Today’s ‘What were they thinking?’ query goes to the team developing the UI for Font Book, the font manager that’s been a part of Mac OS X since 10.3. It’s a nice little utility, making it easy to install, activate and deactivate fonts, but also simply to simply browse and preview them – although in 10.5, the Finder’s icon and Cover Flow views have actually become capable of that as well. 10.5 also provides for auto-activation and a few other nifty features graphic designers will love to have standard in the OS. Still, Font Book can’t (and isn’t meant to) replace a professional font manager like FontExplorer X, which Linotype nicely enough has been providing for free, even though they could easily make quite a bit off money with it (like, say, $99.95).

But I digress. Among the functionality provided of Font Book is font validation. This checks a font file for various common errors, such as malformed or incomplete binary streams. As far as I recall, it even kicks in automatically when you try to install a font, warning you ahead that you may not want to do that.

Disappointed with Spotlight performance, I decided to force a re-index earlier (using sudo mdutil -E -a, for “erase index for all volumes, recreating it where appropriate”). mdworker, the background indexing tool, spits quite a few error message as it descends through the hierarchy, letting advanced users know of particular files it had trouble with. Among them:

11/3/07 8:42:15 PM mdworker[65051] FontImporter: Validation failed - "/Users/chucker/Library/Application Support/Linkinus/Styles/Mmm... IRC.lnkStyle/Contents/Resources/Fixedsys500c.ttf".

Ah, a broken font file. From an application I only really tried once, no less. (Mind you, I didn’t find Linkinus to be bad at all, just not sufficiently better compared to Colloquy to justify paying $20.) I could have just deleted the file, but I was curious enough to see the error. So I had it open in Font Book, and it showed me a preview (as did the Finder). Can’t be too broken. In Font Book’s file menu, we have “Validate Font” and “Validate File…”. But, what’s that? They’re both greyed out.

That’s right: it appears that, if you open Font Book through a font file, it won’t let you validate that font.

If, on the other hand, you open Font Book directly, then choose File → Validate File…, you’ll find that you’re suddenly able to select that same file in the Open dialog that appears and have it validated just fine.

The problem with the file, by the way? Indeed, Font Book did find one: “1 serious error” in “‘post’ table usability”. It’s a shame that this doesn’t tell me squat, and I’ve learnt a lot more about a really strange user interface omission or limitation than I have about this particular font.