtensions & QGLExtensions::NPOTTextures) &&
+        if ( !(QGLExtensions::glExtensions() & QGLExtensions::NPOTTextures) &&
              !(QGLFormat::openGLVersionFlags() & QGLFormat::OpenGL_Version_2_0))
         {
             return false; // Can't use TFP without NPOT
diff --git a/src/opengl/qgl_x11egl.cpp b/src/opengl/qgl_x11egl.cpp
index 85daf95..572834b 100644
--- a/src/opengl/qgl_x11egl.cpp
+++ b/src/opengl/qgl_x11egl.cpp
@@ -55,112 +55,115 @@ QT_BEGIN_NAMESPACE
 
 bool qt_egl_setup_x11_visual(XVisualInfo &vi, EGLDisplay display, EGLConfig config,
                              const QX11Info &x11Info, bool useArgbVisual);
-//
-// QGLTempContext is a class for creating a temporary GL context
-// (which is needed during QGLWidget initialization to retrieve GL
-// extension info).  Faster to construct than a full QGLWidget.
-//
-class QGLTempContext
+
+/*
+    QGLTemporaryContext implementation
+*/
+
+class QGLTemporaryContextPrivate
 {
 public:
-    QGLTempContext(int screen = 0) :
-        initialized(false),
-        window(0),
-        context(0),
-        surface(0)
-    {
-        display = eglGetDisplay(EGLNativeDisplayType(X11->display));
+    bool initialized;
+    Window window;
+    EGLContext context;
+    EGLSurface surface;
+    EGLDisplay display;
+};
 
-        if (!eglInitialize(display, NULL, NULL)) {
-            qWarning("QGLTempContext: Unable to initialize EGL display.");
-            return;
-        }
+QGLTemporaryContext::QGLTemporaryContext(bool, QWidget *)
+    : d(new QGLTemporaryContextPrivate)
+{
+    d->initialized = false;
+    d->window = 0;
+    d->context = 0;
+    d->surface = 0;
+    int screen = 0;
+
+    d->display = eglGetDisplay(EGLNativeDisplayType(X11->display));
 
-        EGLConfig config;
-        int numConfigs = 0;
-        EGLint attribs[] = {
-            EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
+    if (!eglInitialize(d->display, NULL, NULL)) {
+        qWarning("QGLTemporaryContext: Unable to initialize EGL display.");
+        return;
+    }
+
+    EGLConfig config;
+    int numConfigs = 0;
+    EGLint attribs[] = {
+        EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
 #ifdef QT_OPENGL_ES_2
-            EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
 #endif
-            EGL_NONE
-        };
+        EGL_NONE
+    };
 
-        eglChooseConfig(display, attribs, &config, 1, &numConfigs);
-        if (!numConfigs) {
-            qWarning("QGLTempContext: No EGL configurations available.");
-            return;
-        }
+    eglChooseConfig(d->display, attribs, &config, 1, &numConfigs);
+    if (!numConfigs) {
+        qWarning("QGLTemporaryContext: No EGL configurations available.");
+        return;
+    }
 
-        XVisualInfo visualInfo;
-        XVisualInfo *vi;
-        int numVisuals;
-        EGLint id = 0;
-
-        eglGetConfigAttrib(display, config, EGL_NATIVE_VISUAL_ID, &id);
-        if (id == 0) {
-            // EGL_NATIVE_VISUAL_ID is optional and might not be supported
-            // on some implementations - we'll have to do it the hard way
-            QX11Info xinfo;
-            qt_egl_setup_x11_visual(visualInfo, display, config, xinfo, false);
-        } else {
-            visualInfo.visualid = id;
-        }
-        vi = XGetVisualInfo(X11->display, VisualIDMask, &visualInfo, &numVisuals);
-        if (!vi || numVisuals < 1) {
-            qWarning("QGLTempContext: Unable to get X11 visual info id.");
-            return;
-        }
+    XVisualInfo visualInfo;
+    XVisualInfo *vi;
+    int numVisuals;
+    EGLint id = 0;
+
+    eglGetConfigAttrib(d->display, config, EGL_NATIVE_VISUAL_ID, &id);
+    if (id == 0) {
+        // EGL_NATIVE_VISUAL_ID is optional and might not be supported
+        // on some implementations - we'll have to do it the hard way
+        QX11Info xinfo;
+        qt_egl_setup_x11_visual(visualInfo, d->display, config, xinfo, false);
+    } else {
+        visualInfo.visualid = id;
+    }
+    vi = XGetVisualInfo(X11->display, VisualIDMask, &visualInfo, &numVisuals);
+    if (!vi || numVisuals < 1) {
+        qWarning("QGLTemporaryContext: Unable to get X11 visual info id.");
+        return;
+    }
 
