常见的兼容问题及其解决方法。

  1 /**
  2 * DD_belatedPNG: Adds IE6 support: PNG images for CSS background-image and HTML <IMG/>.
  3 * Author: Drew Diller
  4 * Email: drew.diller@gmail.com
  5 * URL: http://www.dillerdesign.com/experiment/DD_belatedPNG/
  6 * Version: 0.0.8a
  7 * Licensed under the MIT License: http://dillerdesign.com/experiment/DD_belatedPNG/#license
  8 *
  9 * Example usage:
 10 * DD_belatedPNG.fix(‘.png_bg‘); // argument is a CSS selector
 11 * DD_belatedPNG.fixPng( someNode ); // argument is an HTMLDomElement
 12 **/
 13 
 14 /*
 15 PLEASE READ:
 16 Absolutely everything in this script is SILLY.  I know this.  IE‘s rendering of certain pixels doesn‘t make sense, so neither does this code!
 17 */
 18 
 19 var DD_belatedPNG = {
 20     ns: ‘DD_belatedPNG‘,
 21     imgSize: {},
 22     delay: 10,
 23     nodesFixed: 0,
 24     createVmlNameSpace: function () { /* enable VML */
 25         if (document.namespaces && !document.namespaces[this.ns]) {
 26             document.namespaces.add(this.ns, ‘urn:schemas-microsoft-com:vml‘);
 27         }
 28     },
 29     createVmlStyleSheet: function () { /* style VML, enable behaviors */
 30         /*
 31             Just in case lots of other developers have added
 32             lots of other stylesheets using document.createStyleSheet
 33             and hit the 31-limit mark, let‘s not use that method!
 34             further reading: http://msdn.microsoft.com/en-us/library/ms531194(VS.85).aspx
 35         */
 36         var screenStyleSheet, printStyleSheet;
 37         screenStyleSheet = document.createElement(‘style‘);
 38         screenStyleSheet.setAttribute(‘media‘, ‘screen‘);
 39         document.documentElement.firstChild.insertBefore(screenStyleSheet, document.documentElement.firstChild.firstChild);
 40         if (screenStyleSheet.styleSheet) {
 41             screenStyleSheet = screenStyleSheet.styleSheet;
 42             screenStyleSheet.addRule(this.ns + ‘\\:*‘, ‘{behavior:url(#default#VML)}‘);
 43             screenStyleSheet.addRule(this.ns + ‘\\:shape‘, ‘position:absolute;‘);
 44             screenStyleSheet.addRule(‘img.‘ + this.ns + ‘_sizeFinder‘, ‘behavior:none; border:none; position:absolute; z-index:-1; top:-10000px; visibility:hidden;‘); /* large negative top value for avoiding vertical scrollbars for large images, suggested by James O‘Brien, http://www.thanatopsic.org/hendrik/ */
 45             this.screenStyleSheet = screenStyleSheet;
 46             
 47             /* Add a print-media stylesheet, for preventing VML artifacts from showing up in print (including preview). */
 48             /* Thanks to Rémi Prévost for automating this! */
 49             printStyleSheet = document.createElement(‘style‘);
 50             printStyleSheet.setAttribute(‘media‘, ‘print‘);
 51             document.documentElement.firstChild.insertBefore(printStyleSheet, document.documentElement.firstChild.firstChild);
 52             printStyleSheet = printStyleSheet.styleSheet;
 53             printStyleSheet.addRule(this.ns + ‘\\:*‘, ‘{display: none !important;}‘);
 54             printStyleSheet.addRule(‘img.‘ + this.ns + ‘_sizeFinder‘, ‘{display: none !important;}‘);
 55         }
 56     },
 57     readPropertyChange: function () {
 58         var el, display, v;
 59         el = event.srcElement;
 60         if (!el.vmlInitiated) {
 61             return;
 62         }
 63         if (event.propertyName.search(‘background‘) != -1 || event.propertyName.search(‘border‘) != -1) {
 64             DD_belatedPNG.applyVML(el);
 65         }
 66         if (event.propertyName == ‘style.display‘) {
 67             display = (el.currentStyle.display == ‘none‘) ? ‘none‘ : ‘block‘;
 68             for (v in el.vml) {
 69                 if (el.vml.hasOwnProperty(v)) {
 70                     el.vml[v].shape.style.display = display;
 71                 }
 72             }
 73         }
 74         if (event.propertyName.search(‘filter‘) != -1) {
 75             DD_belatedPNG.vmlOpacity(el);
 76         }
 77     },
 78     vmlOpacity: function (el) {
 79         if (el.currentStyle.filter.search(‘lpha‘) != -1) {
 80             var trans = el.currentStyle.filter;
 81             trans = parseInt(trans.substring(trans.lastIndexOf(‘=‘)+1, trans.lastIndexOf(‘)‘)), 10)/100;
 82             el.vml.color.shape.style.filter = el.currentStyle.filter; /* complete guesswork */
 83             el.vml.image.fill.opacity = trans; /* complete guesswork */
 84         }
 85     },
 86     handlePseudoHover: function (el) {
 87         setTimeout(function () { /* wouldn‘t work as intended without setTimeout */
 88             DD_belatedPNG.applyVML(el);
 89         }, 1);
 90     },
 91     /**
 92     * This is the method to use in a document.
