Wiki source code of Skin Extension Tutorial

Version 32.4 by Alex Cotiugă on 2016/08/25

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1 {{box cssClass="floatinginfobox" title="**Contents**"}}
2 {{toc/}}
3 {{/box}}
5 This tutorial demonstrates how to write a XWiki Skin Extension.
7 {{velocity}}
8 ## $xwiki.ssx.use("$doc.fullName") ## Load the SSX object held in this document
9 {{/velocity}}
11 = Introduction to XWiki Skin Extensions =
13 XWiki Skins eXtensions (abbreviated as **SX**) is a mechanism available in XWiki that allows to customize the layout of your wiki, or just some pages of your wiki, without the need of changing its skin templates and/or stylesheets. For this, the [[Skin Extension plugin>>extensions:Extension.Skin Extension Plugin]] (bundled in all XWiki Enterprise versions superior to 1.5) provides the ability to send to the browser extra JavaScript and CSS files that are not part of the actual skin of the wiki. The code for these //extensions// is defined in [[wiki objects>>platform:DevGuide.DataModel]].
15 This tutorial assumes that you already have basic knowledge of application development with XWiki. If this is not the case, we strongly advise you to start with the [[FAQ application tutorial>>FAQTutorialManual]] or the [[TODO application tutorial>>]].
16 To illustrate usage of Skin Extension in XWiki, this tutorial will guide you through the creation of minimal JavaScript and StyleSheet working extensions. Then, will push it further to build a fully functional extension based on Natalie Downe's ##addSizes.js## script.
18 A minimal [[JavaScript>>]] and [[CSS>>]] knowledge is also needed to take full advantage of XWiki Skin Extensions, although expert knowledge in those fields is not needed to follow the tutorial.
20 {{info}}
21 If you are interested by the Skin eXtension mechanism itself and its internals, you should read its [[plugin page>>extensions:Extension.Skin Extension Plugin]], and its [[design page on>>dev:Design.Skin Extensions]]. This tutorial does not address this topic. Or, since this is an Open Source project, feel free to {{scm path="xwiki-platform-core/xwiki-platform-skin/xwiki-platform-skin-skinx"}}browse the code{{/scm}}, and [[propose enhancements or improvements>>dev:Community.Contributing]].
22 {{/info}}
24 = My first Skin eXtension =
26 Skin eXtensions are defined as [[XWiki Objects>>platform:DevGuide.DataModel||anchor="HXWikiClasses2CObjects2CandProperties"]]. As a consequence, you can create them from your browser. Two types of extensions are currently supported: JavaScript eXtensions (incarnated by XWiki objects of class **XWiki.JavaScriptExtension**), and StyleSheet eXtensions (incarnated by XWiki objects of class **XWiki.StyleSheetExtension**). The very first step to create an eXtension is then... to create its object!
28 == Minimal JavaScript eXtension ==
30 === Creating an eXtension object ===
32 Point your wiki on the page you want to create your extension in, and edit it with the object editor. The page itself can be any XWiki page - an existing page or a new page. I use in this example the page **XWiki.SkinExt**. From the **New Object** drop-down list of the object editor choose **XWiki.JavaScriptExtension**. Then, click the "Add" button.
34 {{image reference="CreateJSXObject.png"/}}
36 {{info}}
37 The object editor is available only to [[advanced users>>platform:Features.PageEditing||anchor="HAdvancedMode"]].
38 {{/info}}
40 Once the page is loaded, you should see your extension object in the object list.
42 === Writing the eXtension ===
44 Now that the object is available, we can just start writing the actual eXtension. For this, we will fill in all the fields of the created object. The first one is the extension name. This is easy! We can just write here **Hello World** (this information is only descriptive, it is not actually used by the SX plugin). The next field name is **code**, and this is where we will write the javascript code we want our extension to execute. This eXtension is supposed to be minimalist, so let's write something very basic here: a traditional greeting alert
46 {{code}}
47 alert("Hello World!");
48 {{/code}}
50 Now the next field asks us if we want this extension to be used **Always** or **On Demand**. We will explore all the differences between those two modes later in the tutorial, let us for now just precise we want it **On Demand**, which will force us to call the eXtension explicitly to see it executed.
