// 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/



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.



	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;



	// 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);

	});

}