For simple paint, clip by above windows. A missing todo is to still

update only changed areas instead of doing full glXSwapBuffers()
when possible.


svn path=/branches/work/kwin_composite/; revision=595357

COMPOSITE_TODO

@@ -73,7 +73,8 @@ TODO:
 / design framework for graphical effects
     - modelling it after compiz seems to make a lot of sense
 
-* make paintSimpleScreen() clip non-visible parts
-    - clip parts of lower windows by parts of windows above them, so that those parts
-        don't need to be painted
-    - similarly like in scene_xrender.cpp
+* update only those parts of the screen that have been changed
+    - for paintSimpleScreen() - it currently sets region to the whole screen
+    - instead of using glXSwapBuffers() or XCopyArea() that update the whole screen,
+        there should be glCopyPixels() used
+    - compiz has such code in evenLoop() in the if() block for COMP_SCREEN_DAMAGE_REGION_MASK

scene_opengl.cpp

@@ -267,7 +267,7 @@ void SceneOpenGL::paint( QRegion damage, ToplevelList windows )
     glClear( GL_COLOR_BUFFER_BIT );
     glScalef( 1, -1, 1 );
     glTranslatef( 0, -displayHeight(), 0 );
-    if( /*generic case*/true )
+    if( /*generic case*/false )
         paintGenericScreen( windows );
     else
         paintSimpleScreen( damage, windows );
@@ -285,7 +285,7 @@ void SceneOpenGL::paint( QRegion damage, ToplevelList windows )
     checkGLError( "PostPaint" );
     }
     
-// the generic drawing code that should eventually handle even
+// the generic painting code that should eventually handle even
 // transformations
 void SceneOpenGL::paintGenericScreen( ToplevelList windows )
     {
@@ -301,15 +301,18 @@ void SceneOpenGL::paintGenericScreen( ToplevelList windows )
             glEnable( GL_BLEND );
             glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
             }
-        w.draw();
+        w.paint( infiniteRegion());
         glDisable( GL_BLEND );
         }
     }
 
 // the optimized case without any transformations at all
-void SceneOpenGL::paintSimpleScreen( QRegion, ToplevelList windows )
+void SceneOpenGL::paintSimpleScreen( QRegion damage, ToplevelList windows )
     {
-    QList< Window* > phase2;
+    QList< Phase2Data > phase2;
+    QRegion region = damage;
+    // TODO repaint only damaged areas (means also don't do glXSwapBuffers and similar)
+    region = QRegion( 0, 0, displayWidth(), displayHeight());
     for( int i = windows.count() - 1; // top to bottom
          i >= 0;
          --i )
@@ -319,25 +322,35 @@ void SceneOpenGL::paintSimpleScreen( QRegion, ToplevelList windows )
         Window& w = this->windows[ c ];
         if( !w.isVisible())
             continue;
+        if( region.isEmpty()) // completely clipped
+            continue;
         if( !w.isOpaque())
             {
-            phase2.prepend( &w );
+            phase2.prepend( Phase2Data( &w, region ));
             continue;
             }
         w.bindTexture();
-        w.draw();
+        w.paint( region );
+        // window is opaque, clip windows below
+        region -= w.shape().translated( w.x(), w.y());
         }
-    foreach( Window* w2, phase2 )
+    paintBackground( region );
+    foreach( Phase2Data d, phase2 )
         {
-        Window& w = *w2;
+        Window& w = *d.window;
         w.bindTexture();
         glEnable( GL_BLEND );
         glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
-        w.draw();
+        w.paint( d.region );
         glDisable( GL_BLEND );
         }
     }
 
+void SceneOpenGL::paintBackground( QRegion )
+    {
+// TODO?
+    }
+
 void SceneOpenGL::windowAdded( Toplevel* c )
     {
     assert( !windows.contains( c ));
@@ -562,7 +575,7 @@ QRegion SceneOpenGL::Window::shape() const
     return shape_region;
     }
 
-static void quadDraw( int x1, int y1, int x2, int y2, bool invert_y )
+static void quadPaint( int x1, int y1, int x2, int y2, bool invert_y )
     {
     glTexCoord2i( x1, invert_y ? y2 : y1 );
     glVertex2i( x1, y1 );
@@ -574,8 +587,14 @@ static void quadDraw( int x1, int y1, int x2, int y2, bool invert_y )
     glVertex2i( x1, y2 );
     }
 
-void SceneOpenGL::Window::draw()
+void SceneOpenGL::Window::paint( QRegion region )
     {
+    // paint only requested areas
+    if( region != infiniteRegion()) // avoid integer overflow
+        region.translate( -x(), -y());
+    region &= shape();
+    if( region.isEmpty())
+        return;
 // TODO for double-buffered root            glDrawBuffer( GL_BACK );
     glXMakeContextCurrent( display(), glxroot, glxroot, context );
     glPushMatrix();
@@ -602,9 +621,9 @@ void SceneOpenGL::Window::draw()
         }
     glEnable( GL_TEXTURE_RECTANGLE_ARB );
     glBegin( GL_QUADS );
-    foreach( QRect r, shape().rects())
+    foreach( QRect r, region.rects())
         {
-        quadDraw( r.x(), r.y(), r.x() + r.width(), r.y() + r.height(),
+        quadPaint( r.x(), r.y(), r.x() + r.width(), r.y() + r.height(),
             texture_y_inverted );
         }
     glEnd();

scene_opengl.h

@@ -36,6 +36,8 @@ class SceneOpenGL
         bool findConfig( const int* attrs, GLXFBConfig& config, VisualID visual = None );
         void paintGenericScreen( ToplevelList windows );
         void paintSimpleScreen( QRegion damage, ToplevelList windows );
+        void paintBackground( QRegion damage );
+        static QRegion infiniteRegion();
         typedef GLuint Texture;
         GC gcroot;
         Drawable buffer;
@@ -47,6 +49,12 @@ class SceneOpenGL
         static bool tfp_mode;
         class Window;
         QMap< Toplevel*, Window > windows;
+        struct Phase2Data
+            {
+            Phase2Data( Window* w, QRegion r ) : window( w ), region( r ) {}
+            Window* window;
+            QRegion region;
+            };
     };
 
 class SceneOpenGL::Window
@@ -59,7 +67,7 @@ class SceneOpenGL::Window
         int y() const;
         int width() const;
         int height() const;
-        void draw();
+        void paint( QRegion region );
         bool isVisible() const;
         bool isOpaque() const;
         void bindTexture();
@@ -77,6 +85,12 @@ class SceneOpenGL::Window
         mutable bool shape_valid;
     };
 
+inline
+QRegion SceneOpenGL::infiniteRegion()
+    { // INT_MIN / 2 because it's width/height (INT_MIN+INT_MAX==-1)
+    return QRegion( INT_MIN / 2, INT_MIN / 2, INT_MAX, INT_MAX );
+    }
+
 inline
 int SceneOpenGL::Window::x() const
     {