diff --git a/COMPOSITE_TODO b/COMPOSITE_TODO
index 78e506af4d..a452fc6501 100644
--- a/COMPOSITE_TODO
+++ b/COMPOSITE_TODO
@@ -177,6 +177,8 @@ Effects framework TODO
 
 + API for tabbox for effects should be cleaned up
 
+* check Scene::updateTimeDiff() - should the time be 0 or 1?
+
 
 Effects TODO
 ===============================
diff --git a/effects.cpp b/effects.cpp
index b9379afb6c..102302d547 100644
--- a/effects.cpp
+++ b/effects.cpp
@@ -231,6 +231,12 @@ bool EffectsHandlerImpl::borderActivated( ElectricBorder border )
     return ret;
     }
 
+void EffectsHandlerImpl::cursorMoved( const QPoint& pos, Qt::MouseButtons buttons )
+    {
+    foreach( EffectPair ep, loaded_effects )
+        ep.second->cursorMoved( pos, buttons );
+    }
+
 void EffectsHandlerImpl::activateWindow( EffectWindow* c )
     {
     if( Client* cl = dynamic_cast< Client* >( static_cast<EffectWindowImpl*>(c)->window()))
diff --git a/effects.h b/effects.h
index 6c14b8351f..5c9dcfccf0 100644
--- a/effects.h
+++ b/effects.h
@@ -90,6 +90,7 @@ class EffectsHandlerImpl : public EffectsHandler
         void tabBoxClosed();
         void tabBoxUpdated();
         bool borderActivated( ElectricBorder border );
+        void cursorMoved( const QPoint& pos, Qt::MouseButtons buttons );
 
         void loadEffect( const QString& name );
         void unloadEffect( const QString& name );
diff --git a/effects/presentwindows.cpp b/effects/presentwindows.cpp
index b2a370fbe4..aab9033a60 100644
--- a/effects/presentwindows.cpp
+++ b/effects/presentwindows.cpp
@@ -27,11 +27,12 @@ namespace KWin
 
 KWIN_EFFECT( PresentWindows, PresentWindowsEffect )
 
-PresentWindowsEffect::PresentWindowsEffect() : QObject(), Effect()
+PresentWindowsEffect::PresentWindowsEffect()
+    : mShowWindowsFromAllDesktops ( false )
+    , mActivated( false )
+    , mActiveness( 0.0 )
+    , mHoverWindow( NULL )
     {
-    mShowWindowsFromAllDesktops = false;
-    mActivated = false;
-    mActiveness = 0.0;
 
     KActionCollection* actionCollection = new KActionCollection( this );
     KAction* a = (KAction*)actionCollection->addAction( "Expose" );
@@ -126,11 +127,15 @@ void PresentWindowsEffect::paintWindow( EffectWindow* w, int mask, QRegion regio
 
 void PresentWindowsEffect::postPaintScreen()
     {
-    // If mActiveness is between 0 and 1, the effect is still in progress and the
-    //  workspace has to be repainted during the next pass
-    if( mActiveness > 0.0 && mActiveness < 1.0 )
-        effects->addRepaintFull(); // trigger next animation repaint
-
+    if( mActivated && mActiveness < 1.0 ) // activating effect
+        effects->addRepaintFull();
+    if( !mActivated && mActiveness > 0.0 ) // deactivating effect
+        effects->addRepaintFull();
+    foreach( const WindowData& d, mWindowData )
+        {
+        if( d.hover > 0 && d.hover < 1 ) // changing highlight
+            effects->addRepaintFull();
+        }
     // Call the next effect.
     effects->postPaintScreen();
     }
@@ -138,6 +143,25 @@ void PresentWindowsEffect::postPaintScreen()
 void PresentWindowsEffect::windowInputMouseEvent( Window w, QEvent* e )
     {
     assert( w == mInput );
+    if( e->type() == QEvent::MouseMove )
+        { // Repaint if the hovered-over window changed.
+          // (No need to use cursorMoved(), this takes care of it as well)
+        for( QHash<EffectWindow*, WindowData>::ConstIterator it = mWindowData.begin();
+             it != mWindowData.end();
+             ++it )
+            {
+            if( (*it).area.contains( cursorPos()))
+                {
+                if( mHoverWindow != it.key())
+                    {
+                    mHoverWindow = it.key();
+                    effects->addRepaintFull(); // screen is transformed, so paint all
+                    }
+                return;
+                }
+            }
+        return;
+        }
     if( e->type() != QEvent::MouseButtonPress )
         return;
 
