Advicing select-windows, shr rendering, and per-buffer-theme package

Advicing select-windows, shr rendering, and per-buffer-theme package

[Iñigo Serna]

Hi,

I'm the author of “per-buffer-theme”, a simple package available in
MELPA [1], which changes emacs theme when switching to a buffer according to
some configured rules (f.e. use a dark theme when coding, light theme
for email or web navigation). It advices `select-window', checks buffer
name or major-mode, and changes theme.

It worked correctly and fast with emacs 24.5, but now with emacs 25.x it
produces additional “flickering” when switching buffers, especially for
eww/shr buffers, where it makes package useless.

I think problem comes that, when switching to a eww/shr buffer, shr
rendering uses many temporal buffers, so theme changes many times
producing that "flickering" effect. But I'm not sure as my elisp skills
and emacs internals knowledge is quite limited.

I don't know how to solve it… I've tested with before/after variations
to `advice-add' but results are similar. First versions used
`window-configuration-change-hook' but add-advice to select-window was
much better option then. Any ideas?

Thanks in advance,
Iñigo Serna

[1] http://melpa.org/#/per-buffer-theme
    https://bitbucket.org/inigoserna/per-buffer-theme.el

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Clément Pit--Claudel]

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On 03/18/2016 07:04 AM, Iñigo Serna wrote:
> I think problem comes that, when switching to a eww/shr buffer, shr
> rendering uses many temporal buffers, so theme changes many times
> producing that "flickering" effect. But I'm not sure as my elisp skills
> and emacs internals knowledge is quite limited.

Do you need to change theme for temporary buffers? Usually these have a name that starts with a space; did you make sure to blacklist them?

Clément.


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Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Clément Pit--Claudel]

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Another idea; do you need to change the theme per buffer, or per buffer displayed in a window? If the latter, then you could ensure that buffer themes are only changed if a buffer is actually shown on screen.

On 03/18/2016 07:04 AM, Iñigo Serna wrote:
> Hi,
> 
> I'm the author of “per-buffer-theme”, a simple package available in
> MELPA [1], which changes emacs theme when switching to a buffer according to
> some configured rules (f.e. use a dark theme when coding, light theme
> for email or web navigation). It advices `select-window', checks buffer
> name or major-mode, and changes theme.
> 
> It worked correctly and fast with emacs 24.5, but now with emacs 25.x it
> produces additional “flickering” when switching buffers, especially for
> eww/shr buffers, where it makes package useless.
> 
> I think problem comes that, when switching to a eww/shr buffer, shr
> rendering uses many temporal buffers, so theme changes many times
> producing that "flickering" effect. But I'm not sure as my elisp skills
> and emacs internals knowledge is quite limited.
> 
> I don't know how to solve it… I've tested with before/after variations
> to `advice-add' but results are similar. First versions used
> `window-configuration-change-hook' but add-advice to select-window was
> much better option then. Any ideas?
> 
> Thanks in advance,
> Iñigo Serna
> 
> [1] http://melpa.org/#/per-buffer-theme
>     https://bitbucket.org/inigoserna/per-buffer-theme.el
> 
> 


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Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[raman]

See thread I had on this list re  hooking sound themes based on current
mode -- I ran into this issue as well. As far as I know, it's more than
just shr/eww that triggers this: if you look, select-window gets called
way more often than you'd expect.

After suggestions from folks like John, I ended up  implementing my
solution via an idle timer, you can see the relevant code here:
https://github.com/tvraman/emacspeak/blob/master/lisp/soundscape.el#L191
-- 

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Stefan Monnier]

> See thread I had on this list re  hooking sound themes based on current
> mode -- I ran into this issue as well. As far as I know, it's more than
> just shr/eww that triggers this: if you look, select-window gets called
> way more often than you'd expect.

Indeed, `current-buffer' and `selected-window' don't correspond really
to the user's perception, because they can be changed temporarily
without the user even noticing (and it's not just a theoretical
possibility but is something that happens often enough).

> After suggestions from folks like John, I ended up implementing my
> solution via an idle timer, you can see the relevant code here:

Sounds like a better option, indeed.


        Stefan

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[raman]

Hi Stefan,

Yes, the idle-timer solution worked surprisingly well which at least to
me was counter-intuitive --- guess I dont understand Emacs' internals
well enough. So what is it that led folk like yourself and John to
intuitively suggest idle timers for this case?


Incidentally the documentation for  
buffer-list-update-hook is fairly  misleading. I originally tried using
that hook and saw it firing way too often; then adviced select-window
and observed that that fired almost as often which was still too often.

Places where the afore-mentioned hook fires where you wouldn't expect it
to bsed on the doc-string:

A. While transitioning through the minibuffer 

B. When you have completions come and go as you interact with the
minibuffer 

C. shr/eww as the earlier poster pointed out 

D. and many more cases that will fit this margin.
-- 

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Iñigo Serna]

Hi,

Clément Pit--Claudel <clement.pit@gmail.com> writes:

> Do you need to change theme for temporary buffers? Usually these have a name that starts with a space; did you make sure to blacklist them?

I think I checked for them, but not, the regular expression I used didn't
include temporary buffers.
Checking for them before changing theme helps a lot!

> Another idea; do you need to change the theme per buffer, or per buffer displayed in a window? If the latter, then you could ensure that buffer themes are only changed if a buffer is actually shown on screen.

This is useful too.

Finally, combining both suggestions solve the problem. There are some
flickering in some rare cases but most of them have disappeared.

  (when (and (not (string-prefix-p " " (buffer-name buffer)))
             (get-buffer-window buffer))
      ...)

Thanks,
Iñigo Serna

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Stefan Monnier]

> well enough. So what is it that led folk like yourself and John to
> intuitively suggest idle timers for this case?

