=================
GUI configuration
=================


Video RAM adjustment for high-resolution displays
-------------------------------------------------


When a qube starts, a fixed amount of RAM is allocated to the graphics
buffer called video RAM. This buffer needs to be at least as big as the
whole desktop, accounting for all displays that are or will be connected
to the machine. By default, it is as much as needed for the current
display and an additional full HD (FHD) display (1920×1080 8 bit/channel
RGBA). This logic fails when the machine has primary display in FHD
resolution and, after starting some qubes, a 4K display is connected. If
the buffer is too small, and internal desktop resize fails.

To increase the minimum size of the video RAM buffer:

.. code:: bash

      qvm-features dom0 gui-videoram-min $(($WIDTH * $HEIGHT * 4 / 1024))
      qvm-features dom0 gui-videoram-overhead 0


Where ``$WIDTH``× ``$HEIGHT`` is the maximum desktop size that you
anticipate needing. For example, if you expect to use a 1080p display
and a 4k display side-by-side, that is
``(1920 + 3840) × 2160 × 4 / 1024 = 48600``, or slightly more than 48
MiB per qube. After making these adjustments, the qubes need to be
restarted.

In the case of multiple display with different orientations or if you
plug/unplug displays, the following code will set correct memory size
using xrandr.

.. code:: bash

      qvm-features dom0 gui-videoram-min $(xrandr --verbose | grep "Screen 0" | sed -e 's/.*current //' -e 's/\,.*//' | awk '{print $1*$3*4/1024}')


The amount of memory allocated per qube is the maximum of: -
``gui-videoram-min`` - current display + ``gui-videoram-overhead``

Default overhead is about 8 MiB, which is enough for a 1080p display
(see above). So, the ``gui-videoram-overhead`` zeroing is not strictly
necessary; it only avoids allocating memory that will not be used.

You might face issues when playing video, if the video is choppy instead
of smooth display this could be because the X server doesn’t work. You
can use the Linux terminal (Ctrl-Alt-F2) after starting the virtual
machine, login. You can look at the Xorg logs file. As an option you can
have the below config as well present in
``/etc/X11/xorg.conf.d/90-intel.conf``, depends on HD graphics though -

.. code:: bash

      Section "Device"
              Identifier "Intel Graphics"
              Driver "intel"
              Option "TearFree" "true"
      EndSection


GUI Troubleshooting
-------------------


See :doc:`GUI Troubleshooting </user/troubleshooting/gui-troubleshooting>` for issues
relating to the Qubes graphical user interface and how to fix them.