diff --git a/effects/coverswitch.cpp b/effects/coverswitch.cpp
index a4643f6b72..562445107b 100644
--- a/effects/coverswitch.cpp
+++ b/effects/coverswitch.cpp
@@ -261,7 +261,7 @@ void CoverSwitchEffect::paintScreen( int mask, QRegion region, ScreenPaintData&
             frameRect.y() + frameRect.height()*0.1f,
             frameRect.height()*0.8f,
             frameRect.height()*0.8f );
-        icon->render( false, region, iconRect);
+        icon->render( region, iconRect);
         icon->unbind();
         glDisable( GL_BLEND );
         glPopAttrib();
diff --git a/effects/desktopgrid.cpp b/effects/desktopgrid.cpp
index 8bddc442c0..8bb5b99e9e 100644
--- a/effects/desktopgrid.cpp
+++ b/effects/desktopgrid.cpp
@@ -146,11 +146,19 @@ void DesktopGridEffect::paintScreen( int mask, QRegion region, ScreenPaintData&
          ++desktop )
         {
         if( desktop != desktop_with_move )
+            {
+            PaintClipper pc( desktopRect( desktop, true ));
             paintScreenDesktop( desktop, mask, region, data );
+            }
         }
     // paint the desktop with the window being moved as the last one, i.e. on top of others
     if( desktop_with_move != -1 )
+        {
+        QRegion paintreg = desktopRect( desktop_with_move, true ); // paint only the desktop
+        paintreg |= windowRect( window_move ); // and wherever the moved window is
+        PaintClipper pc( paintreg );
         paintScreenDesktop( desktop_with_move, mask, region, data );
+        }
     }
 
