Add `MvLayerDnCmd`

src/Commands/MvLayerDnCmd.cpp

@@ -0,0 +1,45 @@
+#include "MvLayerDnCmd.h"
+
+namespace ofx {
+namespace piMapper {
+
+MvLayerDnCmd::MvLayerDnCmd(BaseSurface * selectedSurface){
+	_selectedSurface = selectedSurface;
+	_selectedSurfaceIndex = -1;
+}
+
+void MvLayerDnCmd::exec(){
+	ofLogNotice("MvLayerDnCmd", "exec");
+	
+	// Find selected surface index in SurfaceStack.
+	for(int i = 0; i < SurfaceStack::instance()->size(); ++i){
+		if(_selectedSurface == SurfaceStack::instance()->at(i)){
+			_selectedSurfaceIndex = i;
+			break;
+		}
+	}
+	
+	if(_selectedSurfaceIndex == -1){
+		throw runtime_error("MvLayerUpCmd used with no surface selected");
+	}
+	
+	if(_selectedSurfaceIndex == 0){
+		throw runtime_error("Check if selected surface is not bottom before using MvLayerUpCmd");
+	}
+	
+	if(SurfaceStack::instance()->size() <= 1){
+		throw runtime_error("Check if there is more than one surface before using MvLayerUpCmd");
+	}
+	
+	// Swap it with the previous surface
+	SurfaceStack::instance()->swap(_selectedSurfaceIndex, _selectedSurfaceIndex - 1);
+}
+
+void MvLayerDnCmd::undo(){
+	ofLogNotice("MvLayerDnCmd", "undo");
+	SurfaceStack::instance()->swap(_selectedSurfaceIndex, _selectedSurfaceIndex - 1);
+}
+
+} // namespace piMapper
+} // namespace ofx
+

src/Commands/MvLayerDnCmd.h

@@ -0,0 +1,26 @@
+#pragma once
+
+#include "BaseCmd.h"
+#include "BaseSurface.h"
+#include "SurfaceStack.h"
+
+namespace ofx {
+namespace piMapper {
+
+class MvLayerDnCmd : public BaseUndoCmd {
+
+	public:
+		MvLayerDnCmd(BaseSurface * selectedSurface);
+		void exec();
+		void undo();
+
+	private:
+		BaseSurface * _selectedSurface;
+	
+		int _selectedSurfaceIndex;
+
+};
+
+} // namespace piMapper
+} // namespace ofx
+