Re: hexl: doesn't play nicely with dynamic-completion-mode

["Chris Moore" <dooglus@gmail.com>]

On 9/10/07, Stefan Monnier <monnier@iro.umontreal.ca> wrote:

> hexl-mode should probably install a before-change-function that checks that
> this-command is among the supported ones.  This won't fix those problems,
> but will at least catch them before they corrupt the buffer.

Is there some way for a before-change-function to prevent a change?
It can call 'error to prevent the change once, but this clears the
before-change-function handler, so the 'bad' key won't be caught a 2nd
time.  Also, I notice that 'this-command is
'completion-separator-self-insert-command rather than
'self-insert-command in the hexl-mode before-change-function (after
applying Richard's fix), so hexl-mode would need to know about all the
modes which remap self-insert-command.