diff --git a/deleted.h b/deleted.h
index 269aef86ab..5e2e38c380 100644
--- a/deleted.h
+++ b/deleted.h
@@ -35,7 +35,7 @@ class Deleted
         void copyToDeleted( Toplevel* c );
         virtual ~Deleted(); // deleted only using unrefWindow()
         int delete_refcount;
-        double window_opacity;
+        float window_opacity;
         int desk;
         QRect contentsRect; // for clientPos()/clientSize()
     };
diff --git a/effects.cpp b/effects.cpp
index 7a5b59bd88..cab0ab1630 100644
--- a/effects.cpp
+++ b/effects.cpp
@@ -172,7 +172,7 @@ void EffectsHandlerImpl::windowUserMovedResized( EffectWindow* c, bool first, bo
         ep.second->windowUserMovedResized( c, first, last );
     }
 
-void EffectsHandlerImpl::windowOpacityChanged( EffectWindow* c, double old_opacity )
+void EffectsHandlerImpl::windowOpacityChanged( EffectWindow* c, float old_opacity )
     {
     if( static_cast<EffectWindowImpl*>(c)->window()->opacity() == old_opacity )
         return;
@@ -853,7 +853,7 @@ bool EffectWindowImpl::isMinimized() const
         return false;
     }
 
-double EffectWindowImpl::opacity() const
+float EffectWindowImpl::opacity() const
     {
     return toplevel->opacity();
     }
diff --git a/effects.h b/effects.h
index bd1e51e247..647c0d0cea 100644
--- a/effects.h
+++ b/effects.h
@@ -92,7 +92,7 @@ class EffectsHandlerImpl : public EffectsHandler
         // internal (used by kwin core or compositing code)
         void startPaint();
         void windowUserMovedResized( EffectWindow* c, bool first, bool last );
-        void windowOpacityChanged( EffectWindow* c, double old_opacity );
+        void windowOpacityChanged( EffectWindow* c, float old_opacity );
         void windowAdded( EffectWindow* c );
         void windowClosed( EffectWindow* c );
         void windowDeleted( EffectWindow* c );
@@ -149,7 +149,7 @@ class EffectWindowImpl : public EffectWindow
         virtual bool isOnAllDesktops() const;
         virtual int desktop() const; // prefer isOnXXX()
         virtual bool isMinimized() const;
-        virtual double opacity() const;
+        virtual float opacity() const;
         virtual QString caption() const;
         virtual QPixmap icon() const;
         virtual QString windowClass() const;
diff --git a/effects/boxswitch.cpp b/effects/boxswitch.cpp
index d7ab72b384..66a0c5a679 100644
--- a/effects/boxswitch.cpp
+++ b/effects/boxswitch.cpp
@@ -524,8 +524,8 @@ void BoxSwitchEffect::paintDesktopThumbnail( int iDesktop )
     QSize size = QSize( displayWidth(), displayHeight());
 
     size.scale( r.size(), Qt::KeepAspectRatio );
-    data.xScale = size.width() / double( displayWidth());
-    data.yScale = size.height() / double( displayHeight());
+    data.xScale = size.width() / float( displayWidth());
+    data.yScale = size.height() / float( displayHeight());
     int width = int( displayWidth() * data.xScale );
     int height = int( displayHeight() * data.yScale );
     int x = r.x() + ( r.width() - width ) / 2;
diff --git a/effects/desktopgrid.cpp b/effects/desktopgrid.cpp
index 66652c1303..52e9316490 100644
--- a/effects/desktopgrid.cpp
+++ b/effects/desktopgrid.cpp
@@ -46,7 +46,7 @@ void DesktopGridEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     if( slide )
         {
-        progress = qMin( 1.0, progress + time / double( PROGRESS_TIME ));
+        progress = qMin( 1.0f, progress + time / float( PROGRESS_TIME ));
         // PAINT_SCREEN_BACKGROUND_FIRST is needed because screen will be actually painted more than once,
         // so with normal screen painting second screen paint would erase parts of the first paint
         if( progress != 1 )
@@ -60,9 +60,9 @@ void DesktopGridEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     else if( progress != 0 || activated )
         {
         if( activated )
-            progress = qMin( 1.0, progress + time / double( PROGRESS_TIME ));
+            progress = qMin( 1.0f, progress + time / float( PROGRESS_TIME ));
         else
-            progress = qMax( 0.0, progress - time / double( PROGRESS_TIME ));
+            progress = qMax( 0.0f, progress - time / float( PROGRESS_TIME ));
         // PAINT_SCREEN_BACKGROUND_FIRST is needed because screen will be actually painted more than once,
         // so with normal screen painting second screen paint would erase parts of the first paint
         if( progress != 0 )
diff --git a/effects/drunken.h b/effects/drunken.h
index 2b665c4536..85ac1a1b8c 100644
--- a/effects/drunken.h
+++ b/effects/drunken.h
@@ -27,7 +27,7 @@ class DrunkenEffect
         virtual void windowAdded( EffectWindow* w );
         virtual void windowClosed( EffectWindow* w );
     private:
-        QHash< EffectWindow*, double > windows; // progress
+        QHash< EffectWindow*, float > windows; // progress
     };
 
