Use glXGetProcAddress to resolve glx extensions

On systems where the GL driver is pluggable (like Mesa), we have to use
the glXGetProcAddressARB extension to resolve other function pointers as
the symbols wont be in the GL library, but rather in a plugin loaded by
the GL library.

This fix basically makes texture-from-pixmap work on Mesa drivers like
intel i915 & friends.

Reviewed-by: Trond

2 files changed, 68 insertions, 57 deletions

diff --git a/src/opengl/qgl_x11.cpp b/src/opengl/qgl_x11.cpp
index da7972d..86e593d 100644
--- a/src/opengl/qgl_x11.cpp
+++ b/src/opengl/qgl_x11.cpp
@@ -331,6 +331,62 @@ static void find_trans_colors()
   QGLFormat UNIX/GLX-specific code
  *****************************************************************************/
 
+void* qglx_getProcAddress(const char* procName)
+{
+    // On systems where the GL driver is pluggable (like Mesa), we have to use
+    // the glXGetProcAddressARB extension to resolve other function pointers as
+    // the symbols wont be in the GL library, but rather in a plugin loaded by
+    // the GL library.
+    typedef void* (*qt_glXGetProcAddressARB)(const char *);
+    static qt_glXGetProcAddressARB glXGetProcAddressARB = 0;
+    static bool triedResolvingGlxGetProcAddress = false;
+    if (!triedResolvingGlxGetProcAddress) {
+        triedResolvingGlxGetProcAddress = true;
+        QString glxExt = QLatin1String(glXGetClientString(QX11Info::display(), GLX_EXTENSIONS));
+        if (glxExt.contains(QLatin1String("GLX_ARB_get_proc_address"))) {
+#if defined(Q_OS_LINUX) || defined(Q_OS_BSD4)
+            void *handle = dlopen(NULL, RTLD_LAZY);
+            if (handle) {
+                glXGetProcAddressARB = (qt_glXGetProcAddressARB) dlsym(handle, "glXGetProcAddressARB");
+                dlclose(handle);
+            }
+            if (!glXGetProcAddressARB)
+#endif
+            {
+#if !defined(QT_NO_LIBRARY)
+                extern const QString qt_gl_library_name();
+                QLibrary lib(qt_gl_library_name());
+                glXGetProcAddressARB = (qt_glXGetProcAddressARB) lib.resolve("glXGetProcAddressARB");
+#endif
+            }
+        }
+    }
+
+    void *procAddress = 0;
+    if (glXGetProcAddressARB)
+        procAddress = glXGetProcAddressARB(procName);
+
+    // If glXGetProcAddress didn't work, try looking the symbol up in the GL library
+#if defined(Q_OS_LINUX) || defined(Q_OS_BSD4)
+    if (!procAddress) {
+        void *handle = dlopen(NULL, RTLD_LAZY);
+        if (handle) {
+            procAddress = dlsym(handle, procName);
+            dlclose(handle);
+        }
+    }
+#endif
+#if !defined(QT_NO_LIBRARY)
+    if (!procAddress) {
+        extern const QString qt_gl_library_name();
+        QLibrary lib(qt_gl_library_name());
+        procAddress = lib.resolve(procName);
+    }
+#endif
+
+    return procAddress;
+}
+
 bool QGLFormat::hasOpenGL()
 {
     return glXQueryExtension(X11->display, 0, 0) != 0;
@@ -819,23 +875,8 @@ void QGLContext::swapBuffers() const
             if (!resolved) {
                 QString glxExt = QLatin1String(glXGetClientString(QX11Info::display(), GLX_EXTENSIONS));
                 if (glxExt.contains(QLatin1String("GLX_SGI_video_sync"))) {
-#if defined(Q_OS_LINUX) || defined(Q_OS_BSD4)
-                    void *handle = dlopen(NULL, RTLD_LAZY);
-                    if (handle) {
-                        glXGetVideoSyncSGI = (qt_glXGetVideoSyncSGI) dlsym(handle, "glXGetVideoSyncSGI");
-                        glXWaitVideoSyncSGI = (qt_glXWaitVideoSyncSGI) dlsym(handle, "glXWaitVideoSyncSGI");
-                        dlclose(handle);
-                    }
-                    if (!glXGetVideoSyncSGI)
-#endif
-                    {
-#if !defined(QT_NO_LIBRARY)
-                        extern const QString qt_gl_library_name();
-                        QLibrary lib(qt_gl_library_name());
-                        glXGetVideoSyncSGI = (qt_glXGetVideoSyncSGI) lib.resolve("glXGetVideoSyncSGI");
-                        glXWaitVideoSyncSGI = (qt_glXWaitVideoSyncSGI) lib.resolve("glXWaitVideoSyncSGI");
-#endif
-                    }
+                    glXGetVideoSyncSGI =  (qt_glXGetVideoSyncSGI)qglx_getProcAddress("glXGetVideoSyncSGI");
+                    glXWaitVideoSyncSGI = (qt_glXWaitVideoSyncSGI)qglx_getProcAddress("glXWaitVideoSyncSGI");
                 }
                 resolved = true;
             }
@@ -1568,21 +1609,8 @@ bool qt_resolveTextureFromPixmap()
 
