Different output between xrandr and xdpyinfo

Böszörményi Zoltán zboszor at pr.hu
Thu Nov 19 08:51:29 UTC 2020


2020. 11. 18. 2:47 keltezéssel, limh at sunray.cn írta:
> Hi
> I'm using hdmi and lvds with touch screen. But the touch screen can move the pointer 
> between two monitors like the picture now.png.
> But I want my touch screen to be applied on lvds like I want.png
> So I follow arch wiki to set the configuration. But I found xrandr showed only one screen:
> root at imx6qsabresd:~# xrandr
> Screen 0: minimum 240 x 240, current 1024 x 768, maximum 8192 x 8192
> DISP3 BG connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
>     1024x768_60.00  59.92*+
> xdpyinfo showed two screens.
> Here is xdpyinfo's output and /etc/X11/xorg.conf
> Also, I found the HDMI screen's cursor is a cross(the same as  'X').
> How to solve these problems?

you can run "xinput map-to-output ..." command after
starting X but it's not persistent and if the touchscreen
is a USB device, the setting doesn't survive hotplugging.

The way I solved it was with fixed configuration
using a template file with "sed" substitutions and
this utility: https://github.com/zboszor/touchscreen-transform

For example, this configuration template snippet is used
for a specific touchscreen and a script that runs before
starting X substitutes "@TRANSMATRIX@" with the output of
this "touchscreen-transform" command:

Section "InputClass"
	Identifier "INTERNAL_TS"
	MatchIsTouchscreen "on"
	MatchProduct "eGalax Inc. eGalaxTouch P80H84 2072 v00_T3 k4.08.165"
	Driver "libinput"
	Option "TransformationMatrix" "@TRANSMATRIX@"

This does work if the USB touchscreen is hotplugged.

The "touchscreen-transform" program expects the list of
screen resolutions and assumes they are located side by side.
It doesn't care if you use separate X screens or Xinerama.
The TransformationMatrix values are identical.

Obviously you need to know the screen resolutions in advance.
Monitor-hotplugging is not supported, as it also need the
touchscreen's TransformationMatrix values to be reset.

Zoltán Böszörményi

> Regards
> Mihan
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