diff --git a/deleted.h b/deleted.h
index 5e2e38c380..269aef86ab 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;
-        float window_opacity;
+        double window_opacity;
         int desk;
         QRect contentsRect; // for clientPos()/clientSize()
     };
diff --git a/effects.cpp b/effects.cpp
index 533c8f75bf..7ec7c56c33 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, float old_opacity )
+void EffectsHandlerImpl::windowOpacityChanged( EffectWindow* c, double old_opacity )
     {
     if( static_cast<EffectWindowImpl*>(c)->window()->opacity() == old_opacity )
         return;
@@ -853,7 +853,7 @@ bool EffectWindowImpl::isMinimized() const
         return false;
     }
 
-float EffectWindowImpl::opacity() const
+double EffectWindowImpl::opacity() const
     {
     return toplevel->opacity();
     }
diff --git a/effects.h b/effects.h
index 647c0d0cea..bd1e51e247 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, float old_opacity );
+        void windowOpacityChanged( EffectWindow* c, double 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 float opacity() const;
+        virtual double 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 c9ce83e5d4..cac369221a 100644
--- a/effects/boxswitch.cpp
+++ b/effects/boxswitch.cpp
@@ -528,8 +528,8 @@ void BoxSwitchEffect::paintDesktopThumbnail( int iDesktop )
     QSize size = QSize( displayWidth(), displayHeight());
 
     size.scale( r.size(), Qt::KeepAspectRatio );
-    data.xScale = size.width() / float( displayWidth());
-    data.yScale = size.height() / float( displayHeight());
+    data.xScale = size.width() / double( displayWidth());
+    data.yScale = size.height() / double( 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/demo_liquid.cpp b/effects/demo_liquid.cpp
index eaf40f1ce0..54a9217ba8 100644
--- a/effects/demo_liquid.cpp
+++ b/effects/demo_liquid.cpp
@@ -121,7 +121,7 @@ void LiquidEffect::postPaintScreen()
 
         // Use the shader
         mShader->bind();
-        mShader->setUniform("time", mTime);
+        mShader->setUniform("time", (float)mTime);
 
         // Render fullscreen quad with screen contents
         glBegin(GL_QUADS);
diff --git a/effects/demo_liquid.h b/effects/demo_liquid.h
index 9a078b2e8a..3450cd98ce 100644
--- a/effects/demo_liquid.h
+++ b/effects/demo_liquid.h
@@ -44,7 +44,7 @@ class LiquidEffect : public Effect
         GLShader* mShader;
         bool mValid;
 
-        float mTime;
+        double mTime;
     };
 
 } // namespace
diff --git a/effects/demo_taskbarthumbnail.cpp b/effects/demo_taskbarthumbnail.cpp
index e1f2155a63..7b1f7b5873 100644
--- a/effects/demo_taskbarthumbnail.cpp
+++ b/effects/demo_taskbarthumbnail.cpp
@@ -59,8 +59,8 @@ void TaskbarThumbnailEffect::postPaintScreen()
         WindowPaintData thumbdata( w );
         thumbdata.xTranslate = thumb.x() - w->x();
         thumbdata.yTranslate = thumb.y() - w->y();
-        thumbdata.xScale = thumb.width() / (float)w->width();
-        thumbdata.yScale = thumb.height() / (float)w->height();
+        thumbdata.xScale = thumb.width() / (double)w->width();
+        thumbdata.yScale = thumb.height() / (double)w->height();
         // From Scene::Window::infiniteRegion()
         QRegion infRegion = QRegion( INT_MIN / 2, INT_MIN / 2, INT_MAX, INT_MAX );
         effects->paintWindow( w, PAINT_WINDOW_TRANSFORMED, infRegion, thumbdata );
@@ -79,7 +79,7 @@ QRect TaskbarThumbnailEffect::getThumbnailPosition( EffectWindow* c, int* space
     if( icon.right() < 40 || ( displayWidth() - icon.left()) < 40 )
         {
         // Vertical taskbar...
-        float scale = qMin(qMax(icon.height(), 100) / (float)c->height(), 200.0f / c->width());
+        double scale = qMin(qMax(icon.height(), 100) / (double)c->height(), 200.0 / c->width());
         thumb.setSize( QSize( int(scale * c->width()),int(scale * c->height()) ));
         if( icon.right() < 40 )  // ...on the left
             thumb.moveTopLeft( QPoint( icon.right() + *space, icon.top() ));
@@ -90,7 +90,7 @@ QRect TaskbarThumbnailEffect::getThumbnailPosition( EffectWindow* c, int* space
     else
         {
         // Horizontal taskbar...
-        float scale = qMin(qMax(icon.width(), 75) / (float)c->width(), 200.0f / c->height());
+        double scale = qMin(qMax(icon.width(), 75) / (double)c->width(), 200.0 / c->height());
         thumb.setSize( QSize( int(scale * c->width()),int(scale * c->height()) ));
         if( icon.top() < ( displayHeight() - icon.bottom()))  // ...at the top
             thumb.moveTopLeft( QPoint( icon.left(), icon.bottom() + *space ));
diff --git a/effects/demo_wavywindows.h b/effects/demo_wavywindows.h
index e060a76a1a..a9944e7d39 100644
--- a/effects/demo_wavywindows.h
+++ b/effects/demo_wavywindows.h
@@ -32,7 +32,7 @@ class WavyWindowsEffect
         virtual void postPaintScreen();
 
     private:
-        float mTimeElapsed;
+        double mTimeElapsed;
     };
 
 } // namespace
diff --git a/effects/desktopgrid.cpp b/effects/desktopgrid.cpp
index 52e9316490..2c87335b33 100644
--- a/effects/desktopgrid.cpp
+++ b/effects/desktopgrid.cpp
@@ -46,7 +46,7 @@ void DesktopGridEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     if( slide )
         {
-        progress = qMin( 1.0f, progress + time / float( PROGRESS_TIME ));
+        progress = qMin( 1.0, progress + time / double( 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( 1.0f, progress + time / float( PROGRESS_TIME ));
+            progress = qMin( 1.0, progress + time / double( PROGRESS_TIME ));
         else
-            progress = qMax( 0.0f, progress - time / float( PROGRESS_TIME ));
+            progress = qMax( 0.0, progress - time / double( 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 )
@@ -150,8 +150,8 @@ void DesktopGridEffect::paintScreenDesktop( int desktop, int mask, QRegion regio
         QRect normal = desktopRect( effects->currentDesktop(), false );
         d.xTranslate += rect.x(); // - normal.x();
         d.yTranslate += rect.y(); // - normal.y();
-        d.xScale *= rect.width() / float( normal.width());
-        d.yScale *= rect.height() / float( normal.height());
+        d.xScale *= rect.width() / double( normal.width());
+        d.yScale *= rect.height() / double( normal.height());
         // TODO mask parts that are not visible?
         effects->paintScreen( mask, region, d );
         }
@@ -280,10 +280,10 @@ QRect DesktopGridEffect::desktopRect( int desktop, bool scaled ) const
     if( !scaled )
         return rect;
     QRect current = desktopRect( effects->currentDesktop(), false );
-    rect = QRect( qRound( interpolate( rect.x() - current.x(), rect.x() / float( x ), progress )),
-        qRound( interpolate( rect.y() - current.y(), rect.y() / float( y ), progress )),
-        qRound( interpolate( rect.width(), displayWidth() / float( x ), progress )),
-        qRound( interpolate( rect.height(), displayHeight() / float( y ), progress )));
+    rect = QRect( qRound( interpolate( rect.x() - current.x(), rect.x() / double( x ), progress )),
+        qRound( interpolate( rect.y() - current.y(), rect.y() / double( y ), progress )),
+        qRound( interpolate( rect.width(), displayWidth() / double( x ), progress )),
+        qRound( interpolate( rect.height(), displayHeight() / double( y ), progress )));
     return rect;
     }
 
