GNU bug report logs - #24153
25.1; Feature request: per-buffer cursor-color variable

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Tej Chajed <tchajed <at> mit.edu>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.1; Feature request: per-buffer cursor-color variable
Date: Thu, 4 Aug 2016 11:08:12 -0400

Currently there's a per-buffer cursor-type variable that is respected
per window and a single cursor-color variable that applies to the
entire frame.

Evil emulates a per-window cursor color in order to have the cursor
color of the active window reflect the buffer state (eg,
distinguishing insert and normal mode). It does so by advising
set-window and calling set-cursor-color if necessary; this can lead to
slowdowns when code calls set-window repeatedly (eg, through
with-selected-window).

It seems like the right way for evil to manage the cursor color is to
have an analogous per-buffer cursor-color variable natively provided
by emacs. Is this a doable feature?

Thanks!
Tej

Message #8 received at 24153 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Tej Chajed <tchajed <at> mit.edu>
Cc: 24153 <at> debbugs.gnu.org
Subject: Re: bug#24153: 25.1; Feature request: per-buffer cursor-color variable
Date: Thu, 04 Aug 2016 20:13:56 +0300

> From: Tej Chajed <tchajed <at> mit.edu>
> Date: Thu, 4 Aug 2016 11:08:12 -0400
> 
> It seems like the right way for evil to manage the cursor color is to
> have an analogous per-buffer cursor-color variable natively provided
> by emacs. Is this a doable feature?

I don't see up front why not.  Patches welcome.

Thanks.

Message #11 received at 24153 <at> debbugs.gnu.org (full text, mbox):

From: npostavs <at> users.sourceforge.net
To: Tej Chajed <tchajed <at> mit.edu>
Cc: 24153 <at> debbugs.gnu.org
Subject: Re: bug#24153: 25.1; Feature request: per-buffer cursor-color variable
Date: Thu, 04 Aug 2016 21:21:17 -0400

Tej Chajed <tchajed <at> mit.edu> writes:
>
> Evil emulates a per-window cursor color in order to have the cursor
> color of the active window reflect the buffer state (eg,
> distinguishing insert and normal mode). It does so by advising
> set-window and calling set-cursor-color if necessary; this can lead to
> slowdowns when code calls set-window repeatedly (eg, through
> with-selected-window).

There's no `set-window' function, did you mean `select-window'?  I find
in the docstring for that function:

    Selections that "really count" are those causing a visible change in
    the next redisplay of WINDOW’s frame and should be always recorded.
    So if you think of running a function each time a window gets
    selected put it on ‘buffer-list-update-hook’.

Perhaps using ‘buffer-list-update-hook’ instead of advising
`select-window' would help?

Message #14 received at 24153 <at> debbugs.gnu.org (full text, mbox):

From: Tej Chajed <tchajed <at> mit.edu>
To: npostavs <at> users.sourceforge.net
Cc: 24153 <at> debbugs.gnu.org
Subject: Re: bug#24153: 25.1; Feature request: per-buffer cursor-color variable
Date: Thu, 4 Aug 2016 22:17:04 -0400

On Thu, Aug 4, 2016 at 9:21 PM,  <npostavs <at> users.sourceforge.net> wrote:
> Tej Chajed <tchajed <at> mit.edu> writes:
>>
>> Evil emulates a per-window cursor color in order to have the cursor
>> color of the active window reflect the buffer state (eg,
>> distinguishing insert and normal mode). It does so by advising
>> set-window and calling set-cursor-color if necessary; this can lead to
>> slowdowns when code calls set-window repeatedly (eg, through
>> with-selected-window).
>
> There's no `set-window' function, did you mean `select-window'?

Yes, my mistake - the advice is on select-window.

>
> Perhaps using ‘buffer-list-update-hook’ instead of advising
> `select-window' would help?

I haven't fully debugged this alternative, but it doesn't seem to
work. company-coq still uses save-window-excursion in
company-coq-ask-prover, which triggers the buffer-list-update-hook. In
addition, even with company-coq disabled this somehow doesn't call
evil-refresh-cursor enough; starting from insert mode, after the first
proof command, the color gets stuck on the normal mode color, and then
doesn't change until some other buffer list update.

Message #17 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Clément Pit--Claudel <clement.pit <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org, npostavs <at> users.sourceforge.net
Subject: Re: bug#24153: 25.1; Feature request: per-buffer cursor-color variable
Date: Thu, 4 Aug 2016 22:49:18 -0400

[Message part 1 (text/plain, inline)]

On 2016-08-04 21:21, npostavs <at> users.sourceforge.net wrote:
> Perhaps using ‘buffer-list-update-hook’ instead of advising
> `select-window' would help?

Hmmm. I don't think that would work.

