I'm running my laptop with an external monitor. The laptop's built in monitor and the external monitor have wildly different DPI, so I scale the external monitor to match the DPI of the internal one:
xrandr --output HDMI1 --scale 2.1x2.1 --pos 2880x0
This gives me
Screen 0: minimum 320 x 200, current 6912 x 2268, maximum 8192 x 8192 eDP1 connected primary 2880x1620+0+0 (normal left inverted right x axis y axis) 340mm x 190mm HDMI1 connected 4032x2268+2880+0 (normal left inverted right x axis y axis) 477mm x 268mm
The transformation matrices are:
eDP1 (laptop built-in screen):
1.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 1.0
HDMI1 (external monitor):
2.099991 0.000000 0.000000 0.000000 2.099991 0.000000 0.000000 0.000000 1.000000
This lets both monitors show things at the same size.
The screens display fine, but now my mouse will only reach a small fraction of the external monitor (roughly the upper left quadrant) and won't move to the bottom portion of the screen or the right portion. When I move it to the extent of its range, xinput reports
ValuatorClass Mode=Relative Proximity=In valuator=4797 valuator=1079 valuator=0 valuator=-348
The problem seems to me to be that the mouse thinks the screen has a size of 4798 x 1080 units, whereas the X screen 0 has a horizontal size of 6192 x 2268.
How can I configure the mouse to reach all of both monitors?
Can anyone suggest a solution?
Hardware: Lenovo Thinkpad W541. Software: Debian jessie