 void DesktopGridEffect::paintScreenDesktop( int desktop, int mask, QRegion region, ScreenPaintData data )
diff --git a/effects/flipswitch.cpp b/effects/flipswitch.cpp
index 3664323a6d..b94ce44385 100644
--- a/effects/flipswitch.cpp
+++ b/effects/flipswitch.cpp
@@ -363,7 +363,7 @@ void FlipSwitchEffect::paintScreen( int mask, QRegion region, ScreenPaintData& d
             frameRect.y() + frameRect.height()*0.1f,
             frameRect.height()*0.8f,
             frameRect.height()*0.8f );
-        icon->render( false, region, iconRect);
+        icon->render( region, iconRect);
         icon->unbind();
         glPopAttrib();
 #endif
diff --git a/effects/magnifier.cpp b/effects/magnifier.cpp
index 0b91dd5a88..430a1e6b46 100644
--- a/effects/magnifier.cpp
+++ b/effects/magnifier.cpp
@@ -81,13 +81,8 @@ void MagnifierEffect::paintScreen( int mask, QRegion region, ScreenPaintData& da
     effects->paintScreen( mask, region, data ); // paint normal screen
     if( zoom != 1.0 )
         { // paint magnifier
-// ## TODO this should be inside KWIN_HAVE_OPENGL_COMPOSITING
-        glPushAttrib( GL_ENABLE_BIT );
         QRect area = magnifierArea();
-        glEnable( GL_SCISSOR_TEST );
-        int dh = displayHeight();
-        // Scissor rect has to be given in OpenGL coords
-        glScissor( area.x(), dh - area.y() - area.height(), area.width(), area.height());
+        PaintClipper::push( area ); // don't allow any painting outside of the area
         mask |= PAINT_SCREEN_TRANSFORMED;
         data2.xScale *= zoom;
         data2.yScale *= zoom;
@@ -96,27 +91,33 @@ void MagnifierEffect::paintScreen( int mask, QRegion region, ScreenPaintData& da
         data2.xTranslate = - int( cursor.x() * ( zoom - 1 ));
         data2.yTranslate = - int( cursor.y() * ( zoom - 1 ));
         effects->paintScreen( mask, region, data2 );
-        glPopAttrib();
+        PaintClipper::pop( area );
+// ## TODO this should be inside KWIN_HAVE_OPENGL_COMPOSITING
         glPushAttrib( GL_CURRENT_BIT );
         glColor4f( 0, 0, 0, 1 ); // black
-        glBegin( GL_QUADS );
-        glVertex2i( area.left() - FRAME_WIDTH, area.top() - FRAME_WIDTH ); // top frame
-        glVertex2i( area.right() + FRAME_WIDTH, area.top() - FRAME_WIDTH );
-        glVertex2i( area.right() + FRAME_WIDTH, area.top() - 1 );
-        glVertex2i( area.left() - FRAME_WIDTH, area.top() - 1 );
-        glVertex2i( area.left() - FRAME_WIDTH, area.top() - FRAME_WIDTH ); // left frame
-        glVertex2i( area.left() - 1, area.top() - FRAME_WIDTH );
-        glVertex2i( area.left() - 1, area.bottom() + FRAME_WIDTH );
-        glVertex2i( area.left() - FRAME_WIDTH, area.bottom() + FRAME_WIDTH );
-        glVertex2i( area.right() + 1, area.top() - FRAME_WIDTH ); // right frame
-        glVertex2i( area.right() + FRAME_WIDTH, area.top() - FRAME_WIDTH );
-        glVertex2i( area.right() + FRAME_WIDTH, area.bottom() + FRAME_WIDTH );
-        glVertex2i( area.right() + 1, area.bottom() + FRAME_WIDTH );
-        glVertex2i( area.left() - FRAME_WIDTH, area.bottom() + 1 ); // bottom frame
-        glVertex2i( area.right() + FRAME_WIDTH, area.bottom() + 1 );
-        glVertex2i( area.right() + FRAME_WIDTH, area.bottom() + FRAME_WIDTH );
-        glVertex2i( area.left() - FRAME_WIDTH, area.bottom() + FRAME_WIDTH );
-        glEnd();
+        for( PaintClipper::Iterator iterator;
+             !iterator.isDone();
+             iterator.next())
+            {
+            glBegin( GL_QUADS );
+            glVertex2i( area.left() - FRAME_WIDTH, area.top() - FRAME_WIDTH ); // top frame
+            glVertex2i( area.right() + FRAME_WIDTH, area.top() - FRAME_WIDTH );
+            glVertex2i( area.right() + FRAME_WIDTH, area.top() - 1 );
+            glVertex2i( area.left() - FRAME_WIDTH, area.top() - 1 );
+            glVertex2i( area.left() - FRAME_WIDTH, area.top() - FRAME_WIDTH ); // left frame
+            glVertex2i( area.left() - 1, area.top() - FRAME_WIDTH );
+            glVertex2i( area.left() - 1, area.bottom() + FRAME_WIDTH );
+            glVertex2i( area.left() - FRAME_WIDTH, area.bottom() + FRAME_WIDTH );
+            glVertex2i( area.right() + 1, area.top() - FRAME_WIDTH ); // right frame
+            glVertex2i( area.right() + FRAME_WIDTH, area.top() - FRAME_WIDTH );
+            glVertex2i( area.right() + FRAME_WIDTH, area.bottom() + FRAME_WIDTH );
+            glVertex2i( area.right() + 1, area.bottom() + FRAME_WIDTH );
+            glVertex2i( area.left() - FRAME_WIDTH, area.bottom() + 1 ); // bottom frame
+            glVertex2i( area.right() + FRAME_WIDTH, area.bottom() + 1 );
+            glVertex2i( area.right() + FRAME_WIDTH, area.bottom() + FRAME_WIDTH );
+            glVertex2i( area.left() - FRAME_WIDTH, area.bottom() + FRAME_WIDTH );
+            glEnd();
+            }
         glPopAttrib();
         }
     }
diff --git a/effects/presentwindows.cpp b/effects/presentwindows.cpp
index 3665d1b361..6412f3f72b 100644
--- a/effects/presentwindows.cpp
+++ b/effects/presentwindows.cpp
@@ -149,7 +149,7 @@ void PresentWindowsEffect::paintScreen( int mask, QRegion region, ScreenPaintDat
         renderRoundBoxWithEdge( filterFrameRect );
         // And then the text on top of it
         filterTexture->bind();
-        filterTexture->render( mask, region, filterTextureRect );
+        filterTexture->render( region, filterTextureRect );
         filterTexture->unbind();
         glPopAttrib();
         }
diff --git a/effects/shadow.cpp b/effects/shadow.cpp
index be016fe431..dbac01d9c0 100644
--- a/effects/shadow.cpp
+++ b/effects/shadow.cpp
@@ -89,7 +89,7 @@ void ShadowEffect::drawWindow( EffectWindow* w, int mask, QRegion region, Window
             {
             // For translucent windows, shadow needs to be drawn before the
             //  window itself.
-            drawShadow( w, mask, region, data, false );
+            drawShadow( w, mask, region, data );
             }
         else
             {
@@ -145,7 +145,7 @@ void ShadowEffect::drawQueuedShadows( EffectWindow* behindWindow )
         //  that are behind that window.
         if( !behindWindow || stack.indexOf(d.w) < stack.indexOf(behindWindow))
             {
-            drawShadow( d.w, d.mask, d.region.subtracted( d.clip ), d.data, true );
+            drawShadow( d.w, d.mask, d.region.subtracted( d.clip ), d.data );
             }
         else
             {
@@ -155,7 +155,7 @@ void ShadowEffect::drawQueuedShadows( EffectWindow* behindWindow )
     shadowDatas = newShadowDatas;
     }
 