@@ -395,9 +395,9 @@ void DesktopGridEffect::slideDesktopChanged( int old )
             { // current position is in new current desktop (e.g. quickly changing back),
               // don't do full progress
             if( abs( currentPos.x() - rect.x()) > abs( currentPos.y() - rect.y()))
-                progress = 1 - abs( currentPos.x() - rect.x()) / float( displayWidth());
+                progress = 1 - abs( currentPos.x() - rect.x()) / double( displayWidth());
             else
-                progress = 1 - abs( currentPos.y() - rect.y()) / float( displayHeight());
+                progress = 1 - abs( currentPos.y() - rect.y()) / double( displayHeight());
             }
         else // current position is not on current desktop, do full progress
             progress = 0;
diff --git a/effects/desktopgrid.h b/effects/desktopgrid.h
index dc13a1aeaa..86d4853f5c 100644
--- a/effects/desktopgrid.h
+++ b/effects/desktopgrid.h
@@ -45,7 +45,7 @@ class DesktopGridEffect
         void paintSlide( int mask, QRegion region, const ScreenPaintData& data );
         void paintScreenDesktop( int desktop, int mask, QRegion region, ScreenPaintData data );
         void slideDesktopChanged( int old );
-        float progress;
+        double progress;
         bool activated;
         int painting_desktop;
         int hover_desktop;
diff --git a/effects/dialogparent.cpp b/effects/dialogparent.cpp
index c683f642bb..e384337900 100644
--- a/effects/dialogparent.cpp
+++ b/effects/dialogparent.cpp
@@ -18,7 +18,7 @@ KWIN_EFFECT( dialogparent, DialogParentEffect )
 void DialogParentEffect::prePaintWindow( EffectWindow* w, WindowPrePaintData& data, int time )
     {
     // How long does it take for the effect to get it's full strength (in ms)
-    const float changeTime = 200;
+    const double changeTime = 200;
 
     // Check if this window has a modal dialog and change the window's
     //  effect's strength accordingly
@@ -26,11 +26,11 @@ void DialogParentEffect::prePaintWindow( EffectWindow* w, WindowPrePaintData& da
     if( hasDialog )
         {
         // Increase effect strength of this window
-        effectStrength[w] = qMin(1.0f, effectStrength[w] + time/changeTime);
+        effectStrength[w] = qMin(1.0, effectStrength[w] + time/changeTime);
         }
     else
         {
-        effectStrength[w] = qMax(0.0f, effectStrength[w] - time/changeTime);
+        effectStrength[w] = qMax(0.0, effectStrength[w] - time/changeTime);
         }
 
     // Call the next effect
@@ -39,7 +39,7 @@ void DialogParentEffect::prePaintWindow( EffectWindow* w, WindowPrePaintData& da
 
 void DialogParentEffect::paintWindow( EffectWindow* w, int mask, QRegion region, WindowPaintData& data )
     {
-    float s = effectStrength[w];
+    double s = effectStrength[w];
     if(s > 0.0f)
         {
         // Brightness will be within [1.0; 0.6]
@@ -54,7 +54,7 @@ void DialogParentEffect::paintWindow( EffectWindow* w, int mask, QRegion region,
 
 void DialogParentEffect::postPaintWindow( EffectWindow* w )
     {
-    float s = effectStrength[w];
+    double s = effectStrength[w];
 
     // If strength is between 0 and 1, the effect is still in progress and the
     //  window has to be repainted during the next pass
diff --git a/effects/dialogparent.h b/effects/dialogparent.h
index 979dfafd48..3b33233d19 100644
--- a/effects/dialogparent.h
+++ b/effects/dialogparent.h
@@ -39,7 +39,7 @@ class DialogParentEffect
         bool hasModalWindow( EffectWindow* t );
     private:
         // The progress of the fading.
-        QHash<EffectWindow*, float> effectStrength;
+        QHash<EffectWindow*, double> effectStrength;
     };
 
 } // namespace
diff --git a/effects/drunken.h b/effects/drunken.h
index 85ac1a1b8c..2b665c4536 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*, float > windows; // progress
+        QHash< EffectWindow*, double > windows; // progress
     };
 
 } // namespace
diff --git a/effects/explosioneffect.cpp b/effects/explosioneffect.cpp
index 9b4ebacef8..f2e16372ce 100644
--- a/effects/explosioneffect.cpp
+++ b/effects/explosioneffect.cpp
@@ -144,8 +144,8 @@ void ExplosionEffect::paintWindow( EffectWindow* w, int mask, QRegion region, Wi
     bool useshader = ( mValid && mWindows.contains( w ) );
     if( useshader )
         {
-        float maxscaleadd = 1.5f;
-        float scale = 1 + maxscaleadd*mWindows[w];
+        double maxscaleadd = 1.5f;
+        double scale = 1 + maxscaleadd*mWindows[w];
         data.xScale = scale;
         data.yScale = scale;
         data.xTranslate += int( w->width() / 2 * ( 1 - scale ));
@@ -153,7 +153,7 @@ void ExplosionEffect::paintWindow( EffectWindow* w, int mask, QRegion region, Wi
         data.opacity *= 0.99;  // Force blending
         mShader->bind();
         mShader->setUniform("factor", (float)mWindows[w]);
-        mShader->setUniform("scale", scale);
+        mShader->setUniform("scale", (float)scale);
         glActiveTexture(GL_TEXTURE4);
         mStartOffsetTex->bind();
         glActiveTexture(GL_TEXTURE5);
diff --git a/effects/explosioneffect.h b/effects/explosioneffect.h
index e570469cc7..b2846cd6aa 100644
--- a/effects/explosioneffect.h
+++ b/effects/explosioneffect.h
@@ -50,7 +50,7 @@ class ExplosionEffect
         GLShader* mShader;
         GLTexture* mStartOffsetTex;
         GLTexture* mEndOffsetTex;
-        QMap< const EffectWindow*, float > mWindows;
+        QMap< const EffectWindow*, double > mWindows;
         int mActiveAnimations;
         bool mValid;
         bool mInited;
diff --git a/effects/fade.cpp b/effects/fade.cpp
index cd5e2e0ecc..90853828a5 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 / float( fadeInTime );
-        fadeOutStep = time / float( fadeOutTime );
+        fadeInStep = time / double( fadeInTime );
+        fadeOutStep = time / double( fadeOutTime );
         }
     effects->prePaintScreen( data, time );
     }
@@ -95,28 +95,28 @@ void FadeEffect::paintWindow( EffectWindow* w, int mask, QRegion region, WindowP
             if( new_data.saturation > windows[ w ].saturation )
                 {
                 windows[ w ].saturation = qMin( new_data.saturation,
-                    windows[ w ].saturation + float( windows[ w ].fadeInStep ));
+                    windows[ w ].saturation + windows[ w ].fadeInStep );
                 }
             else if( new_data.saturation < windows[ w ].saturation )
                 {
                 windows[ w ].saturation = qMax( new_data.saturation,
-                    windows[ w ].saturation - float( windows[ w ].fadeOutStep ));
+                    windows[ w ].saturation - windows[ w ].fadeOutStep );
                 }
 
             if( new_data.brightness > windows[ w ].brightness )
                 {
                 windows[ w ].brightness = qMin( new_data.brightness,
-                    windows[ w ].brightness + float( windows[ w ].fadeInStep ));
+                    windows[ w ].brightness + windows[ w ].fadeInStep );
                 }
             else if( new_data.brightness < windows[ w ].brightness )
                 {
                 windows[ w ].brightness = qMax( new_data.brightness,
-                    windows[ w ].brightness - float( windows[ w ].fadeOutStep ));
+                    windows[ w ].brightness - windows[ w ].fadeOutStep );
                 }
 
