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Re: post-command-hook to slow?

From: Thorsten Jolitz
Subject: Re: post-command-hook to slow?
Date: Thu, 05 Jun 2014 20:11:58 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux)

"Pascal J. Bourguignon" <address@hidden> writes:

> Thorsten Jolitz <address@hidden> writes:
>> Hi List, 
>> I call a command to be executed in a temporary buffer, and that command
>> runs a post-command-hook. Here is some pseudocode:
>> ,----------------------------------
>> | open-temp-buffer
>> | set-buffer-mode
>> | call-interactively cmd
>> | copy-content-and-exit-temp-buffer
>> `----------------------------------
>> Unfortunately the post-command-hook of cmd is executed only after the
>> temp buffer is already exited (i.e. in the original buffer in a
>> different/wrong major-mode with the needed markers lost).
>> Is that to be expected? Will `copy-content-and-exit-temp-buffer' be
>> executed before the post-command-hook of cmd has a chance to be
>> executed?
> post-command-hook is called after each command.  Ie. after each
> character you type!  So indeed, it should be very fast.  Perhaps you
> could keep your temp buffer around (you can hide such a buffer by
> prefixing its name with a space).

right, when tends to forget that ...

> From a quick scan, I don't see anything in call-interactively that would
> make it not execute the command synchronously.
> Furthermore, post-command-hooks are not called by call-interactively.
> If cmd is this-command, then what you are doing, is to call
> this-command a second time, after it has already been called.  This
> call-interactively works with your temp buffer, but the original command
> call was done before post-command-hooks were called of course.

hmmm ... may be a bit more context:

what I do is call `outorg-edit-as-org' in a programming language buffer,
e.g. an emacs-lisp buffer. Then a temporary edit buffer in Org-mode is
opened (not using with-temp-buffer since normally it should stay around
for editing) until it is closed again.

Now I reuse that mechanism for calling Org commands without any user
editing - open the Org-mode temp buffer, execute the command, close the
temp buffer and copy the results to the source buffer.

So the post-command-hooks are not mine, but those from some Org-mode
functions, I just have to deal with them. 

> If what you want to do is to wrap some commands to make them work in a
> different buffer, then you cannot use post-command-hook to do that, and
> just both pre-command-hook and post-command-hook wouldn't be very safe
> (if anything breaks, you could end with a dangling state).  
> In that case, I would advise you to use an around advice on the command
> instead.  cf. defadvice.

unfortunately its not my choice, since very basic Org commands like
org-todo run post-command-hook. 

> Some commands may rely on the selected window in a hidden way, so if the
> commands you call in the post-command-hook use a window, wrapping them in
> a (with-selected-window window (call-interactively …)) could help.

cmd and its hook function is Org-mode code I cannot change ... but
still, I'm going to experiment with this, looks promising.

> Do you use with-temp-buffer?  You probably should, instead of creating
> the buffer and later killing it. 

It would be better for this use case, but I don't want to reimplement
existing functionality, just reuse what is already there and works. 

I put some message-calls printing out `current-buffer' in `cmd' and its
 post-command-hook function, and its really strange - cmd is executed in
 the temp buffer (in Org-mode), the hook in the original emacs-lisp
 source-code buffer


 | open-temp-buffer 
 | set-buffer-mode
 | call-interactively cmd             }<org-mode-buffer>
 | copy-content-and-exit-temp-buffer


although it shouldn't in my view, and everything you wrote seems to
indicate that 

 | call-interactively cmd

should quickly run cmd and post-command-hook before 

 | copy-content-and-exit-temp-buffer

is executed - but apparently not. 

Thanks for your answer.


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