 } // namespace
diff --git a/effects/explosioneffect.h b/effects/explosioneffect.h
index b2846cd6aa..e570469cc7 100644
--- a/effects/explosioneffect.h
+++ b/effects/explosioneffect.h
@@ -50,7 +50,7 @@ class ExplosionEffect
         GLShader* mShader;
         GLTexture* mStartOffsetTex;
         GLTexture* mEndOffsetTex;
-        QMap< const EffectWindow*, double > mWindows;
+        QMap< const EffectWindow*, float > mWindows;
         int mActiveAnimations;
         bool mValid;
         bool mInited;
diff --git a/effects/fade.cpp b/effects/fade.cpp
index 4841ec1706..cd5e2e0ecc 100644
--- a/effects/fade.cpp
+++ b/effects/fade.cpp
@@ -29,8 +29,8 @@ void FadeEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     if( !windows.isEmpty())
         {
-        fadeInStep = time / double( fadeInTime );
-        fadeOutStep = time / double( fadeOutTime );
+        fadeInStep = time / float( fadeInTime );
+        fadeOutStep = time / float( fadeOutTime );
         }
     effects->prePaintScreen( data, time );
     }
@@ -114,7 +114,7 @@ void FadeEffect::paintWindow( EffectWindow* w, int mask, QRegion region, WindowP
                     windows[ w ].brightness - float( windows[ w ].fadeOutStep ));
                 }
 
-            windows[ w ].opacity = qBound( 0.0, windows[ w ].opacity, 1.0 );
+            windows[ w ].opacity = qBound( 0.0f, windows[ w ].opacity, 1.0f );
             windows[ w ].saturation = qBound( 0.0f, windows[ w ].saturation, 1.0f );
             windows[ w ].brightness = qBound( 0.0f, windows[ w ].brightness, 1.0f );
             windows[ w ].fadeInStep = 0.0;
@@ -136,7 +136,7 @@ void FadeEffect::paintWindow( EffectWindow* w, int mask, QRegion region, WindowP
     effects->paintWindow( w, mask, region, data );
     }
 
-void FadeEffect::windowOpacityChanged( EffectWindow* w, double old_opacity )
+void FadeEffect::windowOpacityChanged( EffectWindow* w, float old_opacity )
     {
     if( !windows.contains( w ))
         windows[ w ].opacity = old_opacity;
diff --git a/effects/fade.h b/effects/fade.h
index 0b2f20ae9b..f1f27ef226 100644
--- a/effects/fade.h
+++ b/effects/fade.h
@@ -26,7 +26,7 @@ class FadeEffect
         virtual void paintWindow( EffectWindow* w, int mask, QRegion region, WindowPaintData& data );
 