-void ShadowEffect::drawShadow( EffectWindow* window, int mask, QRegion region, WindowPaintData& data, bool clip )
+void ShadowEffect::drawShadow( EffectWindow* window, int mask, QRegion region, WindowPaintData& data )
     {
     glPushAttrib( GL_CURRENT_BIT | GL_ENABLE_BIT | GL_TEXTURE_BIT );
     glEnable( GL_BLEND );
@@ -219,10 +219,7 @@ void ShadowEffect::drawShadow( EffectWindow* window, int mask, QRegion region, W
     glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
     // We have two elements per vertex in the verts array
     int verticesCount = verts.count() / 2;
-    if( clip )
-        renderGLGeometry( true, region, verticesCount, verts.data(), texcoords.data() );
-    else
-        renderGLGeometry( mask, region, verticesCount, verts.data(), texcoords.data() );
+    renderGLGeometry( region, verticesCount, verts.data(), texcoords.data() );
     mShadowTexture->unbind();
 
     glPopMatrix();
diff --git a/effects/shadow.h b/effects/shadow.h
index 84c63c855a..24e1b0ef9f 100644
--- a/effects/shadow.h
+++ b/effects/shadow.h
@@ -40,7 +40,7 @@ class ShadowEffect
         virtual void windowClosed( EffectWindow* c );
         virtual QRect transformWindowDamage( EffectWindow* w, const QRect& r );
     private:
-        void drawShadow( EffectWindow* w, int mask, QRegion region, WindowPaintData& data, bool clip );
+        void drawShadow( EffectWindow* w, int mask, QRegion region, WindowPaintData& data );
         void addQuadVertices(QVector<float>& verts, float x1, float y1, float x2, float y2) const;
         // transforms window rect -> shadow rect
         QRect shadowRectangle(const QRect& windowRectangle) const;
diff --git a/effects/showfps.cpp b/effects/showfps.cpp
index 256c077da6..db73faf373 100644
--- a/effects/showfps.cpp
+++ b/effects/showfps.cpp
@@ -439,7 +439,7 @@ void ShowFpsEffect::paintFPSText(int fps)
         delete fpsText;
     fpsText = new GLTexture(im);
     fpsText->bind();
-    fpsText->render(false, QRegion(fpsTextRect), fpsTextRect);
+    fpsText->render(QRegion(fpsTextRect), fpsTextRect);
     fpsText->unbind();
     effects->addRepaint(fpsTextRect);
 #endif
diff --git a/effects/snow.cpp b/effects/snow.cpp
index b240dcda03..8efe401f90 100644
--- a/effects/snow.cpp
+++ b/effects/snow.cpp
@@ -142,7 +142,7 @@ void SnowEffect::paintScreen( int mask, QRegion region, ScreenPaintData& data )
             glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
             for (int i=0; i<flakes->count(); i++)
                 {
-                texture->render( false, region, flakes->at(i));
+                texture->render( region, flakes->at(i));
                 }
             texture->unbind();
             glPopAttrib();
diff --git a/effects/trackmouse.cpp b/effects/trackmouse.cpp
index 6b860b9df3..25fef5cf34 100644
--- a/effects/trackmouse.cpp
+++ b/effects/trackmouse.cpp
@@ -77,7 +77,7 @@ void TrackMouseEffect::paintScreen( int mask, QRegion region, ScreenPaintData& d
              ++i )
             {
             QRect r = starRect( i );
-            texture->render( mask, region, r );
+            texture->render( region, r );
             }
         texture->unbind();
         glPopAttrib();
diff --git a/lib/kwineffects.cpp b/lib/kwineffects.cpp
index 3f4d8e58f5..7d1d6b0632 100644
--- a/lib/kwineffects.cpp
+++ b/lib/kwineffects.cpp
@@ -677,4 +677,168 @@ bool WindowQuadList::smoothNeeded() const
     return false;
     }
 
