[RFC] kscreen and touchscreen rotation

[Martin Flöser]

Am 2017-09-11 11:58, schrieb Sebastian Kügler:
> Hi all,
> 
> One of the things we talked about during Akademy was better support for
> convertible hardware. I've played around a bit with my Thinkpad X1 Yoga
> and screen rotation. I can of course rotate the screen "manually"
> through XRandR (Wayland is another story on that altogether), but that
> will screw up the touchscreen. Doing some research, I found out that:
> 
> - touchscreen and display are completely separate things, the system
>   doesn't know they're sitting on top of each other

It does know, it's just not properly exposed. Libinput does have the 
output information, it's just not set through udev in general, so in 
practice we don't have it. But it's in general a fixable problem which 
might need some work together with upstream and downstream. We need to 
figure out whether that is never set or just in all distros except 
Fedora (which is what I would expect).

Anyway for your design planning you should be able to assume that there 
is a link between output and touchscreen.

> - They need to be rotated separately
> - rotation in X goes through XInput2, on Wayland, I don't know

KWin through libinput.

> It's just an idea for now, but I'd like to get some feedback about it
> at this point.

My feedback would be: ignore X11, concentrate on Wayland. Once Wayland 
works, add it to X or ignore it.

Why:
1) Wayland is easier, we control the stack
2) We agreed that anything new should be Wayland first
3) Going X11 first or considering X11 at all might make the work on 
Wayland more difficult

So go for the simple way and change Wayland first.

Cheers
Martin