Stop transition preview if "No transition" is selected.

Currently a transition preview continues playing until it either
completes, a different transition is selected (in which case the
new preview starts) or the user clicks on the preview. However
when "No transition" is selected whilst a preview is still playing
then the prveview continues to play.

This will also be useful for fdo#36946 which would introduce
categories into the list which themselves aren't valid transitions,
therefore we would want to stop any previews on progress when selecting
a non-transition in the list.

Change-Id: I708fcc017a94173c91cb45bef18255f97debfd57

sd/source/ui/animations/SlideTransitionPane.cxx

@@ -874,16 +874,20 @@ void SlideTransitionPane::applyToSelectedPages()
     if( ! mbUpdatingControls )
     {
         ::sd::slidesorter::SharedPageSelection pSelectedPages( getSelectedPages());
+        impl::TransitionEffect aEffect = getTransitionEffectFromControls();
         if( ! pSelectedPages->empty())
         {
             lcl_CreateUndoForPages( pSelectedPages, mrBase );
-            lcl_ApplyToPages( pSelectedPages, getTransitionEffectFromControls() );
+            lcl_ApplyToPages( pSelectedPages, aEffect );
             mrBase.GetDocShell()->SetModified();
         }
         if( mpCB_AUTO_PREVIEW->IsEnabled() &&
             mpCB_AUTO_PREVIEW->IsChecked())
         {
-            playCurrentEffect();
+            if (aEffect.mnType) // mnType = 0 denotes no transition
+                playCurrentEffect();
+            else
+                stopEffects();
         }
     }
 }
@@ -898,6 +902,14 @@ void SlideTransitionPane::playCurrentEffect()
     }
 }
 
+void SlideTransitionPane::stopEffects()
+{
+    if( mxView.is() )
+    {
+        SlideShow::Stop( mrBase );
+    }
+}
+
 void SlideTransitionPane::addListener()
 {
     Link aLink( LINK(this,SlideTransitionPane,EventMultiplexerListener) );

sd/source/ui/animations/SlideTransitionPane.hxx

@@ -77,6 +77,7 @@ private:
 
     void applyToSelectedPages();
     void playCurrentEffect();
+    void stopEffects();
 
     void addListener();
     void removeListener();