From: Eli Zaretskii <eliz@gnu.org>
To: Pip Cet <pipcet@gmail.com>
Cc: 36190@debbugs.gnu.org
Subject: bug#36190: 27.0.50; `put-text-property' etc. with buffer argument calls current buffer's `after-change-functions'
Date: Thu, 13 Jun 2019 23:01:03 +0300 [thread overview]
Message-ID: <83y325xnk0.fsf@gnu.org> (raw)
In-Reply-To: <CAOqdjBfR+A2Y224eEJKCRo5+LK7DorvT_72no8jV1YcNd1mVqw@mail.gmail.com> (message from Pip Cet on Thu, 13 Jun 2019 19:42:29 +0000)
> From: Pip Cet <pipcet@gmail.com>
> Date: Thu, 13 Jun 2019 19:42:29 +0000
> Cc: 36190@debbugs.gnu.org
>
> > Not sure I have a clear idea of how you intend to use that additional
> > argument. Are you suggesting that we switch to that buffer?
>
> Yes:
>
> @@ -2183,6 +2184,9 @@ signal_after_change (ptrdiff_t charpos,
> ptrdiff_t lendel, ptrdiff_t lenins)
> if (inhibit_modification_hooks)
> return;
>
> + record_unwind_current_buffer ();
> + set_buffer_internal (buffer);
Ugh! switching buffers just to run a hook! This will kill performance
in some cases. We had something similar with JSON parsing a few
months ago. I wish we had a better alternative. Maybe we should warn
in the documentation that calling these functions with BUFFER being
other than the current buffer might hurt performance when
after-change-functions is non-nil.
> > Also, passing current_buffer sounds redundant to me anyway, because in
> > that case signal_after_change will not need to do anything that it
> > doesn't already do. I would pass NULL instead.
>
> May I ask why?
To make the code speak for itself. With passing current_buffer, you
now rely on subroutines of set_buffer_internal two or 3 levels down to
test whether we are already in that buffer and do nothing. Meanwhile,
you wasted cycles on 2 or 3 function calls, and forced someone who
reads the code to go down that rabbit hole if they want to understand
what happens in that particular case.
> I think passing current_buffer is the clearest signal we can send to
> someone reusing the code that they might have to change this if
> they're dealing with more than one buffer.
Each function has commentary, where you can say that NULL means not to
switch buffers because we are already there. That is a more clear
signal, IME.
> As a practical matter, it's hard to change the text property functions
> to use NULL when passed a nil argument
How is it harder than passing current_buffer?
> so we'd have functions using current_buffer and others using NULL,
> and that seems needlessly inconsistent.
Sorry, I don't see any inconsistency. We do such things (for other
kinds of arguments) all over the place.
It's really a matter of stylistic preferences, but you did ask why...
next prev parent reply other threads:[~2019-06-13 20:01 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-13 13:48 bug#36190: 27.0.50; `put-text-property' etc. with buffer argument calls current buffer's `after-change-functions' Pip Cet
2019-06-13 16:36 ` Eli Zaretskii
2019-06-13 18:48 ` Pip Cet
2019-06-13 19:05 ` Eli Zaretskii
2019-06-13 19:27 ` Eli Zaretskii
2019-06-13 19:42 ` Pip Cet
2019-06-13 20:01 ` Eli Zaretskii [this message]
2019-06-13 20:57 ` Pip Cet
2019-06-13 21:37 ` Pip Cet
2019-06-14 7:41 ` Eli Zaretskii
2019-06-14 11:14 ` Pip Cet
2019-06-14 12:10 ` Eli Zaretskii
2019-06-15 15:14 ` Pip Cet
2019-06-15 15:23 ` Eli Zaretskii
2019-06-15 19:27 ` Pip Cet
2019-07-06 8:08 ` Eli Zaretskii
2019-07-06 15:27 ` Pip Cet
2019-07-06 16:22 ` Eli Zaretskii
2019-06-14 7:36 ` Eli Zaretskii
2019-06-17 11:38 ` Pip Cet
2019-06-17 15:59 ` Eli Zaretskii
2019-06-18 17:14 ` Pip Cet
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