Re: Problem quitting properly from transient keymap with one keystroke

[Robert Weiner <rsw@gnu.org>]

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On Fri, Oct 20, 2017 at 11:13 AM, Stefan Monnier <monnier@iro.umontreal.ca>
wrote:

> >> > I can't just add a post-command-hook that calls the transient map
> >> > disable function because calling (keyboard-quit) from the
> >> > post-command-hook triggers an error and I imagine that is not a proper
> >> > usage scenario.
> >> Why do you need a post-command-hook?
> > HyControl uses post-command-hook to persist a prefix-argument value
> across
> > commands and to continually display a help message in the minibuffer
> until
> > exit.
>
> But neither of those activities seem related to calling the exit
> function or calling keyboard-quit.
>

​I thought you were just asking about how this library used
post-command-hook with set-transient-map.

When {C-g} is pressed, we want to execute some actions and then terminate
the transient map.  We could
do this in the {C-g} key binding itself rather than in post-command-hook.
I just tested and that does
indeed solve the problem.  Thanks much.

​​
>
> ​​
> > ​​Just curious, why does set-transient-map use pre-command-hook instead
> of
> ​​
> > post-command-hook​ to test whether or not to keep the transient-map
> ​​
> > enabled?
> ​​
>
> ​​
> Because we need to know which is the next command before we know whether
> ​​
> to exit or not: E.g. after hitting C-u we don't know yet whether to
> ​​
> exit, it's only once the user hits the next key that we know whether to
> ​​
> exit (e.g. she pressed `a`) or stay (e.g. she pressed `5`).
> ​​
>
> ​​
> And when she presses `a`, we need to exit *before* running the command
> ​​
> bound to `a`: sometimes it could be OK to linger on until the end of
> ​​
> the command bound to `a`, but not in general.
>

​I understand.  Would it be possible to make the exit function run on both
pre- and post-command hook so that it could use the results of the command​
when needed and eliminate the need in many cases to call the quit function
manually?  Or would that cause problems?

Bob

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