#include <CtrlLib/CtrlLib.h>

using namespace Upp;

class ResponsiveDrag : public TopWindow {
public:
	Image im;
	Point offset;
	
	ResponsiveDrag(){
		Sizeable().MaximizeBox().MinimizeBox();
		Maximize();
		offset=Point(0,0);
		leftdown=false;
	}

	
	virtual void Paint(Draw &w){
		static int64 last;
		int64 now=usecs();
		double fps=1000000/(now-last);
		last=now;
		
		// In Windows SetSurface is about 3x faster than Drawimage on 4k UHD screen
		// However, in Gtk SetSurface fails to display the image correctly
		// and offset is not taken into account at all
		
		SetSurface(w,Rect(GetSize()),~im,im.GetSize(),offset); // Only works on Windows
		// w.DrawImage(Rect(GetSize()),im,Rect(offset,GetSize())); // Works on both Linux and Windows
		
		w.DrawText(10,10,Format("FPS = %.1f",fps));
	}
	
	virtual void Layout(){
		Size sz(GetSize()*3);
		ImageBuffer ib(sz);
		BufferPainter p(ib);
		p.Clear(SColorPaper());
		for(int i=0;i<50;i++){
			p.Move(Random(sz.cx),Random(sz.cy));
			p.Line(Random(sz.cx),Random(sz.cy));
			p.Stroke(3,SColorText());
		}
		im=ib;
		offset=Point(GetSize());
		Refresh();
	}
	
	bool leftdown;
	Point leftdownp;
	
	virtual void LeftDown(Point p, dword keyflags){
		SetCapture();
		leftdown=true;
		leftdownp=p;
	}

	virtual void LeftUp(Point p, dword keyflags){
		ReleaseCapture();
		leftdown=false;
		offset=Point(GetSize());
		Refresh();
	}
	
	virtual void MouseMove(Point p, dword keyflags){
		if(leftdown){
			offset=Point(GetSize())+leftdownp-p;
			Refresh();
		}
	}
};

GUI_APP_MAIN
{
	ResponsiveDrag().Run();
}