         // TODO react also on virtual desktop changes
-        virtual void windowOpacityChanged( EffectWindow* c, double old_opacity );
+        virtual void windowOpacityChanged( EffectWindow* c, float old_opacity );
         virtual void windowAdded( EffectWindow* c );
         virtual void windowClosed( EffectWindow* c );
         virtual void windowDeleted( EffectWindow* c );
@@ -35,7 +35,7 @@ class FadeEffect
     private:
         class WindowInfo;
         QHash< const EffectWindow*, WindowInfo > windows;
-        double fadeInStep, fadeOutStep;
+        float fadeInStep, fadeOutStep;
         int fadeInTime, fadeOutTime;
         bool fadeWindows;
     };
@@ -51,8 +51,8 @@ class FadeEffect::WindowInfo
             , brightness( 1.0 )
             , deleted( false )
             {}
-        double fadeInStep, fadeOutStep;
-        double opacity;
+        float fadeInStep, fadeOutStep;
+        float opacity;
         float saturation, brightness;
         bool deleted;
     };
diff --git a/effects/fallapart.cpp b/effects/fallapart.cpp
index beee4717af..cc4cbeba30 100644
--- a/effects/fallapart.cpp
+++ b/effects/fallapart.cpp
@@ -57,17 +57,17 @@ void FallApartEffect::paintWindow( EffectWindow* w, int mask, QRegion region, Wi
             // make fragments move in various directions, based on where
             // they are (left pieces generally move to the left, etc.)
             QPointF p1( quad[ 0 ].x(), quad[ 0 ].y());
-            double xdiff = 0;
+            float xdiff = 0;
             if( p1.x() < w->width() / 2 )
                 xdiff = -( w->width() / 2 - p1.x()) / w->width() * 100;
             if( p1.x() > w->width() / 2 )
                 xdiff = ( p1.x() - w->width() / 2 ) / w->width() * 100;
-            double ydiff = 0;
+            float ydiff = 0;
             if( p1.y() < w->height() / 2 )
                 ydiff = -( w->height() / 2 - p1.y()) / w->height() * 100;
             if( p1.y() > w->height() / 2 )
                 ydiff = ( p1.y() - w->height() / 2 ) / w->height() * 100;
-            double modif = windows[ w ] * windows[ w ] * 64;
+            float modif = windows[ w ] * windows[ w ] * 64;
             srandom( cnt ); // change direction randomly but consistently
             xdiff += ( rand() % 21 - 10 );
             ydiff += ( rand() % 21 - 10 );
@@ -80,16 +80,16 @@ void FallApartEffect::paintWindow( EffectWindow* w, int mask, QRegion region, Wi
             // also make the fragments rotate around their center
             QPointF center(( quad[ 0 ].x() + quad[ 1 ].x() + quad[ 2 ].x() + quad[ 3 ].x()) / 4,
                 ( quad[ 0 ].y() + quad[ 1 ].y() + quad[ 2 ].y() + quad[ 3 ].y()) / 4 );
-            double adiff = ( rand() % 720 - 360 ) / 360. * 2 * M_PI; // spin randomly
+            float adiff = ( rand() % 720 - 360 ) / 360. * 2 * M_PI; // spin randomly
             for( int j = 0;
                  j < 4;
                  ++j )
                 {
-                double x = quad[ j ].x() - center.x();
-                double y = quad[ j ].y() - center.y();
-                double angle = atan2( y, x );
+                float x = quad[ j ].x() - center.x();
+                float y = quad[ j ].y() - center.y();
+                float angle = atan2( y, x );
                 angle += windows[ w ] * adiff;
-                double dist = sqrt( x * x + y * y );
+                float dist = sqrt( x * x + y * y );
                 x = dist * cos( angle );
                 y = dist * sin( angle );
                 quad[ j ].move( center.x() + x, center.y() + y );
diff --git a/effects/fallapart.h b/effects/fallapart.h
index 90f399aace..f420f32907 100644
--- a/effects/fallapart.h
+++ b/effects/fallapart.h
@@ -27,7 +27,7 @@ class FallApartEffect
         virtual void windowClosed( EffectWindow* c );
         virtual void windowDeleted( EffectWindow* c );
     private:
-        QHash< const EffectWindow*, double > windows;
+        QHash< const EffectWindow*, float > windows;
     };
 
 } // namespace
diff --git a/effects/flame.h b/effects/flame.h
index ee3ac7da53..861e755ad8 100644
--- a/effects/flame.h
+++ b/effects/flame.h
@@ -27,7 +27,7 @@ class FlameEffect
         virtual void windowClosed( EffectWindow* c );
         virtual void windowDeleted( EffectWindow* c );
     private:
-        QHash< const EffectWindow*, double > windows;
+        QHash< const EffectWindow*, float > windows;
     };
 