52 Next thing our eXtension wants to know is if we want its content being parsed or not. This option allows to write **[[velocity code>>platform:DevGuide.Scripting]]**, for example to dynamically generate the javascript code to be executed. We did not write any velocity, so we can just say **No**. We will see later on an example of an extension with parsed content.
54 Finally, we can precise a **caching policy**, to tune the HTTP headers that will be returned with the generated javascript file. Let's not go wild, and chose the **default** one here
56 That's it ! our eXtension is production-ready ! It should by now look like the following:
58 {{image reference="MyFirstJSX.png"/}}
60 //Note: the "code" area size has been intentionally reduced for this screenshot.//
62 === Testing the actual extension ===
64 Let's now test the whole thing! Remember we chose that our extension should be used //on demand// ? Well, that's what we are going to do right now. For this we will make a call to the [[Skin Extension plugin>>extensions:Extension.Skin Extension Plugin]]. We can do it for instance in the wiki content of our extension page, or any other page. For this, we edit the target page in Wiki mode, and write the following:
66 {{code}}
67 {{velocity}}
68 #set ($discard = $xwiki.jsx.use('XWiki.SkinExt.WebHome'))
69 {{/velocity}}
70 {{/code}}
72 Of course, if you did not use this page name for your extension, you should adapt it. Click "Save and View", et voila! If everything is fine, you should see the magic:
74 {{image reference="JSXMagic.png"/}}
76 You may have noticed that the javascript alert displays before the document is fully loaded in the browser. This is actually expected! If you look close at the generated sources, you will see that your extension has actually been added in the HTML header as any other **.js files** from the skin: (comments added for this tutorial)
78 {{code}}
79 <script type="text/javascript" src="/xwiki/skins/albatross/skin.js"></script>
80 <!-- [SNIP] here are all others javascript files from the skin -->
81 <script type="text/javascript" src="/xwiki/bin/skin/skins/albatross/scripts/shortcuts.js"></script>
83 <!-- And here is your JSX ! You can open its URL in a browser and see the code -->
84 <script type='text/javascript' src='/xwiki/bin/jsx/XWiki/SkinExt?lang=en'></script>
85 {{/code}}
87 == Minimal StyleSheet eXtension ==
89 Good, we wrote our first javascript extension. But, we see things big and we already are looking forward to modify the graphical appearance of wiki pages using those eXtensions. That's what **StyleSheet eXtensions** are meant for. And the good news is that it just works the same as javascript extensions, the only difference being that the code written is **CSS code**.
91 Create a new page named **XWiki.MyFirstStylesheetExtension**. From the **New Object** drop-down list of the object editor choose **XWiki.StyleSheetExtension**. Then, click the "Add" button. We will name it **Blue Background**, give it a **default** cache policy, ask it not to parse the content, and write the following **code**:
93 {{code}}
94 #xwikicontent {
95 background-color: lightBlue;
96 }
97 {{/code}}
99 {{info}}
100 If you want to use the colors of your active ColorTheme you can check how to [[call those variables>>extensions:Extension.Color Theme Application||anchor="HUsingColorThemesvariables"]].
101 {{/info}}
103 == Put all together ==
105 Now let's try something new with this eXtension. Instead of loading it "On Demand", we can ask to have it used **"Always on this wiki"**. For this to happen however, you need to save the extension document with [[programming rights>>platform:AdminGuide.Access Rights||anchor="HSpecialpermissions"]].
107 Your StyleSheet eXtension should now look like the following:
109 {{image reference="MyFirstSSX.png"/}}
111 //Note: the "code" area size has been intentionally reduced for this Screenshot.//
113 It's time to test it. No need to call the SkinExtension plugin this time, this is the power of **Use Always** extensions, just click "Save and View" and see the SSX Magic. You can browse your wiki, all pages will be affected by your extension, for example the Main.WebHome page:
115 {{image reference="SSXMagic.png"/}}
117 Note: if you want to use StyleSheet extension on demand, the principle is the same as for javascript, except that the plugin name is **ssx**, not **jsx**. Just make your call like this, and you are done:
119 {{code}}
120 {{velocity}}
121 #set ($discard = $xwiki.ssx.use('XWiki.MyFirstStylesheetExtension.WebHome'))
122 {{/velocity}}
123 {{/code}}
125 {{info}}
126 A document can have as many **ssx** or **jsx** object as it needs, but a skin extension is identified by the name of the document, so in the end an extension is a document. The content of a skin extension is the concatenation of the objects in that document, so it's impossible to write two different extensions in a single document, only different parts of the same extension.
