GNU bug report logs - #38163
GDK does not return the monitor's refresh rate

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

From: Alexandros Theodotou <alex <at> zrythm.org>
To: bug-guix <at> gnu.org
Subject: GDK does not return the monitor's refresh rate
Date: Sun, 10 Nov 2019 16:44:23 +0000

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

I have been developing and testing my GTK app (Zrythm) on many distros
and Guix is the only case that the monitor's refresh rate is returned
as 0.

The API I am using is this:
https://developer.gnome.org/gdk3/stable/GdkMonitor.html#gdk-monitor-get-refresh-rate

I was developing/testing on Parabola GNU/Linux-libre before and it was
giving me a correct rate of 60 Hz.

Other distros I have tested this API before on:
Various ubuntu versions, debian 9 and 10, manjaro (arch), various
fedora versions, plus a few others that users tested on.

I suspect GDK is trying to access something that guix doesn't make
available to it, but I don't have much knowledge of the internals of
GDK or Guix to debug this myself.

I will post a package from my guix channel that you can test this on
soon.

To call the API, one basically calls the following, after including
<gtk/gtk.h>, so any GTK program will do.
```
GdkDisplay * display = gdk_display_get_default ();
GdkMonitor * monitor = gdk_display_get_primary_monitor (display);
int refresh_rate = gdk_monitor_get_refresh_rate (monitor);
```

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Message #8 received at 38163 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: Alexandros Theodotou <alex <at> zrythm.org>
Cc: 38163 <at> debbugs.gnu.org
Subject: Re: bug#38163: GDK does not return the monitor's refresh rate
Date: Mon, 11 Nov 2019 21:53:07 +0100

Hi Alexandros,

Alexandros Theodotou <alex <at> zrythm.org> skribis:

> I have been developing and testing my GTK app (Zrythm) on many distros
> and Guix is the only case that the monitor's refresh rate is returned
> as 0.
>
> The API I am using is this:
> https://developer.gnome.org/gdk3/stable/GdkMonitor.html#gdk-monitor-get-refresh-rate

Looking at GTK+, the ‘init_randr*’ functions in ‘gdkscreen-x11.c’ appear
to be those responsible for setting the ‘refresh_rate’ field.

However, AFAICS, our ‘gtk+’ package does not depend on ‘libxrandr’, and
thus that functionality is simply compiled out (the function returns 0
unconditionally).

Could you try adding that dependency on ‘libxrandr’ in ‘gtk+’?

We won’t make this change in ‘master’ because it entails too many
rebuilds, but it could go on the next branch for massive rebuilds.

Thanks for your report,
Ludo’.

Message #11 received at 38163 <at> debbugs.gnu.org (full text, mbox):

From: Alexandros Theodotou <alex <at> zrythm.org>
To: Ludovic Courtès <ludo <at> gnu.org>
Cc: 38163 <at> debbugs.gnu.org
Subject: Re: bug#38163: GDK does not return the monitor's refresh rate
Date: Mon, 11 Nov 2019 21:31:23 +0000

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

Hi Ludo,

> Looking at GTK+, the ‘init_randr*’ functions in ‘gdkscreen-x11.c’
> appear
> to be those responsible for setting the ‘refresh_rate’ field.
> 
> However, AFAICS, our ‘gtk+’ package does not depend on ‘libxrandr’,
> and
> thus that functionality is simply compiled out (the function returns
> 0
> unconditionally).
> 
> Could you try adding that dependency on ‘libxrandr’ in ‘gtk+’?

Just tried that and it worked! It's returning the correct refresh rate
now:
** Message: 21:20:40.548: refresh rate returned by GDK: 60.0

> We won’t make this change in ‘master’ because it entails too many
> rebuilds, but it could go on the next branch for massive rebuilds. 

Makes sense. I will be using my local gtk+ version for a while then
until this change goes live.

Thanks for taking a look at this.

Alex

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Message #14 received at 38163 <at> debbugs.gnu.org (full text, mbox):

From: Bengt Richter <bokr <at> bokr.com>
To: Alexandros Theodotou <alex <at> zrythm.org>
Cc: Ludovic Courtès <ludo <at> gnu.org>, 38163 <at> debbugs.gnu.org
Subject: Re: bug#38163: GDK does not return the monitor's refresh rate
Date: Wed, 13 Nov 2019 12:56:24 -0800

Hi Guix,

On +2019-11-11 21:31:23 +0000, Alexandros Theodotou wrote:
> Hi Ludo,
> 
> > Looking at GTK+, the ‘init_randr*’ functions in ‘gdkscreen-x11.c’
> > appear
> > to be those responsible for setting the ‘refresh_rate’ field.
> > 
> > However, AFAICS, our ‘gtk+’ package does not depend on ‘libxrandr’,
> > and
> > thus that functionality is simply compiled out (the function returns
> > 0
> > unconditionally).
> > 
> > Could you try adding that dependency on ‘libxrandr’ in ‘gtk+’?
> 
> Just tried that and it worked! It's returning the correct refresh rate
> now:
> ** Message: 21:20:40.548: refresh rate returned by GDK: 60.0
> 
> > We won’t make this change in ‘master’ because it entails too many
> > rebuilds, but it could go on the next branch for massive rebuilds. 
> 
> Makes sense. I will be using my local gtk+ version for a while then
> until this change goes live.
> 
> Thanks for taking a look at this.
> 
> Alex

I'm wondering about a narrowly-X solution.

