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, 45 insertions, 55 deletions

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