Re: Monitor attributes on Windows 11/WSL2

> Date: Sat, 1 Aug 2026 14:11:14 +0200
> Cc: [email protected], [email protected]
> From: martin rudalics <[email protected]>
> 
>  > The code which uses mm-size in our code base seems to assume without
>  > checking that the value is non-zero.  So I wonder how this particular
>  > platform violates the assumption that held since time immemoriam.
>  > Which code is responsible for asking X to provider these values, and
>  > why does it not work in this case?  I tried to answer this question
>  > myself, but was surprised to see the relevant variables set only under
>  > one particular combination of toolkit and use of XRandr.  I'm probably
>  > missing something.
> 
> XRandr should not be involved here.  The relevant code is
> 
> #if GTK_CHECK_VERSION (3, 22, 0)
>        width_mm = gdk_monitor_get_width_mm (monitor);
>        height_mm = gdk_monitor_get_height_mm (monitor);
> #else
>        width_mm = gdk_screen_get_monitor_width_mm (gscreen, i);
>        height_mm = gdk_screen_get_monitor_height_mm (gscreen, i);
>        if (width_mm < 0)
> 	width_mm = rec.width * mm_width_per_pixel + 0.5;
>        if (height_mm < 0)
> 	height_mm = rec.height * mm_height_per_pixel + 0.5;
> #endif
> 
> around line 6991 of xfns.c since the source reported by the OP is Gdk
> (source . "Gdk").  But maybe xrandr can do better (unless the user is on
> Wayland).
> 
>  > We don't officially support WSL, so we could just say that.  But it
>  > would be nice to have a better understanding of what APIs fail us in
>  > this case.  Can you perhaps point to the relevant code, so Arash could
>  > then try working with that user to find out what goes wrong?
> 
> Either gdk_monitor_get_width_mm or gdk_screen_get_monitor_width_mm above
> seem to return 0.

Thanks.  Arash, can that user walk through this code and tell what
happens there?