Add ofxPiMapper::selectNext and PrevSurface methods

src/ofxPiMapper.cpp

@@ -46,6 +46,14 @@ void ofxPiMapper::selectSurface(int i){
 	}
 }
 
+void ofxPiMapper::selectNextSurface(){
+	_application.getState()->selectNextSurface(&_application);
+}
+
+void ofxPiMapper::selectPrevSurface(){
+	_application.getState()->selectPrevSurface(&_application);
+}
+
 void ofxPiMapper::togglePauseForSurface(unsigned int i){
 	ofx::piMapper::BaseSource * s =
 		_application.getSurfaceManager()->getActivePreset()->getSurfaces().at(i)->getSource();

src/ofxPiMapper.h

@@ -57,6 +57,8 @@ class ofxPiMapper {
 		// Surfaces, active preset
 		unsigned int getNumSurfaces();
 		void selectSurface(int i);
+		void selectNextSurface();
+		void selectPrevSurface();
 		void togglePauseForSurface(unsigned int i);
 
 		bool loadXmlSettings(string fileName);