-        window = XCreateWindow(X11->display, RootWindow(X11->display, screen),
-                               0, 0, 1, 1, 0,
-                               vi->depth, InputOutput, vi->visual,
-                               0, 0);
+    d->window = XCreateWindow(X11->display, RootWindow(X11->display, screen),
+                              0, 0, 1, 1, 0,
+                              vi->depth, InputOutput, vi->visual,
+                              0, 0);
 
-        surface = eglCreateWindowSurface(display, config, (EGLNativeWindowType) window, NULL);
+    d->surface = eglCreateWindowSurface(d->display, config, (EGLNativeWindowType) d->window, NULL);
 
-        if (surface == EGL_NO_SURFACE) {
-            qWarning("QGLTempContext: Error creating EGL surface.");
-            XFree(vi);
-            XDestroyWindow(X11->display, window);
-            return;
-        }
+    if (d->surface == EGL_NO_SURFACE) {
+        qWarning("QGLTemporaryContext: Error creating EGL surface.");
+        XFree(vi);
+        XDestroyWindow(X11->display, d->window);
+        return;
+    }
 
-        EGLint contextAttribs[] = {
+    EGLint contextAttribs[] = {
 #ifdef QT_OPENGL_ES_2
-            EGL_CONTEXT_CLIENT_VERSION, 2,
+        EGL_CONTEXT_CLIENT_VERSION, 2,
 #endif
-            EGL_NONE
-        };
-        context = eglCreateContext(display, config, 0, contextAttribs);
-        if (context != EGL_NO_CONTEXT
-            && eglMakeCurrent(display, surface, surface, context))
-        {
-            initialized = true;
-        } else {
-            qWarning("QGLTempContext: Error creating EGL context.");
-            eglDestroySurface(display, surface);
-            XDestroyWindow(X11->display, window);
-        }
-        XFree(vi);
+        EGL_NONE
+    };
+    d->context = eglCreateContext(d->display, config, 0, contextAttribs);
+    if (d->context != EGL_NO_CONTEXT
+        && eglMakeCurrent(d->display, d->surface, d->surface, d->context))
+    {
+        d->initialized = true;
+    } else {
+        qWarning("QGLTemporaryContext: Error creating EGL context.");
+        eglDestroySurface(d->display, d->surface);
+        XDestroyWindow(X11->display, d->window);
     }
+    XFree(vi);
+}
 
-    ~QGLTempContext() {
-        if (initialized) {
-            eglMakeCurrent(display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
-            eglDestroyContext(display, context);
-            eglDestroySurface(display, surface);
-            XDestroyWindow(X11->display, window);
-        }
+QGLTemporaryContext::~QGLTemporaryContext()
+{
+    if (d->initialized) {
+        eglMakeCurrent(d->display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+        eglDestroyContext(d->display, d->context);
+        eglDestroySurface(d->display, d->surface);
+        XDestroyWindow(X11->display, d->window);
     }
-
-private:
-    bool initialized;
-    Window window;
-    EGLContext context;
-    EGLSurface surface;
-    EGLDisplay display;
-};
+}
 
 bool QGLFormat::hasOpenGLOverlays()
 {
@@ -547,19 +550,6 @@ void QGLWidget::setColormap(const QGLColormap &)
 {
 }
 
-void QGLExtensions::init()
-{
-    static bool init_done = false;
-
-    if (init_done)
-        return;
-    init_done = true;
-
-    // We need a context current to initialize the extensions.
-    QGLTempContext context;
-    init_extensions();
-}
-
 // Re-creates the EGL surface if the window ID has changed or if force is true
 void QGLWidgetPrivate::recreateEglSurface(bool force)
 {
diff --git a/src/opengl/qglframebufferobject.cpp b/src/opengl/qglframebufferobject.cpp
index ed21923..ce80796 100644
--- a/src/opengl/qglframebufferobject.cpp
+++ b/src/opengl/qglframebufferobject.cpp
@@ -396,7 +396,7 @@ void QGLFramebufferObjectPrivate::init(QGLFramebufferObject *q, const QSize &sz,
     QGLContext *ctx = const_cast<QGLContext *>(QGLContext::currentContext());
     fbo_guard.setContext(ctx);
 
-    bool ext_detected = (QGLExtensions::glExtensions & QGLExtensions::FramebufferObject);
+    bool ext_detected = (QGLExtensions::glExtensions() & QGLExtensions::FramebufferObject);
     if (!ext_detected || (ext_detected && !qt_resolve_framebufferobject_extensions(ctx)))
         return;
 
