/* Respond.js: min/max-width media query polyfill. (c) Scott Jehl. MIT Lic. j.mp/respondjs */
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(function( w ){
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"use strict";
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//exposed namespace
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var respond = {};
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w.respond = respond;
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//define update even in native-mq-supporting browsers, to avoid errors
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respond.update = function(){};
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//define ajax obj
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var requestQueue = [],
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xmlHttp = (function() {
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var xmlhttpmethod = false;
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try {
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xmlhttpmethod = new w.XMLHttpRequest();
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}
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catch( e ){
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xmlhttpmethod = new w.ActiveXObject( "Microsoft.XMLHTTP" );
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}
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return function(){
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return xmlhttpmethod;
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};
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})(),
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//tweaked Ajax functions from Quirksmode
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ajax = function( url, callback ) {
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var req = xmlHttp();
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if (!req){
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return;
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}
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req.open( "GET", url, true );
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req.onreadystatechange = function () {
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if ( req.readyState !== 4 || req.status !== 200 && req.status !== 304 ){
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return;
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}
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callback( req.responseText );
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};
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if ( req.readyState === 4 ){
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return;
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}
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req.send( null );
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},
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isUnsupportedMediaQuery = function( query ) {
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return query.replace( respond.regex.minmaxwh, '' ).match( respond.regex.other );
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};
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//expose for testing
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respond.ajax = ajax;
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respond.queue = requestQueue;
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respond.unsupportedmq = isUnsupportedMediaQuery;
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respond.regex = {
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media: /@media[^\{]+\{([^\{\}]*\{[^\}\{]*\})+/gi,
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keyframes: /@(?:\-(?:o|moz|webkit)\-)?keyframes[^\{]+\{(?:[^\{\}]*\{[^\}\{]*\})+[^\}]*\}/gi,
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comments: /\/\*[^*]*\*+([^/][^*]*\*+)*\//gi,
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urls: /(url\()['"]?([^\/\)'"][^:\)'"]+)['"]?(\))/g,
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findStyles: /@media *([^\{]+)\{([\S\s]+?)$/,
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only: /(only\s+)?([a-zA-Z]+)\s?/,
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minw: /\(\s*min\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
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maxw: /\(\s*max\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
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minmaxwh: /\(\s*m(in|ax)\-(height|width)\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/gi,
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other: /\([^\)]*\)/g
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};
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//expose media query support flag for external use
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respond.mediaQueriesSupported = w.matchMedia && w.matchMedia( "only all" ) !== null && w.matchMedia( "only all" ).matches;
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//if media queries are supported, exit here
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if( respond.mediaQueriesSupported ){
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return;
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}
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//define vars
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var doc = w.document,
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docElem = doc.documentElement,
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mediastyles = [],
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rules = [],
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appendedEls = [],
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parsedSheets = {},
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resizeThrottle = 30,
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head = doc.getElementsByTagName( "head" )[0] || docElem,
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base = doc.getElementsByTagName( "base" )[0],
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links = head.getElementsByTagName( "link" ),
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lastCall,
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resizeDefer,
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//cached container for 1em value, populated the first time it's needed
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eminpx,
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// returns the value of 1em in pixels
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getEmValue = function() {
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var ret,
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div = doc.createElement('div'),
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body = doc.body,
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originalHTMLFontSize = docElem.style.fontSize,
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originalBodyFontSize = body && body.style.fontSize,
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fakeUsed = false;
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div.style.cssText = "position:absolute;font-size:1em;width:1em";
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if( !body ){
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body = fakeUsed = doc.createElement( "body" );
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body.style.background = "none";
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}
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// 1em in a media query is the value of the default font size of the browser
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// reset docElem and body to ensure the correct value is returned
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docElem.style.fontSize = "100%";
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body.style.fontSize = "100%";
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body.appendChild( div );
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if( fakeUsed ){
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docElem.insertBefore( body, docElem.firstChild );
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}
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ret = div.offsetWidth;
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if( fakeUsed ){
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docElem.removeChild( body );
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}
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else {
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body.removeChild( div );
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}
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// restore the original values
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docElem.style.fontSize = originalHTMLFontSize;
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if( originalBodyFontSize ) {
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body.style.fontSize = originalBodyFontSize;
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}
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//also update eminpx before returning
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ret = eminpx = parseFloat(ret);
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return ret;
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},
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//enable/disable styles
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applyMedia = function( fromResize ){
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var name = "clientWidth",
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docElemProp = docElem[ name ],
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currWidth = doc.compatMode === "CSS1Compat" && docElemProp || doc.body[ name ] || docElemProp,
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styleBlocks = {},
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lastLink = links[ links.length-1 ],
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now = (new Date()).getTime();
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//throttle resize calls
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if( fromResize && lastCall && now - lastCall < resizeThrottle ){
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w.clearTimeout( resizeDefer );
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resizeDefer = w.setTimeout( applyMedia, resizeThrottle );
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return;
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}
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else {
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lastCall = now;
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}
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for( var i in mediastyles ){
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if( mediastyles.hasOwnProperty( i ) ){
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var thisstyle = mediastyles[ i ],
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min = thisstyle.minw,
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max = thisstyle.maxw,
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minnull = min === null,
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maxnull = max === null,
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em = "em";
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if( !!min ){
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min = parseFloat( min ) * ( min.indexOf( em ) > -1 ? ( eminpx || getEmValue() ) : 1 );
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}
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if( !!max ){
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max = parseFloat( max ) * ( max.indexOf( em ) > -1 ? ( eminpx || getEmValue() ) : 1 );
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}
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// if there's no media query at all (the () part), or min or max is not null, and if either is present, they're true
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if( !thisstyle.hasquery || ( !minnull || !maxnull ) && ( minnull || currWidth >= min ) && ( maxnull || currWidth <= max ) ){
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if( !styleBlocks[ thisstyle.media ] ){
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styleBlocks[ thisstyle.media ] = [];
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}
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styleBlocks[ thisstyle.media ].push( rules[ thisstyle.rules ] );
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}
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}
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}
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//remove any existing respond style element(s)
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for( var j in appendedEls ){
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if( appendedEls.hasOwnProperty( j ) ){
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if( appendedEls[ j ] && appendedEls[ j ].parentNode === head ){
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head.removeChild( appendedEls[ j ] );
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}
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}
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}
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appendedEls.length = 0;
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//inject active styles, grouped by media type
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for( var k in styleBlocks ){
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if( styleBlocks.hasOwnProperty( k ) ){
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var ss = doc.createElement( "style" ),
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css = styleBlocks[ k ].join( "\n" );
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ss.type = "text/css";
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ss.media = k;
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//originally, ss was appended to a documentFragment and sheets were appended in bulk.
