bug#65896: 30.0.50; folding text with text properties prevents background from extending past the newline

[Kévin Le Gouguec]

Juri Linkov <juri@linkov.net> writes:

>> FWIW, I would invite motivated hackers to check out magit-section and
>> see if outline-mode could be taught a new "folding style" that would use
>> the same folding principles.  My own wandering through the EIEIO maze
>> has been too brief to yield anything useful, but AFAICT the salient
>> points are:
>>
>> * setting the 'invisible overlay's BEG at the start of the "section
>> body" (after the heading's newline),
>>
>> * storing bookkeeping information (such as this beginning position) in a
>> 'magit-section property applied to the heading, so that
>> magit-section-show can retrieve that information when invoked by the
>> user with point on that heading.
>>
>> I would imagine outline.el could grow a user option to adjust overlay
>> boundaries this way, so the heading's newline would remain visible, and
>> so would any :extend property on that newline… although perhaps I'm
>> missing some key differences between outline-mode and magit-section-mode
>> that may derail this train of thought.
>
> I tried, but the conclusion was that this requires changes in the display 
> engine.

Could you expand on what exactly you tried, and what limitations you
faced?  (Apologies if you went over this somewhere else and I missed it)

My point was that magit-section exists right now, with no changes to the
display engine, with the exact feature set of outline.el *and* the
ability to keep heading faces extended after folding sections.  So,
unless I've missed a crucial difference between the two libraries, I
don't see why outline.el could not "learn new tricks".

(FWIW magit-section advertises itself as "sections for read-only
buffers", but if there's something in there that could not be made to
work for writable buffers, I have not found it yet)