-            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 ].opacity = qBound( 0.0, windows[ w ].opacity, 1.0 );
+            windows[ w ].saturation = qBound( 0.0, windows[ w ].saturation, 1.0 );
+            windows[ w ].brightness = qBound( 0.0, windows[ w ].brightness, 1.0 );
             windows[ w ].fadeInStep = 0.0;
             windows[ w ].fadeOutStep = 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, float old_opacity )
+void FadeEffect::windowOpacityChanged( EffectWindow* w, double old_opacity )
     {
     if( !windows.contains( w ))
         windows[ w ].opacity = old_opacity;
diff --git a/effects/fade.h b/effects/fade.h
index f1f27ef226..0554e3b709 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, float old_opacity );
+        virtual void windowOpacityChanged( EffectWindow* c, double 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;
-        float fadeInStep, fadeOutStep;
+        double fadeInStep, fadeOutStep;
         int fadeInTime, fadeOutTime;
         bool fadeWindows;
     };
@@ -51,9 +51,9 @@ class FadeEffect::WindowInfo
             , brightness( 1.0 )
             , deleted( false )
             {}
-        float fadeInStep, fadeOutStep;
-        float opacity;
-        float saturation, brightness;
+        double fadeInStep, fadeOutStep;
+        double opacity;
+        double saturation, brightness;
         bool deleted;
     };
 
diff --git a/effects/fallapart.cpp b/effects/fallapart.cpp
index cc4cbeba30..beee4717af 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());
-            float xdiff = 0;
+            double 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;
-            float ydiff = 0;
+            double 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;
-            float modif = windows[ w ] * windows[ w ] * 64;
+            double 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 );
-            float adiff = ( rand() % 720 - 360 ) / 360. * 2 * M_PI; // spin randomly
+            double adiff = ( rand() % 720 - 360 ) / 360. * 2 * M_PI; // spin randomly
             for( int j = 0;
                  j < 4;
                  ++j )
                 {
-                float x = quad[ j ].x() - center.x();
-                float y = quad[ j ].y() - center.y();
-                float angle = atan2( y, x );
+                double x = quad[ j ].x() - center.x();
+                double y = quad[ j ].y() - center.y();
+                double angle = atan2( y, x );
                 angle += windows[ w ] * adiff;
-                float dist = sqrt( x * x + y * y );
+                double 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 f420f32907..90f399aace 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*, float > windows;
+        QHash< const EffectWindow*, double > windows;
     };
 
 } // namespace
diff --git a/effects/flame.cpp b/effects/flame.cpp
index 5e2da48cc5..797293abed 100644
--- a/effects/flame.cpp
+++ b/effects/flame.cpp
@@ -50,7 +50,7 @@ void FlameEffect::paintWindow( EffectWindow* w, int mask, QRegion region, Window
     if( windows.contains( w ))
         {
         WindowQuadList new_quads;
-        float ylimit = windows[ w ] * w->height(); // parts above this are already away
+        double ylimit = windows[ w ] * w->height(); // parts above this are already away
         foreach( WindowQuad quad, data.quads )
             {
             if( quad.bottom() <= ylimit )
diff --git a/effects/flame.h b/effects/flame.h
index 861e755ad8..ee3ac7da53 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*, float > windows;
+        QHash< const EffectWindow*, double > windows;
     };
 
 } // namespace
diff --git a/effects/lookingglass.cpp b/effects/lookingglass.cpp
index c2dbaa909a..7f2e08b0c8 100644
--- a/effects/lookingglass.cpp
+++ b/effects/lookingglass.cpp
@@ -53,7 +53,7 @@ void LookingGlassEffect::toggle()
 
 void LookingGlassEffect::zoomIn()
     {
-    target_zoom = qMin(7.0f, target_zoom + 0.5f);
+    target_zoom = qMin(7.0, target_zoom + 0.5);
     setEnabled( true );
     effects->addRepaint( cursorPos().x() - radius, cursorPos().y() - radius, 2*radius, 2*radius );
     }
@@ -73,18 +73,18 @@ void LookingGlassEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     if( zoom != target_zoom )
         {
-        float diff = time / 500.0f;
+        double diff = time / 500.0;
         if( target_zoom > zoom )
-            zoom = qMin( zoom * qMax( 1.0f + diff, 1.2f ), target_zoom );
+            zoom = qMin( zoom * qMax( 1.0 + diff, 1.2 ), target_zoom );
         else
-            zoom = qMax( zoom * qMin( 1.0f - diff, 0.8f ), target_zoom );
+            zoom = qMax( zoom * qMin( 1.0 - diff, 0.8 ), target_zoom );
         kDebug() << "zoom is now " << zoom;
-        radius = qBound(200.0f, 200.0f * zoom, 500.0f);
+        radius = qBound(200.0, 200.0 * zoom, 500.0);
 
         if( zoom > 1.0f )
             {
             shader()->bind();
-            shader()->setUniform("zoom", zoom);
+            shader()->setUniform("zoom", (float)zoom);
             shader()->setUniform("radius", (float)radius);
             shader()->unbind();
             }
diff --git a/effects/lookingglass.h b/effects/lookingglass.h
index bbb6307186..086c63e919 100644
--- a/effects/lookingglass.h
+++ b/effects/lookingglass.h
@@ -36,8 +36,8 @@ class LookingGlassEffect : public QObject, public ShaderEffect
         void zoomOut();
 
     private:
-        float zoom;
-        float target_zoom;
+        double zoom;
+        double target_zoom;
         int radius;
     };
 
diff --git a/effects/magnifier.cpp b/effects/magnifier.cpp
index cb34f238d9..d8c9e6f5c8 100644
--- a/effects/magnifier.cpp
+++ b/effects/magnifier.cpp
@@ -46,11 +46,11 @@ void MagnifierEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     if( zoom != target_zoom )
         {
-        float diff = time / 500.0;
+        double diff = time / 500.0;
         if( target_zoom > zoom )
-            zoom = qMin( zoom * qMax( 1 + diff, 1.2f ), target_zoom );
+            zoom = qMin( zoom * qMax( 1 + diff, 1.2 ), target_zoom );
         else
-            zoom = qMax( zoom * qMin( 1 - diff, 0.8f ), target_zoom );
+            zoom = qMax( zoom * qMin( 1 - diff, 0.8 ), target_zoom );
         }
     effects->prePaintScreen( data, time );
     if( zoom != 1.0 )
diff --git a/effects/magnifier.h b/effects/magnifier.h
index 8d08670fb1..548bbe7e12 100644
--- a/effects/magnifier.h
+++ b/effects/magnifier.h
@@ -33,8 +33,8 @@ class MagnifierEffect
         void toggle();
     private:
         QRect magnifierArea( QPoint pos = cursorPos()) const;
-        float zoom;
-        float target_zoom;
+        double zoom;
+        double target_zoom;
         QSize magnifier_size;
     };
 
diff --git a/effects/maketransparent.h b/effects/maketransparent.h
index 36660542c2..88d04914e1 100644
--- a/effects/maketransparent.h
+++ b/effects/maketransparent.h
@@ -25,9 +25,9 @@ class MakeTransparentEffect
         virtual void prePaintWindow( EffectWindow* w, WindowPrePaintData& data, int time );
         virtual void paintWindow( EffectWindow* w, int mask, QRegion region, WindowPaintData& data );
     private:
-        float decoration;
-        float moveresize;
-        float dialogs;
+        double decoration;
+        double moveresize;
+        double dialogs;
     };
 