127 {{/info}}
129 = Real-world eXtension with addSizes.js =
131 Let's now go further with this idea, and build a complete extension that will dynamically add the file type and size next to certain links that are present in a wiki document. This extension will make usage of the **addSizes.js** script published by Natalie Downe. This Javascript snippet itself relies on **json-head**, a Google App Engine application by Simon Willison which //"provides a JSON-P API for running [[HEAD requests>>]] against an arbitrary URL"//. **addSizes.js** consumes this service to dynamically add the file type and size next to links in HTML documents. And this is what we will do in our new eXtension, using the aforementioned script and service.
133 Our new skin extension will be composed of a javascript and a stylesheet extension. We will hold the two objects in the same wiki page, namely **XWiki.AddSizesExtension**.
135 Once the document is loaded the javascript extension will be in charge of finding all the interesting links we want to decorate with sizes and file type icons, actually query for their size on the cloud, and finally inject this information next to each concerned link.
137 The stylesheet extension will just define the style we want for the extra size information that is injected next to the links.
139 The implementation below looks for the following file formats:
141 * Writer, Calc, and Impress (.odt, .ods, .odp)
142 * The most well known proprietary equivalents of the formats above
143 * Zip archives (.zip)
144 * PDFs (.pdf)
146 Of course, this can adapted to look for other formats that are relevant for your business
148 == Requesting and injecting files size with JSX ==
150 Our javascript extension will be composed of two code snippets. The second one will be the actual addSizes.js code, ported to work with Prototype instead of jQuery. The first one is a function needed by this portage.
152 AddSizes.js relies on the [[JSON with padding technique>>]] to query the **json-head** service, which is located on a different domain than the wiki, in a transparent manner. An alternative to this would be to have a similar service on the wiki itself (for example, in the [[groovy language>>platform:DevGuide.Scripting||anchor="HGroovy"]]), and query it using a traditional AJAX request. [[Prototype.js>>]], the javascript framework bundled with XWiki, does not yet provide support for JSON-P requests. We will use for this a code snippet by Juriy Zaytsev written for this purpose. Let's first paste his code in a new **JSX** object, in **XWiki.AddSizesExtension** :
154 {{code}}
155 // getJSON function by Juriy Zaytsev
156 //
157 (function(){
158 var id = 0, head = $$('head')[0], global = this;
159 global.getJSON = function(url, callback) {
160 var script = document.createElement('script'), token = '__jsonp' + id;
162 // callback should be a global function
163 global[token] = callback;
165 // url should have "?" parameter which is to be replaced with a global callback name
166 script.src = url.replace(/\?(&|$)/, '__jsonp' + id + '$1');
168 // clean up on load: remove script tag, null script variable and delete global callback function
169 script.onload = function() {
170 script.remove();
171 script = null;
172 delete global[token];
173 };
174 head.appendChild(script);
176 // callback name should be unique
177 id++;
178 }
179 })();
180 {{/code}}
182 With this, we can now have a prototype version of addSizes.js. We can just paste this second snippet under the first one in the **code** are of our extension object, or add a new JavaScriptExtension object to the page (as SX combines all the objects of the same page into a single response):
184 {{code}}
185 // addSizes was written by Natalie Downe
186 //
187 // ported to prototype.js by Jerome Velociter, and adapted to XWiki for this tutorial
189 // Copyright (c) 2008, Natalie Downe under the BSD license
190 //
192 Event.observe(window, 'load', function(event) {
193 $('xwikicontent').select(
194 'a[href$=".pdf"], a[href$=".doc"], a[href$=".zip"], a[href$=".xls"], a[href$=".odt"], a[href$=".ods"], a[href$=".odp"], a[href$=".ppt"]')
195 .each(function(link){
196 var bits = link.href.split('.');
197 var type = bits[bits.length -1];
199 var url = ""+encodeURIComponent (link.href)+"&callback=?";
201 getJSON(url, function(json){
202 var content_length = json.headers['Content-Length'];
203 if(!content_length) {
204 content_length = json.headers['content-length'];
205 }
206 if(json.ok && content_length) {
207 var length = parseInt(content_length, 10);
209 // divide the length into its largest unit
210 var units = [
211 [1024 * 1024 * 1024, 'GB'],
212 [1024 * 1024, 'MB'],
213 [1024, 'KB'],
214 [1, 'bytes']
215 ];
217 for(var i = 0; i < units.length; i++){
219 var unitSize = units[i][0];
220 var unitText = units[i][1];
221 if (length >= unitSize) {
222 length = length / unitSize;
223 // 1 decimal place
224 length = Math.ceil(length * 10) / 10;
225 var lengthUnits = unitText;
226 break;
227 }
228 }
230 // insert the text in a span directly after the link and add a class to the link
231 Element.insert(link, {'after':
232 ' <span class="filesize">(' + length + ' ' + lengthUnits + ')</span>'});
233 link.addClassName(type);
234 }
235 });
236 }); // each matched link
237 });
238 {{/code}}
240 This is it! At this point, the extension should be already functional. If you test it now, you should be able to see the size of links getting injected next to matching each link in the content of a wiki document.