+/***************************************************************
+ PaintClipper
+***************************************************************/
+
+QStack< QRegion >* PaintClipper::areas = NULL;
+
+PaintClipper::PaintClipper( const QRegion& allowed_area )
+    : area( allowed_area )
+    {
+    push( area );
+    }
+
+PaintClipper::~PaintClipper()
+    {
+    pop( area );
+    }
+
+void PaintClipper::push( const QRegion& allowed_area )
+    {
+    if( allowed_area == infiniteRegion()) // don't push these
+        return;
+    if( areas == NULL )
+        areas = new QStack< QRegion >;
+    areas->push( allowed_area );
+    }
+
+void PaintClipper::pop( const QRegion& allowed_area )
+    {
+    if( allowed_area == infiniteRegion())
+        return;
+    Q_ASSERT( areas != NULL );
+    Q_ASSERT( areas->top() == allowed_area );
+    areas->pop();
+    if( areas->isEmpty())
+        {
+        delete areas;
+        areas = NULL;
+        }
+    }
+
+bool PaintClipper::clip()
+    {
+    return areas != NULL;
+    }
+
+QRegion PaintClipper::paintArea()
+    {
+    QRegion ret = QRegion( 0, 0, displayWidth(), displayHeight());
+    foreach( QRegion r, *areas )
+        ret &= r;
+    return ret;
+    }
+
+struct PaintClipper::Iterator::Data
+    {
+    Data() : index( 0 ) {}
+    int index;
+#ifdef KWIN_HAVE_OPENGL_COMPOSITING
+    QVector< QRect > rects;
+#endif
+    };
+
+PaintClipper::Iterator::Iterator()
+    : data( new Data )
+    {
+#ifdef KWIN_HAVE_OPENGL_COMPOSITING
+    if( clip() && effects->compositingType() == OpenGLCompositing )
+        {
+        glPushAttrib( GL_SCISSOR_BIT );
+        glEnable( GL_SCISSOR_TEST );
+        data->rects = paintArea().rects();
+        data->index = -1;
+        next(); // move to the first one
+        }
+#endif
+#ifdef KWIN_HAVE_XRENDER_COMPOSITING
+    if( clip() && effects->compositingType() == XRenderCompositing )
+        {
+        XserverRegion region = toXserverRegion( paintArea());
+        XFixesSetPictureClipRegion( display(), effects->xrenderBufferPicture(), 0, 0, region );
+        XFixesDestroyRegion( display(), region ); // it's ref-counted
+        }
+#endif
+    }
+
+PaintClipper::Iterator::~Iterator()
+    {
+#ifdef KWIN_HAVE_OPENGL_COMPOSITING
+    if( clip() && effects->compositingType() == OpenGLCompositing )
+        glPopAttrib();
+#endif
+#ifdef KWIN_HAVE_XRENDER_COMPOSITING
+    if( clip() && effects->compositingType() == XRenderCompositing )
+        XFixesSetPictureClipRegion( display(), effects->xrenderBufferPicture(), 0, 0, None );
+#endif
+    delete data;
+    }
+
+bool PaintClipper::Iterator::isDone()
+    {
+    if( !clip())
+        return data->index == 1; // run once
+#ifdef KWIN_HAVE_OPENGL_COMPOSITING
+    if( effects->compositingType() == OpenGLCompositing )
+        return data->index >= data->rects.count(); // run once per each area
+#endif
+#ifdef KWIN_HAVE_XRENDER_COMPOSITING
+    if( effects->compositingType() == XRenderCompositing )
+        return data->index == 1; // run once
+#endif
+    assert( false );
+    }
+
+void PaintClipper::Iterator::next()
+    {
+    data->index++;
+#ifdef KWIN_HAVE_OPENGL_COMPOSITING
+    if( clip() && effects->compositingType() == OpenGLCompositing && data->index < data->rects.count())
+        {
+        const QRect& r = data->rects[ data->index ];
+        // Scissor rect has to be given in OpenGL coords
+        glScissor( r.x(), displayHeight() - r.y() - r.height(), r.width(), r.height());
+        }
+#endif
+    }
+
+QRect PaintClipper::Iterator::boundingRect() const
+    {
+    if( !clip())
+        return infiniteRegion();
+#ifdef KWIN_HAVE_OPENGL_COMPOSITING
+    if( effects->compositingType() == OpenGLCompositing )
+        return data->rects[ data->index ];
+#endif
+#ifdef KWIN_HAVE_XRENDER_COMPOSITING
+    if( effects->compositingType() == XRenderCompositing )
+        return paintArea().boundingRect();
+#endif
+    assert( false );
+    }
+
+
+// Convert QRegion to XserverRegion. All code uses XserverRegion
+// only when really necessary as the shared implementation uses
+// QRegion.
+XserverRegion toXserverRegion( QRegion region )
+    {
+    QVector< QRect > rects = region.rects();
+    XRectangle* xr = new XRectangle[ rects.count() ];
+    for( int i = 0;
+         i < rects.count();
+         ++i )
+        {
+        xr[ i ].x = rects[ i ].x();
+        xr[ i ].y = rects[ i ].y();
+        xr[ i ].width = rects[ i ].width();
+        xr[ i ].height = rects[ i ].height();
+        }
+    XserverRegion ret = XFixesCreateRegion( display(), xr, rects.count());
+    delete[] xr;
+    return ret;
+    }
+
+
 } // namespace
diff --git a/lib/kwineffects.h b/lib/kwineffects.h
index 3871591666..6b98f6511f 100644
--- a/lib/kwineffects.h
+++ b/lib/kwineffects.h
@@ -32,12 +32,17 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QtCore/QVector>
 #include <QtCore/QList>
 #include <QtCore/QHash>
+#include <QtCore/QStack>
 