 } // namespace
diff --git a/effects/minimizeanimation.cpp b/effects/minimizeanimation.cpp
index 0862e4fab3..d59d649f61 100644
--- a/effects/minimizeanimation.cpp
+++ b/effects/minimizeanimation.cpp
@@ -34,7 +34,7 @@ void MinimizeAnimationEffect::prePaintScreen( ScreenPrePaintData& data, int time
 
 void MinimizeAnimationEffect::prePaintWindow( EffectWindow* w, WindowPrePaintData& data, int time )
     {
-    const float changeTime = 500;
+    const double changeTime = 500;
     if( mAnimationProgress.contains( w ))
         {
         if( w->isMinimized() )
@@ -71,7 +71,7 @@ void MinimizeAnimationEffect::paintWindow( EffectWindow* w, int mask, QRegion re
     if( mAnimationProgress.contains( w ))
     {
         // 0 = not minimized, 1 = fully minimized
-        float progress = mAnimationProgress[w];
+        double progress = mAnimationProgress[w];
 
         QRect geo = w->geometry();
         QRect icon = w->iconGeometry();
@@ -79,8 +79,8 @@ void MinimizeAnimationEffect::paintWindow( EffectWindow* w, int mask, QRegion re
         if( !icon.isValid() )
             icon = QRect( displayWidth() / 2, displayHeight() / 2, 0, 0 );
 
-        data.xScale *= interpolate(1.0, icon.width() / (float)geo.width(), progress);
-        data.yScale *= interpolate(1.0, icon.height() / (float)geo.height(), progress);
+        data.xScale *= interpolate(1.0, icon.width() / (double)geo.width(), progress);
+        data.yScale *= interpolate(1.0, icon.height() / (double)geo.height(), progress);
         data.xTranslate = (int)interpolate(data.xTranslate, icon.x() - geo.x(), progress);
         data.yTranslate = (int)interpolate(data.yTranslate, icon.y() - geo.y(), progress);
     }
diff --git a/effects/minimizeanimation.h b/effects/minimizeanimation.h
index 4e67e0f8aa..39cb7d3734 100644
--- a/effects/minimizeanimation.h
+++ b/effects/minimizeanimation.h
@@ -36,7 +36,7 @@ class MinimizeAnimationEffect
         virtual void windowUnminimized( EffectWindow* c );
 
     private:
-        QHash< EffectWindow*, float > mAnimationProgress;
+        QHash< EffectWindow*, double > mAnimationProgress;
         int mActiveAnimations;
     };
 
diff --git a/effects/presentwindows.cpp b/effects/presentwindows.cpp
index 85f79bad97..dfb52df50e 100644
--- a/effects/presentwindows.cpp
+++ b/effects/presentwindows.cpp
@@ -73,17 +73,17 @@ PresentWindowsEffect::~PresentWindowsEffect()
 void PresentWindowsEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     // How long does it take for the effect to get it's full strength (in ms)
-    const float changeTime = 300;
+    const double changeTime = 300;
     if(mActivated)
         {
-        mActiveness = qMin(1.0f, mActiveness + time/changeTime);
+        mActiveness = qMin(1.0, mActiveness + time/changeTime);
         if( mRearranging < 1 )
-            mRearranging = qMin(1.0f, mRearranging + time/changeTime);
+            mRearranging = qMin(1.0, mRearranging + time/changeTime);
         }
-    else if(mActiveness > 0.0f)
+    else if(mActiveness > 0.0)
         {
-        mActiveness = qMax(0.0f, mActiveness - time/changeTime);
-        if(mActiveness <= 0.0f)
+        mActiveness = qMax(0.0, mActiveness - time/changeTime);
+        if(mActiveness <= 0.0)
             effectTerminated();
         }
 
@@ -111,11 +111,11 @@ void PresentWindowsEffect::prePaintWindow( EffectWindow* w, WindowPrePaintData&
                 data.setTranslucent();
             // Change window's hover according to cursor pos
             WindowData& windata = mWindowData[w];
-            const float hoverchangetime = 200;
+            const double hoverchangetime = 200;
             if( windata.area.contains(cursorPos()) )
-                windata.hover = qMin(1.0f, windata.hover + time / hoverchangetime);
+                windata.hover = qMin(1.0, windata.hover + time / hoverchangetime);
             else
-                windata.hover = qMax(0.0f, windata.hover - time / hoverchangetime);
+                windata.hover = qMax(0.0, windata.hover - time / hoverchangetime);
             }
         else if( !w->isDesktop())
             w->disablePainting( EffectWindow::PAINT_DISABLED );
@@ -195,10 +195,10 @@ void PresentWindowsEffect::paintWindow( EffectWindow* w, int mask, QRegion regio
         paintWindowIcon( w, data );
 
         QString text = w->caption();
-        float centerx = w->x() + data.xTranslate + w->width() * data.xScale * 0.5f;
-        float centery = w->y() + data.yTranslate + w->height() * data.yScale * 0.5f;
+        double centerx = w->x() + data.xTranslate + w->width() * data.xScale * 0.5f;
+        double centery = w->y() + data.yTranslate + w->height() * data.yScale * 0.5f;
         int maxwidth = (int)(w->width() * data.xScale - 20);
-        float opacity = (0.7 + 0.2*windata.hover) * data.opacity;
+        double opacity = (0.7 + 0.2*windata.hover) * data.opacity;
         QColor textcolor( 255, 255, 255, (int)(255*opacity) );
         QColor bgcolor( 0, 0, 0, (int)(255*opacity) );
         QFont f;
@@ -421,7 +421,7 @@ void PresentWindowsEffect::calculateWindowTransformationsDumb(EffectWindowList w
         int r = i / cols;
         int c = i % cols;
         mWindowData[window].hover = 0.0f;
-        mWindowData[window].scale = qMin(cellwidth / (float)window->width(), cellheight / (float)window->height());
+        mWindowData[window].scale = qMin(cellwidth / (double)window->width(), cellheight / (double)window->height());
         mWindowData[window].area.setLeft(placementRect.left() + cellwidth * c);
         mWindowData[window].area.setTop(placementRect.top() + cellheight * r);
         mWindowData[window].area.setWidth((int)(window->width() * mWindowData[window].scale));
@@ -434,19 +434,19 @@ void PresentWindowsEffect::calculateWindowTransformationsDumb(EffectWindowList w
         }
     }
 
-float PresentWindowsEffect::windowAspectRatio(EffectWindow* c)
+double PresentWindowsEffect::windowAspectRatio(EffectWindow* c)
     {
-    return c->width() / (float)c->height();
+    return c->width() / (double)c->height();
     }
 
 int PresentWindowsEffect::windowWidthForHeight(EffectWindow* c, int h)
     {
-    return (int)((h / (float)c->height()) * c->width());
+    return (int)((h / (double)c->height()) * c->width());
     }
 
 int PresentWindowsEffect::windowHeightForWidth(EffectWindow* c, int w)
     {
-    return (int)((w / (float)c->width()) * c->height());
+    return (int)((w / (double)c->width()) * c->height());
     }
 
 void PresentWindowsEffect::calculateWindowTransformationsKompose(EffectWindowList windowlist)
@@ -458,17 +458,17 @@ void PresentWindowsEffect::calculateWindowTransformationsKompose(EffectWindowLis
 
     int spacing = 10;
     int rows, columns;
-    float parentRatio = availRect.width() / (float)availRect.height();
+    double parentRatio = availRect.width() / (double)availRect.height();
     // Use more columns than rows when parent's width > parent's height
     if ( parentRatio > 1 )
     {
         columns = (int)ceil( sqrt(windowlist.count()) );
-        rows = (int)ceil( (float)windowlist.count() / (float)columns );
+        rows = (int)ceil( (double)windowlist.count() / (double)columns );
     }
     else
     {
         rows = (int)ceil( sqrt(windowlist.count()) );
-        columns = (int)ceil( (float)windowlist.count() / (float)rows );
+        columns = (int)ceil( (double)windowlist.count() / (double)rows );
     }
     kDebug() << "Using " << rows << " rows & " << columns << " columns for " << windowlist.count() << " clients";
 