@@ -161,20 +185,26 @@ void PresentWindowsEffect::windowInputMouseEvent( Window w, QEvent* e )
 
 void PresentWindowsEffect::windowActivated( EffectWindow* )
     {
-        rearrangeWindows();
+    rearrangeWindows();
     }
 
-void PresentWindowsEffect::windowClosed( EffectWindow* )
+void PresentWindowsEffect::windowClosed( EffectWindow* w )
     {
-        rearrangeWindows();
+    if( mHoverWindow == w )
+        mHoverWindow = NULL;
+    rearrangeWindows();
     }
 
 void PresentWindowsEffect::setActive(bool active)
     {
+    if( mActivated == active )
+        return;
     mActivated = active;
+    mHoverWindow = NULL;
     rearrangeWindows();
     if( mActivated && mActiveness == 0.0f )
         effectActivated();
+    effects->addRepaintFull(); // trigger next animation repaint
     }
 
 void PresentWindowsEffect::effectActivated()
diff --git a/effects/presentwindows.h b/effects/presentwindows.h
index 58aba8413b..e1c6f89a89 100644
--- a/effects/presentwindows.h
+++ b/effects/presentwindows.h
@@ -78,6 +78,7 @@ class PresentWindowsEffect
             float hover;
             };
         QHash<EffectWindow*, WindowData> mWindowData;
+        EffectWindow* mHoverWindow;
 
         ElectricBorder borderActivate;
         ElectricBorder borderActivateAll;
diff --git a/lib/kwineffects.cpp b/lib/kwineffects.cpp
index 61e2ed8eda..8f98d449ef 100644
--- a/lib/kwineffects.cpp
+++ b/lib/kwineffects.cpp
@@ -114,6 +114,10 @@ bool Effect::borderActivated( ElectricBorder )
     return false;
     }
 
+void Effect::cursorMoved( const QPoint&, Qt::MouseButtons )
+    {
+    }
+
 void Effect::prePaintScreen( int* mask, QRegion* region, int time )
     {
     effects->prePaintScreen( mask, region, time );
diff --git a/lib/kwineffects.h b/lib/kwineffects.h
index d28c84a150..1764884975 100644
--- a/lib/kwineffects.h
+++ b/lib/kwineffects.h
@@ -98,6 +98,7 @@ class KWIN_EXPORT Effect
         virtual void desktopChanged( int old );
         virtual void windowDamaged( EffectWindow* w, const QRect& r );
         virtual void windowGeometryShapeChanged( EffectWindow* w, const QRect& old );
+        virtual void cursorMoved( const QPoint& pos, Qt::MouseButtons buttons );
 
         virtual void tabBoxAdded( int mode );
         virtual void tabBoxClosed();
diff --git a/scene.cpp b/scene.cpp
index 8435df714a..0b30a9df88 100644
--- a/scene.cpp
+++ b/scene.cpp
@@ -129,13 +129,14 @@ void Scene::updateTimeDiff()
         {
         // Painting has been idle (optimized out) for some time,
         // which means time_diff would be huge and would break animations.
-        // Simply set it to zero.
-        time_diff = 0;
+        // Simply set it to one (zero would mean no change at all and could
+        // cause problems).
+        time_diff = 1;
         }
     else
         time_diff = last_time.elapsed();
     if( time_diff < 0 ) // check time rollback
-        time_diff = 0;
+        time_diff = 1;
     last_time.start();;
     }