diff --git a/client.h b/client.h
index 1161a9c3a7..b05e29fc8a 100644
--- a/client.h
+++ b/client.h
@@ -286,7 +286,7 @@ class Client
         
         // Decorations <-> Effects
         QList<QRect> shadowQuads( ShadowType type ) const;
-        double shadowOpacity( ShadowType type, double dataOpacity ) const;
+        double shadowOpacity( ShadowType type ) const;
         double shadowBrightness( ShadowType type ) const;
         double shadowSaturation( ShadowType type ) const;
 
@@ -802,11 +802,11 @@ inline QList<QRect> Client::shadowQuads( ShadowType type ) const
     return QList<QRect>();
     }
 
-inline double Client::shadowOpacity( ShadowType type, double dataOpacity ) const
+inline double Client::shadowOpacity( ShadowType type ) const
     {
     if( KDecorationUnstable* decoration2 = dynamic_cast< KDecorationUnstable* >( decoration ))
-        return decoration2->shadowOpacity( type, dataOpacity );
-    return dataOpacity;
+        return decoration2->shadowOpacity( type );
+    return 1.0;
     }
 
 inline double Client::shadowBrightness( ShadowType type ) const
diff --git a/clients/oxygen/oxygen.cpp b/clients/oxygen/oxygen.cpp
index 90941a1251..ea5eef697e 100644
--- a/clients/oxygen/oxygen.cpp
+++ b/clients/oxygen/oxygen.cpp
@@ -367,9 +367,9 @@ QList<QRect> OxygenFactory::shadowQuads( ShadowType type, QSize size ) const
     return quads;
 }
 
-double OxygenFactory::shadowOpacity( ShadowType type, double dataOpacity ) const
+double OxygenFactory::shadowOpacity( ShadowType type ) const
 {
-    return dataOpacity;
+    return 1.0;
 }
 
 } //namespace Oxygen
diff --git a/clients/oxygen/oxygen.h b/clients/oxygen/oxygen.h
index b6fafed5ad..4376c179c6 100644
--- a/clients/oxygen/oxygen.h
+++ b/clients/oxygen/oxygen.h
@@ -65,7 +65,7 @@ public:
     virtual QList< QList<QImage> > shadowTextures();
     virtual int shadowTextureList( ShadowType type ) const;
     virtual QList<QRect> shadowQuads( ShadowType type, QSize size ) const;
-    virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+    virtual double shadowOpacity( ShadowType type ) const;
 
     static bool initialized();
     static Qt::Alignment titleAlignment();
diff --git a/clients/oxygen/oxygenclient.cpp b/clients/oxygen/oxygenclient.cpp
index ab7035ea46..1d453050e9 100644
--- a/clients/oxygen/oxygenclient.cpp
+++ b/clients/oxygen/oxygenclient.cpp
@@ -449,12 +449,12 @@ QList<QRect> OxygenClient::shadowQuads( ShadowType type ) const
     return quads;
 }
 
-double OxygenClient::shadowOpacity( ShadowType type, double dataOpacity ) const
+double OxygenClient::shadowOpacity( ShadowType type ) const
 {
     switch( type ) {
         case ShadowBorderedActive:
             if( isActive() )
-                return dataOpacity;
+                return 1.0;
             return 0.0;
         case ShadowBorderedInactive:
             if( isActive() )
diff --git a/clients/oxygen/oxygenclient.h b/clients/oxygen/oxygenclient.h
index 9ead2a1ffe..0e99eb3d19 100644
--- a/clients/oxygen/oxygenclient.h
+++ b/clients/oxygen/oxygenclient.h
@@ -52,7 +52,7 @@ public:
     virtual void init();
 
     virtual QList<QRect> shadowQuads( ShadowType type ) const;
-    virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+    virtual double shadowOpacity( ShadowType type ) const;
 
 private:
     void paintEvent(QPaintEvent *e);
diff --git a/clients/ozone/oxygen.cpp b/clients/ozone/oxygen.cpp
index 91799c8148..7c6ab8a420 100644
--- a/clients/ozone/oxygen.cpp
+++ b/clients/ozone/oxygen.cpp
@@ -373,9 +373,9 @@ QList<QRect> OxygenFactory::shadowQuads( ShadowType type, QSize size ) const
     return quads;
 }
 
