configuration
A few HTML5 questions that need answering
Challenge Accepted 
Earlier this week Christian Heilmann posted a talk and some interesting questions on his blog. Perhaps foolishly I decided to accept the challenge of answering them and what follows are my answers to his questions. My hope is to stimulate a bit of civilised debate and so I hope that people challenge what I have written. I’ve tried not to be too opinionated and qualify things with ‘I think’, ‘probably’ etc where possible, but these are inevitably my opinions (and nobody else’s) and should be interpreted as just that.
I think Christian has done a great job putting these questions together – if they make other people think as much as they made me think they’ve certainly been worthwhile. Like many of life’s great questions the answers don’t always boil down to yes and no. In fact usually there is a grey area in which a judgment call is required, and so I apologise in advance if some of the answers are simply ‘it depends’.
Can innovation be based on “people never did this correctly anyways”?
Yes, I’d say that innovation can be based on almost anything. It’s probably better if innovation is based on solid foundations, however I believe the web is more of a bazaar than a cathedral and so solid foundations aren’t always feasible.
If we look at some older browsers where let’s say the spec was interpreted in an unexpected way, take specifically IE5.5 and the CSS box model – hacks are required to get around its ‘creative’ implementation and due to the huge win of being able to write cross-browser web-pages with the same markup, hacks are almost always found. Often hacks by their very nature will be ugly, but this can help serve to remind us of their existence.* Once the hack is found innovation continues again at its usual pace. I’d argue that innovation on the web is built on a series of (often ugly) hacks.
To answer the question in the context of HTML5′s tolerance for sloppy markup, it’s interesting to note that HTML5 does allow you to markup as XHTML if you so choose, personally and maybe because I’m over fastidious, this is what I try to do. Whether the browser picks up my mistakes or just silently corrects them is another issue. Modern editors’ text highlighting helps a lot but if you are taking your markup seriously you may want to validate it. At the end of the day innovation will take place regardless.
*http://tantek.com/log/2005/11.html
Is it HTML or BML? (HyperText Markup Language or Browser Markup Language)
I think HTML should be accessible to more than what we traditionally view as the browser, yes. From an accessibility standpoint it should be a responsibility to make sure that pages are reasonably accessible from a range of devices such as screenreaders. What ‘reasonably accessible’ means could be cause for considerable debate. Additionally it is in most people’s interest to make their pages readable by a search-engine bot. Some developers may find that they want their pages to be parseable in which case they should probably mark them up in XHTML.
I think though, that the most effective way to encourage people to mark up their pages for devices other than browsers is to make clear the benefits of doing so. Search bots and screenreaders will eventually catch up and I think at that point we will be in a better place.
On a side note hypertext is what the web is founded on – it’s the essence of the web if you like. If you stripped down the web to just hypertext you’d still have a web, albeit a limited version of what we have today. Hypertext is really just text or documents endowed with the ability to link to other documents. This ability to link is of course extremely powerful and enables anyone to create a web page that is instantly ‘part’ of the web. Some companies are starting to rely less on the humble hyperlink and invent markup for themselves that relies on JavaScript to actually work, Facebook’s FBML is an example of this and I would perhaps put this ‘extension’ of HTML in the BML camp.
But while so much has been added to HTML, the hyperlink still remains and developers are encouraged to use it, even if in some cases it is just a fallback for more complex interactions. Only the other day we experienced the fallout from Google’s hashbang method of ajaxifying a link, I feel that a large part of this stemmed from the fact that developers felt that they no longer had to populate their hrefs, but in reality it is still highly recommended they do. So no matter how complex a web application becomes I’d argue that it should always be based fundamentally on the good old hyperlink in which case, strictly speaking it would be HTML.
Should HTML be there only for browsers? What about conversion Services? Search bots? Content scrapers?
Some would argue that information published publicly on the web is there to be consumed by however or whatever chooses to consume it. However a semantic web not only makes content more accessible to humans but also to algorithm running computers that seek to diseminate and categorise the wealth of information out there, this new information could then be presented back to a human and so the wheel turns and the machine cranks on. Again I feel developers should be shown the benefits.
