multiple monitor detection

multiple monitor detection

[Psionic K]

I was going to add multiple monitor support to the dslide package.  I
have to physical monitors active now.

However `display-monitor-attributes-list` returns the following:

    (((name . "combined screen") (geometry 0 0 6400 2160) (workarea
6400 2080 0 80)
      (mm-size 1693 572) (frames #<frame Emacs 0x3cca5d50>) (source .
"fallback")))

When running `xrandr`, xrandr is installed, so I'm not sure why the
source is fallback.  I restarted Emacs.  (30.0.91).

Xrandr's output more distinctly shows the two physical monitors:

    $ xrandr
    Screen 0: minimum 320 x 200, current 6400 x 2160, maximum 16384 x 16384
    eDP connected 2560x1440+3840+0 (normal left inverted right x axis
y axis) 309mm x 174mm
       2560x1440     60.01*+  48.01
       <snip>
    HDMI-A-0 connected primary 3840x2160+0+0 (normal left inverted
right x axis y axis) 600mm x 340mm
       3840x2160     60.00*+  50.00    59.94    30.00    30.00
25.00    24.00    29.97    23.98
       <snip>

I'm not sure why the fallback is being used by
`display-monitor-attribute-list'.  Xrandr is available to
`executible-find`.

My goal is to detect the physical monitor and allow the user to
display dslide presentations on the other physical monitor and switch
between them.  I'm presently unable to decide how to recognize the two
physical monitors without rolling my own solution on top of xrandr.

Re: multiple monitor detection

[Robert Pluim]

>>>>> On Mon, 21 Oct 2024 15:05:01 +0900, Psionic K <psionik@positron.solutions> said:

    Psionic> I was going to add multiple monitor support to the dslide package.  I
    Psionic> have to physical monitors active now.

    Psionic> However `display-monitor-attributes-list` returns the following:

    Psionic>     (((name . "combined screen") (geometry 0 0 6400 2160) (workarea
    Psionic> 6400 2080 0 80)
    Psionic>       (mm-size 1693 572) (frames #<frame Emacs 0x3cca5d50>) (source .
    Psionic> "fallback")))

    Psionic> When running `xrandr`, xrandr is installed, so I'm not sure why the
    Psionic> source is fallback.  I restarted Emacs.  (30.0.91).

Emacs doesnʼt use 'xrandr' the executable, it uses the "Xrandr"
extension, so the header files and the library need to be available
when building Emacs. Check your config.log to see if 'configure' found
them.

If not, you should try installing the "Xrandr" dev package for your
distribution and re-run 'configure'. On Debian the package you need is
called 'libxrandr-dev'

Robert
-- 

Re: multiple monitor detection

[Óscar Fuentes]

Psionic K <psionik@positron.solutions> writes:

> I was going to add multiple monitor support to the dslide package.  I
> have to physical monitors active now.
>
> However `display-monitor-attributes-list` returns the following:
>
>     (((name . "combined screen") (geometry 0 0 6400 2160) (workarea
> 6400 2080 0 80)
>       (mm-size 1693 572) (frames #<frame Emacs 0x3cca5d50>) (source .
> "fallback")))
>
> When running `xrandr`, xrandr is installed, so I'm not sure why the
> source is fallback.  I restarted Emacs.  (30.0.91).
>
> Xrandr's output more distinctly shows the two physical monitors:
>
>     $ xrandr
>     Screen 0: minimum 320 x 200, current 6400 x 2160, maximum 16384 x 16384
>     eDP connected 2560x1440+3840+0 (normal left inverted right x axis
> y axis) 309mm x 174mm
>        2560x1440     60.01*+  48.01
>        <snip>
>     HDMI-A-0 connected primary 3840x2160+0+0 (normal left inverted
> right x axis y axis) 600mm x 340mm
>        3840x2160     60.00*+  50.00    59.94    30.00    30.00
> 25.00    24.00    29.97    23.98
>        <snip>
>
> I'm not sure why the fallback is being used by
> `display-monitor-attribute-list'.  Xrandr is available to
> `executible-find`.
>
> My goal is to detect the physical monitor and allow the user to
> display dslide presentations on the other physical monitor and switch
> between them.  I'm presently unable to decide how to recognize the two
> physical monitors without rolling my own solution on top of xrandr.

Which is your O.S.? What is the output of xrandr -v ?

Here (display-monitor-attribute-list) shows

(((name . "HDMI-2") (geometry 0 0 1920 1080) (workarea 44 0 1876 1080)
(mm-size 480 270) (frames #<frame Emacs: *Minibuf-1* ** @ sky
0x557560867c50>) (source . "XRandR 1.5")) ((name . "HDMI-3") (geometry
1920 0 1680 1050) (workarea 1920 0 1680 1050) (mm-size 474 296) (frames
#<frame pdf 0x5575618a4550>) (source . "XRandR 1.5")) ((name . "DP-1")
(geometry 3600 0 3840 2160) (workarea 3600 0 3840 2160) (mm-size 600
340) (frames) (source . "XRandR 1.5")))

This is GNU/Linux, X window system, KDE, xrandr 1.5.2

Anyways, depending on xrandr is a bit too specific, isn't it? With
Wayland becoming more and more used, but maybe the GTK Wayland port does
the right thing already on this regard.

Re: multiple monitor detection

[Robert Pluim]

>>>>> On Mon, 21 Oct 2024 11:32:28 +0200, Óscar Fuentes <ofv@wanadoo.es> said:

    Óscar> Anyways, depending on xrandr is a bit too specific, isn't it? With
    Óscar> Wayland becoming more and more used, but maybe the GTK Wayland port does
    Óscar> the right thing already on this regard.

The Emacs pgtk build uses gdk functions to get the monitor info. What
they do internally I have no idea, but they get the right answers on Wayland.

Robert
--