@@ -466,7 +466,7 @@ void QGLFramebufferObjectPrivate::init(QGLFramebufferObject *q, const QSize &sz,
     }
 
     if (attachment == QGLFramebufferObject::CombinedDepthStencil
-        && (QGLExtensions::glExtensions & QGLExtensions::PackedDepthStencil)) {
+        && (QGLExtensions::glExtensions() & QGLExtensions::PackedDepthStencil)) {
         // depth and stencil buffer needs another extension
         glGenRenderbuffers(1, &depth_stencil_buffer);
         Q_ASSERT(!glIsRenderbuffer(depth_stencil_buffer));
@@ -1028,8 +1028,7 @@ QPaintEngine *QGLFramebufferObject::paintEngine() const
 */
 bool QGLFramebufferObject::hasOpenGLFramebufferObjects()
 {
-    QGLExtensions::init();
-    return (QGLExtensions::glExtensions & QGLExtensions::FramebufferObject);
+    return (QGLExtensions::glExtensions() & QGLExtensions::FramebufferObject);
 }
 
 /*!
@@ -1188,8 +1187,7 @@ bool QGLFramebufferObject::isBound() const
 */
 bool QGLFramebufferObject::hasOpenGLFramebufferBlit()
 {
-    QGLExtensions::init();
-    return (QGLExtensions::glExtensions & QGLExtensions::FramebufferBlit);
+    return (QGLExtensions::glExtensions() & QGLExtensions::FramebufferBlit);
 }
 
 /*!
@@ -1229,7 +1227,7 @@ void QGLFramebufferObject::blitFramebuffer(QGLFramebufferObject *target, const Q
                                            GLbitfield buffers,
                                            GLenum filter)
 {
-    if (!(QGLExtensions::glExtensions & QGLExtensions::FramebufferBlit))
+    if (!(QGLExtensions::glExtensions() & QGLExtensions::FramebufferBlit))
         return;
 
     const QGLContext *ctx = QGLContext::currentContext();
diff --git a/src/opengl/qglpixelbuffer_mac.mm b/src/opengl/qglpixelbuffer_mac.mm
index 49c1845..6731dd8 100644
--- a/src/opengl/qglpixelbuffer_mac.mm
+++ b/src/opengl/qglpixelbuffer_mac.mm
@@ -92,7 +92,7 @@ bool QGLPixelBufferPrivate::init(const QSize &size, const QGLFormat &f, QGLWidge
 
     GLenum target = GL_TEXTURE_2D;
 
-    if ((QGLExtensions::glExtensions & QGLExtensions::TextureRectangle)
+    if ((QGLExtensions::glExtensions() & QGLExtensions::TextureRectangle)
         && (size.width() != nearest_gl_texture_size(size.width())
             || size.height() != nearest_gl_texture_size(size.height())))
     {
@@ -223,7 +223,7 @@ bool QGLPixelBufferPrivate::init(const QSize &size, const QGLFormat &f, QGLWidge
 
     GLenum target = GL_TEXTURE_2D;
 
