Make highlight-symbol.el perfect?

Make highlight-symbol.el perfect?

[Steven Degutis]

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It's a great package, but it does something silly: it changes the actual
face on matched regions of the buffer. It should just add overlays. The
code should get simpler, including removing the overlays when you
un-highlight matches, because that's just `(mapcat #'delete-overlay
existing-overlays)`.

Does anyone want to take the challenge and make this package perfect? I'm
willing to volunteer my time to do it, except I have absolutely no idea
what I'm doing, I don't know elisp, I'm a terrible programmer, and I'm
almost guaranteed to just make things worse instead of better.

-Steven

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Re: Make highlight-symbol.el perfect?

[Stefan Monnier]

> face on matched regions of the buffer. It should just add overlays. The
> code should get simpler, including removing the overlays when you
> un-highlight matches, because that's just `(mapcat #'delete-overlay
> existing-overlays)`.

Better would be to add "text-property planes".  So font-lock could
add&remove its `face' property and highlight-symbol could add&remove its
own `face' property without conflict.

I think this would make a nice GSoC project.


        Stefan

Re: Make highlight-symbol.el perfect?

[Steven Degutis]

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Isn't that what overlays would do? How is text-property planes better?

-Steven


On Thu, Apr 11, 2013 at 10:45 AM, Stefan Monnier
<monnier@iro.umontreal.ca>wrote:

> > face on matched regions of the buffer. It should just add overlays. The
> > code should get simpler, including removing the overlays when you
> > un-highlight matches, because that's just `(mapcat #'delete-overlay
> > existing-overlays)`.
>
> Better would be to add "text-property planes".  So font-lock could
> add&remove its `face' property and highlight-symbol could add&remove its
> own `face' property without conflict.
>
> I think this would make a nice GSoC project.
>
>
>         Stefan
>
>
>

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Re: Make highlight-symbol.el perfect?

[Stefan Monnier]

> Isn't that what overlays would do? How is text-property planes better?

You can partly do that with overlays, yes.

But the current implementation of overlays comes with some performance
problems when you have many overlays (we also know how to fix it, which
would also be a nice GSoC project).

Furthermore, the main issue with resolving conflicts between multiple
packages wanting to use the same property is how to *merge* those
conflicting property values.

My proposal for text-property planes resolves those conflicts by merging
the values via Elisp functions invoked when the text-properties are
applied.  This could also work for overlays, of course, but it's
currently missing not only from text-properties but also from overlays.


        Stefan