         QString glxExt = QLatin1String(glXGetClientString(QX11Info::display(), GLX_EXTENSIONS));
         if (glxExt.contains(QLatin1String("GLX_EXT_texture_from_pixmap"))) {
-#if defined(Q_OS_LINUX) || defined(Q_OS_BSD4)
-            void *handle = dlopen(NULL, RTLD_LAZY);
-            if (handle) {
-                glXBindTexImageEXT = (qt_glXBindTexImageEXT) dlsym(handle, "glXBindTexImageEXT");
-                glXReleaseTexImageEXT = (qt_glXReleaseTexImageEXT) dlsym(handle, "glXReleaseTexImageEXT");
-                dlclose(handle);
-            }
-            if (!glXBindTexImageEXT)
-#endif
-            {
-                extern const QString qt_gl_library_name();
-                QLibrary lib(qt_gl_library_name());
-                glXBindTexImageEXT = (qt_glXBindTexImageEXT) lib.resolve("glXBindTexImageEXT");
-                glXReleaseTexImageEXT = (qt_glXReleaseTexImageEXT) lib.resolve("glXReleaseTexImageEXT");
-            }
+            glXBindTexImageEXT = (qt_glXBindTexImageEXT) qglx_getProcAddress("glXBindTexImageEXT");
+            glXReleaseTexImageEXT = (qt_glXReleaseTexImageEXT) qglx_getProcAddress("glXReleaseTexImageEXT");
         }
     }
 
diff --git a/src/opengl/qglpixelbuffer_x11.cpp b/src/opengl/qglpixelbuffer_x11.cpp
index 793471d..6971133 100644
--- a/src/opengl/qglpixelbuffer_x11.cpp
+++ b/src/opengl/qglpixelbuffer_x11.cpp
@@ -93,6 +93,8 @@ static _glXMakeContextCurrent qt_glXMakeContextCurrent = 0;
 #define glXGetFBConfigAttrib qt_glXGetFBConfigAttrib
 #define glXMakeContextCurrent qt_glXMakeContextCurrent
 
+extern void* qglx_getProcAddress(const char* procName); // in qgl_x11.cpp
+
 static bool qt_resolve_pbuffer_extensions()
 {
     static int resolved = false;
@@ -101,31 +103,12 @@ static bool qt_resolve_pbuffer_extensions()
     else if (resolved)
         return false;
 
-#if defined(Q_OS_LINUX) || defined(Q_OS_BSD4)
-    void *handle = dlopen(NULL, RTLD_LAZY);
-    if (handle) {
-        qt_glXChooseFBConfig = (_glXChooseFBConfig) dlsym(handle, "glXChooseFBConfig");
-        qt_glXCreateNewContext = (_glXCreateNewContext) dlsym(handle, "glXCreateNewContext");
-        qt_glXCreatePbuffer = (_glXCreatePbuffer) dlsym(handle, "glXCreatePbuffer");
-        qt_glXDestroyPbuffer = (_glXDestroyPbuffer) dlsym(handle, "glXDestroyPbuffer");
-        qt_glXGetFBConfigAttrib = (_glXGetFBConfigAttrib) dlsym(handle, "glXGetFBConfigAttrib");
-        qt_glXMakeContextCurrent = (_glXMakeContextCurrent) dlsym(handle, "glXMakeContextCurrent");
-        dlclose(handle);
-    }
-    if (!qt_glXChooseFBConfig)
-#endif
-    {
-#if !defined(QT_NO_LIBRARY)
-        extern const QString qt_gl_library_name();
-        QLibrary gl(qt_gl_library_name());
-        qt_glXChooseFBConfig = (_glXChooseFBConfig) gl.resolve("glXChooseFBConfig");
-        qt_glXCreateNewContext = (_glXCreateNewContext) gl.resolve("glXCreateNewContext");
-        qt_glXCreatePbuffer = (_glXCreatePbuffer) gl.resolve("glXCreatePbuffer");
-        qt_glXDestroyPbuffer = (_glXDestroyPbuffer) gl.resolve("glXDestroyPbuffer");
-        qt_glXGetFBConfigAttrib = (_glXGetFBConfigAttrib) gl.resolve("glXGetFBConfigAttrib");
-        qt_glXMakeContextCurrent = (_glXMakeContextCurrent) gl.resolve("glXMakeContextCurrent");
-#endif
-    }
+    qt_glXChooseFBConfig = (_glXChooseFBConfig) qglx_getProcAddress("glXChooseFBConfig");
+    qt_glXCreateNewContext = (_glXCreateNewContext) qglx_getProcAddress("glXCreateNewContext");
+    qt_glXCreatePbuffer = (_glXCreatePbuffer) qglx_getProcAddress("glXCreatePbuffer");
+    qt_glXDestroyPbuffer = (_glXDestroyPbuffer) qglx_getProcAddress("glXDestroyPbuffer");
+    qt_glXGetFBConfigAttrib = (_glXGetFBConfigAttrib) qglx_getProcAddress("glXGetFBConfigAttrib");
+    qt_glXMakeContextCurrent = (_glXMakeContextCurrent) qglx_getProcAddress("glXMakeContextCurrent");
 
     resolved = qt_glXMakeContextCurrent ? true : false;
     return resolved;