@@ -495,7 +495,7 @@ void PresentWindowsEffect::calculateWindowTransformationsKompose(EffectWindowLis
             window = *it;
 
             // Calculate width and height of widget
-            float ratio = windowAspectRatio(window);
+            double ratio = windowAspectRatio(window);
 
             int widgetw = 100;
             int widgeth = 100;
@@ -525,8 +525,8 @@ void PresentWindowsEffect::calculateWindowTransformationsKompose(EffectWindowLis
                 }
             else
                 {
-                float widthForHeight = windowWidthForHeight(window, usableH);
-                float heightForWidth = windowHeightForWidth(window, usableW);
+                double widthForHeight = windowWidthForHeight(window, usableH);
+                double heightForWidth = windowHeightForWidth(window, usableW);
                 if ( (ratio >= 1.0 && heightForWidth <= usableH) ||
                       (ratio < 1.0 && widthForHeight > usableW)   )
                     {
@@ -576,7 +576,7 @@ void PresentWindowsEffect::calculateWindowTransformationsKompose(EffectWindowLis
             QRect geom = geometryRects[pos];
             geom.setY( geom.y() + topOffset );
             mWindowData[window].area = geom;
-            mWindowData[window].scale = geom.width() / (float)window->width();
+            mWindowData[window].scale = geom.width() / (double)window->width();
             mWindowData[window].hover = 0.0f;
 
             kDebug() << "Window '" << window->caption() << "' gets moved to (" <<
@@ -592,7 +592,7 @@ 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() / float( columns )));
+    int rows = int( ceil( windowlist.count() / double( columns )));
     foreach( EffectWindow* w, windowlist )
         mWindowData[ w ].slot = -1;
     for(;;)
@@ -621,17 +621,17 @@ void PresentWindowsEffect::calculateWindowTransformationsClosest(EffectWindowLis
             area.y() + ((*it).slot / columns ) * slotheight,
             slotwidth, slotheight );
         geom.adjust( 10, 10, -10, -10 ); // borders
-        float scale;
+        double scale;
         EffectWindow* w = it.key();
-        if( geom.width() / float( w->width()) < geom.height() / float( w->height()))
+        if( geom.width() / double( w->width()) < geom.height() / double( w->height()))
             { // center vertically
-            scale = geom.width() / float( w->width());
+            scale = geom.width() / double( w->width());
             geom.moveTop( geom.top() + ( geom.height() - int( w->height() * scale )) / 2 );
             geom.setHeight( int( w->height() * scale ));
             }
         else
             { // center horizontally
-            scale = geom.height() / float( w->height());
+            scale = geom.height() / double( w->height());
             geom.moveLeft( geom.left() + ( geom.width() - int( w->width() * scale )) / 2 );
             geom.setWidth( int( w->width() * scale ));
             }
@@ -713,9 +713,9 @@ 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() / float( columns )));
+    int rows = int( ceil( windowlist.count() / double( columns )));
     int old_columns = int( ceil( sqrt( mWindowData.count())));
-    int old_rows = int( ceil( mWindowData.count() / float( columns )));
+    int old_rows = int( ceil( mWindowData.count() / double( columns )));
     return old_columns != columns || old_rows != rows;
     }
 
diff --git a/effects/presentwindows.h b/effects/presentwindows.h
index 62dbc6c2bf..08054938a4 100644
--- a/effects/presentwindows.h
+++ b/effects/presentwindows.h
@@ -61,7 +61,7 @@ class PresentWindowsEffect
         bool canRearrangeClosest(EffectWindowList windowlist);
 
         // Helper methods for layout calculation
-        float windowAspectRatio(EffectWindow* c);
+        double windowAspectRatio(EffectWindow* c);
         int windowWidthForHeight(EffectWindow* c, int h);
         int windowHeightForWidth(EffectWindow* c, int w);
 
@@ -84,9 +84,9 @@ class PresentWindowsEffect
         // Whether the effect is currently activated by the user
         bool mActivated;
         // 0 = not active, 1 = fully active
-        float mActiveness;
+        double mActiveness;
         // 0 = start of rearranging (old_area), 1 = done
-        float mRearranging;
+        double mRearranging;
 
         Window mInput;
         bool hasKeyboardGrab;
@@ -96,9 +96,9 @@ class PresentWindowsEffect
             {
             QRect area;
             QRect old_area; // when rearranging, otherwise unset
-            float scale;
-            float old_scale; // when rearranging, otherwise unset
-            float hover;
+            double scale;
+            double old_scale; // when rearranging, otherwise unset
+            double hover;
             int slot;
             int slot_distance;
             QPixmap icon;
diff --git a/effects/scalein.h b/effects/scalein.h
index b1ea088b1d..a687043973 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*, float > windows;
+        QHash< const EffectWindow*, double > windows;
     };
 
 } // namespace
diff --git a/effects/shadow.cpp b/effects/shadow.cpp
index 2ec061e9ea..005ab05366 100644
--- a/effects/shadow.cpp
+++ b/effects/shadow.cpp
@@ -25,7 +25,7 @@ ShadowEffect::ShadowEffect()
     KConfigGroup conf = effects->effectConfig("Shadow");
     shadowXOffset = conf.readEntry( "XOffset", 10 );
     shadowYOffset = conf.readEntry( "YOffset", 10 );
-    shadowOpacity = (float)conf.readEntry( "Opacity", 0.2 );
+    shadowOpacity = conf.readEntry( "Opacity", 0.2 );
     shadowFuzzyness = conf.readEntry( "Fuzzyness", 10 );
 
     QString shadowtexture =  KGlobal::dirs()->findResource("data", "kwin/shadow-texture.png");
@@ -125,7 +125,7 @@ void ShadowEffect::drawShadow( EffectWindow* window, int mask, QRegion region, W
     mShadowTexture->bind();
     // Take the transparency settings and window's transparency into account.
     // Also make the shadow more transparent if we've made it bigger
-    glColor4f(0, 0, 0, shadowOpacity * data.opacity * (window->width() / (float)w) * (window->height() / (float)h));
+    glColor4f(0, 0, 0, shadowOpacity * data.opacity * (window->width() / (double)w) * (window->height() / (double)h));
     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;
diff --git a/effects/shadow.h b/effects/shadow.h
index 85b0e38216..a2434f3440 100644
--- a/effects/shadow.h
+++ b/effects/shadow.h
@@ -35,7 +35,7 @@ class ShadowEffect
         QRect shadowRectangle(const QRect& windowRectangle) const;
 
         int shadowXOffset, shadowYOffset;
-        float shadowOpacity;
+        double shadowOpacity;
         int shadowFuzzyness;
         GLTexture* mShadowTexture;
     };
diff --git a/effects/showfps.h b/effects/showfps.h
index cc58b80bd2..e85dc98381 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
-        float alpha;
+        double alpha;
         int x;
         int y;
     };
diff --git a/effects/test_fbo.h b/effects/test_fbo.h
index 9b7eff1c33..a0dee8a593 100644
--- a/effects/test_fbo.h
+++ b/effects/test_fbo.h
@@ -41,7 +41,7 @@ class TestFBOEffect : public Effect
         GLRenderTarget* mRenderTarget;
         bool mValid;
 
