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2 12/2010 Using the WebFont Loader to Make Browsers Behave the Same

by Richard Rutter

Web fonts give us designers a whole new typographic palette with which to work. However, browsers handle the loading of web fonts in different ways, and this can lead to inconsistent user experiences.

Safari, Chrome and Internet Explorer leave a blank space in place of the styled text while the web font is loading. Opera and Firefox show text with the default font which switches over when the web font has loaded, resulting in the so-called Flash of Unstyled Text (aka FOUT). Some people prefer Safari’s approach as it eliminates FOUT, others think the Firefox way is more appropriate as content can be read whilst fonts download. Whatever your preference, the WebFont Loader can make all browsers behave the same way.

The WebFont Loader is a JavaScript library that gives you extra control over font loading. It was co-developed by Google and Typekit, and released as open source. The WebFont Loader works with most web font services as well as with self-hosted fonts.

The WebFont Loader tells you when the following events happen as a browser downloads web fonts (or loads them from cache):

  • when fonts start to download (‘loading’)
  • when fonts finish loading (‘active’)
  • if fonts fail to load (‘inactive’)

If your web page requires more than one font, the WebFont Loader will trigger events for individual fonts, and for all the fonts as a whole. This means you can find out when any single font has loaded, and when all the fonts have loaded (or failed to do so).

The WebFont Loader notifies you of these events in two ways: by applying special CSS classes when each event happens; and by firing JavaScript events. For our purposes, we’ll be using just the CSS classes.

Implementing the WebFont Loader

As stated above, the WebFont Loader works with most web font services as well as with self-hosted fonts.

Self-hosted fonts

To use the WebFont Loader when you are hosting the font files on your own server, paste the following code into your web page:

<script type="text/javascript">
WebFontConfig = {
	custom: { families: ['Font Family Name', 'Another Font Family'],
	urls: [ 'http://yourwebsite.com/styles.css' ] }
};

(function() { var wf = document.createElement(‘script’); wf.src = (‘https:’ == document.location.protocol ? ‘https’ : ‘http’) + ‘://ajax.googleapis.com/ajax/libs/webfont/1/webfont.js’; wf.type = ‘text/javascript’; wf.async = ‘true’; var s = document.getElementsByTagName(‘script’)0; s.parentNode.insertBefore(wf, s);
})();

Replace Font Family Name and Another Font Family with a comma-separated list of the font families you want to check against, and replace http://yourwebsite.com/styles.css with the URL of the style sheet where your @font-face rules reside.

Fontdeck

Assuming you have added some fonts to a website project in Fontdeck, use the afore-mentioned code for self-hosted solutions and replace http://yourwebsite.com/styles.css with the URL of the <link> tag in your Fontdeck website settings page. It will look something like http://f.fontdeck.com/s/css/xxxx/domain/nnnn.css.

Typekit

Typekit’s JavaScript-based implementation incorporates the WebFont Loader events by default, so you won’t need to include any WebFont Loader code.

Making all browsers behave like Safari

To make Firefox and Opera work in the same way as WebKit browsers (Safari, Chrome, etc.) and Internet Explorer, and thus minimise FOUT, you need to hide the text while the fonts are loading.

While fonts are loading, the WebFont Loader adds a class of wf-loading to the <html> element. Once the fonts have loaded, the wf-loading class is removed and replaced with a class of wf-active (or wf-inactive if all of the fonts failed to load). This means you can style elements on the page while the fonts are loading and then style them differently when the fonts have finished loading.

So, let’s say the text you need to hide while fonts are loading is contained in all paragraphs and top-level headings. By writing the following style rule into your CSS, you can hide the text while the fonts are loading:

.wf-loading h1, .wf-loading p {
	visibility:hidden;
}

Because the wf-loading class is removed once the the fonts have loaded, the visibility:hidden rule will stop being applied, and the text revealed. You can see this in action on this simple example page.

That works nicely across the board, but the situation is slightly more complicated. WebKit doesn’t wait for all fonts to load before displaying text: it displays text elements as soon as the relevant font is loaded.

To emulate WebKit more accurately, we need to know when individual fonts have loaded, and apply styles accordingly. Fortunately, as mentioned earlier, the WebFont Loader has events for individual fonts too.

When a specific font is loading, a class of the form wf-fontfamilyname-n4-loading is applied. Assuming headings and paragraphs are styled in different fonts, we can make our CSS more specific as follows:

.wf-fontfamilyname-n4-loading h1, 
.wf-anotherfontfamily-n4-loading p {
	visibility:hidden;
}

Note that the font family name is transformed to lower case, with all spaces removed. The n4 is a shorthand for the weight and style of the font family. In most circumstances you’ll use n4 but refer to the WebFont Loader documentation for exceptions.

You can see it in action on this Safari example page (you’ll probably need to disable your cache to see any change occur).

Making all browsers behave like Firefox

To make WebKit browsers and Internet Explorer work like Firefox and Opera, you need to explicitly show text while the fonts are loading. In order to make this happen, you need to specify a font family which is not a web font while the fonts load, like this:

.wf-fontfamilyname-n4-loading h1 { 
    font-family: 'arial narrow', sans-serif; 
}
.wf-anotherfontfamily-n4-loading p { 
    font-family: arial, sans-serif; 
}

You can see this in action on the Firefox example page (again you’ll probably need to disable your cache to see any change occur).

And there’s more

That’s just the start of what can be done with the WebFont Loader. More areas to explore would be tweaking font sizes to reduce the impact of reflowing text and to better cater for very narrow fonts. By using the JavaScript events much more can be achieved too, such as fading in text as the fonts load.

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About the author

Richard Rutter

Richard Rutter is a user experience consultant and director of Clearleft. In 2009 he cofounded the webfont service, Fontdeck. He runs an ongoing project called The Elements of Typographic Style Applied to the Web, where he extols the virtues of good web typography. Richard occasionally blogs at Clagnut, where he writes about design, accessibility and web standards issues, as well as his passion for music and mountain biking.

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