Too late, the inimitable Owen Taylor proposed this a while ago, and the implementation is alread in GTK+ trunk.

While a transient indication is useful I don't think it is a replacement for a modal indicator.  For one, tooltips are generally not considered important enough to read.  Secondly, it is too easy to dismiss it by hovering over it.  I've noticed that if the mouse pointer is already in the area where the tip would popup it doesn't show at all.

> I've noticed that if the mouse pointer is already in the area where the tip
> would popup it doesn't show at all.

Hmm, that sounds like a bug

Also worth noting that the popup won't help us in the screensaver dialog.

Why not ?

Personally I don't quite like that this special kind of tooltip covers widgets and doesn't actually behave like a tooltip.

However it works fine for me and admittedly does a good job in making it obvious that one should switch off caps lock.

Note that it does only *not* work with ktsuss, but I'm not sure why.

I've redone this using an icon now.