Tags: webfonts

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Icon fonts, unicode ranges, and IE8’s compatibility mode

While doing some browser testing this week, Mark come across a particularly wicked front-end problem. Something was triggering compatibility mode in Internet Explorer 8 and he couldn’t figure out what it was.

Compatibility mode was something introduced in IE8 to try not to “break the web”, as Microsoft kept putting it. Effectively it makes IE8 behave like IE7. Why would you ever want to do that? Well, if you make websites exactly the wrong way and code for a specific browser (like, say, IE7), then better, improved browsers are something to be feared and battled against. For the rest of us, better, improved browsers are something to be welcomed.

Shockingly, Microsoft originally planned to have compatibility mode enabled by default in Internet Explorer 8. It was bad enough that they were going to ship a browser with a built-in thermal exhaust port, they also contemplated bundling a proton torpedo with it too. Needless to say, right-minded people were upset at that possibility. I wrote about my concerns back in 2008.

Microsoft changed their mind about the default behaviour, but they still shipped IE8 with the compatibility mode “feature”, which Mark was very much experiencing as a bug. Something in the CSS was triggering compatibility mode, but frustratingly, there was no easy way of figuring out what was doing it. So he began removing chunks of CSS, reducing until he could focus in on the exact piece of CSS that was triggering IE8’s errant behaviour.

Finally, he found it. He was using an icon font. Now, that in itself isn’t enough to give IE8 its conniptions—an icon font is just a web font like any other. The only difference is that this font was using the private use area of the unicode range. That’s the default setting if you’re creating an icon font using the excellent icomoon service. There’s a good reason for that:

Using Latin letters is not recommended for icon fonts. Using the Private Use Area of Unicode is the best option for icon fonts. By using PUA characters, your icon font will be compatible with screen readers. But if you use Latin characters, the screen reader might read single, meaningless letters, which would be confusing.

Well, it turns out that using assigning glyphs to this private use area was causing IE8 to flip into compatibility mode. Once Mark assigned the glyphs to different characters, IE8 started behaving itself.

Now, we haven’t tested to see if this is triggered by all of the 6400 available slots in the UTF-8 private use range. If someone wants to run that test (presumably using some kind of automation), ’twould be much appreciated.

Meantime, just be careful if you’re using the private use area for your icon fonts—you may just inadvertently wake the slumbering beast of compatibility mode.

Iconic imagery

There’s been some fantastic collaborative work done recently on the tricky issue of responsive images. Witness the community group and its attendant website, complete with logo.

Meanwhile, there’s been some great research into dealing with high-DPI displays (which the world and its dog have decided to label “retina”). There’s the in-depth analysis by Daan Jobsis which looks at what you can get away with when it comes to compression and quality for “retina” displays: quite a lot, as it turns out.

In fact, you may well be able to double the dimensions of an image while simultaneously bringing down its quality and end up with an image that is smaller in file size than the original, while still looking great on high-DP..“retina” displays. The guys over at Filament group have labelled this Compressive Images. Nice.

I like that approach. No JavaScript polyfills. No lobbying of standards bodies.

I’m generally fan of solutions that look for ways of avoiding the problem in the first place. Hence my approach to image optimisation for all devices, widescreen or narrow.

Of course this whole issue of responsive (or compressive) images should really only apply to photographic imagery. If you’re dealing with “text as images” …don’t. Use web fonts. If you’re dealing with logos or icons, there are other options, like SVG.

Then there’s the combination of web fonts and iconography. Why not use a small web font containing just the icons you need?

I tried this recently, diligently following Josh’s excellent blog post detailing how to get icon shapes out of Fireworks, into a font editor, and then into an actual font. It works a treat, although I concur with Josh’s suggestion that the technique should really only be implemented using the ::before and ::after pseudo-elements in combination with base-64 encoding the font file. That means it won’t work in every single browser, but that’s the point: these icons should be an enhancement, not a requirement.

Having gone through the tortuous steps required to get my Mac all set up with the software required to follow Josh’s tutorial, I then spotted the note at the end of his article that pointed to Icomoon. That turns out to be a fantastic service. You can pick and choose from the icons provided or you can upload your own vector shapes. Then you can assign the unicode slots you want to use for the icons and you can get the resulting font file base-64 encoded. Very, very cool!

There’s a whole slew of icon-font services like that out there now: Pictos, Web Symbols, and Symbolset with its ingenious use of ligatures to allow for an accessible fallback.

Jenn is currently casting a critical eye over each of these service over on the Nerdary: part one, part two, and part three are all deserving of your time and attention.