 } // namespace
diff --git a/effects/magnifier.cpp b/effects/magnifier.cpp
index d8c9e6f5c8..cb34f238d9 100644
--- a/effects/magnifier.cpp
+++ b/effects/magnifier.cpp
@@ -46,11 +46,11 @@ void MagnifierEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     if( zoom != target_zoom )
         {
-        double diff = time / 500.0;
+        float diff = time / 500.0;
         if( target_zoom > zoom )
-            zoom = qMin( zoom * qMax( 1 + diff, 1.2 ), target_zoom );
+            zoom = qMin( zoom * qMax( 1 + diff, 1.2f ), target_zoom );
         else
-            zoom = qMax( zoom * qMin( 1 - diff, 0.8 ), target_zoom );
+            zoom = qMax( zoom * qMin( 1 - diff, 0.8f ), target_zoom );
         }
     effects->prePaintScreen( data, time );
     if( zoom != 1.0 )
diff --git a/effects/magnifier.h b/effects/magnifier.h
index 548bbe7e12..8d08670fb1 100644
--- a/effects/magnifier.h
+++ b/effects/magnifier.h
@@ -33,8 +33,8 @@ class MagnifierEffect
         void toggle();
     private:
         QRect magnifierArea( QPoint pos = cursorPos()) const;
-        double zoom;
-        double target_zoom;
+        float zoom;
+        float target_zoom;
         QSize magnifier_size;
     };
 
diff --git a/effects/presentwindows.cpp b/effects/presentwindows.cpp
index 7f29c36c98..d45132c525 100644
--- a/effects/presentwindows.cpp
+++ b/effects/presentwindows.cpp
@@ -443,12 +443,12 @@ void PresentWindowsEffect::calculateWindowTransformationsKompose(EffectWindowLis
     if ( parentRatio > 1 )
     {
         columns = (int)ceil( sqrt(windowlist.count()) );
-        rows = (int)ceil( (double)windowlist.count() / (double)columns );
+        rows = (int)ceil( (float)windowlist.count() / (float)columns );
     }
     else
     {
         rows = (int)ceil( sqrt(windowlist.count()) );
-        columns = (int)ceil( (double)windowlist.count() / (double)rows );
+        columns = (int)ceil( (float)windowlist.count() / (float)rows );
     }
     kDebug() << k_funcinfo << "Using " << rows << " rows & " << columns << " columns for " << windowlist.count() << " clients";
 
@@ -505,8 +505,8 @@ void PresentWindowsEffect::calculateWindowTransformationsKompose(EffectWindowLis
                 }
             else
                 {
-                double widthForHeight = windowWidthForHeight(window, usableH);
-                double heightForWidth = windowHeightForWidth(window, usableW);
+                float widthForHeight = windowWidthForHeight(window, usableH);
+                float heightForWidth = windowHeightForWidth(window, usableW);
                 if ( (ratio >= 1.0 && heightForWidth <= usableH) ||
                       (ratio < 1.0 && widthForHeight > usableW)   )
                     {
@@ -572,7 +572,7 @@ void PresentWindowsEffect::calculateWindowTransformationsClosest(EffectWindowLis
     {
     QRect area = effects->clientArea( PlacementArea, QPoint( 0, 0 ), effects->currentDesktop());
     int columns = int( ceil( sqrt( windowlist.count())));
-    int rows = int( ceil( windowlist.count() / double( columns )));
+    int rows = int( ceil( windowlist.count() / float( columns )));
     foreach( EffectWindow* w, windowlist )
         mWindowData[ w ].slot = -1;
     for(;;)
@@ -693,9 +693,9 @@ bool PresentWindowsEffect::canRearrangeClosest(EffectWindowList windowlist)
     {
     QRect area = effects->clientArea( PlacementArea, QPoint( 0, 0 ), effects->currentDesktop());
     int columns = int( ceil( sqrt( windowlist.count())));
-    int rows = int( ceil( windowlist.count() / double( columns )));
+    int rows = int( ceil( windowlist.count() / float( columns )));
     int old_columns = int( ceil( sqrt( mWindowData.count())));
-    int old_rows = int( ceil( mWindowData.count() / double( columns )));
+    int old_rows = int( ceil( mWindowData.count() / float( columns )));
     return old_columns != columns || old_rows != rows;
     }
 
diff --git a/effects/scalein.h b/effects/scalein.h
index a687043973..b1ea088b1d 100644
--- a/effects/scalein.h
+++ b/effects/scalein.h
@@ -28,7 +28,7 @@ class ScaleInEffect
         virtual void windowAdded( EffectWindow* c );
         virtual void windowClosed( EffectWindow* c );
     private:
-        QHash< const EffectWindow*, double > windows;
+        QHash< const EffectWindow*, float > windows;
     };
 
