When changing the DPI via xrandr --dpi <DPI>, xrandr will send a
RRScreenChangeEvent and the DPI value should get adjusted.
Falsely, we thought randr_update() would catch up and query the right
monitor values. But nothing changes, because we query the
XRRMonitorInfo. The monitor info contains the real physical width and
height of the monitor's screen.
But xrandr --dpi only changes the - let's say - virtual screen size of
the virtual overall screen (and therefore changing the DPI to the
matching value).
Important commands to understand:
- Changes dpi of the virtual screen
xrandr --dpi
- Gives info about the "virtual" screen size (used by DisplayWidth)
xdpyinfo | grep -B1 resolution
- Gives info about the "physical" screen size (used by XRRMonitorInfo)
xrandr -q
I know, that I'm probably not right and might not understand the topic
in its full size yet[0]. But I'm 100% sure, that the terms "monitor",
"screen", "screens", "output" and "display" do not have a consistent
naming scheme.
[0] https://twitter.com/dechampsgu/status/857924498280124416Fixes#382
4f510e1703