Touching again on accessibility, laws exist and I think rightly so, to mandate that certain websites should be accessible to all, just as they do for certain buildings especially public ones. Whether your house or say a merry-go-round should be accessible is less clear. During the development of jPlayer we decided to make elements of it accessible because we felt it was the right thing to do, but the very first versions weren’t. The ‘right-thing-to-do’ can often be more a powerful motivator than any rule, especially if it is difficult to enforce.
Should we shoe-horn new technology into legacy browsers?
I think we should aim to support as many legacy browsers as reasonably possible – yes. What is ‘reasonably possible’ has always been a contentious issue but I think most developers broadly agree on what this means.
A key decision is how consistent you want each browser’s interpretation of your web page or application to be. Note that the experience will never be identical across all browsers, even the modern ones, so a certain degree of comprimise is always required. I really just view the shoe-horning of new technology into legacy browsers as just another hack, although instead of correcting a misimplemented feature its aim is to augment the legacy browser’s feature set to more closely match newer browsers.
Do patches add complexity as we need to test their performance? (there is no point in giving an old browser functionality that simply looks bad or grinds it down to a halt)
If we take patches to mean any code styling or markup that can adequately add missing functionality to a browser, (are also referred to as shims, shivs or more recently polyfills), yes patches do add complexity, but well written patches that can easily be dropped into a project should mask the complexities from the web developer. You could argue that patches are essential if we are to start using new technologies like HTML5 in the wild. Again a decision needs to be made as to whether a patch slows down a browser unacceptedly, whether to fallback to a less complete solution for legacy browsers or whether not to use the new technology at all yet.
How about moving IE fixes to the server side? Padding with DIVs with classes in PHP/Ruby/Python after checking the browser and no JS for IE?
The trouble with moving fixes to the server-side is that, in my experience at least, front-end developers and especially designers (whose lives these fixes affect) like to be able to develop applications with as little contact with the server as possible. Some web pages don’t even require any real server-side interaction and so we would be creating an added burden to the designer or developer’s development cycle. That said if the web developer could continue to work as usual on a web application that relied on the server-side anyway, safe in the knowledge that the server would take care of any differences then I suppose that would be one possible solution.
Another issue is server-side solutions tend to be less transparent and this could cause unneccessary resistance to those who might seek to change and evolve these fixes. You would also have to deal with the situation where several server-side fixes existed (PHP/Ruby/Python etc), the exception perhaps being mods to the actual webserver (although webservers do vary).
It is true that developers or designers are unlikey to work without a webserver these days but on balance I think there are a lot of issues to be resolved before all but the simplest fixes get moved to the server-side. So I’d say some IE fixes on the server-side could well make sense, anything more complex probably isn’t warranted.
Can we expect content creators to create video in many formats to support an open technology?
I don’t think we can expect content creators to create a video in many formats to support a certain technology just because it is open. It’s more likely to depend on the content creators and the market that they are appealing to – whether they are creating a true native cross-platform solution or whether they are willing to fallback to say Flash to deliver content that a browser doesn’t natively support. I think this is an area where some sort of server-side video format conversion module could be useful in encouraging developers to support native video in every browser. Ironically any tool that converts to or from certain types of encoded video could be subject to royalties (I’d love to be proved wrong here). A content creator could decide to support only open video formats but for example if H.264 is assumed not to be open, the big question is how do you create a video fallback for iOS whose browser doesn’t support Flash or similar.
Can a service like vid.ly be trusted for content creation and storage?
The question that immediately springs to mind is what happens if vid.ly goes down? You are essentially introducing another point of failure and it’s probably a good idea to keep these to a minimum, depending of course on how crucial it is that that content is always available. You could also argue that depending on CDNs to host your favourite JavaScript library is a bad idea so I guess it’s a judgment call on how likely it is that a particular service is to go down. Leaving aside the issue of reliability, what happens if a service like vid.ly gets bought out or hacked or decide to change their policy? All these are important questions that we’d probably do well to ask ourselves before relying on such a service.
