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, 58 insertions, 80 deletions

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