not that it's a problem, but why?
You have screens mocked already.

if you fetch the geometry here you'll get both the size and topLeft in an easier to read way.

you're not updating in deviceAdded(), so hypothetically if one adds a touch screen at runtime, and plugs in the HDMI cable before the USB cable it won't have the right screen.

You could put this method (and the screens changed connect) in Device as you're not doing anything with Connection in this method.

It's failing to compile in tests/ directory. There I don't have the mockscreens, so I didn't think of it. Will try with the mockscreens. Thanks for the suggestion.

You could put this method (and the screens changed connect) in Device as you're not doing anything with Connection in this method.

I didn't want to add the screens dependency to Device. I need it in Connection for the touch point translation, so I added it there. Device itself doesn't have any dependencies of KWin yet, Connection is kind of the "firewall" between them.

Didn't get it to compile with the mockscreens.

Shouldn't we be multiplying the default matrix for the device by the matrix you're generating here then setting that?

If a user has set a static calibration we want to keep that.

Hmm, you might be right. That's something I didn't think about. Only took the matrices provided in the docs.