Inconsistent Screen Resolution for Fedora VMs

[xme...@gmail.com]

I just did a clean install of Qubes 3.2. For some reason the resolution off apps in Fedora VMs is wildly inconsistent. The borders of the windows, dom0, and the Debian VMs are correct but the apps in Fedora VMs range from consistent with the others to so low as to be almost unusable. I can't figure out what causes them to change and xrandr outputs the same thing no matter what the displayed resolution is.

[Jeremy Rand]

xme...@gmail.com:

> I just did a clean install of Qubes 3.2. For some reason the resolution off apps in Fedora VMs is wildly inconsistent. The borders of the windows, dom0, and the Debian VMs are correct but the apps in Fedora VMs range from consistent with the others to so low as to be almost unusable. I can't figure out what causes them to change and xrandr outputs the same thing no matter what the displayed resolution is.

I think this occurred for me a few weeks ago. If I recall correctly,
the HiDPI settings in GNOME had somehow been set to 0. No magnification
is 1, double magnification is 2. 0 gets interpreted as 2, for reasons
that only the GNOME people are likely to understand. The standard GNOME
procedures for changing HiDPI settings fixed it for me (I restored it to 1).

Sorry I don't have more details for you, I don't believe I wrote down
the fix at the time.

-Jeremy

[Marek Marczykowski-Górecki]

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On Sat, Oct 22, 2016 at 07:15:16AM +0000, Jeremy Rand wrote:
> xme...@gmail.com:
> > I just did a clean install of Qubes 3.2. For some reason the resolution off apps in Fedora VMs is wildly inconsistent. The borders of the windows, dom0, and the Debian VMs are correct but the apps in Fedora VMs range from consistent with the others to so low as to be almost unusable. I can't figure out what causes them to change and xrandr outputs the same thing no matter what the displayed resolution is.
>
> I think this occurred for me a few weeks ago. If I recall correctly,
> the HiDPI settings in GNOME had somehow been set to 0. No magnification
> is 1, double magnification is 2. 0 gets interpreted as 2, for reasons
> that only the GNOME people are likely to understand.

I've looked at gnome-settings-daemon code and AFAIR those reasons are:
1. Have DPI at least 192, and
2. Have vertical resolution at least 1200.

Relevant code:
https://github.com/GNOME/gnome-settings-daemon/blob/master/plugins/xsettings/gsd-xsettings-manager.c#L233-L241

#define DPI_FALLBACK 96

/* The minimum resolution at which we turn on a window-scale of 2 */
#define HIDPI_LIMIT (DPI_FALLBACK * 2)

/* The minimum screen height at which we turn on a window-scale of 2;
* below this there just isn't enough vertical real estate for GNOME
* apps to work, and it's better to just be tiny */
#define HIDPI_MIN_HEIGHT 1200

There is also lengthy comment about it.
Anyway the above looks reasonable for me for automatically turning HiDPI
mode on. So, if it was incorrect, I'd guess something gone wrong with
retrieving input values (DPI, vertical resolution).

- --
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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[xme...@gmail.com]

Thanks! I'm without a computer right now but I will look into soon to see if I can figure out exactly where it's messing up.

[Jeremy Rand]

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Jeremy Rand:

For future reference of anyone stumbling across this thread, you can
disable HiDPI in your Fedora VM's by running this terminal command in
each of your Fedora VM's and then rebooting those VM's:

gsettings set org.gnome.desktop.interface scaling-factor 1

Until you reboot those VM's, their GUI will have weird glitches.

Hope this helps anyone who runs into this.

- -Jeremy
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