 #include <KDE/KPluginFactory>
 #include <KDE/KShortcutsEditor>
 
 #include <assert.h>
+#include <limits.h>
 
+#ifdef KWIN_HAVE_XRENDER_COMPOSITING
+#include <X11/extensions/Xfixes.h>
+#endif
 
 class KLibrary;
 class KConfigGroup;
@@ -160,10 +165,26 @@ X-KDE-Library=kwin4_effect_cooleffect
 
 #define KWIN_EFFECT_API_MAKE_VERSION( major, minor ) (( major ) << 8 | ( minor ))
 #define KWIN_EFFECT_API_VERSION_MAJOR 0
-#define KWIN_EFFECT_API_VERSION_MINOR 6
+#define KWIN_EFFECT_API_VERSION_MINOR 7
 #define KWIN_EFFECT_API_VERSION KWIN_EFFECT_API_MAKE_VERSION( \
     KWIN_EFFECT_API_VERSION_MAJOR, KWIN_EFFECT_API_VERSION_MINOR )
 
+/**
+ * Infinite region (i.e. a special region type saying that everything needs to be painted).
+ */
+KWIN_EXPORT inline
+QRect infiniteRegion()
+    { // INT_MIN / 2 because width/height is used (INT_MIN+INT_MAX==-1)
+    return QRect( INT_MIN / 2, INT_MIN / 2, INT_MAX, INT_MAX );
+    }
+
+#ifdef KWIN_HAVE_XRENDER_COMPOSITING
+/**
+ * Convert QRegion to XserverRegion.
+ */
+KWIN_EXPORT XserverRegion toXserverRegion( QRegion region );
+#endif
+
 /**
  * @short Base class for all KWin effects
  *
@@ -822,6 +843,71 @@ class KWIN_EXPORT ScreenPrePaintData
         QRegion paint;
     };
 
+/**
+ * @short Helper class for restricting painting area only to allowed area.
+ *
+ * This helper class helps specifying areas that should be painted, clipping
+ * out the rest. The simplest usage is creating an object on the stack
+ * and giving it the area that is allowed to be painted to. When the object
+ * is destroyed, the restriction will be removed.
+ * Note that all painting code must use paintArea() to actually perform the clipping.
+ */
+class KWIN_EXPORT PaintClipper
+    {
+    public:
+        /**
+         * Calls push().
+         */
+        PaintClipper( const QRegion& allowed_area );
+        /**
+         * Calls pop().
+         */
+        ~PaintClipper();
+        /**
+         * Allows painting only in the given area. When areas have been already
+         * specified, painting is allowed only in the intersection of all areas.
+         */
+        static void push( const QRegion& allowed_area );
+        /**
+         * Removes the given area. It must match the top item in the stack.
+         */
+        static void pop( const QRegion& allowed_area );
+        /**
+         * Returns true if any clipping should be performed.
+         */
+        static bool clip();
+        /**
+         * If clip() returns true, this function gives the resulting area in which
+         * painting is allowed. It is usually simpler to use the helper Iterator class.
+         */
+        static QRegion paintArea();
+        /**
+         * Helper class to perform the clipped painting. The usage is:
+         * @code
+         * for( PaintClipper::Iterator iterator;
+         *      !iterator.isDone();
+         *      iterator.next())
+         *     { // do the painting, possibly use iterator.boundingRect()
+         *     }
+         * @endcode
+         */
+        class Iterator
+            {
+            public:
+                Iterator();
+                ~Iterator();
+                bool isDone();
+                void next();
+                QRect boundingRect() const;
+            private:
+                struct Data;
+                Data* data;
+            };
+    private:
+        QRegion area;
+        static QStack< QRegion >* areas;
+    };
+
 /**
  * Pointer to the global EffectsHandler object.
  **/
diff --git a/lib/kwinglutils.cpp b/lib/kwinglutils.cpp
index afc4a9d491..0d047ce4fb 100644
--- a/lib/kwinglutils.cpp
+++ b/lib/kwinglutils.cpp
@@ -128,18 +128,10 @@ int nearestPowerOfTwo( int x )
 void renderGLGeometry( int count, const float* vertices, const float* texture, const float* color,
     int dim, int stride )
     {
-    return renderGLGeometry( false, QRegion(), count, vertices, texture, color, dim, stride );
+    return renderGLGeometry( infiniteRegion(), count, vertices, texture, color, dim, stride );
     }
 
