// IE5.5+ PNG Alpha Fix v2.0 Alpha: Background Tiling Support
// (c) 2008 Angus Turnbull http://www.twinhelix.com

// This is licensed under the GNU LGPL, version 2.1 or later.
// For details, see: http://creativecommons.org/licenses/LGPL/2.1/

String.prototype.trim = function()
{
	return this.replace(/^\s\s*/, '').replace(/\s\s*$/, '');
}

var IEPNGFix = window.IEPNGFix || {};

IEPNGFix.tileBG = function(elm, pngSrc, ready) {
	// Params: A reference to a DOM element, the PNG src file pathname, and a
	// hidden "ready-to-run" passed when called back after image preloading.

	if (elm != null && elm.clientWidth != null 
		&& elm.clientHeight != null 
		&& !isNaN(elm.clientWidth) 
		&& !isNaN(elm.clientHeight))
	{
		var data = this.data[elm.uniqueID],
			elmW = Math.max(elm.clientWidth, elm.scrollWidth),
			elmH = Math.max(elm.clientHeight, elm.scrollHeight),
			bgX = elm.currentStyle.backgroundPositionX,
			bgY = elm.currentStyle.backgroundPositionY,
			bgR = elm.currentStyle.backgroundRepeat;
	
		if (elm.rel != null)
		{
			var attrs = elm.rel.split(";");
			
			for(var idx = 0; idx < attrs.length; idx++)
			{
				var attrib = attrs[idx];
				
				var pair = attrib.split(":");
				
				var key = new String(pair[0]).trim();
				var value = new String(pair[1]).trim();
				
				if (key == "forceX") { elmW = value; }
				if (key == "forceY") { elmH = value; }
			}
		}
		
		// Cache of DIVs created per element, and image preloader/data.
		if (!data.tiles) {
			data.tiles = {
				elm: elm,
				src: '',
				cache: [],
				img: new Image(),
				old: {}
			};
		}
		var tiles = data.tiles,
			pngW = tiles.img.width,
			pngH = tiles.img.height;
	
		if (pngSrc) {
			if (!ready && pngSrc != tiles.src) {
				// New image? Preload it with a callback to detect dimensions.
				tiles.img.onload = function() {
					this.onload = null;
					IEPNGFix.tileBG(elm, pngSrc, 1);
				};
				return tiles.img.src = pngSrc;
			}
		} else {
			// No image?
			if (tiles.src) ready = 1;
			pngW = pngH = 0;
		}
		tiles.src = pngSrc;
	
		if (!ready && elmW == tiles.old.w && elmH == tiles.old.h &&
			bgX == tiles.old.x && bgY == tiles.old.y && bgR == tiles.old.r) {
			return;
		}
	
		// Convert English and percentage positions to pixels.
		var pos = {
				top: '0%',
				left: '0%',
				center: '50%',
				bottom: '100%',
				right: '100%'
			},
			x,
			y,
			pc;
		x = pos[bgX] || bgX;
		y = pos[bgY] || bgY;
		if (pc = x.match(/(\d+)%/)) {
			x = Math.round((elmW - pngW) * (parseInt(pc[1]) / 100));
		}
		if (pc = y.match(/(\d+)%/)) {
			y = Math.round((elmH - pngH) * (parseInt(pc[1]) / 100));
		}
		x = parseInt(x);
		y = parseInt(y);
	
		// Handle backgroundRepeat.
		var repeatX = { 'repeat': 1, 'repeat-x': 1 }[bgR],
			repeatY = { 'repeat': 1, 'repeat-y': 1 }[bgR];
		if (repeatX) {
			x %= pngW;
			if (x > 0) x -= pngW;
		}
		if (repeatY) {
			y %= pngH;
			if (y > 0) y -= pngH;
		}
	
		// Go!
		this.hook.enabled = 0;
		if (!({ relative: 1, absolute: 1 }[elm.currentStyle.position])) {
			elm.style.position = 'relative';
		}
		var count = 0,
			xPos,
			maxX = repeatX ? elmW : x + 0.1,
			yPos,
			maxY = repeatY ? elmH : y + 0.1,
			d,
			s,
			isNew;
		if (pngW && pngH) {
			for (xPos = x; xPos < maxX; xPos += pngW) {
				for (yPos = y; yPos < maxY; yPos += pngH) {
					isNew = 0;
					if (!tiles.cache[count]) {
						tiles.cache[count] = document.createElement('div');
						isNew = 1;
					}
					var clipR = (xPos + pngW > elmW ? elmW - xPos : pngW),
						clipB = (yPos + pngH > elmH ? elmH - yPos : pngH);
					d = tiles.cache[count];
					s = d.style;
					s.behavior = 'none';
					s.left = xPos + 'px';
					s.top = yPos + 'px';
					s.width = clipR + 'px';
					s.height = clipB + 'px';
					s.clip = 'rect(' +
						(yPos < 0 ? 0 - yPos : 0) + 'px,' +
						clipR + 'px,' +
						clipB + 'px,' +
						(xPos < 0 ? 0 - xPos : 0) + 'px)';
					s.display = 'block';
					if (isNew) {
						s.position = 'absolute';
						s.zIndex = -999;
						if (elm.firstChild) {
							elm.insertBefore(d, elm.firstChild);
						} else {
							elm.appendChild(d);
						}
					}
					this.fix(d, pngSrc, 0);
					count++;
				}
			}
		}
		while (count < tiles.cache.length) {
			this.fix(tiles.cache[count], '', 0);
			tiles.cache[count++].style.display = 'none';
		}
	
		this.hook.enabled = 1;
	
		// Cache so updates are infrequent.
		tiles.old = {
			w: elmW,
			h: elmH,
			x: bgX,
			y: bgY,
			r: bgR
		};
	}
};


IEPNGFix.update = function() {
	// Update all PNG backgrounds.
	for (var i in IEPNGFix.data) {
		var t = IEPNGFix.data[i].tiles;
		if (t && t.elm && t.src) {
			IEPNGFix.tileBG(t.elm, t.src);
		}
	}
};
IEPNGFix.update.timer = 0;

if (window.attachEvent && !window.opera) {
	window.attachEvent('onresize', function() {
		clearTimeout(IEPNGFix.update.timer);
		IEPNGFix.update.timer = setTimeout(IEPNGFix.update, 100);
	});
}