-double OxygenFactory::shadowOpacity( ShadowType type, double dataOpacity ) const
+double OxygenFactory::shadowOpacity( ShadowType type ) const
 {
-    return dataOpacity;
+    return 1.0;
 }
 
 } //namespace Oxygen
diff --git a/clients/ozone/oxygen.h b/clients/ozone/oxygen.h
index e4f034100e..2c6457c9c9 100644
--- a/clients/ozone/oxygen.h
+++ b/clients/ozone/oxygen.h
@@ -67,7 +67,7 @@ public:
     virtual QList< QList<QImage> > shadowTextures();
     virtual int shadowTextureList( ShadowType type ) const;
     virtual QList<QRect> shadowQuads( ShadowType type, QSize size ) const;
-    virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+    virtual double shadowOpacity( ShadowType type ) const;
 
     static bool initialized();
     static Qt::Alignment titleAlignment();
diff --git a/clients/ozone/oxygenclient.cpp b/clients/ozone/oxygenclient.cpp
index 19425816f5..896f69581b 100644
--- a/clients/ozone/oxygenclient.cpp
+++ b/clients/ozone/oxygenclient.cpp
@@ -458,12 +458,12 @@ QList<QRect> OxygenClient::shadowQuads( ShadowType type ) const
     return quads;
 }
 
-double OxygenClient::shadowOpacity( ShadowType type, double dataOpacity ) const
+double OxygenClient::shadowOpacity( ShadowType type ) const
 {
     switch( type ) {
         case ShadowBorderedActive:
             if( isActive() )
-                return dataOpacity;
+                return 1.0;
             return 0.0;
         case ShadowBorderedInactive:
             if( isActive() )
diff --git a/clients/ozone/oxygenclient.h b/clients/ozone/oxygenclient.h
index 76b8d75bac..70af9f246c 100644
--- a/clients/ozone/oxygenclient.h
+++ b/clients/ozone/oxygenclient.h
@@ -54,7 +54,7 @@ public:
     virtual void init();
 
     virtual QList<QRect> shadowQuads( ShadowType type ) const;
-    virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+    virtual double shadowOpacity( ShadowType type ) const;
 
 private:
     void paintEvent(QPaintEvent *e);
diff --git a/effects.cpp b/effects.cpp
index c0886442ea..488b0438c9 100644
--- a/effects.cpp
+++ b/effects.cpp
@@ -1347,16 +1347,15 @@ QList<QRect> EffectWindowImpl::shadowQuads( ShadowType type ) const
     return toplevel->workspace()->decorationShadowQuads( type, toplevel->size() );
     }
 
-double EffectWindowImpl::shadowOpacity( ShadowType type, double dataOpacity ) const
+double EffectWindowImpl::shadowOpacity( ShadowType type ) const
     {
-    dataOpacity *= opacity();
     if( type == ShadowBorderedActive ||  type == ShadowBorderedInactive )
         {
         if( Client* c = dynamic_cast< Client* >( toplevel ))
-            return c->shadowOpacity( type, dataOpacity );
-        return dataOpacity;
+            return c->shadowOpacity( type );
+        return 1.0;
         }
-    return toplevel->workspace()->decorationShadowOpacity( type, dataOpacity );
+    return toplevel->workspace()->decorationShadowOpacity( type );
     }
 
 double EffectWindowImpl::shadowBrightness( ShadowType type ) const
diff --git a/effects.h b/effects.h
index f00f87d378..8eaeb4fb7c 100644
--- a/effects.h
+++ b/effects.h
@@ -239,7 +239,7 @@ class EffectWindowImpl : public EffectWindow
         virtual EffectWindowList mainWindows() const;
 
         virtual QList<QRect> shadowQuads( ShadowType type ) const;
-        virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+        virtual double shadowOpacity( ShadowType type ) const;
         virtual double shadowBrightness( ShadowType type ) const;
         virtual double shadowSaturation( ShadowType type ) const;
 