Content creation could be a winner though, in the sense that it would be nice to upload one format and several other formats be made available to you. It’s a bit unfashionable but I sometimes wonder whether the WordPress model of being able to download and drop in a useful module on to your LAMP stack makes more sense. I’d love to be able to host my own personal version of vid.ly for use on my website only – it also makes sense from a distributed computing point of view.
Is HTML5 not applicable for premium content?
If we take premium content to mean content available for a fee, it is certainly more difficult to protect that content from being downloaded with HTML5. Being able to view source is arguably one of the most important aspects of open technology and HTML5 is a group of open technologies. However there is almost always a way to grab premium content whether it is based upon open technology or not, so at the end of the day we’re really talking about how difficult you make this.
Mark B
HTML5 Media, Seeking and the Buffered Attribute
It can be very exciting playing with new technologies, HTML5 media being a case in point. The spec is still evolving and although native audio and video have only been about for little over a year in any useable form, we are already seeing browsers makers pushing the envelope and developers rushing to create new libraries.
We aim to incorporate features into the jPlayer library as they become available. Recently we have been looking at browser’s ability to jump to a point in a track that has not yet downloaded. A seeking of sorts. All the major HTML5 supporting browsers allow this type of seek (with the exception of Safari for Windows), but at the moment it seems only Chrome and Safari (both mobile and desktop versions) have taken this a step further by implementing the buffered attribute, although Firefox 4 also does, it is still in beta.
The buffered attribute allows us to determine what parts of a media track have been buffered so that we can seek or skip directly to that part without the need to pause.
More info on the buffered attribute can be found in this article HTML5 video ‘buffered’ property available in Firefox 4
Mark B
Add a Stylish Audio Player to your Blog Without using Plugins
Admittedly, it’s a little crude, but it’s simple and it works.
If you’ve ever wanted to add an audio player to your blog post and didn’t want to go to the trouble of installing a specific plugin to do so, you can always embed jPlayer within an iFrame. The one-liner you need to achieve this would probably look a lot like this:
which could give you something like this :
Sure, it’s not that efficient, you may end up loading jQuery twice if it’s already included as part of your blog, but there’s the added advantage that the page will render progressively and you have a nice little sandbox to play in should you just want to alter the player.
I used to hate iFrames and shudder at their very mention, but I must admit I’m coming around to them.
Mark B
A Simple and Robust jQuery 1.4 CDN Failover in One Line
Google, Yahoo, Microsoft and others host a variety of JavaScript libraries on their Content Delivery Networks (CDN) – the most popular of these libraries being jQuery. But it’s not until the release of jQuery 1.4 that we were able to create a robust failover solution should the CDN not be available.
First off, lets look into why you might want to use a CDN for your JavaScript libraries:
1. Caching – The chances are the person already has the resource cached from another website that linked to it.
2. Reduced Latency – For the vast majority the CDN is very likely to be much faster and closer than your own server.
3. Parallelism – There is a limit to the number of simultaneously connections you can make to the same server. By offloading resource to the CDN you free up a connection.
4. Cleanliness – Serving your static content from another domain can help ensure that you don’t get unnecessary cookies coming back with the request.
All these aspects are likely to add up to better performance for your website – something we should all be striving for.
For more discussion of this issue I highly recommend this article from Billy Hoffman : Should You Use JavaScript Library CDNs? which includes arguments for and against.
The fly in the ointment is that we are introducing another point of failure.
Major CDNs do occasionally experience outages and when that happens this means that potentially all the sites relying on that CDN go down too. So far this has happened fairly infrequently but it is always good practice to keep your points of failure to a minimum or at least provide a failover. A failover being a backup method you use if your primary method fails.
