// IE5.5+ PNG Alpha Fix v2.0beta1: 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/



if (!window.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 = {

            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

    };

};