Assume there are two windows, one showing a buffer in evil's normal editing mode, and one showing a buffer in evil's edit mode.  If the user has configured evil to show the normal-mode cursor in green and the insert-mode cursor in purple, then evil needs to change the cursor color every time the user switches between these two windows, and (I don't think that) buffer-list-update-hook won't be sufficient for that.

Cheers,
Clément.

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Message #20 received at 24153 <at> debbugs.gnu.org (full text, mbox):

From: martin rudalics <rudalics <at> gmx.at>
To: Tej Chajed <tchajed <at> mit.edu>, npostavs <at> users.sourceforge.net
Cc: 24153 <at> debbugs.gnu.org
Subject: Re: bug#24153: 25.1; Feature request: per-buffer cursor-color variable
Date: Fri, 05 Aug 2016 18:37:11 +0200

>>> Evil emulates a per-window cursor color in order to have the cursor
>>> color of the active window reflect the buffer state (eg,
>>> distinguishing insert and normal mode). It does so by advising
>>> set-window and calling set-cursor-color if necessary; this can lead to
>>> slowdowns when code calls set-window repeatedly (eg, through
>>> with-selected-window).
>>
>> There's no `set-window' function, did you mean `select-window'?
>
> Yes, my mistake - the advice is on select-window.
>
>>
>> Perhaps using ‘buffer-list-update-hook’ instead of advising
>> `select-window' would help?
>
> I haven't fully debugged this alternative, but it doesn't seem to
> work. company-coq still uses save-window-excursion in
> company-coq-ask-prover, which triggers the buffer-list-update-hook.

Please tell us more about where and why ‘buffer-list-update-hook’
doesn't work in any of your use cases.  From what you say here you
expect ‘save-window-excursion’ to _not_ run ‘buffer-list-update-hook’.
Is that correct?

> In
> addition, even with company-coq disabled this somehow doesn't call
> evil-refresh-cursor enough; starting from insert mode, after the first
> proof command, the color gets stuck on the normal mode color, and then
> doesn't change until some other buffer list update.

But IIUC you do not set the buffer of any window in these steps, so why
would you expect ‘buffer-list-update-hook’ to run?

martin

Message #23 received at 24153 <at> debbugs.gnu.org (full text, mbox):

From: martin rudalics <rudalics <at> gmx.at>
To: Clément Pit--Claudel <clement.pit <at> gmail.com>, 
 24153 <at> debbugs.gnu.org, npostavs <at> users.sourceforge.net
Subject: Re: bug#24153: 25.1; Feature request: per-buffer cursor-color variable
Date: Fri, 05 Aug 2016 18:37:18 +0200

> Assume there are two windows, one showing a buffer in evil's normal
> editing mode, and one showing a buffer in evil's edit mode.  If the
> user has configured evil to show the normal-mode cursor in green and
> the insert-mode cursor in purple, then evil needs to change the cursor
> color every time the user switches between these two windows, and (I
> don't think that) buffer-list-update-hook won't be sufficient for
> that.

This would be a bug.  ‘select-window’ should always run
‘buffer-list-update-hook’ when NORECORD is nil.

martin

Message #26 received at 24153 <at> debbugs.gnu.org (full text, mbox):

From: Clément Pit--Claudel <clement.pit <at> gmail.com>
To: martin rudalics <rudalics <at> gmx.at>, 24153 <at> debbugs.gnu.org,
 npostavs <at> users.sourceforge.net
Subject: Re: bug#24153: 25.1; Feature request: per-buffer cursor-color variable
Date: Fri, 5 Aug 2016 21:59:35 -0400

[Message part 1 (text/plain, inline)]

On 2016-08-05 12:37, martin rudalics wrote:
>> Assume there are two windows, one showing a buffer in evil's normal
>> editing mode, and one showing a buffer in evil's edit mode.  If the
>> user has configured evil to show the normal-mode cursor in green and
>> the insert-mode cursor in purple, then evil needs to change the cursor
>> color every time the user switches between these two windows, and (I
>> don't think that) buffer-list-update-hook won't be sufficient for
>> that.
> 
> This would be a bug.  ‘select-window’ should always run
> ‘buffer-list-update-hook’ when NORECORD is nil.

I see; thanks for clarifying!

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Message #29 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Clément Pit--Claudel <clement.pit <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Re: bug#24153: 25.1; Feature request: per-buffer cursor-color variable
Date: Fri, 5 Aug 2016 22:10:07 -0400

[Message part 1 (text/plain, inline)]

On 2016-08-04 22:17, Tej Chajed wrote:
>>> Perhaps using ‘buffer-list-update-hook’ instead of advising
>>> `select-window' would help?
>
> I haven't fully debugged this alternative, but it doesn't seem to
> work. company-coq still uses save-window-excursion in
> company-coq-ask-prover, which triggers the buffer-list-update-hook. 

IIRC I added this save-window-excursion call to work a Proof General issue, back when I didn't know much about PG.  Now that I have commit rights there, I could probably move the fix upstream and remove the save-window-excursion call.

Clément.

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