I started looking at a failover solution for loading jQuery1.3.2 from a CDN some months ago. Unfortunately jQuery 1.3.2 doesn’t recognise that the DOM is ready if it is added to a page AFTER the page has loaded. This made making a simple but robust JavaScript failover solution more difficult as the possibility existed for a race condition to occur with jQuery loading after the page is ready. Alternative methods that relied on blocking the page load and retrying an alternative source if the primary returned a 404 (page not found) error code were complicated by the fact that the Opera browser didn’t fire the "load" event in this situation, so when creating a cross-browser solution it was difficult to move on to the backup resource.
In short, writing a robust failover solution wasn’t easy and would consume significant resource. It was doubtful that the benefit would justify the expense.
The good news is that jQuery1.4 now checks for the dom-ready state and doesn’t just rely on the dom-ready event to detect when the DOM is ready, meaning that we can now use a simpler solution with more confidence.
Note that importantly the dom-ready state is now implemented in Firefox 3.6, bringing it in line with Chrome, Safari, Opera and Internet Explorer. This then gives us great browser coverage.
So now in order to provide an acceptably robust failover solution all you need do is include your link to the CDN hosted version of jQuery as usual :
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js"></script>
and add some JS inline, similar to this:
<script type="text/javascript">
if (typeof jQuery === 'undefined') {
var e = document.createElement('script');
e.src = '/local/jquery-1.4.min.js';
e.type='text/javascript';
document.getElementsByTagName("head")[0].appendChild(e);
}
</script>
You are then free to load your own JavaScript as usual:
<script type="text/javascript" src="my.js"></script>
It should be well noted however that the above approach does not "defer" execution of other script loading (such as jQuery plugins) or script-execution (such as inline JavaScript) until after jQuery has fully loaded. Because the fallbacks rely on appending script tags, further script tags after it in the markup would load/execute immediately and not wait for the local jQuery to load, which could cause dependency errors.
One such solution is:
<script type="text/javascript">
if (typeof jQuery === 'undefined')
document.write('script type="text/javascript" src="/local/jquery-1.4.min.js"><\/script>');
</script>
Not quite as neat perhaps, but crucially if you use a document.write() you will block other JavaScript included lower in the page from loading and executing.
Alternatively you can use Getify‘s excellent JavaScript Loading and Blocking library LABjs to create a more solid solution, something like this :
<script type="text/javascript" src="LAB.js">
<script type="text/javascript">
function loadDependencies(){
$LAB.script("jquery-ui.js").script("jquery.myplugin.js").wait(...);
}
$LAB
.script("http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js").wait(function(){
if (typeof window.jQuery === "undefined")
// first load failed, load local fallback, then dependencies
$LAB.script("/local/jquery-1.4.min.js").wait(loadDependencies);
else
// first load was a success, proceed to loading dependencies.
loadDependencies();
});
</script>
Note that since the dom-ready state is only available in Firefox 3.6 + <script> only solutions without something like LABjs are still not guaranteed to work well with versions of Firefox 3.5 and below and even with LABjs only with jQuery 1.4 (and above).
This is because LABjs contains a patch to add the missing "document.readyState" to those older Firefox browsers, so that when jQuery comes in, it sees the property with the correct value and dom-ready works as expected.
If you don’t want to use LABjs you could implement a similar patch like so:
<script type="text/javascript">
(function(d,r,c,addEvent,domLoaded,handler){
if (d[r] == null && d[addEvent]){
d[r] = "loading";
d[addEvent](domLoaded,handler = function(){
d.removeEventListener(domLoaded,handler,false);
d[r] = c;
},false);
}
})(window.document,"readyState","complete","addEventListener","DOMContentLoaded");
</script>
(Adapted from a hack suggested by Andrea Giammarchi.)
So far we have talked about CDN failure but what happens if the CDN is simply taking a long time to respond? The page-load will be delayed for that whole time before proceeding. To avoid this situation some sort of time based solution is required.