diff --git a/effects/shadow.cpp b/effects/shadow.cpp
index 54d5c78111..d07401589b 100644
--- a/effects/shadow.cpp
+++ b/effects/shadow.cpp
@@ -530,7 +530,7 @@ void ShadowEffect::drawShadow( EffectWindow* window, int mask, QRegion region, c
                         { // Decorated windows
                         // Active shadow
                         mShadowTextures.at( texture ).at( quad.id() )->bind();
-                        glColor4f( 1.0, 1.0, 1.0, window->shadowOpacity( ShadowBorderedActive, data.opacity ));
+                        glColor4f( 1.0, 1.0, 1.0, data.opacity * window->shadowOpacity( ShadowBorderedActive ));
                         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
                         mShadowTextures.at( texture ).at( quad.id() )->enableNormalizedTexCoords();
                         renderGLGeometry( region, 4, verts.data(), texcoords.data() );
@@ -540,7 +540,7 @@ void ShadowEffect::drawShadow( EffectWindow* window, int mask, QRegion region, c
                         // Inactive shadow
                         texture = effects->shadowTextureList( ShadowBorderedInactive );
                         mShadowTextures.at( texture ).at( quad.id() )->bind();
-                        glColor4f( 1.0, 1.0, 1.0, window->shadowOpacity( ShadowBorderedInactive, data.opacity ));
+                        glColor4f( 1.0, 1.0, 1.0, data.opacity * window->shadowOpacity( ShadowBorderedInactive ));
                         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
                         mShadowTextures.at( texture ).at( quad.id() )->enableNormalizedTexCoords();
                         renderGLGeometry( region, 4, verts.data(), texcoords.data() );
@@ -550,11 +550,13 @@ void ShadowEffect::drawShadow( EffectWindow* window, int mask, QRegion region, c
                     else if( effects->shadowTextureList( ShadowBorderlessActive ) == texture )
                         { // Decoration-less normal windows
                         if( effects->activeWindow() == window )
-                            glColor4f( 1.0, 1.0, 1.0, window->shadowOpacity( ShadowBorderlessActive, data.opacity ));
+                            glColor4f( 1.0, 1.0, 1.0,
+                                       data.opacity * window->shadowOpacity( ShadowBorderlessActive ));
                         else
                             {
                             texture = effects->shadowTextureList( ShadowBorderlessInactive );
-                            glColor4f( 1.0, 1.0, 1.0, window->shadowOpacity( ShadowBorderlessInactive, data.opacity ));
+                            glColor4f( 1.0, 1.0, 1.0,
+                                       data.opacity * window->shadowOpacity( ShadowBorderlessInactive ));
                             }
                         mShadowTextures.at( texture ).at( quad.id() )->bind();
                         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
@@ -566,7 +568,7 @@ void ShadowEffect::drawShadow( EffectWindow* window, int mask, QRegion region, c
                     else
                         { // Other windows
                         mShadowTextures.at( texture ).at( quad.id() )->bind();
-                        glColor4f( 1.0, 1.0, 1.0, window->shadowOpacity( ShadowOther, data.opacity ));
+                        glColor4f( 1.0, 1.0, 1.0, data.opacity * window->shadowOpacity( ShadowOther ));
                         glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
                         mShadowTextures.at( texture ).at( quad.id() )->enableNormalizedTexCoords();
                         renderGLGeometry( region, 4, verts.data(), texcoords.data() );
diff --git a/lib/kcommondecoration.cpp b/lib/kcommondecoration.cpp
index 76ac14270f..2330119a39 100644
--- a/lib/kcommondecoration.cpp
+++ b/lib/kcommondecoration.cpp
@@ -1238,12 +1238,12 @@ QList<QRect> KCommonDecorationUnstable::shadowQuads( ShadowType type ) const
     Q_UNUSED( type );
     return QList<QRect>();
     }
-double KCommonDecorationUnstable::shadowOpacity( ShadowType type, double dataOpacity ) const
+double KCommonDecorationUnstable::shadowOpacity( ShadowType type ) const
     {
     if( isActive() && type == ShadowBorderedActive )
-        return dataOpacity;
+        return 1.0;
     else if( !isActive() && type == ShadowBorderedInactive )
-        return dataOpacity;
+        return 1.0;
     return 0.0;
     }
 double KCommonDecorationUnstable::shadowBrightness( ShadowType type ) const
diff --git a/lib/kcommondecoration.h b/lib/kcommondecoration.h
index d194e5ca15..4b2cb867db 100644
--- a/lib/kcommondecoration.h
+++ b/lib/kcommondecoration.h
@@ -370,7 +370,7 @@ class KWIN_EXPORT KCommonDecorationUnstable
         KCommonDecorationUnstable(KDecorationBridge* bridge, KDecorationFactory* factory);
         virtual ~KCommonDecorationUnstable();
         virtual QList<QRect> shadowQuads( ShadowType type ) const;
-        virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+        virtual double shadowOpacity( ShadowType type ) const;
         virtual double shadowBrightness( ShadowType type ) const;
         virtual double shadowSaturation( ShadowType type ) const;
         void repaintShadow();
diff --git a/lib/kcommondecoration_p.cpp b/lib/kcommondecoration_p.cpp
index d5697e9ce6..733b9d93d8 100644
--- a/lib/kcommondecoration_p.cpp
+++ b/lib/kcommondecoration_p.cpp
@@ -120,11 +120,11 @@ QList<QRect> KCommonDecorationWrapper::shadowQuads( ShadowType type ) const
     return QList<QRect>();
     }
 
