// 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)
{
    try
    {
        // 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
        };
    }
    catch (e) { }
};


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);
	});
}