-    if ((QGLExtensions::glExtensions & QGLExtensions::TextureRectangle)
+    if ((QGLExtensions::glExtensions() & QGLExtensions::TextureRectangle)
         && (size.width() != nearest_gl_texture_size(size.width())
             || size.height() != nearest_gl_texture_size(size.height())))
     {
diff --git a/src/opengl/qglpixelbuffer_p.h b/src/opengl/qglpixelbuffer_p.h
index f40b7c5..c85dc5a 100644
--- a/src/opengl/qglpixelbuffer_p.h
+++ b/src/opengl/qglpixelbuffer_p.h
@@ -154,7 +154,6 @@ class QGLPixelBufferPrivate {
 public:
     QGLPixelBufferPrivate(QGLPixelBuffer *q) : q_ptr(q), invalid(true), qctx(0), pbuf(0), ctx(0)
     {
-        QGLExtensions::init();
 #ifdef Q_WS_WIN
         dc = 0;
 #elif defined(Q_WS_MACX)
diff --git a/src/opengl/qglpixelbuffer_win.cpp b/src/opengl/qglpixelbuffer_win.cpp
index a986ccf..8d0d105 100644
--- a/src/opengl/qglpixelbuffer_win.cpp
+++ b/src/opengl/qglpixelbuffer_win.cpp
@@ -221,7 +221,7 @@ static void qt_format_to_attrib_list(bool has_render_texture, const QGLFormat &f
     }
     if ((f.redBufferSize() > 8 || f.greenBufferSize() > 8
          || f.blueBufferSize() > 8 || f.alphaBufferSize() > 8)
-        && (QGLExtensions::glExtensions & QGLExtensions::NVFloatBuffer))
+        && (QGLExtensions::glExtensions() & QGLExtensions::NVFloatBuffer))
     {
         attribs[i++] = WGL_FLOAT_COMPONENTS_NV;
         attribs[i++] = TRUE;
@@ -368,11 +368,9 @@ void QGLPixelBuffer::releaseFromDynamicTexture()
 bool QGLPixelBuffer::hasOpenGLPbuffers()
 {
     bool ret = false;
-    QGLWidget *dmy = 0;
-    if (!QGLContext::currentContext()) {
-        dmy = new QGLWidget;
-        dmy->makeCurrent();
-    }
+    QGLTemporaryContext *tmpContext = 0;
+    if (!QGLContext::currentContext())
+        tmpContext = new QGLTemporaryContext;
     PFNWGLGETEXTENSIONSSTRINGARBPROC wglGetExtensionsStringARB =
         (PFNWGLGETEXTENSIONSSTRINGARBPROC) wglGetProcAddress("wglGetExtensionsStringARB");
     if (wglGetExtensionsStringARB) {
@@ -382,8 +380,8 @@ bool QGLPixelBuffer::hasOpenGLPbuffers()
             ret = true;
         }
     }
-    if (dmy)
-        delete dmy;
+    if (tmpContext)
+        delete tmpContext;
     return ret;
 }
 
diff --git a/src/opengl/qpaintengine_opengl.cpp b/src/opengl/qpaintengine_opengl.cpp
index c823187..57918d0 100644
--- a/src/opengl/qpaintengine_opengl.cpp
+++ b/src/opengl/qpaintengine_opengl.cpp
@@ -108,6 +108,10 @@ static bool DEBUG_TEMP_FLAG;
 #define DEBUG_ONCE_STR(str) DEBUG_ONCE qDebug() << (str);
 #endif
 
+#ifdef Q_WS_X11
+static bool qt_nvidiaFboNeedsFinish = false;
+#endif
+
 static inline void qt_glColor4ubv(unsigned char *col)
 {
     glColor4f(col[0]/255.0f, col[1]/255.0f, col[2]/255.0f, col[3]/255.0f);
@@ -423,7 +427,7 @@ inline void QGLOffscreen::release()
 
 #ifdef Q_WS_X11
     // workaround for bug in nvidia driver versions 9x.xx
-    if (QGLExtensions::nvidiaFboNeedsFinish)
+    if (qt_nvidiaFboNeedsFinish)
         glFinish();
 #endif
 
@@ -477,7 +481,7 @@ inline QGLContext *QGLOffscreen::context() const
 
 bool QGLOffscreen::isSupported()
 {
-    return (QGLExtensions::glExtensions & QGLExtensions::FramebufferObject); // for fbo
+    return (QGLExtensions::glExtensions() & QGLExtensions::FramebufferObject); // for fbo
 }
 
 struct QDrawQueueItem
@@ -1266,7 +1270,7 @@ bool QOpenGLPaintEngine::begin(QPaintDevice *pdev)
         for (int j = 0; j < 4; ++j)
             d->mv_matrix[i][j] = (i == j ? qreal(1) : qreal(0));
 
-    bool has_frag_program = (QGLExtensions::glExtensions & QGLExtensions::FragmentProgram)
+    bool has_frag_program = (QGLExtensions::glExtensions() & QGLExtensions::FragmentProgram)
                             && (pdev->devType() != QInternal::Pixmap);
 
     QGLContext *ctx = const_cast<QGLContext *>(d->device->context());
@@ -1279,11 +1283,27 @@ bool QOpenGLPaintEngine::begin(QPaintDevice *pdev)
         has_frag_program = qt_resolve_frag_program_extensions(ctx) && qt_resolve_version_1_3_functions(ctx);
 
     d->use_stencil_method = d->device->format().stencil()
-                            && (QGLExtensions::glExtensions & QGLExtensions::StencilWrap);
+                            && (QGLExtensions::glExtensions() & QGLExtensions::StencilWrap);
     if (d->device->format().directRendering()
-        && (d->use_stencil_method && QGLExtensions::glExtensions & QGLExtensions::StencilTwoSide))
+        && (d->use_stencil_method && QGLExtensions::glExtensions() & QGLExtensions::StencilTwoSide))
         d->has_stencil_face_ext = qt_resolve_stencil_face_extension(ctx);
 