-        float mRot;
+        double mRot;
     };
 
 } // namespace
diff --git a/effects/thumbnailaside.cpp b/effects/thumbnailaside.cpp
index 59f8d83d49..53f72a4e93 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());
-    float scale = area.height() / float( height );
-    scale = qMin( scale, maxwidth / float( mwidth )); // don't be wider than maxwidth pixels
+    double scale = area.height() / double( height );
+    scale = qMin( scale, maxwidth / double( mwidth )); // don't be wider than maxwidth pixels
     int add = 0;
     for( int i = 0;
          i < windows.size();
diff --git a/effects/thumbnailaside.h b/effects/thumbnailaside.h
index 2b632f3d0e..7c071fe1ca 100644
--- a/effects/thumbnailaside.h
+++ b/effects/thumbnailaside.h
@@ -51,7 +51,7 @@ class ThumbnailAsideEffect
         QHash< EffectWindow*, Data > windows;
         int maxwidth;
         int spacing;
-        float opacity;
+        double opacity;
     };
 
 } // namespace
diff --git a/effects/zoom.cpp b/effects/zoom.cpp
index 5fbeefc52b..965fe776fe 100644
--- a/effects/zoom.cpp
+++ b/effects/zoom.cpp
@@ -37,11 +37,11 @@ void ZoomEffect::prePaintScreen( ScreenPrePaintData& data, int time )
     {
     if( zoom != target_zoom )
         {
-        float diff = time / 500.0;
+        double diff = time / 500.0;
         if( target_zoom > zoom )
-            zoom = qMin( zoom * qMax( 1 + diff, 1.2f ), target_zoom );
+            zoom = qMin( zoom * qMax( 1 + diff, 1.2 ), target_zoom );
         else
-            zoom = qMax( zoom * qMin( 1 - diff, 0.8f ), target_zoom );
+            zoom = qMax( zoom * qMin( 1 - diff, 0.8 ), target_zoom );
         }
     if( zoom != 1.0 )
         data.mask |= PAINT_SCREEN_TRANSFORMED;
diff --git a/effects/zoom.h b/effects/zoom.h
index af54fe2ec5..f198b7391f 100644
--- a/effects/zoom.h
+++ b/effects/zoom.h
@@ -32,8 +32,8 @@ class ZoomEffect
         void zoomOut();
         void actualSize();
     private:
-        float zoom;
-        float target_zoom;
+        double zoom;
+        double target_zoom;
     };
 
 } // namespace
diff --git a/lib/kwineffects.cpp b/lib/kwineffects.cpp
index 60c46b9235..60400e2f7e 100644
--- a/lib/kwineffects.cpp
+++ b/lib/kwineffects.cpp
@@ -84,7 +84,7 @@ void Effect::windowUserMovedResized( EffectWindow* , bool, bool )
     {
     }
 
-void Effect::windowOpacityChanged( EffectWindow*, float )
+void Effect::windowOpacityChanged( EffectWindow*, double )
     {
     }
 
@@ -197,8 +197,8 @@ void Effect::setPositionTransformations( WindowPaintData& data, QRect& region, E
     {
     QSize size = w->size();
     size.scale( r.size(), aspect );
-    data.xScale = size.width() / float( w->width());
-    data.yScale = size.height() / float( w->height());
+    data.xScale = size.width() / double( w->width());
+    data.yScale = size.height() / double( w->height());
     int width = int( w->width() * data.xScale );
     int height = int( w->height() * data.yScale );
     int x = r.x() + ( r.width() - width ) / 2;
@@ -425,7 +425,7 @@ EffectWindowGroup::~EffectWindowGroup()
  WindowQuad
 ***************************************************************/
 
-WindowQuad WindowQuad::makeSubQuad( float x1, float y1, float x2, float y2 ) const
+WindowQuad WindowQuad::makeSubQuad( double x1, double y1, double x2, double y2 ) const
     {
     assert( x1 < x2 && y1 < y2 && x1 >= left() && x2 <= right() && y1 >= top() && y2 <= bottom());
 #ifndef NDEBUG
@@ -451,14 +451,14 @@ WindowQuad WindowQuad::makeSubQuad( float x1, float y1, float x2, float y2 ) con
     ret.verts[ 1 ].oy = y1;
     ret.verts[ 2 ].oy = y2;
     ret.verts[ 3 ].oy = y2;
-    float my_tleft = verts[ 0 ].tx;
-    float my_tright = verts[ 2 ].tx;
-    float my_ttop = verts[ 0 ].ty;
-    float my_tbottom = verts[ 2 ].ty;
-    float tleft = ( x1 - left()) / ( right() - left()) * ( my_tright - my_tleft ) + my_tleft;
-    float tright = ( x2 - left()) / ( right() - left()) * ( my_tright - my_tleft ) + my_tleft;
-    float ttop = ( y1 - top()) / ( bottom() - top()) * ( my_tbottom - my_ttop ) + my_ttop;
-    float tbottom = ( y2 - top()) / ( bottom() - top()) * ( my_tbottom - my_ttop ) + my_ttop;
+    double my_tleft = verts[ 0 ].tx;
+    double my_tright = verts[ 2 ].tx;
+    double my_ttop = verts[ 0 ].ty;
+    double my_tbottom = verts[ 2 ].ty;
+    double tleft = ( x1 - left()) / ( right() - left()) * ( my_tright - my_tleft ) + my_tleft;
+    double tright = ( x2 - left()) / ( right() - left()) * ( my_tright - my_tleft ) + my_tleft;
+    double ttop = ( y1 - top()) / ( bottom() - top()) * ( my_tbottom - my_ttop ) + my_ttop;
+    double tbottom = ( y2 - top()) / ( bottom() - top()) * ( my_tbottom - my_ttop ) + my_ttop;
     ret.verts[ 0 ].tx = tleft;
     ret.verts[ 3 ].tx = tleft;
     ret.verts[ 1 ].tx = tright;
@@ -473,8 +473,8 @@ WindowQuad WindowQuad::makeSubQuad( float x1, float y1, float x2, float y2 ) con
 bool WindowQuad::smoothNeeded() const
     {
     // smoothing is needed if the width or height of the quad does not match the original size
-    float width = verts[ 1 ].ox - verts[ 0 ].ox;
-    float height = verts[ 2 ].oy - verts[ 1 ].oy;
+    double width = verts[ 1 ].ox - verts[ 0 ].ox;
+    double height = verts[ 2 ].oy - verts[ 1 ].oy;
     return( verts[ 1 ].px - verts[ 0 ].px != width || verts[ 2 ].px - verts[ 3 ].px != width
         || verts[ 2 ].py - verts[ 1 ].py != height || verts[ 3 ].py - verts[ 0 ].py != height );
     }
@@ -483,7 +483,7 @@ bool WindowQuad::smoothNeeded() const
  WindowQuadList
 ***************************************************************/
 
-WindowQuadList WindowQuadList::splitAtX( float x ) const
+WindowQuadList WindowQuadList::splitAtX( double x ) const
     {
     WindowQuadList ret;
     foreach( WindowQuad quad, *this )
@@ -514,7 +514,7 @@ WindowQuadList WindowQuadList::splitAtX( float x ) const
     return ret;
     }
 
