wrong touch position in Debian 10 Buster (aarch64)

[AndroidDesigner]

Hello
I have a debian 10 buster touch panel and used the compositor-ng branch to be able to run my app (issue_328).
But I don't know why touch positions are wrong when I run the app (in both portrait & landscape).
for example, suppose I have a button in bottom-left of the screen. So if I click on it, nothing happens while if I click on bottom-right side of the screen, the button's event triggers.

I used sudo libinput debug-events to be able to check touched positions and it seems the (x,y) are correct (for example top-left shows 0/ 0 (0/ 0mm) and right-bottom shows 100/ 100 (1280/ 800mm)).
Also, $xrandr output:

xrandr
Screen 0: minimum 320 x 200, current 1280 x 800, maximum 8192 x 8192
DSI-1 connected primary 1280x800+0+0 right (normal left inverted right x axis y axis) 0mm x 0mm
   800x1280      56.24*+

what is the problem?
Are you sure touch handler in the compositor-ng branch is correct?

[AndroidDesigner]

My touch screen works fine in the Desktop environment of my debian OS, but is wrong in the flutter app.
I used sudo libinput debug-events to log touch positions.
As I said, my touch panel is 1280*800 in landscape shape with a camera in top-center of it. So :

• top-left side of the screen (relative to the camera) shows (0,0)
• bottom-left side of the screen (relative to the camera) shows (0, 800).
• top-right side of the screen (relative to the camera) shows (1280, 0).
• bottom-right side of the screen (relative to the camera) shows (1280, 800).
  In the flutter app, it seems we have a 90 degree shift between physically touched position and affected position on the app.
  No recommendation?

[ardera]

It's a bit weird, in the flutter-pi log in issue #328 (comment) it says the resolution is 800x1280, but xrandr says it's 1280x800 also somehow 800x1280, and says it's 1280x800.

Did you launch libinput from inside the desktop environment / while the desktop environment is running? Or from console, when no desktop environment was running?

How do you launch flutter-pi? Are you using -r <90/180/270> or -o something else?

When running, is the flutter app displaying in landscape or portrait mode?

[AndroidDesigner]

I found the solution finally.
I read about the flutter-pi and found that it provides touch input support through the tslib library.
So I installed it and did a calibration by using ts_calibrate.
Then I added the below to the /etc/udev/rules.d/98-touchscreen-cal.rules path:

ATTRS{name}=="gt9xx", ENV{LIBINPUT_CALIBRATION_MATRIX}="0.0 -1.0 1.0 1.0 0.0 0.0"

And finally touch works in the flutter app too.

[ardera]

Nice that you got it working!

flutter-pi uses libinput, but other than that it's correct :) I also have flutter_libinput_calibrator for this, but specifying an exact rotation matrix like you did is better

[AndroidDesigner]

The flutter_libinput_calibrator is so useful too.
Thank you.