bug#73530: [PATCH] Add imenu index function for Djvu files in doc-view

[jao <jao@gnu.org>]

On Sat, Sep 28 2024, Tassilo Horn wrote:

> Visuwesh <visuweshm@gmail.com> writes:
>
>>>> doc-view-imenu-enabled
>>>
>>> Indeed.  And while we are here: doesn anyone know why we have an
>>> option to disable imenu support?  I see that we have that since Jose
>>> contributed the initial imenu support but why?  I can't see any harm
>>> done if it was always enabled and would give a user-error like "For
>>> imenu support for XXX files, program YYY has to be installed" or
>>> something when invoking imenu.  And why someone might want to disable
>>> it even if the required program is available is beyond my
>>> imagination.  I mean, if you don't want to use imenu, then just don't
>>> invoke it...
>>
>> I was wondering the same thing, especially since the cost of making the
>> imenu index is not that high.
>
> So lets ask Jose (added to Cc).

If I recall correctly, that flag is there to save CPU cycles in case
users of doc-view are not interested in imenu.

The PDF's outline is scanned using mutool when doc-view-mode is
activated if doc-view-imenu-enabled is true, and for big files that can
take a second or two.

I am not sure why I didn't delay creation of the index, but it's
probably because there are menu entries to create and I didn't bother to
investigate deeper. Also, because I didn't want to see a pause the first
time imenu was invoked on a PDF.

Admittedly, most of the time the pause is small enough to make all of
the above moot.

Cheers,
jao
-- 
Many people take no care of their money till they come nearly to the end
of it, and others do just the same with their time.
  -Johann Wolfgang von Goethe (1749-1832)