//
// AlphaPainter: Paint pictures by changing the alpha channel 
// of boxes in a grid
//
// Author:
// 	Eric Butler <eric@extremeboredom.net>
//
// To Compile:
// 	 mcs -debug AlphaPainter.cs -pkg:gtk-sharp-2.0 -pkg:mono-cairo
//


using System;
using Cairo;
using GLib;
using Gtk;

public class AlphaPainter
{
	public static void Main ()
	{
		Application.Init ();
		new AlphaPainter ();
		Application.Run ();
	}

	public AlphaPainter ()
	{
		Window window = new Window ("Alpha Painter");
		window.AppPaintable = true;
		window.SetSizeRequest (400, 400);

		on_alpha_screen_changed (window, null, null);
		
		AlphaPainterWidget painterWidget = new AlphaPainterWidget ();
		window.Add (painterWidget);
		window.ShowAll ();
	}

	private void on_alpha_screen_changed (Gtk.Widget pWidget,
					       		Gdk.Screen oldScreen,
							Widget label)
	{
		Gdk.Screen pScreen = pWidget.Screen;
		Gdk.Colormap pColormap = pScreen.RgbaColormap;

		if (pColormap == null) 
		{
			//pColormap = pScreen.RgbColormap;
			throw new Exception ("screen does NOT support alpha - are you running Xgl/compmgr?");
		}
		else
			Console.WriteLine ("screen supports alpha!");

		pWidget.Colormap = pColormap;
	}
}

public class AlphaPainterWidget : DrawingArea
{

	const int pixelCount = 10;

	double pixelWidth;
	double pixelHeight;

	double[,] pixels = new double[pixelCount, pixelCount];

	bool leftButtonDown = false;
	bool rightButtonDown = false;
	double mouseX = 0;
	double mouseY = 0;

	PointD activePoint = new PointD (-1, -1);

	TimeoutHandler updateTimeout;

	double r = .2, g = .3, b = 0.4, a = 0.8;

	public AlphaPainterWidget ()
	{
		for (int y = 0; y < pixelCount; y++) {
			for (int x = 0; x < pixelCount; x++) {
				pixels [x,y] = a;
			}
		}

		this.Events = this.Events |
			Gdk.EventMask.PointerMotionMask |
			Gdk.EventMask.ButtonPressMask |
			Gdk.EventMask.ButtonReleaseMask;

		updateTimeout = new TimeoutHandler (UpdateTick);
		GLib.Timeout.Add (200, updateTimeout);
	}
	
	private bool UpdateTick ()
	{
		if (leftButtonDown | rightButtonDown) {
			ChangePixel ();
		}
		return true;
	}


	
	protected override bool OnButtonPressEvent (Gdk.EventButton eb)
	{
		if (eb.Button == 1)
			leftButtonDown = true;
		else if (eb.Button == 3)
			rightButtonDown = true;

		mouseX = eb.X;
		mouseY = eb.Y;

		ChangePixel ();
		
		return base.OnButtonPressEvent (eb);
	}

	protected override bool OnButtonReleaseEvent (Gdk.EventButton eb)
	{
		if (eb.Button == 1)
			leftButtonDown = false;
		else if (eb.Button == 3)
			rightButtonDown = false;
			
		return base.OnButtonReleaseEvent (eb);
	}

	protected override bool OnMotionNotifyEvent (Gdk.EventMotion em)
	{
		mouseX = em.X;
		mouseY = em.Y;
		
		ChangePixel ();

		return base.OnMotionNotifyEvent (em);
	}

	private void ChangePixel ()
	{
		int x = (int)mouseX / (int)pixelWidth;
		int y = (int)mouseY / (int)pixelHeight;

		if (x <= pixelCount & y <= pixelCount & y >= 0 & x >= 0)
			activePoint = new PointD (x * pixelWidth, y * pixelHeight);
		else
			activePoint = new PointD (-1, -1);

		if (leftButtonDown | rightButtonDown) {
			if (x >= pixelCount | y >= pixelCount | y <= 0 | x <= 0)
				return;
	
			if (leftButtonDown)
				pixels [Convert.ToInt32 (x), Convert.ToInt32 (y)] -= 0.05f;
			else
				pixels [Convert.ToInt32 (x), Convert.ToInt32 (y)] += 0.05f;
		}

		this.QueueDraw ();
	}
	
	protected override bool OnExposeEvent (Gdk.EventExpose args)
	{
		Gdk.Window win = args.Window;
		Cairo.Context g = Gdk.CairoHelper.Create (win);
		g.Operator = Operator.Source;
		int x, y, w, h, d;
		win.GetGeometry (out x, out y, out w, out h, out d);
		Draw (g, w, h);
		(g as IDisposable).Dispose ();
		return true;
	}


	void Draw (Cairo.Context gr, int width, int height)
        {
		gr.Color = new Color (r, g, b, a);
		gr.Paint ();



		pixelWidth = Math.Floor ((double)width / (double)pixelCount);
		pixelHeight = Math.Floor ((double)height / (double)pixelCount);

		for (int y = 0; y < pixelCount; y++) {
			for (int x = 0; x < pixelCount; x++) {

				double rectX = (double)x * (double)pixelWidth;
				double rectY = (double)y * (double)pixelHeight;

				gr.Color = new Color (r, g, b, pixels[x,y]);
				gr.Rectangle (new Rectangle (rectX, rectY, pixelWidth, pixelHeight));
				gr.Fill ();
			}
		}

		if (activePoint.X != -1 && activePoint.Y != -1) {
			gr.Color = new Color (1, 1, 1, 1);
			gr.Rectangle (activePoint.X, activePoint.Y, pixelWidth, pixelHeight);
			gr.Stroke ();
		}
        }
}