Add EffectsHandler::decorationsHaveAlpha().

Effects can use this method to check if the decorations use
the alpha channel.

svn path=/trunk/KDE/kdebase/workspace/; revision=1099522

effects.cpp

@@ -238,6 +238,11 @@ bool EffectsHandlerImpl::hasDecorationShadows() const
     return Workspace::self()->hasDecorationShadows();
     }
 
+bool EffectsHandlerImpl::decorationsHaveAlpha() const
+    {
+    return Workspace::self()->decorationHasAlpha();
+    }
+
 // start another painting pass
 void EffectsHandlerImpl::startPaint()
     {

effects.h

@@ -139,6 +139,8 @@ class EffectsHandlerImpl : public EffectsHandler
 
         virtual bool hasDecorationShadows() const;
 
+        virtual bool decorationsHaveAlpha() const;
+
         // internal (used by kwin core or compositing code)
         void startPaint();
         void windowUserMovedResized( EffectWindow* c, bool first, bool last );

lib/kwineffects.h

@@ -730,6 +730,12 @@ class KWIN_EXPORT EffectsHandler
          */
         virtual bool hasDecorationShadows() const = 0;
 
+        /**
+         * Returns @a true if the window decorations use the alpha channel, and @a false otherwise.
+         * @since 4.5
+         */
+        virtual bool decorationsHaveAlpha() const = 0;
+
         /**
          * @deprecated
          * @see EffectFrame