-void renderGLGeometry( int mask, const QRegion& region, int count,
-    const float* vertices, const float* texture, const float* color,
-    int dim, int stride )
-    {
-    return renderGLGeometry( !( mask & ( Effect::PAINT_WINDOW_TRANSFORMED | Effect::PAINT_SCREEN_TRANSFORMED )),
-        region, count, vertices, texture, color, dim, stride );
-    }
-
-void renderGLGeometry( bool clip, const QRegion& region, int count,
+void renderGLGeometry( const QRegion& region, int count,
     const float* vertices, const float* texture, const float* color,
     int dim, int stride )
     {
@@ -166,40 +158,17 @@ void renderGLGeometry( bool clip, const QRegion& region, int count,
             }
         }
 
-    // Render
-    if( !clip )
+    // Clip using scissoring
+    PaintClipper pc( region );
+    for( PaintClipper::Iterator iterator;
+         !iterator.isDone();
+         iterator.next())
         {
-        // Just draw the entire window, no clipping
         if( use_arrays )
             glDrawArrays( GL_QUADS, 0, count );
         else
             renderGLGeometryImmediate( count, vertices, texture, color, dim, stride );
         }
-    else
-        {
-        // Make sure there's only a single quad (no transformed vertices)
-        // Clip using scissoring
-        glEnable( GL_SCISSOR_TEST );
-        int dh = displayHeight();
-        if( use_arrays )
-            {
-            foreach( QRect r, region.rects())
-                {
-                // Scissor rect has to be given in OpenGL coords
-                glScissor(r.x(), dh - r.y() - r.height(), r.width(), r.height());
-                glDrawArrays( GL_QUADS, 0, count );
-                }
-            }
-        else
-            {
-            foreach( QRect r, region.rects())
-                {
-                // Scissor rect has to be given in OpenGL coords
-                glScissor(r.x(), dh - r.y() - r.height(), r.width(), r.height());
-                renderGLGeometryImmediate( count, vertices, texture, color, dim, stride );
-                }
-            }
-        }
 
     if( use_arrays )
         {
@@ -500,13 +469,7 @@ void GLTexture::unbind()
     glDisable( mTarget );
     }
 
-void GLTexture::render( int mask, QRegion region, const QRect& rect )
-    {
-    return render( !( mask & ( Effect::PAINT_WINDOW_TRANSFORMED | Effect::PAINT_SCREEN_TRANSFORMED )),
-        region, rect );
-    }
-
-void GLTexture::render( bool clip, QRegion region, const QRect& rect )
+void GLTexture::render( QRegion region, const QRect& rect )
     {
     const float verts[ 4 * 2 ] =
         {
@@ -522,7 +485,7 @@ void GLTexture::render( bool clip, QRegion region, const QRect& rect )
         1, 0,
         1, 1
         };
-    renderGLGeometry( clip, region, 4, verts, texcoords );
+    renderGLGeometry( region, 4, verts, texcoords );
     }
 
 void GLTexture::enableUnnormalizedTexCoords()
diff --git a/lib/kwinglutils.h b/lib/kwinglutils.h
index 0ffc53ec6d..96ed9037c7 100644
--- a/lib/kwinglutils.h
+++ b/lib/kwinglutils.h
@@ -82,22 +82,17 @@ int KWIN_EXPORT nearestPowerOfTwo( int x );
  * @param stride byte offset of consecutive elements in arrays. If 0, then
  *  arrays must be tighly packed. Stride must be a multiple of sizeof(float)!
  **/
-KWIN_EXPORT void renderGLGeometry( bool clip, const QRegion& region, int count,
+KWIN_EXPORT void renderGLGeometry( const QRegion& region, int count,
     const float* vertices, const float* texture = 0, const float* color = 0,
     int dim = 2, int stride = 0 );
 /**
- * Same as above, sets clip parameter according to mask.
- **/
-KWIN_EXPORT void renderGLGeometry( int mask, const QRegion& region, int count,
-    const float* vertices, const float* texture = 0, const float* color = 0,
-    int dim = 2, int stride = 0 );
-/**
- * Same as above, renders without clipping
+ * Same as above, renders without specified region
  **/
 KWIN_EXPORT void renderGLGeometry( int count,
     const float* vertices, const float* texture = 0, const float* color = 0,
     int dim = 2, int stride = 0 );
 