Shouldn't this really come from udevd noticing display changes?
What about a multi-display seat, with potentially different refresh rates?

IIUC it seems like libdrm and KMS can get at all that, so a light-weight solution
should be possible, ISTM, and accessible from console command line without X.
-- 
Regards,
Bengt Richter

Message #17 received at 38163 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: Bengt Richter <bokr <at> bokr.com>
Cc: Alexandros Theodotou <alex <at> zrythm.org>, 38163 <at> debbugs.gnu.org
Subject: Re: bug#38163: GDK does not return the monitor's refresh rate
Date: Thu, 14 Nov 2019 22:00:30 +0100

Hi Bengt,

Bengt Richter <bokr <at> bokr.com> skribis:

> On +2019-11-11 21:31:23 +0000, Alexandros Theodotou wrote:

[...]

>> > Could you try adding that dependency on ‘libxrandr’ in ‘gtk+’?
>> 
>> Just tried that and it worked! It's returning the correct refresh rate
>> now:
>> ** Message: 21:20:40.548: refresh rate returned by GDK: 60.0

[...]

> I'm wondering about a narrowly-X solution.
>
> Shouldn't this really come from udevd noticing display changes?
> What about a multi-display seat, with potentially different refresh rates?
>
> IIUC it seems like libdrm and KMS can get at all that, so a light-weight solution
> should be possible, ISTM, and accessible from console command line without X.

You’re right, but note that GDK has several backends (not just X11), and
this issue was about fixing the problem with the X11 backend.

Thanks,
Ludo’.

Message #20 received at 38163 <at> debbugs.gnu.org (full text, mbox):

From: Marius Bakke <mbakke <at> fastmail.com>
To: Alexandros Theodotou <alex <at> zrythm.org>, Ludovic Courtès
 <ludo <at> gnu.org>
Cc: 38163 <at> debbugs.gnu.org
Subject: Re: bug#38163: GDK does not return the monitor's refresh rate
Date: Fri, 15 Nov 2019 19:24:12 +0100

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

Alexandros Theodotou <alex <at> zrythm.org> writes:

> Hi Ludo,
>
>> We won’t make this change in ‘master’ because it entails too many
>> rebuilds, but it could go on the next branch for massive rebuilds. 
>
> Makes sense. I will be using my local gtk+ version for a while then
> until this change goes live.

Note that this change is already in the staging branch since commit
52b61e999101724c7e2d341586e9a6150614f208.

Unfortunately the branch has gone stale due to some Qt/qmake plugin
issues & I haven't had time to work on it.  I will try to find a
workaround this weekend, if nothing else, as only a handful packages are
affected.

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Message #23 received at 38163 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: Marius Bakke <mbakke <at> fastmail.com>
Cc: Alexandros Theodotou <alex <at> zrythm.org>, 38163 <at> debbugs.gnu.org
Subject: Re: bug#38163: GDK does not return the monitor's refresh rate
Date: Sat, 16 Nov 2019 16:07:34 +0100

Hi,

Marius Bakke <mbakke <at> fastmail.com> skribis:

> Alexandros Theodotou <alex <at> zrythm.org> writes:
>
>> Hi Ludo,
>>
>>> We won’t make this change in ‘master’ because it entails too many
>>> rebuilds, but it could go on the next branch for massive rebuilds. 
>>
>> Makes sense. I will be using my local gtk+ version for a while then
>> until this change goes live.
>
> Note that this change is already in the staging branch since commit
> 52b61e999101724c7e2d341586e9a6150614f208.

Nice! I wasn’t aware of it.

> Unfortunately the branch has gone stale due to some Qt/qmake plugin
> issues & I haven't had time to work on it.  I will try to find a
> workaround this weekend, if nothing else, as only a handful packages are
> affected.

Let’s motivate each other on IRC over the week-end.  I’d be happy to
give a hand to get that branch merged!

Thanks,
Ludo’.

Message #28 received at 38163-done <at> debbugs.gnu.org (full text, mbox):

From: Alexandros Theodotou <alex <at> zrythm.org>
To: 38163-done <at> debbugs.gnu.org
Subject: Re: bug#38163: GDK does not return the monitor's refresh rate
Date: Wed, 27 May 2020 01:10:35 +0100

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This was fixed a long time ago.

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