-WindowQuadList WindowQuadList::splitAtY( float y ) const
+WindowQuadList WindowQuadList::splitAtY( double y ) const
     {
     WindowQuadList ret;
     foreach( WindowQuad quad, *this )
@@ -550,10 +550,10 @@ WindowQuadList WindowQuadList::makeGrid( int maxquadsize ) const
     if( empty())
         return *this;
     // find the bounding rectangle
-    float left = first().left();
-    float right = first().right();
-    float top = first().top();
-    float bottom = first().bottom();
+    double left = first().left();
+    double right = first().right();
+    double top = first().top();
+    double bottom = first().bottom();
     foreach( WindowQuad quad, *this )
         {
 #ifndef NDEBUG
@@ -566,11 +566,11 @@ WindowQuadList WindowQuadList::makeGrid( int maxquadsize ) const
         bottom = qMax( bottom, quad.bottom());
         }
     WindowQuadList ret;
-    for( float x = left;
+    for( double x = left;
          x < right;
          x += maxquadsize )
         {
-        for( float y = top;
+        for( double y = top;
              y < bottom;
              y += maxquadsize )
             {
diff --git a/lib/kwineffects.h b/lib/kwineffects.h
index ae608a8ca8..6553bc58a0 100644
--- a/lib/kwineffects.h
+++ b/lib/kwineffects.h
@@ -97,7 +97,7 @@ 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, float old_opacity );
+        virtual void windowOpacityChanged( EffectWindow* c, double old_opacity );
         virtual void windowAdded( EffectWindow* c );
         virtual void windowClosed( EffectWindow* c );
         virtual void windowDeleted( EffectWindow* c );
@@ -122,7 +122,7 @@ class KWIN_EXPORT Effect
         static QPoint cursorPos();
 
         // Interpolates between x and y
-        static float interpolate(float x, float y, float a)
+        static double interpolate(double x, double y, double a)
             {
             return x * (1 - a) + y * a;
             }
@@ -309,7 +309,7 @@ class KWIN_EXPORT EffectWindow
         virtual bool isDeleted() const = 0;
 
         virtual bool isMinimized() const = 0;
-        virtual float opacity() const = 0;
+        virtual double opacity() const = 0;
 
         virtual bool isOnDesktop( int d ) const;
         virtual bool isOnCurrentDesktop() const;
@@ -379,21 +379,21 @@ class KWIN_EXPORT EffectWindowGroup
 class KWIN_EXPORT WindowVertex
     {
     public:
-        float x() const;
-        float y() const;
-        void move( float x, float y );
-        void setX( float x );
-        void setY( float y );
-        float originalX() const;
-        float originalY() const;
+        double x() const;
+        double y() const;
+        void move( double x, double y );
+        void setX( double x );
+        void setY( double y );
+        double originalX() const;
+        double originalY() const;
         WindowVertex();
-        WindowVertex( float x, float y, float tx, float ty );
+        WindowVertex( double x, double y, double tx, double ty );
     private:
         friend class WindowQuad;
         friend class WindowQuadList;
-        float px, py; // position
-        float ox, oy; // origional position
-        float tx, ty; // texture coords
+        double px, py; // position
+        double ox, oy; // origional position
+        double tx, ty; // texture coords
     };
 
 enum WindowQuadType
@@ -412,18 +412,18 @@ class KWIN_EXPORT WindowQuad
     {
     public:
         explicit WindowQuad( WindowQuadType type );
-        WindowQuad makeSubQuad( float x1, float y1, float x2, float y2 ) const;
+        WindowQuad makeSubQuad( double x1, double y1, double x2, double y2 ) const;
         WindowVertex& operator[]( int index );
         const WindowVertex& operator[]( int index ) const;
         bool decoration() const;
-        float left() const;
-        float right() const;
-        float top() const;
-        float bottom() const;
-        float originalLeft() const;
-        float originalRight() const;
-        float originalTop() const;
-        float originalBottom() const;
+        double left() const;
+        double right() const;
+        double top() const;
+        double bottom() const;
+        double originalLeft() const;
+        double originalRight() const;
+        double originalTop() const;
+        double originalBottom() const;
         bool smoothNeeded() const;
         bool isTransformed() const;
     private:
@@ -436,8 +436,8 @@ class KWIN_EXPORT WindowQuadList
     : public QList< WindowQuad >
     {
     public:
-        WindowQuadList splitAtX( float x ) const;
-        WindowQuadList splitAtY( float y ) const;
+        WindowQuadList splitAtX( double x ) const;
+        WindowQuadList splitAtY( double y ) const;
         WindowQuadList makeGrid( int maxquadsize ) const;
         WindowQuadList select( WindowQuadType type ) const;
         WindowQuadList filterOut( WindowQuadType type ) const;
@@ -472,11 +472,11 @@ class KWIN_EXPORT WindowPaintData
          * Opacity for contents is opacity*contents_opacity, the same
          * way for decoration.
          */
-        float opacity;
-        float contents_opacity;
-        float decoration_opacity;
-        float xScale;
-        float yScale;
+        double opacity;
+        double contents_opacity;
+        double decoration_opacity;
+        double xScale;
+        double yScale;
         int xTranslate;
         int yTranslate;
         /**
@@ -485,13 +485,13 @@ class KWIN_EXPORT WindowPaintData
          *  unsaturated (greyscale). 0.5 would make the colors less intense,
          *  but not completely grey
          **/
-        float saturation;
+        double saturation;
         /**
          * Brightness of the window, in range [0; 1]
          * 1 means that the window is unchanged, 0 means that it's completely
          * black. 0.5 would make it 50% darker than usual
          **/
-        float brightness;
+        double brightness;
         WindowQuadList quads;
         /**
          * Shader to be used for rendering, if any.
@@ -503,8 +503,8 @@ class KWIN_EXPORT ScreenPaintData
     {
     public:
         ScreenPaintData();
-        float xScale;
-        float yScale;
+        double xScale;
+        double yScale;
         int xTranslate;
         int yTranslate;
     };
@@ -529,50 +529,50 @@ WindowVertex::WindowVertex()
     }
 
 inline
-WindowVertex::WindowVertex( float _x, float _y, float _tx, float _ty )
+WindowVertex::WindowVertex( double _x, double _y, double _tx, double _ty )
     : px( _x ), py( _y ), ox( _x ), oy( _y ), tx( _tx ), ty( _ty )
     {
     }
 
 inline
-float WindowVertex::x() const
+double WindowVertex::x() const
     {
     return px;
     }
 
 inline
-float WindowVertex::y() const
+double WindowVertex::y() const
     {
     return py;
     }
 
 inline
-float WindowVertex::originalX() const
+double WindowVertex::originalX() const
     {
     return ox;
     }
 
 inline
-float WindowVertex::originalY() const
+double WindowVertex::originalY() const
     {
     return oy;
     }
 
 inline
-void WindowVertex::move( float x, float y )
+void WindowVertex::move( double x, double y )
     {
     px = x;
     py = y;
     }
 
 inline
-void WindowVertex::setX( float x )
+void WindowVertex::setX( double x )
     {
     px = x;
     }
 
 inline
-void WindowVertex::setY( float y )
+void WindowVertex::setY( double y )
     {
     py = y;
     }
@@ -618,49 +618,49 @@ bool WindowQuad::isTransformed() const
     }
 
 inline
-float WindowQuad::left() const
+double WindowQuad::left() const
     {
     return qMin( verts[ 0 ].px, qMin( verts[ 1 ].px, qMin( verts[ 2 ].px, verts[ 3 ].px )));
     }
 
 inline
-float WindowQuad::right() const
+double WindowQuad::right() const
     {
     return qMax( verts[ 0 ].px, qMax( verts[ 1 ].px, qMax( verts[ 2 ].px, verts[ 3 ].px )));
     }
 
 inline
-float WindowQuad::top() const
+double WindowQuad::top() const
     {
     return qMin( verts[ 0 ].py, qMin( verts[ 1 ].py, qMin( verts[ 2 ].py, verts[ 3 ].py )));
     }
 
