From: "Daniel Colascione" <dancol@dancol.org>
To: "Eli Zaretskii" <eliz@gnu.org>
Cc: Daniel Colascione <dancol@dancol.org>, emacs-devel@gnu.org
Subject: Re: [RFC PATCH] Per-window face support
Date: Sat, 16 Jun 2018 08:30:52 -0700 [thread overview]
Message-ID: <fca4ee182ea7720f5f91144f48ddbf0b.squirrel@dancol.org> (raw)
In-Reply-To: <83lgbezs6q.fsf@gnu.org>
>> Cc: emacs-devel@gnu.org
>> From: Daniel Colascione <dancol@dancol.org>
>> Date: Sat, 16 Jun 2018 07:24:13 -0700
>>
>> >>> + if (w) {
>> >>> + Lisp_Object found = assq_no_quit (parameter,
>> w->window_parameters);
>> >>> + if (!NILP (found) && EQ (XCDR (found), value))
>> >>> + match = true;
>> >>> + }
>> >>
>> >> [...]
>> >>
>> >> Also, I wonder whether EQ should actually be equal_no_quit, because
>> >> the latter would allow parameters with values that are not just
>> >> integers or symbols.
>> >
>> > I still wonder why we only allow EQ there, it sounds unnecessarily
>> > restrictive.
>>
>> Because there's no need for greater power. All you need is simple
>> classification.
>
> That's not the Emacs way, IMO. Being able to use only integers or
> symbols as filtering parameters sounds too restrictive to me, and I
> see no reason for such restrictions.
There's no loss of generality in allowing only eq at face filtering time:
you can set an integer or symbol to reflect the result of any other
computation, as I do at
https://github.com/dcolascione/emacs-window-highlight/blob/master/window-highlight.el.
If you want to evaluate a condition more complex than eq can handle, you
arrange to run some code when your condition changes, then store the
result of your comparison in a property that the face filter can inspect
with eq. Anything you can do by allowing equal in filters, you can do
using this technique.
Also, the code and the
> documentation were clearly written with an eye towards future
> extensions, which seems to contradict "no need for greater power".
>
> But if I'm the only one who's bothered by these restrictions, then so
> be it.
Contractually allowing something more powerful than eq here can really
screw us over later: what happens when we equal-compare large data
structures? What happens when we eventually get custom type-by-type
equality predicates? What happens if we want to cache the result of
applying face filters? The way it is now, with an eq-test, the result of a
face filter operation can change _only_ after a call to
set-window-parameter or an update of a face spec somewhere. I don't want
to give up this invariant for no reason.
Limiting the test to eq greatly simplifies the contract while not reducing
power. _That's_ the Emacs way.
next prev parent reply other threads:[~2018-06-16 15:30 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-07 23:42 [RFC PATCH] Per-window face support dancol
2018-06-08 2:57 ` Stefan Monnier
2018-06-08 3:18 ` Daniel Colascione
2018-06-08 3:53 ` Stefan Monnier
2018-06-08 9:15 ` Eli Zaretskii
2018-06-16 10:29 ` Eli Zaretskii
2018-06-16 14:24 ` Daniel Colascione
2018-06-16 15:06 ` Eli Zaretskii
2018-06-16 15:30 ` Daniel Colascione [this message]
2018-06-16 16:09 ` Eli Zaretskii
2018-06-16 17:35 ` Stefan Monnier
2018-06-16 21:03 ` Daniel Colascione
2018-06-17 18:20 ` Stefan Monnier
2018-06-17 18:48 ` Daniel Colascione
2018-06-17 19:03 ` Stefan Monnier
2018-06-17 19:21 ` Daniel Colascione
2018-06-17 20:51 ` Stefan Monnier
2018-06-17 21:16 ` Daniel Colascione
2018-06-17 21:34 ` Paul Eggert
2018-06-17 22:25 ` Aliasing EQ to EQL (was: [RFC PATCH] Per-window face support) Stefan Monnier
2018-06-17 23:49 ` Daniel Colascione
2018-06-18 2:14 ` Aliasing EQ to EQL Stefan Monnier
2018-06-18 3:48 ` Daniel Colascione
2018-06-18 13:56 ` Stefan Monnier
2018-06-17 19:23 ` [RFC PATCH] Per-window face support Stefan Monnier
2018-06-17 19:25 ` Daniel Colascione
2018-06-17 19:32 ` Stefan Monnier
2018-06-17 19:49 ` Daniel Colascione
2018-06-17 20:57 ` Stefan Monnier
2018-06-18 23:22 ` Richard Stallman
2018-06-19 1:21 ` Stefan Monnier
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