 } // namespace
diff --git a/effects/showfps.h b/effects/showfps.h
index e85dc98381..cc58b80bd2 100644
--- a/effects/showfps.h
+++ b/effects/showfps.h
@@ -36,7 +36,7 @@ class ShowFpsEffect
         enum { MAX_FPS = 200 };
         int frames[ MAX_FPS ]; // (sec*1000+msec) of the time the frame was done
         int frames_pos; // position in the queue
-        double alpha;
+        float alpha;
         int x;
         int y;
     };
diff --git a/effects/thumbnailaside.cpp b/effects/thumbnailaside.cpp
index 53f72a4e93..59f8d83d49 100644
--- a/effects/thumbnailaside.cpp
+++ b/effects/thumbnailaside.cpp
@@ -127,8 +127,8 @@ void ThumbnailAsideEffect::arrange()
         pos[ d.index ] = d.window->height();
         }
     QRect area = effects->clientArea( WorkArea, QPoint(), effects->currentDesktop());
-    double scale = area.height() / double( height );
-    scale = qMin( scale, maxwidth / double( mwidth )); // don't be wider than maxwidth pixels
+    float scale = area.height() / float( height );
+    scale = qMin( scale, maxwidth / float( mwidth )); // don't be wider than maxwidth pixels
     int add = 0;
     for( int i = 0;
          i < windows.size();
diff --git a/effects/zoom.cpp b/effects/zoom.cpp
index 965fe776fe..5fbeefc52b 100644
--- a/effects/zoom.cpp
+++ b/effects/zoom.cpp
@@ -37,11 +37,11 @@ void ZoomEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     if( zoom != target_zoom )
         {
-        double diff = time / 500.0;
+        float diff = time / 500.0;
         if( target_zoom > zoom )
-            zoom = qMin( zoom * qMax( 1 + diff, 1.2 ), target_zoom );
+            zoom = qMin( zoom * qMax( 1 + diff, 1.2f ), target_zoom );
         else
-            zoom = qMax( zoom * qMin( 1 - diff, 0.8 ), target_zoom );
+            zoom = qMax( zoom * qMin( 1 - diff, 0.8f ), target_zoom );
         }
     if( zoom != 1.0 )
         data.mask |= PAINT_SCREEN_TRANSFORMED;
diff --git a/effects/zoom.h b/effects/zoom.h
index f198b7391f..af54fe2ec5 100644
--- a/effects/zoom.h
+++ b/effects/zoom.h
@@ -32,8 +32,8 @@ class ZoomEffect
         void zoomOut();
         void actualSize();
     private:
-        double zoom;
-        double target_zoom;
+        float zoom;
+        float target_zoom;
     };
 
 } // namespace
diff --git a/lib/kwineffects.cpp b/lib/kwineffects.cpp
index de324b1db7..d4bf4fa9d0 100644
--- a/lib/kwineffects.cpp
+++ b/lib/kwineffects.cpp
@@ -74,7 +74,7 @@ void Effect::windowUserMovedResized( EffectWindow* , bool, bool )
     {
     }
 
-void Effect::windowOpacityChanged( EffectWindow*, double )
+void Effect::windowOpacityChanged( EffectWindow*, float )
     {
     }
 
@@ -187,8 +187,8 @@ void Effect::setPositionTransformations( WindowPaintData& data, QRect& region, E
     {
     QSize size = w->size();
     size.scale( r.size(), aspect );
-    data.xScale = size.width() / double( w->width());
-    data.yScale = size.height() / double( w->height());
+    data.xScale = size.width() / float( w->width());
+    data.yScale = size.height() / float( w->height());
     int width = int( w->width() * data.xScale );
     int height = int( w->height() * data.yScale );
     int x = r.x() + ( r.width() - width ) / 2;
diff --git a/lib/kwineffects.h b/lib/kwineffects.h
index 2a26ac0a74..69989c0bd1 100644
--- a/lib/kwineffects.h
+++ b/lib/kwineffects.h
@@ -96,7 +96,7 @@ class KWIN_EXPORT Effect
 