 93     * @param {String} selector - REQUIRED - a CSS selector, such as ‘#doc .container‘
 94     **/
 95     fix: function (selector) {
 96         if (this.screenStyleSheet) {
 97             var selectors, i;
 98             selectors = selector.split(‘,‘); /* multiple selectors supported, no need for multiple calls to this anymore */
 99             for (i=0; i<selectors.length; i++) {
100                 this.screenStyleSheet.addRule(selectors[i], ‘behavior:expression(DD_belatedPNG.fixPng(this))‘); /* seems to execute the function without adding it to the stylesheet - interesting... */
101             }
102         }
103     },
104     applyVML: function (el) {
105         el.runtimeStyle.cssText = ‘‘;
106         this.vmlFill(el);
107         this.vmlOffsets(el);
108         this.vmlOpacity(el);
109         if (el.isImg) {
110             this.copyImageBorders(el);
111         }
112     },
113     attachHandlers: function (el) {
114         var self, handlers, handler, moreForAs, a, h;
115         self = this;
116         handlers = {resize: ‘vmlOffsets‘, move: ‘vmlOffsets‘};
117         if (el.nodeName == ‘A‘) {
118             moreForAs = {mouseleave: ‘handlePseudoHover‘, mouseenter: ‘handlePseudoHover‘, focus: ‘handlePseudoHover‘, blur: ‘handlePseudoHover‘};
119             for (a in moreForAs) {            
120                 if (moreForAs.hasOwnProperty(a)) {
121                     handlers[a] = moreForAs[a];
122                 }
123             }
124         }
125         for (h in handlers) {
126             if (handlers.hasOwnProperty(h)) {
127                 handler = function () {
128                     self[handlers[h]](el);
129                 };
130                 el.attachEvent(‘on‘ + h, handler);
131             }
132         }
133         el.attachEvent(‘onpropertychange‘, this.readPropertyChange);
134     },
135     giveLayout: function (el) {
136         el.style.zoom = 1;
137         if (el.currentStyle.position == ‘static‘) {
138             el.style.position = ‘relative‘;
139         }
140     },
141     copyImageBorders: function (el) {
142         var styles, s;
143         styles = {‘borderStyle‘:true, ‘borderWidth‘:true, ‘borderColor‘:true};
144         for (s in styles) {
145             if (styles.hasOwnProperty(s)) {
146                 el.vml.color.shape.style[s] = el.currentStyle[s];
147             }
148         }
149     },
150     vmlFill: function (el) {
151         if (!el.currentStyle) {
152             return;
153         } else {
154             var elStyle, noImg, lib, v, img, imgLoaded;
155             elStyle = el.currentStyle;
156         }
157         for (v in el.vml) {
158             if (el.vml.hasOwnProperty(v)) {
159                 el.vml[v].shape.style.zIndex = elStyle.zIndex;
160             }
161         }
162         el.runtimeStyle.backgroundColor = ‘‘;
163         el.runtimeStyle.backgroundImage = ‘‘;
164         noImg = true;
165         if (elStyle.backgroundImage != ‘none‘ || el.isImg) {
166             if (!el.isImg) {
167                 el.vmlBg = elStyle.backgroundImage;
168                 el.vmlBg = el.vmlBg.substr(5, el.vmlBg.lastIndexOf(‘")‘)-5);
169             }
170             else {
171                 el.vmlBg = el.src;
172             }
173             lib = this;
174             if (!lib.imgSize[el.vmlBg]) { /* determine size of loaded image */
175                 img = document.createElement(‘img‘);
176                 lib.imgSize[el.vmlBg] = img;
177                 img.className = lib.ns + ‘_sizeFinder‘;