Using LABjs, you could construct a (somewhat more elaborate) solution that would also deal with the timeout issue:
<script type="text/javascript" src="LAB.js"></script>
<script type="text/javascript">
function test_jQuery() { jQuery(""); }
function success_jQuery() { alert("jQuery is loaded!");
var successfully_loaded = false;
function loadOrFallback(scripts,idx) {
function testAndFallback() {
clearTimeout(fallback_timeout);
if (successfully_loaded) return; // already loaded successfully, so just bail
try {
scripts[idx].test();
successfully_loaded = true; // won't execute if the previous "test" fails
scripts[idx].success();
} catch(err) {
if (idx < scripts.length-1) loadOrFallback(scripts,idx+1);
}
}
if (idx == null) idx = 0;
$LAB.script(scripts[idx].src).wait(testAndFallback);
var fallback_timeout = setTimeout(testAndFallback,10*1000); // only wait 10 seconds
}
loadOrFallback([
{src:"http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js", test:test_jQuery, success:success_jQuery),
{src:"/local/jquery-1.4.min.js", test:test_jQuery, success:success_jQuery}
]);
</script>
To sum up – creating a truly robust failover solution is not simple. We need to consider browser incompatabilities, document states and events, dependencies, deferred loading and time-outs! Thankfully tools like LABjs exist to help us ease the pain by giving us complete control over the loading of our JavaScript files. Having said that, you may find that in many cases the <script> only solutions may be good enough for your needs.
Either way my hope is that these methods and techniques provide you with the means to implement a robust and efficient failover mechanism in very few bytes.
A big thanks to Kyle Simpson, John Resig, Phil Dokas, Aaoran Saray and Andrea Giammarchi for the inspiration and information for this post.
Related articles / resources:
3.http://aaronsaray.com/blog/2009/11/30/auto-failover-for-cdn-based-javascript/
4.http://snipt.net/pdokas/load-jquery-even-if-the-google-cdn-is-down/
5.http://stackoverflow.com/questions/1447184/microsoft-cdn-for-jquery-or-google-cdn
6.http://webreflection.blogspot.com/2009/11/195-chars-to-help-lazy-loading.html
7.http://zoompf.com/blog/2010/01/should-you-use-javascript-library-cdns/
Moving a Java project between Eclipse installations
The quickest way I have found of moving a Java project from one Eclipse installation to another.
(I am using Eclipse 3.4.1)
1. Copy the directory from your source Workspace to your target Workspace.
2. Remove the .classpath and .project files from the target. (These will be regenerated by Eclipse).
3. In your target installation of Eclipse go to File->New->Java Project
4. Enter a project name and click the ‘Create project from existing source’. radio button
5. Browse to your target directory in Workspace, click ‘Finish’
6. In your target Eclipse go to Project->Properties , select Java Build Path
7. Assuming you have copied over all jars that you are using, refer to your source installation of Eclipse Project->Properties->Java Build Path, Libraries tab and add all your jars.
8. (Target Eclipse) Project->Build Project and it should build.
Optional – Defining the output directory of your class files.
9. (Target Eclipse) Project->Properties->Java Build Path, Source, Browse button
10. Click ‘Create New Folder’, specify Folder name (this can be anything), click ‘Advanced’
11. Tick ‘Link to folder in the file system’, browse to output folder (usually WEB-INF/classes)
12. Click, ok, ok, ok.
The next time you build – your classes should be compiled into your chosen output directory.
If you know of a quicker/better way – let me know!
Mark B
Previous Posts
- The Hyperaudio Pad – Next Steps and Media Literacy
- Breaking Out – The Making Of
- Breaking Out – Web Audio and Perceptive Media
- Altrepreneurial vs Entrepreneurial and Why I am going to Work with Al Jazeera
- HTML5 Audio APIs – How Low can we Go?
- Hyperaudio at the Mozilla Festival
- The Hyperaudio Pad – a Software Product Proposal
- Introducing the Hyperaudio Pad (working title)
- Accessibility, Community and Simplicity
- Build First, Ask Questions Later
- Further Experimentation with Hyper Audio
- Hyper Audio – A New Way to Interact
- P2P Web Apps – Brace yourselves, everything is about to change
- A few HTML5 questions that need answering
- Drumbeat Demo – HTML5 Audio Text Sync
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