Re: The overlay branch (yet again)

[Stefan Monnier <monnier@iro.umontreal.ca>]

>>  > Given that nobody replied to my original email I assume everybody is
>>  > busy with the new release.

Not exactly with the new release, but yes your message fell into the
"todo" black hole, sorry :-(

>>  > Is anybody interested in me doing this work?
>> I definitely am interested.

Me too.

> But Andreas almost made it! So I want to reuse some of that massive
> effort: merge tests at the very least, untangle overlay code a bit and
> - hopefully - replace those linked lists.

Yes, please!

Also, I hope the new code can capture some of the insights learned along
the way, and the design choices, e.g. in the form of comments describing the
various performance aspects that were considered (complexity of
`make-overlay`, `delete-overlay`, `overlay-start`, `overlays-at/in`,
`previous-char-property-change`, of updating overlays in response to
buffer text modifications, ...).

Also, some performance tests would be great.  IIRC a few months ago
someone here posted some simple tests showing some percentage
improvement in some cases, but there has to be situations where the new
code is massively faster (after all, the new code uses a different data
structure specifically to change the algorithmic complexity of some
operations).  It's quite possible that those situations don't "occur
naturally" in current code, but it should be possible to trigger them in
artificial but realistic situations (maybe changing font-lock to use
overlays instead of text-properties, or forcing nhexl-mode to nhexlify
eagerly the whole buffer, I don't know).

But merging the tests into `master` would be a great first step.


        Stefan