bug#24389: [PATCH] Support completion of classes and IDs in CSS mode

[Simen Heggestøyl]

Hi Stefan, thanks for the feedback.

On Wed, Sep 7, 2016 at 10:01 PM, Stefan Monnier 
<monnier@IRO.UMontreal.CA> wrote:
> I don't see where this is used.

Oops, that was left over from an earlier revision.

> I urge you to use alists rather than plist whenever you can.  I only
> recommend plists for those rare cases where they're likely to often be
> written down by end-users who'd be bothered by the need to add dots
> and parentheses.

Noted, thanks.

> I think this design won't work well.  How 'bout instead just always
> calling the function and let the other side handle the caching?
>
> This way the cache can work correctly even in case the list of
> completions depends on sources other than the buffer's content (a case
> which even your costly buffer-hash won't catch).  Also, it means that
> depending on the cost of the extraction itself, the cache may be 
> flushed
> more or less eagerly.

True. Considering the things you've mentioned, I also think it will be
much better to let the other side (optionally) handle their own
cache. Please see the revised patch.

> The definition of those global variables seems to be missing.
> IIUC they should be in css-mode.el, so their name should start with
> "css-" I think (tho I agree that it's debatable).

Hm, is it wrong to let them stay void, and then check whether they're
bound in each buffer we visit?

I ran som benchmarks to assess whether the expensive buffer-hash cache
is worth it, results follow below. All the tests were run with 583 HTML
mode buffers open, with content totaling 7.5 MB.

* No cache:
(benchmark 1 '(css--foreign-completions 'css-class-list-function))
   "Elapsed time: 1.597629s (0.797973s in 55 GCs)"
(benchmark 10 '(css--foreign-completions 'css-class-list-function))
   "Elapsed time: 15.322130s (7.589323s in 549 GCs)"

* Cold cache:
(benchmark 1 '(css--foreign-completions 'css-class-list-function))
   "Elapsed time: 1.609650s (0.786968s in 54 GCs)"

* Warm cache:
(benchmark 1 '(css--foreign-completions 'css-class-list-function))
   "Elapsed time: 0.471924s (0.102814s in 6 GCs)"
(benchmark 10 '(css--foreign-completions 'css-class-list-function))
   "Elapsed time: 4.376787s (0.981541s in 59 GCs)"

-- Simen

0001-Support-completion-of-classes-and-IDs-in-CSS-mode.patch
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