xrandr-keystone-helper
This program helps finding the parameters for xrandr --transform. This can be helpful for setting up keystone-correction for projectors.
Transformed pictures with "xrandr --tranform" may (very likely) still have some issues especially around the cursor. The result could be sufficient for viewing movies or presenting slides.
Use Python 3.x and install the matplotlib dependencies with:
pip3 install matplotlib --user
Execution:
python3 xrandr-keystone-helper.py
Adjust the red tetragon/quadrilateral and test the result until you find the right parameters. The string to use with xrandr --transform gets printed to the terminal.
To get the Test button working change the eDP1 to the output you want to configure e.g. VGA-1 or HDMI-1.