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

["Tassilo Horn" <tsdh@gnu.org>]

Hi again, 

of course we should do the nameddest thing in another patch. No reason to put this one on hold.

Thanks, 
  Tassilo 

Am Do, 3. Okt 2024, um 13:10, schrieb Visuwesh:
> [வியாழன் அக்டோபர் 03, 2024] Tassilo Horn wrote:
>
>> Tassilo Horn <tsdh@gnu.org> writes:
>>
>> Hi again,
>>
>>>> The PDF generated by LaTeX can have a wildly different outline than
>>>> matched by doc-view's regexp:
>>>>
>>>>     % mutool show test.pdf outline
>>>>     |	"Text"	#nameddest=section.1
>>>>     |	"Annotations"	#nameddest=section.2
>>>>
>>>> Compare it with:
>>>>
>>>>     % mutool show atkins_physical_chemistry.pdf outline
>>>>     |	"Cover"	#page=1&view=Fit
>>>>     |	"PREFACE"	#page=7&view=Fit
>>>>     |	"USING THE BOOK"	#page=8&view=Fit
>>>
>>> Ok, I see.  All my LaTeX PDFs have #nameddest=section.x values instead
>>> of #page=X values, so that's the reason they don't work.  It would be
>>> good if we could mention that it won't work because there are no page
>>> references in the outline in the error message.
>>
>> Would you mind doing that in a new version of the patch?
>>
>> And I wonder if it mutool could spit out page references in addition to
>> the nameddest references.  Do you know if there's a technical limitation
>> or if it's just not implemented?
>
> Unfortunately, I have no idea.  I actually don't use doc-view for PDF
> files, only for docx and DjVu.
>
>> Sadly, their communication platform seems to be Discord where I didn't
>> want to register an account to ask.  They seem to use the ghostscript
>> bugzilla, so one could create a ticket there...  If nobody else here in
>> the discussion already has an account there, I wouldn't mind creating
>> ony myself and asking.
>
> If I cannot find anything in the man page, I can ask in their Discord.
> I do have an account lying around, I can at least put it to good use.
>
> Can this be done in another patch later on?  I am not sure if I will get
> the time soon to follow up on this part of the problem.  It would be
> cleaner if we open another bug report to track this too.
>
>>>>> For DjVu, my sample size is 1, and that's a presentation, so at least
>>>>> here I'm not sure if there should be an index available...
>>>>
>>>> I will send the link to the DjVu file that I wrote the feature for
>>>> off-list.  I will send a link to a PDF file too.
>>>
>>> Thanks, will try with those two files.
>>
>> I did so now and it is blazingly fast for those 80+mb PDF/DjVu files
>> even on my almost 10 years old laptop, so I'd say your simpler approach
>> is the right choice.
>>
>>>> On this note, should we use doc-view-pdfdraw-program in place of
>>>> mutool in doc-view--pdf-outline?
>>>
>>> Yes, but only if the older names pdfdraw and mudraw already had the
>>> "show <file> outline" feature.
>>
>> I revert the "but only if" part.  If mupdf is old and comes with, e.g.,
>> the pdfdraw executable, chances are almost zero that mutool is
>> installed, too.  And if it is, then we should prefer it anywhere.  So I
>> think the way to go is to (executable-find "mutool") in
>> doc-view-pdfdraw-program first so that it takes precedence and use
>> doc-view-pdfdraw-program in doc-view--pdf-outline.
>
> OK, I will post a patch if you're okay with opening another bug report
> for the nameddest PDF thingy.
>
>>>>> Well, I actually have no strong opinion here.  Technically, I like
>>>>> your approach better because of its simplicity.  I would like to test
>>>>> with some larger documents to see how long index building takes,
>>>>> though.
>>>>
>>>> I tried the function with a large PDF file:
>>>
>>> Will try with the large two you've linked later.
>>
>> As said above, it's more than fast enough, so let's take your approach.
>
> Great, thank you for taking the time to test the patch.