         // called when moved/resized or once after it's finished
         virtual void windowUserMovedResized( EffectWindow* c, bool first, bool last );
-        virtual void windowOpacityChanged( EffectWindow* c, double old_opacity );
+        virtual void windowOpacityChanged( EffectWindow* c, float old_opacity );
         virtual void windowAdded( EffectWindow* c );
         virtual void windowClosed( EffectWindow* c );
         virtual void windowDeleted( EffectWindow* c );
@@ -294,7 +294,7 @@ class KWIN_EXPORT EffectWindow
         virtual bool isDeleted() const = 0;
 
         virtual bool isMinimized() const = 0;
-        virtual double opacity() const = 0;
+        virtual float opacity() const = 0;
 
         virtual bool isOnDesktop( int d ) const;
         virtual bool isOnCurrentDesktop() const;
@@ -457,11 +457,11 @@ class KWIN_EXPORT WindowPaintData
          * Opacity for contents is opacity*contents_opacity, the same
          * way for decoration.
          */
-        double opacity;
-        double contents_opacity;
-        double decoration_opacity;
-        double xScale;
-        double yScale;
+        float opacity;
+        float contents_opacity;
+        float decoration_opacity;
+        float xScale;
+        float yScale;
         int xTranslate;
         int yTranslate;
         /**
@@ -488,8 +488,8 @@ class KWIN_EXPORT ScreenPaintData
     {
     public:
         ScreenPaintData();
-        double xScale;
-        double yScale;
+        float xScale;
+        float yScale;
         int xTranslate;
         int yTranslate;
     };
diff --git a/scene_opengl.cpp b/scene_opengl.cpp
index 1d66ee55aa..2c75296e9a 100644
--- a/scene_opengl.cpp
+++ b/scene_opengl.cpp
@@ -1168,7 +1168,7 @@ void SceneOpenGL::Window::renderQuads( int mask, const QRegion& region, const Wi
     delete[] texcoords;
     }
 
-void SceneOpenGL::Window::prepareStates( double opacity, double brightness, double saturation, GLShader* shader )
+void SceneOpenGL::Window::prepareStates( float opacity, float brightness, float saturation, GLShader* shader )
     {
     if(shader)
         prepareShaderRenderStates( opacity, brightness, saturation, shader );
@@ -1176,7 +1176,7 @@ void SceneOpenGL::Window::prepareStates( double opacity, double brightness, doub
         prepareRenderStates( opacity, brightness, saturation );
     }
 
-void SceneOpenGL::Window::prepareShaderRenderStates( double opacity, double brightness, double saturation, GLShader* shader )
+void SceneOpenGL::Window::prepareShaderRenderStates( float opacity, float brightness, float saturation, GLShader* shader )
     {
     // setup blending of transparent windows
     glPushAttrib( GL_ENABLE_BIT );
@@ -1191,7 +1191,7 @@ void SceneOpenGL::Window::prepareShaderRenderStates( double opacity, double brig
     shader->setUniform("brightness", (float)brightness);
     }
 
-void SceneOpenGL::Window::prepareRenderStates( double opacity, double brightness, double saturation )
+void SceneOpenGL::Window::prepareRenderStates( float opacity, float brightness, float saturation )
     {
     // setup blending of transparent windows
     glPushAttrib( GL_ENABLE_BIT );
@@ -1316,7 +1316,7 @@ void SceneOpenGL::Window::prepareRenderStates( double opacity, double brightness
         }
     }
 
-void SceneOpenGL::Window::restoreStates( double opacity, double brightness, double saturation, GLShader* shader )
+void SceneOpenGL::Window::restoreStates( float opacity, float brightness, float saturation, GLShader* shader )
     {
     if(shader)
         restoreShaderRenderStates( opacity, brightness, saturation, shader );
@@ -1324,7 +1324,7 @@ void SceneOpenGL::Window::restoreStates( double opacity, double brightness, doub
         restoreRenderStates( opacity, brightness, saturation );
     }
 
-void SceneOpenGL::Window::restoreShaderRenderStates( double opacity, double brightness, double saturation, GLShader* shader )
+void SceneOpenGL::Window::restoreShaderRenderStates( float opacity, float brightness, float saturation, GLShader* shader )
     {
     Q_UNUSED( opacity );
     Q_UNUSED( brightness );
@@ -1333,7 +1333,7 @@ void SceneOpenGL::Window::restoreShaderRenderStates( double opacity, double brig
     glPopAttrib();  // ENABLE_BIT
     }
 
