Responsive design – a simpler approach

If you’ve spent a bit of time working on responsive websites, you’ll have hit two problems or frustrations …

1. Scrolling up and down your css file comparing values between media query sections
2. Using mediaListeners, or checking body width just to work out what media query / display mode your page is currently using.

Inspired by libraries like moderniser or templates like html5 boilerplate that places classes in the head or body tag, I thought it would make life easier if you could place a class on an element (usually the body tag but any element is supported) and then go forth and style and code as usual.

The result is the mediaQuery plug-in for jQuery. If you want to use this plug-in you need to be comfortable with the following: you are already going to use jQuery, and you don’t mind your site being non-responsive for non-javascript users.

On the positive side, the plug-in includes polyfills for css media queries and the matchMedia and addEventListener javascript functions – so you wont need to include any other code to support responsive across all browsers.

Usage is really simple:


$('body').mediaQuery({
  w320: 'only screen and (min-width: 320px)',
  w480: 'only screen and (min-width: 480px) ',
  w768: 'only screen and (min-width: 768px)',
  w1024: 'only screen and (min-width: 1024px)'
});

This code will add the classes w320, w480, w768, w1024 to the body tag depending on each of the corresponding media queries matching.

Your css is then as simple as this eg:


.w320 .content p {
  background-color:#d45354;
}

.w480 .content p {
font-size:3em;
width:360px;
height:360px;
line-height:360px;
background-color:#818b85;
}

Checking for different media queries is now as simple as this line of jQuery code:


if ($(element).hasClass('w1024')) ...

You can view an example of the technique here: http://jameswestgate.github.com/mediaQuery/examples/

Responsive design – a simpler approach

Responsively adding webP images

Whilst working out an approach to selectively loading responsive images, I realised I had finally found a place for the webP format. A quick feature detect confirmed this would be possible. This post wraps everything up in the responsive images series by combining the feature detect with the responsive images code to provide a hearty complete solution to your responsive image needs.

If you view the page at http://opencomponents.com/flexible/ using the latest Opera or Chrome client, and inspect the images, you should notice that the image paths end in the .webp extension. This saves up to 50% download size on the larger images without any loss in quality.

On the smaller version of the images it was interesting to note that at default quality, the images were actually bigger. If I dropped the quality slightly, a more modest 20% gain was usually found. Must say though that the quality is still excellent.

Responsively adding webP images

Altering image sizes responsively in all browsers

If you view the responsive web page page by Ethan Marcott in IE8, you’ll notice that it doesn’t work in the same way as modern browsers. This is because IE8 and below doesn’t support media queries – the smart bit of css we use to conditionally style our page based on current or device width. We also need to evaluate media queries to set our img tag through javascript using windows.matchMedia and media query list addListener– this isn’t supported in IE9 or less.

We need another polyfill – to add media queries to IE8 and below and to add media query matching and listening in IE9 (as well as any other unsupported platforms). The responsive polyfill I’ve written combines elements of Scott Jehl’s respond.js polyfill for media queries, Paul Irish’s matchMedia.js polyfill and my own code for media query listeners whilst keeping performance a priority.

This allows us to use code to detect when to change the image or image size in the browser and set the correct image path on initial page load. We thus take the following steps:

– set up a media query to detect changes at a width of 600 pixels
– read the contents of noscript tags and add an image to the dom depending on the media query
– listen to the media query so that when it changes we can modify the image path accordingly.

var mql = window.matchMedia('only screen and (max-width: 600px)');
var elements;
	
//Get contents of noscript tags 
var tags = document.getElementsByTagName("noscript");

//Add image to dom depending on media query
for (var i=0, len=tags.length; i<len; i++) {
  var markup = tags[i].textContent.trim();

  if (mql.matches) markup = markup.replace("/large/", "/small/");
  tags[i].insertAdjacentHTML('afterend', markup);
}

//Scale up to large / down to small when media query changes
mql.addListener(function() {

  if (!elements) elements = document.getElementsByTagName("img");
		
  var from = (mql.matches) ? "/large/" : "/small/";
  var to = (mql.matches) ? "/small/" : "/large/";

  for (var i=0, len=elements.length; i<len; i++) {
    if (elements[i].className.indexOf("responsive") > -1)
      elements[i].src = elements[i].src.replace(from, to);
  }
});

View the example

Thoughts on this technique

It should be pointed out that strictly speaking, once we have the large image we dont need the small image - it is better just to scale it down. However I also think that the smaller image in a responsive design may often be different - perhaps a more cropped version - anyway this page exists to demonstrate the basic technique only.

We also dont use a jQuery style document.ready type approach - this is simply not needed for such a simple example - placing the code in the footer is more than sufficient. However - because the images are loaded fairly late in the day you can see the image 'waterfall' as they are loaded. A more advanced technique may only display them once they are fully loaded, perhaps with css such as

img.responsive {display:none}
noscript img.responsive {display:block}

Is it worth the extra script vs the reduced download? Probably. Certainly the noscript code is small. Making IE9 and below fully responsive may not be worth it however.

PS. The responsive script doesn't currently read style tags in the parent document - it could easily be modified to do so however.

Altering image sizes responsively in all browsers

A lightweight script loader

Script loaders are the Javascript blogosphere topic de jour and so I thought I’d weigh in with my own contribution. Use a script loader to delay the download and execution of portions of your page’s Javascript code, increasing page render/load performance. Script loaders originated with performance guru Steve Souders and some excellent libraries have sprung up as a result of his work.

Most script loading libraries I’ve looked quickly become over-complicated, whereas I wanted to make something ultra-light, and easy to use. Here’s a simple technique I use because the code is neat and should address 80% of requirements. It’s based on Steve’s asynchronous script loading technique, with some code added to attach a callback function once all scripts have loaded.

The script loader should be called as follows:

loadScript('script1.js', 'script2.js', function() {
  //code to run when both scripts have been loaded
});

The function works by placing a correctly formatted script tag into the header of the page and attaching a load handler to each script to enable the execution of a callback (if required). I like this technique because debugging tools such as Firebug continue to work as normal, respects any cache settings, but still provides the performance parallel script downloading – plus its seriously lightweight.

To create dependancy chains, use the function like so:

loadScript('script1.js', 'script2.js', function() {
  loadScript('script3.js', function() {
    //Execute code 
  });
});

You can view the source code here.

A lightweight script loader

Why Firefox 4 wont be Acid3 compliant

The Acid Tests are useful tests used to gauge whether a browser conforms to web standards and are often used to rate progress on beta builds of new browser versions, as well as a way to nudge older browsers (Internet Explorer) towards compliance.

So you may be surprised to find that it is unlikely that Firefox4 will be fully Acid3 compliant. According to a comment on Slashdot by Mozilla’s Boris Zbarsky and a follow up post by Alexander Limi, the three remaining items are to do with SVG fonts and have only been partially implemented in Opera and Webkit (Safari and Chrome) – just enough for those browsers to pass Acid3.

Currently IE9 Beta scores 95 on the Acid3 test and it’s unlikely that it will meet the 100% mark either. Which raises the question: just how important is the Acid3 test these days anyway?

Why Firefox 4 wont be Acid3 compliant