178                 img.runtimeStyle.cssText = ‘behavior:none; position:absolute; left:-10000px; top:-10000px; border:none; margin:0; padding:0;‘; /* make sure to set behavior to none to prevent accidental matching of the helper elements! */
179                 imgLoaded = function () {
180                     this.width = this.offsetWidth; /* weird cache-busting requirement! */
181                     this.height = this.offsetHeight;
182                     lib.vmlOffsets(el);
183                 };
184                 img.attachEvent(‘onload‘, imgLoaded);
185                 img.src = el.vmlBg;
186                 img.removeAttribute(‘width‘);
187                 img.removeAttribute(‘height‘);
188                 document.body.insertBefore(img, document.body.firstChild);
189             }
190             el.vml.image.fill.src = el.vmlBg;
191             noImg = false;
192         }
193         el.vml.image.fill.on = !noImg;
194         el.vml.image.fill.color = ‘none‘;
195         el.vml.color.shape.style.backgroundColor = elStyle.backgroundColor;
196         el.runtimeStyle.backgroundImage = ‘none‘;
197         el.runtimeStyle.backgroundColor = ‘transparent‘;
198     },
199     /* IE can‘t figure out what do when the offsetLeft and the clientLeft add up to 1, and the VML ends up getting fuzzy... so we have to push/enlarge things by 1 pixel and then clip off the excess */
200     vmlOffsets: function (el) {
201         var thisStyle, size, fudge, makeVisible, bg, bgR, dC, altC, b, c, v;
202         thisStyle = el.currentStyle;
203         size = {‘W‘:el.clientWidth+1, ‘H‘:el.clientHeight+1, ‘w‘:this.imgSize[el.vmlBg].width, ‘h‘:this.imgSize[el.vmlBg].height, ‘L‘:el.offsetLeft, ‘T‘:el.offsetTop, ‘bLW‘:el.clientLeft, ‘bTW‘:el.clientTop};
204         fudge = (size.L + size.bLW == 1) ? 1 : 0;
205         /* vml shape, left, top, width, height, origin */
206         makeVisible = function (vml, l, t, w, h, o) {
207             vml.coordsize = w+‘,‘+h;
208             vml.coordorigin = o+‘,‘+o;
209             vml.path = ‘m0,0l‘+w+‘,0l‘+w+‘,‘+h+‘l0,‘+h+‘ xe‘;
210             vml.style.width = w + ‘px‘;
211             vml.style.height = h + ‘px‘;
212             vml.style.left = l + ‘px‘;
213             vml.style.top = t + ‘px‘;
214         };
215         makeVisible(el.vml.color.shape, (size.L + (el.isImg ? 0 : size.bLW)), (size.T + (el.isImg ? 0 : size.bTW)), (size.W-1), (size.H-1), 0);
216         makeVisible(el.vml.image.shape, (size.L + size.bLW), (size.T + size.bTW), (size.W), (size.H), 1 );
217         bg = {‘X‘:0, ‘Y‘:0};
218         if (el.isImg) {
219             bg.X = parseInt(thisStyle.paddingLeft, 10) + 1;
220             bg.Y = parseInt(thisStyle.paddingTop, 10) + 1;
221         }
222         else {
223             for (b in bg) {
224                 if (bg.hasOwnProperty(b)) {
225                     this.figurePercentage(bg, size, b, thisStyle[‘backgroundPosition‘+b]);
226                 }
227             }
228         }
229         el.vml.image.fill.position = (bg.X/size.W) + ‘,‘ + (bg.Y/size.H);
230         bgR = thisStyle.backgroundRepeat;
231         dC = {‘T‘:1, ‘R‘:size.W+fudge, ‘B‘:size.H, ‘L‘:1+fudge}; /* these are defaults for repeat of any kind */
232         altC = { ‘X‘: {‘b1‘: ‘L‘, ‘b2‘: ‘R‘, ‘d‘: ‘W‘}, ‘Y‘: {‘b1‘: ‘T‘, ‘b2‘: ‘B‘, ‘d‘: ‘H‘} };
233         if (bgR != ‘repeat‘ || el.isImg) {
234             c = {‘T‘:(bg.Y), ‘R‘:(bg.X+size.w), ‘B‘:(bg.Y+size.h), ‘L‘:(bg.X)}; /* these are defaults for no-repeat - clips down to the image location */
235             if (bgR.search(‘repeat-‘) != -1) { /* now let‘s revert to dC for repeat-x or repeat-y */
236                 v = bgR.split(‘repeat-‘)[1].toUpperCase();
237                 c[altC[v].b1] = 1;
238                 c[altC[v].b2] = size[altC[v].d];