-void SceneOpenGL::Window::restoreRenderStates( double opacity, double brightness, double saturation )
+void SceneOpenGL::Window::restoreRenderStates( float opacity, float brightness, float saturation )
     {
     if( opacity != 1.0 || saturation != 1.0 || brightness != 1.0f )
         {
diff --git a/scene_opengl.h b/scene_opengl.h
index e30d00db84..ca2e3a0e43 100644
--- a/scene_opengl.h
+++ b/scene_opengl.h
@@ -124,12 +124,12 @@ class SceneOpenGL::Window
 
     protected:
         void renderQuads( int mask, const QRegion& region, const WindowQuadList& quads );
-        void prepareStates( double opacity, double brightness, double saturation, GLShader* shader );
-        void prepareRenderStates( double opacity, double brightness, double saturation );
-        void prepareShaderRenderStates( double opacity, double brightness, double saturation, GLShader* shader );
-        void restoreStates( double opacity, double brightness, double saturation, GLShader* shader );
-        void restoreRenderStates( double opacity, double brightness, double saturation );
-        void restoreShaderRenderStates( double opacity, double brightness, double saturation, GLShader* shader );
+        void prepareStates( float opacity, float brightness, float saturation, GLShader* shader );
+        void prepareRenderStates( float opacity, float brightness, float saturation );
+        void prepareShaderRenderStates( float opacity, float brightness, float saturation, GLShader* shader );
+        void restoreStates( float opacity, float brightness, float saturation, GLShader* shader );
+        void restoreRenderStates( float opacity, float brightness, float saturation );
+        void restoreShaderRenderStates( float opacity, float brightness, float saturation, GLShader* shader );
 
     private:
         Texture texture;
diff --git a/scene_xrender.cpp b/scene_xrender.cpp
index cf99e2a9c8..0e7174c4aa 100644
--- a/scene_xrender.cpp
+++ b/scene_xrender.cpp
@@ -394,7 +394,7 @@ void SceneXrender::Window::discardAlpha()
     }
 
 // Create XRender picture for the alpha mask.
-Picture SceneXrender::Window::alphaMask( double opacity )
+Picture SceneXrender::Window::alphaMask( float opacity )
     {
     if( isOpaque() && opacity == 1.0 )
         return None;
@@ -469,8 +469,8 @@ void SceneXrender::Window::performPaint( int mask, QRegion region, WindowPaintDa
     int y = toplevel->y();
     int width = toplevel->width();
     int height = toplevel->height();
-    double xscale = 1;
-    double yscale = 1;
+    float xscale = 1;
+    float yscale = 1;
     transformed_shape = shape();
     if( mask & PAINT_WINDOW_TRANSFORMED )
         {
diff --git a/scene_xrender.h b/scene_xrender.h
index ae1de60018..cefa27d4fa 100644
--- a/scene_xrender.h
+++ b/scene_xrender.h
@@ -67,11 +67,11 @@ class SceneXrender::Window
         void setTransformedShape( const QRegion& shape );
     private:
         Picture picture();
-        Picture alphaMask( double opacity );
+        Picture alphaMask( float opacity );
         Picture _picture;
         XRenderPictFormat* format;
         Picture alpha;
-        double alpha_cached_opacity;
+        float alpha_cached_opacity;
         QRegion transformed_shape;
     };
 
diff --git a/toplevel.cpp b/toplevel.cpp
index 322836d97b..a5d37e7b21 100644
--- a/toplevel.cpp
+++ b/toplevel.cpp
@@ -294,17 +294,17 @@ void Toplevel::getResourceClass()
         }
     }
 
-double Toplevel::opacity() const
+float Toplevel::opacity() const
     {
     if( info->opacity() == 0xffffffff )
         return 1.0;
     return info->opacity() * 1.0 / 0xffffffff;
     }
 
-void Toplevel::setOpacity( double new_opacity )
+void Toplevel::setOpacity( float new_opacity )
     {
-    double old_opacity = opacity();
-    new_opacity = qBound( 0.0, new_opacity, 1.0 );
+    float old_opacity = opacity();
+    new_opacity = qBound( 0.0f, new_opacity, 1.0f );
     if( old_opacity == new_opacity )
         return;
     info->setOpacity( static_cast< unsigned long >( new_opacity * 0xffffffff ));
diff --git a/toplevel.h b/toplevel.h
index b8cf559804..1b224297c7 100644
--- a/toplevel.h
+++ b/toplevel.h
@@ -90,8 +90,8 @@ class Toplevel
         bool readyForPainting() const; // true if the window has been already painted its contents
         Visual* visual() const;
         bool shape() const;
-        void setOpacity( double opacity );
-        double opacity() const;
+        void setOpacity( float opacity );
+        float opacity() const;
         int depth() const;
         bool hasAlpha() const;
         void setupCompositing();