+#ifdef Q_WS_X11
+    static bool nvidia_workaround_needs_init = true;
+    if (nvidia_workaround_needs_init) {
+        // nvidia 9x.xx unix drivers contain a bug which requires us to
+        // call glFinish before releasing an fbo to avoid painting
+        // artifacts
+        const QByteArray versionString(reinterpret_cast<const char*>(glGetString(GL_VERSION)));
+        const int pos = versionString.indexOf("NVIDIA");
+        if (pos >= 0) {
+            const float nvidiaDriverVersion = versionString.mid(pos + strlen("NVIDIA")).toFloat();
+            qt_nvidiaFboNeedsFinish = nvidiaDriverVersion >= 90.0 && nvidiaDriverVersion < 100.0;
+        }
+        nvidia_workaround_needs_init = false;
+    }
+#endif
+
 #ifndef QT_OPENGL_ES
     if (!ctx->d_ptr->internal_context) {
         glGetDoublev(GL_PROJECTION_MATRIX, &d->projection_matrix[0][0]);
@@ -1333,10 +1353,10 @@ bool QOpenGLPaintEngine::begin(QPaintDevice *pdev)
         glDisableClientState(GL_TEXTURE_COORD_ARRAY);
         glDisableClientState(GL_VERTEX_ARRAY);
 
-        if (QGLExtensions::glExtensions & QGLExtensions::SampleBuffers)
+        if (QGLExtensions::glExtensions() & QGLExtensions::SampleBuffers)
             glDisable(GL_MULTISAMPLE);
         glDisable(GL_TEXTURE_2D);
-        if (QGLExtensions::glExtensions & QGLExtensions::TextureRectangle)
+        if (QGLExtensions::glExtensions() & QGLExtensions::TextureRectangle)
             glDisable(GL_TEXTURE_RECTANGLE_NV);
         glDisable(GL_STENCIL_TEST);
         glDisable(GL_CULL_FACE);
@@ -1534,7 +1554,7 @@ void QOpenGLPaintEnginePrivate::updateGradient(const QBrush &brush, const QRectF
 #ifdef QT_OPENGL_ES
     Q_UNUSED(brush);
 #else
-    bool has_mirrored_repeat = QGLExtensions::glExtensions & QGLExtensions::MirroredRepeat;
+    bool has_mirrored_repeat = QGLExtensions::glExtensions() & QGLExtensions::MirroredRepeat;
     Qt::BrushStyle style = brush.style();
 
     QTransform m = brush.transform();
@@ -2098,7 +2118,7 @@ static inline bool needsEmulation(Qt::BrushStyle style)
 {
     return !(style == Qt::SolidPattern
              || (style == Qt::LinearGradientPattern
-                 && (QGLExtensions::glExtensions & QGLExtensions::MirroredRepeat)));
+                 && (QGLExtensions::glExtensions() & QGLExtensions::MirroredRepeat)));
 }
 
 void QOpenGLPaintEnginePrivate::updateUseEmulation()
@@ -2420,12 +2440,12 @@ void QOpenGLPaintEngine::updateRenderHints(QPainter::RenderHints hints)
             d->high_quality_antialiasing = true;
         } else {
             d->high_quality_antialiasing = false;
-            if (QGLExtensions::glExtensions & QGLExtensions::SampleBuffers)
+            if (QGLExtensions::glExtensions() & QGLExtensions::SampleBuffers)
                 glEnable(GL_MULTISAMPLE);
         }
     } else {
         d->high_quality_antialiasing = false;
-        if (QGLExtensions::glExtensions & QGLExtensions::SampleBuffers)
+        if (QGLExtensions::glExtensions() & QGLExtensions::SampleBuffers)
             glDisable(GL_MULTISAMPLE);
     }
 
@@ -2435,14 +2455,14 @@ void QOpenGLPaintEngine::updateRenderHints(QPainter::RenderHints hints)
         if (!d->offscreen.isValid()) {
             DEBUG_ONCE_STR("Unable to initialize offscreen, disabling high quality antialiasing");
             d->high_quality_antialiasing = false;
-            if (QGLExtensions::glExtensions & QGLExtensions::SampleBuffers)
+            if (QGLExtensions::glExtensions() & QGLExtensions::SampleBuffers)
                 glEnable(GL_MULTISAMPLE);
         }
     }
 
     d->has_antialiasing = d->high_quality_antialiasing
                           || ((hints & QPainter::Antialiasing)
-                              && (QGLExtensions::glExtensions & QGLExtensions::SampleBuffers));
+                              && (QGLExtensions::glExtensions() & QGLExtensions::SampleBuffers));
 }
 
 
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);