GNU bug report logs - #14694
24.3; format-mode-line failing with :eval form via a variable in a conditional construct

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Message #14 received at 14694 <at> debbugs.gnu.org (full text, mbox):

From: Phil Sainty <psainty <at> orcon.net.nz>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 14694 <at> debbugs.gnu.org
Subject: Re: bug#14694: 24.3; format-mode-line failing with :eval form via
 a variable in a conditional construct
Date: Mon, 24 Jun 2013 05:48:23 +1200

On 24/06/2013 04:45, Stefan Monnier wrote:
> ELISP> (setq indirect-eval '(:eval "indirect eval"))
> ELISP> (format-mode-line '(t indirect-eval "else"))
>> ""
>
> You need (put 'indirect-eval 'risky-local-variable t)

Argh, I see that in the documentation now. Thank you Stefan
(and Eli).

I'm afraid I made an embarrassing rookie mistake in checking
the result of (format-mode-line indirect-eval) instead of
(format-mode-line 'indirect-eval), and thinking that I was
seeing an inconsistency when there was none. Otherwise I'd no
doubt have spotted the information about that property.

My apologies; please close.


Eli asked:
> And anyway, why would you need format-mode-line to produce a
> different value?

The specific goal was to enable customisation of the display of
`mode-name' in the mode line (generally to abbreviate it and reduce
the space used) *without* also affecting what is displayed when that
variable is processed in other contexts (such as by `describe-mode'),
in which cases `format-mode-line' will be called.

Advising `format-mode-line' to provide an indicator variable to use
in a conditional construct does facilitate this. I just wanted check
that I wasn't missing another approach which didn't require the advice.


-Phil

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