242 We will now make this information look nicer, and add an icon to represent the file type of the link, thanks to a stylesheet extension.
244 == Making it look nice with SSX ==
246 This time, we will take advantage of the **Parse** attribute of extensions that has been evoked upper in this tutorial. This way, we can be lazy and generate the CSS code using the velocity templating language, instead of writing a rule for each file format manually. Thanks to velocity and to the XWiki api, we will also be able to reference images attached to the extension document.
248 The class name that is added to each matching link by the JSX is actually the matching file extension itself (doc, pdf, etc.). Thus, we can then iterate over the extensions that we target, and generate a rule for each one of them. And more, if we name our icons with the convention of using the file extension, we can also reference the image within the same iteration.
250 You can [[download here>>]] an archive with the set of icons used for this tutorial. The icons for MS products and for zip and pdf files are from the **[[Silk Icons Set>>]]** by Mark James, under the [[Creative Commons Attribution 2.5 License>>]] license. To add the icons to your extension, just unzip the archive and attach them manually to your **XWiki.AddSizesExtension** document. Of course, you can also use your own set of icons. If you change the name of the files however, keep in mind you will have to adapt the stylesheet extension below.
252 Once you have the icons attached, create the stylesheet extension, set its parse attribute to **Yes**, and paste this code in the "Code" section:
254 {{code language="velocity"}}
255 /* A little padding on the right of links for the icons to fit */
256 #foreach($ext in ['odt', 'ods', 'odp', 'doc', 'xls', 'ppt', 'pdf', 'zip'])
257 #xwikicontent a.${ext} #if($velocityCount < 8), #end
258 #end {
259 padding-right:20px;
260 }
262 /* Files icons as background for the links */
263 #foreach($ext in ['odt', 'ods', 'odp', 'doc', 'xls', 'ppt', 'pdf', 'zip'])
264 #xwikicontent a.${ext} {
265 background:transparent url($doc.getAttachmentURL("${ext}.png")) no-repeat scroll right center;
266 }
267 #end
269 /* Nice spans for file size information */
270 #xwikicontent span.filesize {
271 font-size: 0.6em;
272 background-color:lightYellow;
273 }
274 {{/code}}
276 When asked to serve the CSS file, XWiki will evaluate this code using its Velocity Rendering engine, and will return a file that contains pure CSS code!
278 == Testing the final eXtension ==
280 Ok, it's time for us to see the whole thing in action! The snippet below is intended to showcase the extension on its own wiki page. It request to the **jsx** and **ssx** plugins the use of the contained objects, and then give an example of all the supported links.
282 {{code}}
283 {{velocity}}
284 #set($discard = $xwiki.jsx.use($doc.fullName))
285 #set($discard = $xwiki.ssx.use($doc.fullName))
286 {{/velocity}}
288 * [[An Writer document>>]]
289 * [[A MS Word document>>]]
290 * [[An OOo Spreadshet>>]]
291 * [[Link to a MS Excel document>>]]
292 * [[An OOo Presentation>>]]
293 * [[Link to a MS Powerpoint file>>]]
294 * [[A great archive>>]]
295 * [[A PDF file>>]]
296 {{/code}}
298 Now there are two things to keep in mind :
300 * The browser must be able to reach the Internet, since the extension does need the help of the json-head service hosted on Google App Engine.