+
 KWIN_EXPORT void renderGLGeometryImmediate( int count,
     const float* vertices, const float* texture = 0, const float* color = 0,
     int dim = 2, int stride = 0 );
@@ -125,8 +120,7 @@ class KWIN_EXPORT GLTexture
         virtual void discard();
         virtual void bind();
         virtual void unbind();
-        void render( bool clip, QRegion region, const QRect& rect );
-        void render( int mask, QRegion region, const QRect& rect );
+        void render( QRegion region, const QRect& rect );
         void enableUnnormalizedTexCoords();
         void disableUnnormalizedTexCoords();
 
diff --git a/scene.cpp b/scene.cpp
index 0848122258..bab07ccaa0 100644
--- a/scene.cpp
+++ b/scene.cpp
@@ -135,6 +135,8 @@ void Scene::paintScreen( int* mask, QRegion* region )
     *region |= painted_region;
     // make sure not to go outside of the screen area
     *region &= QRegion( 0, 0, displayWidth(), displayHeight());
+    // make sure all clipping is restored
+    Q_ASSERT( !PaintClipper::clip());
     }
 
 // Compute time since the last painting pass.
diff --git a/scene.h b/scene.h
index a5b0c70d6f..870ec32a67 100644
--- a/scene.h
+++ b/scene.h
@@ -105,8 +105,6 @@ class Scene
         virtual void paintWindow( Window* w, int mask, QRegion region, WindowQuadList quads );
         // called after all effects had their drawWindow() called
         void finalDrawWindow( EffectWindowImpl* w, int mask, QRegion region, WindowPaintData& data );
-        // infinite region, i.e. everything
-        static QRegion infiniteRegion();
         // compute time since the last repaint
         void updateTimeDiff();
         // saved data for 2nd pass of optimized screen painting
@@ -197,12 +195,6 @@ class Scene::Window
 
 extern Scene* scene;
 
-inline
-QRegion Scene::infiniteRegion()
-    { // INT_MIN / 2 because width/height is used (INT_MIN+INT_MAX==-1)
-    return QRegion( INT_MIN / 2, INT_MIN / 2, INT_MAX, INT_MAX );
-    }
-
 inline
 int Scene::Window::x() const
     {
diff --git a/scene_opengl.cpp b/scene_opengl.cpp
index 4376b164a7..821b36071e 100644
--- a/scene_opengl.cpp
+++ b/scene_opengl.cpp
@@ -723,22 +723,24 @@ void SceneOpenGL::paintGenericScreen( int mask, ScreenPaintData data )
 
 void SceneOpenGL::paintBackground( QRegion region )
     {
-    if( region == infiniteRegion())
+    PaintClipper pc( region );
+    if( !PaintClipper::clip())
         {
         glClearColor( 0, 0, 0, 1 ); // black
         glClear( GL_COLOR_BUFFER_BIT );
+        return;
         }
-    else
+    glColor4f( 0, 0, 0, 1 ); // black
+    for( PaintClipper::Iterator iterator;
+         !iterator.isDone();
+         iterator.next())
         {
-        glColor4f( 0, 0, 0, 1 ); // black
         glBegin( GL_QUADS );
-        foreach( QRect r, region.rects())
-            {
-            glVertex2i( r.x(), r.y());
-            glVertex2i( r.x() + r.width(), r.y());
-            glVertex2i( r.x() + r.width(), r.y() + r.height());
-            glVertex2i( r.x(), r.y() + r.height());
-            }
+        QRect r = iterator.boundingRect();
+        glVertex2i( r.x(), r.y());
+        glVertex2i( r.x() + r.width(), r.y());
+        glVertex2i( r.x() + r.width(), r.y() + r.height());
+        glVertex2i( r.x(), r.y() + r.height());
         glEnd();
         }
     }
@@ -1257,7 +1259,7 @@ void SceneOpenGL::Window::performPaint( int mask, QRegion region, WindowPaintDat
     glPopMatrix();
     }
 
-void SceneOpenGL::Window::renderQuads( int mask, const QRegion& region, const WindowQuadList& quads )
+void SceneOpenGL::Window::renderQuads( int, const QRegion& region, const WindowQuadList& quads )
     {
     if( quads.isEmpty())
         return;
@@ -1265,7 +1267,7 @@ void SceneOpenGL::Window::renderQuads( int mask, const QRegion& region, const Wi
     float* vertices;
     float* texcoords;
     quads.makeArrays( &vertices, &texcoords );
-    renderGLGeometry( mask, region, quads.count() * 4,
+    renderGLGeometry( region, quads.count() * 4,
             vertices, texcoords, NULL, 2, 0 );
     delete[] vertices;
     delete[] texcoords;
diff --git a/scene_xrender.cpp b/scene_xrender.cpp
index c392d98772..7432a75958 100644
--- a/scene_xrender.cpp
+++ b/scene_xrender.cpp
@@ -267,15 +267,14 @@ void SceneXrender::paintTransformedScreen( int orig_mask )
 // fill the screen background
 void SceneXrender::paintBackground( QRegion region )
     {
-    if( region != infiniteRegion())
+    PaintClipper pc( region );
+    for( PaintClipper::Iterator iterator;
+         !iterator.isDone();
+         iterator.next())
         {
-        XserverRegion background_region = toXserverRegion( region );
-        XFixesSetPictureClipRegion( display(), buffer, 0, 0, background_region );
-        XFixesDestroyRegion( display(), background_region );
+        XRenderColor col = { 0, 0, 0, 0xffff }; // black
+        XRenderFillRectangle( display(), PictOpSrc, buffer, &col, 0, 0, displayWidth(), displayHeight());
         }
-    XRenderColor col = { 0, 0, 0, 0xffff }; // black
-    XRenderFillRectangle( display(), PictOpSrc, buffer, &col, 0, 0, displayWidth(), displayHeight());
-    XFixesSetPictureClipRegion( display(), buffer, 0, 0, None );
     }
 
