Comment 2 for bug 16492

I hadn't noticed that it works for GTK single-line text fields. That's good. But
it doesn't work for other keyboard-controlled areas in Nautilus, Dictionary,
File Roller, Gnometris, Robots (when played using the keyboard), Gimp, gThumb,
xpdf, ggv (and Evince), Evolution (and Thunderbird), Gaim, GnomeMeeting, X-Chat,
Rhythmbox, Totem, gconf-editor, Network Tools, System Log Viewer, System
Monitor, CD Database Server, Desktop Background Preferences, File Management
Preferences, Keyboard Preferences, Keyboard Shortcuts, Network Proxy
Preferences, Screensaver Preferences, Sessions, Sound preferences, Theme
Preferences, Device Manager, Login Screen Setup, Network settings, Printers,
Synaptic, Users and Groups, and Yelp. So no, I don't think it's a bug in Firefox.

Even if the HIG said that applications should do it, and I went and reported
bugs on all those apps, some would still forget to implement it, or not bother
to do it, or do it incorrectly. And even if GTK did it for listboxes as well as
text fields, that would fix less than half the programs I listed above. Better
to implement it in a single place at a lower level, which is why I suggest it's
X's job.