-double KCommonDecorationWrapper::shadowOpacity( ShadowType type, double dataOpacity ) const
+double KCommonDecorationWrapper::shadowOpacity( ShadowType type ) const
     {
     if( KCommonDecorationUnstable *decoration2 = dynamic_cast<KCommonDecorationUnstable*>( decoration ))
-        return decoration2->shadowOpacity( type, dataOpacity );
-    return dataOpacity;
+        return decoration2->shadowOpacity( type );
+    return 1.0;
     }
 
 double KCommonDecorationWrapper::shadowBrightness( ShadowType type ) const
diff --git a/lib/kcommondecoration_p.h b/lib/kcommondecoration_p.h
index e389e5b059..e152a28b87 100644
--- a/lib/kcommondecoration_p.h
+++ b/lib/kcommondecoration_p.h
@@ -60,7 +60,7 @@ class KCommonDecorationWrapper
         virtual void reset( unsigned long changed );
 
         virtual QList<QRect> shadowQuads( ShadowType type ) const;
-        virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+        virtual double shadowOpacity( ShadowType type ) const;
         virtual double shadowBrightness( ShadowType type ) const;
         virtual double shadowSaturation( ShadowType type ) const;
     private:
diff --git a/lib/kdecoration.cpp b/lib/kdecoration.cpp
index 837b5cbf2e..b1d349907c 100644
--- a/lib/kdecoration.cpp
+++ b/lib/kdecoration.cpp
@@ -399,12 +399,12 @@ QList<QRect> KDecorationUnstable::shadowQuads( ShadowType type ) const
     return QList<QRect>();
     }
 
-double KDecorationUnstable::shadowOpacity( ShadowType type, double dataOpacity ) const
+double KDecorationUnstable::shadowOpacity( ShadowType type ) const
     {
     if( isActive() && type == ShadowBorderedActive )
-        return dataOpacity;
+        return 1.0;
     else if( !isActive() && type == ShadowBorderedInactive )
-        return dataOpacity;
+        return 1.0;
     return 0.0;
     }
 
