dojo.provide("dojo.widget.AnimatedPng");

dojo.require("dojo.widget.*");
dojo.require("dojo.widget.HtmlWidget");

// usage
//	<img dojoType="AnimatedPng"
//		src="images/animatedpng_static.gif"		(for degradation; in case javascript is disabled)
//		aniSrc="images/animatedpng_frames.gif"
//		width="20"
//		height="20"
//		interval="50"
//	/>
//
//	var params = {src: "images/animatedpng_static.gif", aniSrc: "images/animatedpng_frames.gif", width: 20, height: 20, interval: 50};
//	var widget = dojo.widget.createWidget("AnimatedPng", params, document.getElementById("pngContainer"));
//
dojo.widget.defineWidget(
	"dojo.widget.AnimatedPng",
	dojo.widget.HtmlWidget,
	{
		// summary
		//	PNGs have great tranparency, but lack animation.
		//	This widget lets you point an img tag at an animated gif for graceful degrading,
		//	while letting you specify a png containing a grid of cells to animate between.

		isContainer: false,

		// width: Integer
		//	width (of each frame) in pixels
		width: 0,
		
		// height: Integer
		//	height (of each frame) in pixels
		height: 0,
		
		// aniSrc: String
		//	pathname to png file containing frames to be animated (ie, displayed sequentially)
		aniSrc: '',
		
		// interval: Integer
		//	time to display each frame
		interval: 100,

		_blankSrc: dojo.uri.dojoUri("src/widget/templates/images/blank.gif"),

		templateString: '<img class="dojoAnimatedPng" />',

		postCreate: function(){
			this.cellWidth = this.width;
			this.cellHeight = this.height;

			var img = new Image();
			var self = this;

			img.onload = function(){ self._initAni(img.width, img.height); };
			img.src = this.aniSrc;
		},

		_initAni: function(w, h){
			this.domNode.src = this._blankSrc;
			this.domNode.width = this.cellWidth;
			this.domNode.height = this.cellHeight;
			this.domNode.style.backgroundImage = 'url('+this.aniSrc+')';
			this.domNode.style.backgroundRepeat = 'no-repeat';

			this.aniCols = Math.floor(w/this.cellWidth);
			this.aniRows = Math.floor(h/this.cellHeight);
			this.aniCells = this.aniCols * this.aniRows;
			this.aniFrame = 0;

			window.setInterval(dojo.lang.hitch(this, '_tick'), this.interval);
		},

		_tick: function(){
			this.aniFrame++;
			if (this.aniFrame == this.aniCells) this.aniFrame = 0;

			var col = this.aniFrame % this.aniCols;
			var row = Math.floor(this.aniFrame / this.aniCols);

			var bx = -1 * col * this.cellWidth;
			var by = -1 * row * this.cellHeight;

			this.domNode.style.backgroundPosition = bx+'px '+by+'px';
		}
	}
);