301 * As Natalie Downe wrote, //"this may not be 100% reliable due to App Engine being occasionally and unavoidably flakey"//. You may for example experience a long loading time (but since the extension triggers only once the whole wiki document is loaded, this will not penalize the wiki users).
303 In a future extension of this tutorial, we will address those two issues writing our own version of the json-head service on the wiki itself, using the [[groovy programming language>>platform:DevGuide.Scripting||anchor="HGroovy"]].
305 Enough talk, let us see the result !
307 {{image reference="AddSizesMagic.png"/}}
309 == Bonus: links to activate/deactivate the extension ==
311 [[image:bonus.gif]]
313 You can add this snippet in the wiki content of the extension document, and users with the programming right granted will be provided a link to activate or not the extension on all pages of the wiki:
315 {{code}}
316 {{velocity}}{{html}}
317 #if($xwiki.hasAccessLevel('programming', $context.user)) ## Only programmers should be able to change the loading type
318 ## otherwise, Always-used extensions will not work
320 #if($doc.getObject('XWiki.JavaScriptExtension').getProperty('use').value == 'always')
321 #info('This extension is configured to be loaded on all the pages of this wiki.')
323 <span class=buttonwrapper>
324 <a href="$doc.getURL('save','XWiki.JavaScriptExtension_0_use=onDemand&XWiki.StyleSheetExtension_0_use=onDemand')">
325 De-activate loading for all pages.
326 </a>
327 </span>
328 #else
329 #info('This extension is configured to be loaded only on pages that request it.')
331 <span class=buttonwrapper>
332 <a href="$doc.getURL('save','XWiki.JavaScriptExtension_0_use=always&XWiki.StyleSheetExtension_0_use=always')">
333 Activate loading for all pages.
334 </a>
335 </span>
336 #end
338 #end
339 {{/html}}{{/velocity}}
340 {{/code}}
342 = Additional Details =
344 == How to use Velocity in parsed content ==
346 Example for **XWiki.JavaScriptExtension** code:
348 {{code}}
349 #if (!$xcontext.userReference)
350 alert("Hello guest!");
351 #else
352 alert("Hello user!");
353 #end
354 {{/code}}
356 will show different alerts for different users on page refresh.
358 Example for **XWiki.StyleSheetExtension** code:
360 {{code}}
361 #if (!$xcontext.userReference)
362 #mainContentArea {
363 background-color: grey;
364 }
365 #else
366 #mainContentArea {
367 background-color: blue;
368 }
369 #end
370 {{/code}}
372 will show different background colors for authenticated and anonymous users.
374 Velocity doesn't know about CSS. Everything that looks like a Velocity macro or variable is evaluated. So, undefined macros and
375 variables are printed as is. E.g. **#xwikicontent** will be used as CSS ID field, unless **xwikicontent** Velocity macro is defined.
377 Velocity is a template language, so when the Velocity code is evaluated the Velocity variables are simply substituted in the template by their values. So:
379 {{code}}
380 alert(false);
381 {{/code}}
383 works because **false*** is a literal boolean value in JavaScript.
385 Though:
387 {{code}}
388 alert($xcontext.user);
389 {{/code}}
391 will be evaluated e.g. as **alert(XWiki.User);** which will throw an exception unless **User** is a JavaScript variable previously defined, therefor you need to wrap the value in quotes, e.g.
393 {{code}}
394 alert('$xcontext.user');
395 {{/code}}
397 Or even more, because the value coming from Velocity can contain characters that are not allowed in a JavaScript string literal. So safest is to write:
399 {{code}}
400 alert('$escapetool.javascript($xcontext.user)');
401 {{/code}}
403 {{info}}
404 You can use XWiki global velocity variables **$doc**, **$request** and **$xcontext** in parsed content.
405 {{/info}}
407 = LESS =
409 Since XWiki 6.4M2, you can use [[LESS>>]] in your Skin Extensions. Get a look to [[extensions:Extension.Skin Extension Plugin||anchor="HUseLESS"]] for more informations.
411 = References =
413 * [[extensions:Extension.Skin Extension Plugin]]
414 * [[JSON with Padding>>]]
415 * [[HTTP HEAD Request>>]]
416 * [[get_json.js>>]]
417 * [[json-head>>]]

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