added virtual function reset() in baseSource that can be overridden in Source classes to reset source variables on re-entry, if needed

src/Sources/BaseSource.h

@@ -21,6 +21,8 @@ class BaseSource {
 		virtual void clear(){}
         virtual void togglePause(){}
 
+        virtual void reset(){} // called by surfaceManager to optionally allow users to reset a source's variables
+
 		// TODO: add virtual increaseReferenceCount and decreaseReferenceCount methods
 		// and make the variable protected
 		int referenceCount;

src/Surfaces/SurfaceManager.cpp

@@ -461,6 +461,10 @@ void SurfaceManager::setPreset(unsigned int i){
 	}
 	
 	_activePresetIndex = i;
+
+    for (int i=0; i<_presets[_activePresetIndex]->getSurfaces().size(); i++){
+        _presets[_activePresetIndex]->getSurfaces()[i]->getSource()->reset();
+    }
 }
 
 void SurfaceManager::cloneActivePreset(){