Re: Signal `quit' in a `font-lock-fontify-region-function'

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I think a larger (apparent) problem is to let user know what's going on.
> Naively issued messages would get overridden with "Quit" in the echo
> area, because the natural response (at least mine) in such situation is
> to mash C-g continuosly, not do it accurately and watch if there is any
> change. And those "excessive" C-g would result in "Quit" message.
> This is also part of the reason I haven't continued with implementing
> this just for my mode, but rather feel it would be better as a general
> Emacs feature.

Right, here's how I could imagine a "desirable" behavior:

- everytime some operation may block Emacs, it should "register"
  somewhere (probably some let-binding of a global var is all it takes).
- After hitting C-g, a timer is started.
- If this timer is reached before the C-g has had to chance to be
  processed, emit a message in the echo area explaining what Emacs is
  currently doing (based on the "registered" information above).
- when we reach the Nth C-g in a row within the same "registered"
  operation, we abort the operation (e.g. by calling an ad-hoc
  function provided while "registering").


-- Stefan