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//this caused crashes in IE in a number of circumstances, such as when the HTML element had a bg image set, so appending beforehand seems best. Thanks to @dvelyk for the initial research on this one!
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head.insertBefore( ss, lastLink.nextSibling );
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if ( ss.styleSheet ){
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ss.styleSheet.cssText = css;
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}
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else {
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ss.appendChild( doc.createTextNode( css ) );
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}
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//push to appendedEls to track for later removal
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appendedEls.push( ss );
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}
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}
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},
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//find media blocks in css text, convert to style blocks
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translate = function( styles, href, media ){
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var qs = styles.replace( respond.regex.comments, '' )
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.replace( respond.regex.keyframes, '' )
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.match( respond.regex.media ),
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ql = qs && qs.length || 0;
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//try to get CSS path
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href = href.substring( 0, href.lastIndexOf( "/" ) );
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var repUrls = function( css ){
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return css.replace( respond.regex.urls, "$1" + href + "$2$3" );
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},
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useMedia = !ql && media;
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//if path exists, tack on trailing slash
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if( href.length ){ href += "/"; }
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//if no internal queries exist, but media attr does, use that
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//note: this currently lacks support for situations where a media attr is specified on a link AND
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//its associated stylesheet has internal CSS media queries.
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//In those cases, the media attribute will currently be ignored.
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if( useMedia ){
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ql = 1;
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}
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for( var i = 0; i < ql; i++ ){
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var fullq, thisq, eachq, eql;
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//media attr
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if( useMedia ){
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fullq = media;
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rules.push( repUrls( styles ) );
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}
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//parse for styles
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else{
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fullq = qs[ i ].match( respond.regex.findStyles ) && RegExp.$1;
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rules.push( RegExp.$2 && repUrls( RegExp.$2 ) );
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}
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eachq = fullq.split( "," );
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eql = eachq.length;
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for( var j = 0; j < eql; j++ ){
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thisq = eachq[ j ];
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if( isUnsupportedMediaQuery( thisq ) ) {
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continue;
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}
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mediastyles.push( {
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media : thisq.split( "(" )[ 0 ].match( respond.regex.only ) && RegExp.$2 || "all",
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rules : rules.length - 1,
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hasquery : thisq.indexOf("(") > -1,
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minw : thisq.match( respond.regex.minw ) && parseFloat( RegExp.$1 ) + ( RegExp.$2 || "" ),
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maxw : thisq.match( respond.regex.maxw ) && parseFloat( RegExp.$1 ) + ( RegExp.$2 || "" )
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} );
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}
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}
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applyMedia();
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},
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//recurse through request queue, get css text
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makeRequests = function(){
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if( requestQueue.length ){
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var thisRequest = requestQueue.shift();
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ajax( thisRequest.href, function( styles ){
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translate( styles, thisRequest.href, thisRequest.media );
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parsedSheets[ thisRequest.href ] = true;
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// by wrapping recursive function call in setTimeout
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// we prevent "Stack overflow" error in IE7
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w.setTimeout(function(){ makeRequests(); },0);
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} );
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}
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},
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//loop stylesheets, send text content to translate
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ripCSS = function(){
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for( var i = 0; i < links.length; i++ ){
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var sheet = links[ i ],
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href = sheet.href,
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media = sheet.media,
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isCSS = sheet.rel && sheet.rel.toLowerCase() === "stylesheet";
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//only links plz and prevent re-parsing
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if( !!href && isCSS && !parsedSheets[ href ] ){
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// selectivizr exposes css through the rawCssText expando
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if (sheet.styleSheet && sheet.styleSheet.rawCssText) {
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translate( sheet.styleSheet.rawCssText, href, media );
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parsedSheets[ href ] = true;
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} else {
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if( (!/^([a-zA-Z:]*\/\/)/.test( href ) && !base) ||
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href.replace( RegExp.$1, "" ).split( "/" )[0] === w.location.host ){
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// IE7 doesn't handle urls that start with '//' for ajax request
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// manually add in the protocol
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if ( href.substring(0,2) === "//" ) { href = w.location.protocol + href; }
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requestQueue.push( {
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href: href,
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media: media
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} );
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}
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}
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}
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}
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makeRequests();
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};
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//translate CSS
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ripCSS();
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//expose update for re-running respond later on
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respond.update = ripCSS;
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//expose getEmValue
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respond.getEmValue = getEmValue;
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//adjust on resize
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function callMedia(){
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applyMedia( true );
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}
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if( w.addEventListener ){
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w.addEventListener( "resize", callMedia, false );
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}
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else if( w.attachEvent ){
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w.attachEvent( "onresize", callMedia );
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}
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})(this);
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