diff --git a/lib/kdecoration.h b/lib/kdecoration.h
index e90c948d39..cf3a8abb35 100644
--- a/lib/kdecoration.h
+++ b/lib/kdecoration.h
@@ -882,10 +882,9 @@ class KWIN_EXPORT KDecorationUnstable
          */
         virtual QList<QRect> shadowQuads( ShadowType type ) const;
         /**
-         * This function should return the opacity of the shadow. This is not multiplied
-         * with the opacity of the window afterwards but is instead provided as \a dataOpacity
+         * This function should return the desired opacity of the shadow.
          */
-        virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+        virtual double shadowOpacity( ShadowType type ) const;
         /**
          * This function should return the desired brightness of the shadow.
          */
diff --git a/lib/kdecorationfactory.cpp b/lib/kdecorationfactory.cpp
index 2485c31e5f..a5314b98c8 100644
--- a/lib/kdecorationfactory.cpp
+++ b/lib/kdecorationfactory.cpp
@@ -97,10 +97,10 @@ QList<QRect> KDecorationFactoryUnstable::shadowQuads( ShadowType type, QSize siz
     return QList<QRect>();
     }
 
-double KDecorationFactoryUnstable::shadowOpacity( ShadowType type, double dataOpacity ) const
+double KDecorationFactoryUnstable::shadowOpacity( ShadowType type ) const
     {
     Q_UNUSED( type );
-    return dataOpacity;
+    return 1.0;
     }
 
 double KDecorationFactoryUnstable::shadowBrightness( ShadowType type ) const
diff --git a/lib/kdecorationfactory.h b/lib/kdecorationfactory.h
index 984fd02d63..f61a0da6a8 100644
--- a/lib/kdecorationfactory.h
+++ b/lib/kdecorationfactory.h
@@ -141,10 +141,9 @@ class KWIN_EXPORT KDecorationFactoryUnstable
          */
         virtual QList<QRect> shadowQuads( ShadowType type, QSize size ) const;
         /**
-         * This function should return the opacity of the shadow. This is not multiplied
-         * with the opacity of the window afterwards but is instead provided as \a dataOpacity
+         * This function should return the desired opacity of the shadow.
          */
-        virtual double shadowOpacity( ShadowType type, double dataOpacity ) const;
+        virtual double shadowOpacity( ShadowType type ) const;
         /**
          * This function should return the desired brightness of the shadow.
          */
diff --git a/lib/kwineffects.h b/lib/kwineffects.h
index d51a30e9ae..0afd8f0931 100644
--- a/lib/kwineffects.h
+++ b/lib/kwineffects.h
@@ -825,10 +825,9 @@ class KWIN_EXPORT EffectWindow
          */
         virtual QList<QRect> shadowQuads( ShadowType type ) const = 0;
         /**
-         * Returns the opacity of the shadow. This has already been pre-multiplied by
-         * the window's opacity if the decoration desires so.
+         * Returns the desired opacity of the shadow.
          */
-        virtual double shadowOpacity( ShadowType type, double dataOpacity ) const = 0;
+        virtual double shadowOpacity( ShadowType type ) const = 0;
         /**
          * Returns the desired brightness of the shadow.
          */
diff --git a/workspace.h b/workspace.h
index 3eeb622f64..9203c601fd 100644
--- a/workspace.h
+++ b/workspace.h
@@ -248,7 +248,7 @@ class Workspace : public QObject, public KDecorationDefines
         QList< QList<QImage> > decorationShadowTextures();
         int decorationShadowTextureList( ShadowType type ) const;
         QList<QRect> decorationShadowQuads( ShadowType type, QSize size ) const;
-        double decorationShadowOpacity( ShadowType type, double dataOpacity ) const;
+        double decorationShadowOpacity( ShadowType type ) const;
         double decorationShadowBrightness( ShadowType type ) const;
         double decorationShadowSaturation( ShadowType type ) const;
 
@@ -1022,11 +1022,11 @@ QList<QRect> Workspace::decorationShadowQuads( ShadowType type, QSize size ) con
     }
 
 inline
-double Workspace::decorationShadowOpacity( ShadowType type, double dataOpacity ) const
+double Workspace::decorationShadowOpacity( ShadowType type ) const
     {
     if( KDecorationFactoryUnstable* factory = dynamic_cast< KDecorationFactoryUnstable* >( mgr->factory() ))
-        return factory->shadowOpacity( type, dataOpacity );
-    return dataOpacity;
+        return factory->shadowOpacity( type );
+    return 1.0;
     }
 
 inline