Actually, I would have suggested post-command-hook, but if you want to
do it a bit more lazily (e.g. not react to changes within
a keyboard-macro, for example), then an idle hook is the next
logical step.

The main issue is that you want to deal with "the user-perceived
changes", rather than actual detailed changes, and the user only
perceives changes when a redisplay occurs or between commands.


        Stefan

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Iñigo Serna]

Hi,

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Indeed, `current-buffer' and `selected-window' don't correspond really
> to the user's perception, because they can be changed temporarily
> without the user even noticing (and it's not just a theoretical
> possibility but is something that happens often enough).

I noticed this when I started writing this package and was investigating
the best way to achieve it, experimenting with different alternatives
(hooks, advice, etc).


raman <raman@google.com> writes:

> See thread I had on this list re  hooking sound themes based on current
> mode -- I ran into this issue as well. As far as I know, it's more than
> just shr/eww that triggers this: if you look, select-window gets called
> way more often than you'd expect.
>
> After suggestions from folks like John, I ended up  implementing my
> solution via an idle timer, you can see the relevant code here:
> https://github.com/tvraman/emacspeak/blob/master/lisp/soundscape.el#L191

The ideas Clément provided where enough to solve the problems I
have. Not perfect but good enough for my case.

Anyway, I'll search for that thread you mention and read it to look for
better ideas.


Thanks for the suggestions,
Iñigo Serna

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Clément Pit--Claudel]

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On 03/18/2016 12:45 PM, Iñigo Serna wrote:
> ...
> Finally, combining both suggestions solve the problem. There are some
> flickering in some rare cases but most of them have disappeared.

Great, glad I could help :)


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Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Iñigo Serna]

Clément Pit--Claudel <clement.pit@gmail.com> writes:

> Great, glad I could help :)

In my case, problem is aggravated as I use "perspective" package and
persp-mode activates each buffer when switching perspective.
As I see, it happens in `persp-reactivate-buffers' function to put
the buffers in current perspective on top of visited list.

But this should not occur with plain emacs.

Anyway, as the solution is not perfect and I'm learning I will look at
Raman's & Stefan's suggestion of using an idle timer. Sounds ugly but…

Thanks again, 
Iñigo Serna

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[raman]

Iñigo Serna <inigoserna@gmail.com> writes:

Like you I too asserted that the idle-timer solution was "ugly" before I
 swallowed my pride and implemented it --- then got surprized that it
 worked well. You should be able to clone the code I pointed you at in
 the soundscapes.el module -- look at function soundscape-update.> Clément Pit--Claudel <clement.pit@gmail.com> writes:
>
>> Great, glad I could help :)
>
> In my case, problem is aggravated as I use "perspective" package and
> persp-mode activates each buffer when switching perspective.
> As I see, it happens in `persp-reactivate-buffers' function to put
> the buffers in current perspective on top of visited list.
>
> But this should not occur with plain emacs.
>
> Anyway, as the solution is not perfect and I'm learning I will look at
> Raman's & Stefan's suggestion of using an idle timer. Sounds ugly but…
>
> Thanks again, 
> Iñigo Serna
>

-- 

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[Iñigo Serna]

Hello,

raman <raman@google.com> writes:

> Yes, the idle-timer solution worked surprisingly well which at least to
> me was counter-intuitive --- guess I dont understand Emacs' internals
> well enough. So what is it that led folk like yourself and John to
> intuitively suggest idle timers for this case?

I've been experimenting with idle-timer and I must agree, it is very
easy to implement and works *surprisingly* well.
Even so, that I've left it as the default method to check buffer and
theme in my package.

> Places where the afore-mentioned hook fires where you wouldn't expect it
> to bsed on the doc-string:
>
> A. While transitioning through the minibuffer 
>
> B. When you have completions come and go as you interact with the
> minibuffer 
>
> C. shr/eww as the earlier poster pointed out 
>
> D. and many more cases that will fit this margin.

In my case, C was the main headache when switching to eww/shr-based
buffers. Looks like 25.x shr use lots of temporary buffers for its
rendering tasks.

Then A and B (using helm here) causes some "flickering" with
select-window advicing method too.
As I've mentioned in other email, perspective package also aggravated
what I saw.

Thanks again to all for your help and suggestions,
Iñigo Serna

Re: Advicing select-windows, shr rendering, and per-buffer-theme package

[raman]

Iñigo Serna <inigoserna@gmail.com> writes:

In emacs 25, EWW renders buffers asynchronously so that emacs doesn't
lock up while a web page is opening. That necessarily causes a lot of
context switches.> Hello,
>
> raman <raman@google.com> writes:
>
>> Yes, the idle-timer solution worked surprisingly well which at least to
>> me was counter-intuitive --- guess I dont understand Emacs' internals
>> well enough. So what is it that led folk like yourself and John to
>> intuitively suggest idle timers for this case?
>
> I've been experimenting with idle-timer and I must agree, it is very
> easy to implement and works *surprisingly* well.
> Even so, that I've left it as the default method to check buffer and
> theme in my package.
>
>> Places where the afore-mentioned hook fires where you wouldn't expect it
>> to bsed on the doc-string:
>>
>> A. While transitioning through the minibuffer 
>>
>> B. When you have completions come and go as you interact with the
>> minibuffer 
>>
>> C. shr/eww as the earlier poster pointed out 
>>
>> D. and many more cases that will fit this margin.
>
> In my case, C was the main headache when switching to eww/shr-based
> buffers. Looks like 25.x shr use lots of temporary buffers for its
> rendering tasks.
>
> Then A and B (using helm here) causes some "flickering" with
> select-window advicing method too.
> As I've mentioned in other email, perspective package also aggravated
> what I saw.
>
> Thanks again to all for your help and suggestions,
> Iñigo Serna

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