 void SceneXrender::windowGeometryShapeChanged( Toplevel* c )
@@ -326,27 +325,6 @@ void SceneXrender::windowAdded( Toplevel* c )
     c->effectWindow()->setSceneWindow( windows[ c ]);
     }
 
-// Convert QRegion to XserverRegion. This code uses XserverRegion
-// only when really necessary as the shared implementation uses
-// QRegion.
-XserverRegion SceneXrender::toXserverRegion( QRegion region )
-    {
-    QVector< QRect > rects = region.rects();
-    XRectangle* xr = new XRectangle[ rects.count() ];
-    for( int i = 0;
-         i < rects.count();
-         ++i )
-        {
-        xr[ i ].x = rects[ i ].x();
-        xr[ i ].y = rects[ i ].y();
-        xr[ i ].width = rects[ i ].width();
-        xr[ i ].height = rects[ i ].height();
-        }
-    XserverRegion ret = XFixesCreateRegion( display(), xr, rects.count());
-    delete[] xr;
-    return ret;
-    }
-
 //****************************************
 // SceneXrender::Window
 //****************************************
@@ -451,12 +429,6 @@ void SceneXrender::Window::performPaint( int mask, QRegion region, WindowPaintDa
         if( opaque )
             return;
         }
-    if( region != infiniteRegion())
-        {
-        XserverRegion clip_region = toXserverRegion( region );
-        XFixesSetPictureClipRegion( display(), buffer, 0, 0, clip_region );
-        XFixesDestroyRegion( display(), clip_region );
-        }
     Picture pic = picture(); // get XRender picture
     if( pic == None ) // The render format can be null for GL and/or Xv visuals
         return;
@@ -522,17 +494,23 @@ void SceneXrender::Window::performPaint( int mask, QRegion region, WindowPaintDa
         }
     if( x != toplevel->x() || y != toplevel->y())
         transformed_shape.translate( x, y );
-    if( opaque )
+    PaintClipper pc( region );
+    for( PaintClipper::Iterator iterator;
+         !iterator.isDone();
+         iterator.next())
         {
-        XRenderComposite( display(), PictOpSrc, pic, None, buffer, 0, 0, 0, 0,
-            x, y, width, height);
-        }
-    else
-        {
-        Picture alpha = alphaMask( data.opacity );
-        XRenderComposite( display(), PictOpOver, pic, alpha, buffer, 0, 0, 0, 0,
-            x, y, width, height);
-        transformed_shape = QRegion();
+        if( opaque )
+            {
+            XRenderComposite( display(), PictOpSrc, pic, None, buffer, 0, 0, 0, 0,
+                x, y, width, height);
+            }
+        else
+            {
+            Picture alpha = alphaMask( data.opacity );
+            XRenderComposite( display(), PictOpOver, pic, alpha, buffer, 0, 0, 0, 0,
+                x, y, width, height);
+            transformed_shape = QRegion();
+            }
         }
     if( xscale != 1 || yscale != 1 )
         {
@@ -545,7 +523,6 @@ void SceneXrender::Window::performPaint( int mask, QRegion region, WindowPaintDa
         if( filter == ImageFilterGood )
             XRenderSetPictureFilter( display(), pic, const_cast< char* >( "fast" ), NULL, 0 );
         }
-    XFixesSetPictureClipRegion( display(), buffer, 0, 0, None );
     }
 
 } // namespace
diff --git a/scene_xrender.h b/scene_xrender.h
index 854bb48711..5492e41cd7 100644
--- a/scene_xrender.h
+++ b/scene_xrender.h
@@ -54,7 +54,6 @@ class SceneXrender
     private:
         void paintTransformedScreen( int mask );
         void createBuffer();
-        static XserverRegion toXserverRegion( QRegion region );
         XRenderPictFormat* format;
         Picture front;
         static Picture buffer;