239             }
240             if (c.B > size.H) {
241                 c.B = size.H;
242             }
243             el.vml.image.shape.style.clip = ‘rect(‘+c.T+‘px ‘+(c.R+fudge)+‘px ‘+c.B+‘px ‘+(c.L+fudge)+‘px)‘;
244         }
245         else {
246             el.vml.image.shape.style.clip = ‘rect(‘+dC.T+‘px ‘+dC.R+‘px ‘+dC.B+‘px ‘+dC.L+‘px)‘;
247         }
248     },
249     figurePercentage: function (bg, size, axis, position) {
250         var horizontal, fraction;
251         fraction = true;
252         horizontal = (axis == ‘X‘);
253         switch(position) {
254             case ‘left‘:
255             case ‘top‘:
256                 bg[axis] = 0;
257                 break;
258             case ‘center‘:
259                 bg[axis] = 0.5;
260                 break;
261             case ‘right‘:
262             case ‘bottom‘:
263                 bg[axis] = 1;
264                 break;
265             default:
266                 if (position.search(‘%‘) != -1) {
267                     bg[axis] = parseInt(position, 10) / 100;
268                 }
269                 else {
270                     fraction = false;
271                 }
272         }
273         bg[axis] = Math.ceil(  fraction ? ( (size[horizontal?‘W‘: ‘H‘] * bg[axis]) - (size[horizontal?‘w‘: ‘h‘] * bg[axis]) ) : parseInt(position, 10)  );
274         if (bg[axis] % 2 === 0) {
275             bg[axis]++;
276         }
277         return bg[axis];
278     },
279     fixPng: function (el) {
280         el.style.behavior = ‘none‘;
281         var lib, els, nodeStr, v, e;
282         if (el.nodeName == ‘BODY‘ || el.nodeName == ‘TD‘ || el.nodeName == ‘TR‘) { /* elements not supported yet */
283             return;
284         }
285         el.isImg = false;
286         if (el.nodeName == ‘IMG‘) {
287             if(el.src.toLowerCase().search(/\.png$/) != -1) {
288                 el.isImg = true;
289                 el.style.visibility = ‘hidden‘;
290             }
291             else {
292                 return;
293             }
294         }
295         else if (el.currentStyle.backgroundImage.toLowerCase().search(‘.png‘) == -1) {
296             return;
297         }
298         lib = DD_belatedPNG;
299         el.vml = {color: {}, image: {}};
300         els = {shape: {}, fill: {}};
301         for (v in el.vml) {
302             if (el.vml.hasOwnProperty(v)) {
303                 for (e in els) {
304                     if (els.hasOwnProperty(e)) {
305                         nodeStr = lib.ns + ‘:‘ + e;
306                         el.vml[v][e] = document.createElement(nodeStr);
307                     }
308                 }
309                 el.vml[v].shape.stroked = false;
310                 el.vml[v].shape.appendChild(el.vml[v].fill);
311                 el.parentNode.insertBefore(el.vml[v].shape, el);
312             }
313         }
314         el.vml.image.shape.fillcolor = ‘none‘; /* Don‘t show blank white shapeangle when waiting for image to load. */
315         el.vml.image.fill.type = ‘tile‘; /* Makes image show up. */
316         el.vml.color.fill.on = false; /* Actually going to apply vml element‘s style.backgroundColor, so hide the whiteness. */
317         lib.attachHandlers(el);
318         lib.giveLayout(el);
319         lib.giveLayout(el.offsetParent);
320         el.vmlInitiated = true;
321         lib.applyVML(el); /* Render! */
322     }
323 };
324 try {
325     document.execCommand("BackgroundImageCache", false, true); /* TredoSoft Multiple IE doesn‘t like this, so try{} it */
326 } catch(r) {}
327 DD_belatedPNG.createVmlNameSpace();
328 DD_belatedPNG.createVmlStyleSheet();