 inline
-float WindowQuad::bottom() const
+double WindowQuad::bottom() const
     {
     return qMax( verts[ 0 ].py, qMax( verts[ 1 ].py, qMax( verts[ 2 ].py, verts[ 3 ].py )));
     }
 
 inline
-float WindowQuad::originalLeft() const
+double WindowQuad::originalLeft() const
     {
     return verts[ 0 ].ox;
     }
 
 inline
-float WindowQuad::originalRight() const
+double WindowQuad::originalRight() const
     {
     return verts[ 2 ].ox;
     }
 
 inline
-float WindowQuad::originalTop() const
+double WindowQuad::originalTop() const
     {
     return verts[ 0 ].oy;
     }
 
 inline
-float WindowQuad::originalBottom() const
+double WindowQuad::originalBottom() const
     {
     return verts[ 2 ].oy;
     }
diff --git a/lib/kwinshadereffect.cpp b/lib/kwinshadereffect.cpp
index 98565afc3b..45f775a83f 100644
--- a/lib/kwinshadereffect.cpp
+++ b/lib/kwinshadereffect.cpp
@@ -145,7 +145,7 @@ void ShaderEffect::postPaintScreen()
 
         // Use the shader
         mShader->bind();
-        mShader->setUniform("time", mTime);
+        mShader->setUniform("time", (float)mTime);
         mShader->setUniform("cursorX", (float)cursorPos().x());
         mShader->setUniform("cursorY", (float)cursorPos().y());
 
diff --git a/lib/kwinshadereffect.h b/lib/kwinshadereffect.h
index 890d6bf1d9..639dd0de7a 100644
--- a/lib/kwinshadereffect.h
+++ b/lib/kwinshadereffect.h
@@ -46,7 +46,7 @@ class KWIN_EXPORT ShaderEffect : public Effect
         GLShader* mShader;
         bool mValid;
 
-        float mTime;
+        double mTime;
 
         bool mEnabled;
 };
diff --git a/scene_opengl.cpp b/scene_opengl.cpp
index 77cbfdeb29..1820ea69bc 100644
--- a/scene_opengl.cpp
+++ b/scene_opengl.cpp
@@ -1177,7 +1177,7 @@ void SceneOpenGL::Window::renderQuads( int mask, const QRegion& region, const Wi
     delete[] texcoords;
     }
 
-void SceneOpenGL::Window::prepareStates( float opacity, float brightness, float saturation, GLShader* shader )
+void SceneOpenGL::Window::prepareStates( double opacity, double brightness, double saturation, GLShader* shader )
     {
     if(shader)
         prepareShaderRenderStates( opacity, brightness, saturation, shader );
@@ -1185,7 +1185,7 @@ void SceneOpenGL::Window::prepareStates( float opacity, float brightness, float
         prepareRenderStates( opacity, brightness, saturation );
     }
 
-void SceneOpenGL::Window::prepareShaderRenderStates( float opacity, float brightness, float saturation, GLShader* shader )
+void SceneOpenGL::Window::prepareShaderRenderStates( double opacity, double brightness, double saturation, GLShader* shader )
     {
     // setup blending of transparent windows
     glPushAttrib( GL_ENABLE_BIT );
@@ -1200,7 +1200,7 @@ void SceneOpenGL::Window::prepareShaderRenderStates( float opacity, float bright
     shader->setUniform("brightness", (float)brightness);
     }
 
-void SceneOpenGL::Window::prepareRenderStates( float opacity, float brightness, float saturation )
+void SceneOpenGL::Window::prepareRenderStates( double opacity, double brightness, double saturation )
     {
     // setup blending of transparent windows
     glPushAttrib( GL_ENABLE_BIT );
@@ -1325,7 +1325,7 @@ void SceneOpenGL::Window::prepareRenderStates( float opacity, float brightness,
         }
     }
 
-void SceneOpenGL::Window::restoreStates( float opacity, float brightness, float saturation, GLShader* shader )
+void SceneOpenGL::Window::restoreStates( double opacity, double brightness, double saturation, GLShader* shader )
     {
     if(shader)
         restoreShaderRenderStates( opacity, brightness, saturation, shader );
@@ -1333,7 +1333,7 @@ void SceneOpenGL::Window::restoreStates( float opacity, float brightness, float
         restoreRenderStates( opacity, brightness, saturation );
     }
 
-void SceneOpenGL::Window::restoreShaderRenderStates( float opacity, float brightness, float saturation, GLShader* shader )
+void SceneOpenGL::Window::restoreShaderRenderStates( double opacity, double brightness, double saturation, GLShader* shader )
     {
     Q_UNUSED( opacity );
     Q_UNUSED( brightness );
@@ -1342,7 +1342,7 @@ void SceneOpenGL::Window::restoreShaderRenderStates( float opacity, float bright
     glPopAttrib();  // ENABLE_BIT
     }
 
-void SceneOpenGL::Window::restoreRenderStates( float opacity, float brightness, float saturation )
+void SceneOpenGL::Window::restoreRenderStates( double opacity, double brightness, double saturation )
     {
     if( opacity != 1.0 || saturation != 1.0 || brightness != 1.0f )
         {
diff --git a/scene_opengl.h b/scene_opengl.h
index 71fc2a5ba5..92a4af89ce 100644
--- a/scene_opengl.h
+++ b/scene_opengl.h
@@ -125,12 +125,12 @@ class SceneOpenGL::Window
 
     protected:
         void renderQuads( int mask, const QRegion& region, const WindowQuadList& quads );
-        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 );
+        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 );
 
     private:
         Texture texture;
diff --git a/scene_xrender.cpp b/scene_xrender.cpp
index 0e7174c4aa..cf99e2a9c8 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( float opacity )
+Picture SceneXrender::Window::alphaMask( double 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();
-    float xscale = 1;
-    float yscale = 1;
+    double xscale = 1;
+    double yscale = 1;
     transformed_shape = shape();
     if( mask & PAINT_WINDOW_TRANSFORMED )
         {
diff --git a/scene_xrender.h b/scene_xrender.h
index cefa27d4fa..ae1de60018 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( float opacity );
+        Picture alphaMask( double opacity );
         Picture _picture;
         XRenderPictFormat* format;
         Picture alpha;
-        float alpha_cached_opacity;
+        double alpha_cached_opacity;
         QRegion transformed_shape;
     };
 
diff --git a/toplevel.cpp b/toplevel.cpp
index a5d37e7b21..322836d97b 100644
--- a/toplevel.cpp
+++ b/toplevel.cpp
@@ -294,17 +294,17 @@ void Toplevel::getResourceClass()
         }
     }
 
-float Toplevel::opacity() const
+double Toplevel::opacity() const
     {
     if( info->opacity() == 0xffffffff )
         return 1.0;
     return info->opacity() * 1.0 / 0xffffffff;
     }
 
-void Toplevel::setOpacity( float new_opacity )
+void Toplevel::setOpacity( double new_opacity )
     {
-    float old_opacity = opacity();
-    new_opacity = qBound( 0.0f, new_opacity, 1.0f );
+    double old_opacity = opacity();
+    new_opacity = qBound( 0.0, new_opacity, 1.0 );
     if( old_opacity == new_opacity )
         return;
     info->setOpacity( static_cast< unsigned long >( new_opacity * 0xffffffff ));
diff --git a/toplevel.h b/toplevel.h
index 1b224297c7..b8cf559804 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( float opacity );
-        float opacity() const;
+        void setOpacity( double opacity );
+        double opacity() const;
         int depth() const;
         bool hasAlpha() const;
         void setupCompositing();