Sync to vblank, patch by Philip Falkner.

svn path=/branches/work/kwin_composite/; revision=606795

COMPOSITE_TODO

@@ -96,10 +96,9 @@ OpenGL TODO
       one for the root window (or for the window used in the XComposite overlay)
       and the best one for every depth of drawables
 
-+ sync to vblank
+/ sync to vblank
     - currently the compositing code is run with 20ms timer, i.e. constant 50fps
     - the GLX_SGI_video_sync extension should be used
-    - compiz uses this, no idea about it though
 
 + GL_ARB_texture_rectangle vs GL_ARB_texture_non_power_of_two
     - code currently uses GL_ARB_texture_rectangle (GL_TEXTURE_RECTANGLE_ARB), using

glutils.cpp

@@ -33,6 +33,9 @@ glXBindTexImageEXT_func glXBindTexImageEXT;
 glActiveTexture_func glActiveTexture;
 // glXCopySubBufferMESA
 glXCopySubBuffer_func glXCopySubBuffer;
+// video_sync extension functions
+glXGetVideoSync_func glXGetVideoSync;
+glXWaitVideoSync_func glXWaitVideoSync;
 
 
 // Functions
@@ -74,6 +77,16 @@ void initGLX()
         glXCopySubBuffer = (glXCopySubBuffer_func) getProcAddress( "glXCopySubBufferMESA" );
     else
         glXCopySubBuffer = NULL;
+    if( hasGLExtension( "GLX_SGI_video_sync" ))
+        {
+        glXGetVideoSync = (glXGetVideoSync_func) getProcAddress( "glXGetVideoSyncSGI" );
+        glXWaitVideoSync = (glXWaitVideoSync_func) getProcAddress( "glXWaitVideoSyncSGI" );
+        }
+    else
+        {
+        glXGetVideoSync = NULL;
+        glXWaitVideoSync = NULL;
+        }
     }
 
 void initGL()

glutils.h

@@ -85,6 +85,11 @@ extern glActiveTexture_func glActiveTexture;
 // glXCopySubBufferMESA
 typedef void (*glXCopySubBuffer_func) ( Display* , GLXDrawable, int, int, int, int );
 extern glXCopySubBuffer_func glXCopySubBuffer;
+// video_sync extension functions
+typedef void (*glXGetVideoSync_func)( unsigned int *count );
+typedef void (*glXWaitVideoSync_func)( int divisor, int remainder, unsigned int *count );
+extern glXGetVideoSync_func glXGetVideoSync;
+extern glXWaitVideoSync_func glXWaitVideoSync;
 
 } // namespace
 

options.cpp

@@ -203,6 +203,7 @@ unsigned long Options::updateSettings()
         glMode = GLFallback;
     glAlwaysRebind = config->readEntry("GLAlwaysRebind", false );
     glDirect = config->readEntry("GLDirect", true );
+    glVSync = config->readEntry("GLVSync", true );
     
     config->setGroup( "EffectShowFps" );
     effectShowFpsAlpha = config->readEntry( "Alpha", 0.5 );

options.h

@@ -304,6 +304,7 @@ class Options : public KDecorationOptions
         GLMode glMode;
         bool glAlwaysRebind;
         bool glDirect;
+        bool glVSync;
 
         double effectShowFpsAlpha;
         int effectShowFpsX;

scene_opengl.cpp

@@ -450,6 +450,22 @@ void SceneOpenGL::paint( QRegion damage, ToplevelList toplevels )
     ungrabXServer();
     }
 
+// wait for vblank signal before painting
+void SceneOpenGL::waitSync()
+    { // NOTE that vsync has no effect with indirect rendering
+    bool vsync = options->glVSync;
+    unsigned int sync;
+
+    if( !vsync )
+        return;
+    if( glXGetVideoSync )
+        {
+        glFlush();
+        glXGetVideoSync( &sync );
+        glXWaitVideoSync( 2, ( sync + 1 ) % 2, &sync );
+        }
+    }
+
 // actually paint to the screen (double-buffer swap or copy from pixmap buffer)
 void SceneOpenGL::flushBuffer( int mask, const QRegion& damage )
     {
@@ -457,6 +473,7 @@ void SceneOpenGL::flushBuffer( int mask, const QRegion& damage )
         {
         if( mask & PAINT_SCREEN_REGION )
             {
+            waitSync();
             if( glXCopySubBuffer )
                 {
                 foreach( QRect r, damage.rects())
@@ -483,7 +500,10 @@ void SceneOpenGL::flushBuffer( int mask, const QRegion& damage )
                 }
             }
         else
+            {
+            waitSync();
             glXSwapBuffers( display(), glxbuffer );
+            }
         glXWaitGL();
         XFlush( display());
         }
@@ -491,6 +511,7 @@ void SceneOpenGL::flushBuffer( int mask, const QRegion& damage )
         {
         glFlush();
         glXWaitGL();
+        waitSync();
         if( mask & PAINT_SCREEN_REGION )
             foreach( QRect r, damage.rects())
                 XCopyArea( display(), buffer, rootWindow(), gcroot, r.x(), r.y(), r.width(), r.height(), r.x(), r.y());

scene_opengl.h

@@ -44,6 +44,7 @@ class SceneOpenGL
         void initBuffer();
         void initRenderingContext();
         bool findConfig( const int* attrs, GLXFBConfig* config, VisualID visual = None );
+        void waitSync();
         void flushBuffer( int mask, const QRegion& damage );
         typedef GLuint Texture;
         GC gcroot;