[PATCH libinput 5/7] tablet: add support for relative x/y motion deltas

[Bill Spitzak]

On Mon, Jan 18, 2016 at 1:57 PM, Peter Hutterer <peter.hutterer at who-t.net>
wrote:

>
> mapping aspect ratio will be the job of the compositor. In reality, this
> will mean that one of the axes will be shortened to match the ratio.
>

Yes I believe the compositor has to do this. libinput obviously cannot, and
I don't think clients can do this.

if absolute mode on your tablet is "completely useless" that would indicate
> you never looked at wacom(4) or any instructions on how to fix this. We've
> had config options to adjust this for years.
>

I am well aware of the wacom command, and use it. Setting a working
relative mode is really painful, and also does not survive reboot or
sleep/wakeup. I have a batch file that I run every time in order to fix the
tablet, here are the contents:

xsetwacom --set "Wacom Intuos3 6x8 stylus" Mode Relative
xsetwacom --set "Wacom Intuos3 6x8 stylus" Area "0 0 162560 121920"
xsetwacom --set "Wacom Intuos3 6x8 eraser" Mode Relative
xsetwacom --set "Wacom Intuos3 6x8 eraser" Area "0 0 162560 121920"

Absolute mode on my tablet is completely useless, at least for drawing and
3d modelling. The tablet is 8" wide and 6" tall. My two HDTV monitors side
by side are about 43" wide and 12" tall. Therefore the physical scaling
from pen motion to cursor motion is about 5x horizontally and 2x
vertically. This scale makes it impossible to do fine detail without so
much zooming in that I have cropped off all useful context, and the aspect
ratio difference makes it impossible to transfer muscle memory used for
drawing with a physical pen or a tablet on a different device to this one.

I still find it hard to believe my situation is unique. Vastly more small
tablets are sold than big desktop-sized ones.

A few ideas that will make xsetwacom a bit less painful:

1. Should be able to set the relative and absolute mapping with one
command, rather than one per tool. This is independent of whether the tool
is relative or absolute. If you really want add a way to override it per
tool, but setting the default would help. My above code only works because
I only have a pen and eraser, if I added another tool I would have to fix
this.

2. Relative mode should default to some square aspect and the size should
not depend on the screens in any way. I think this basically means that the
relative and absolute rectangles are different. The absolute rectangle is
completely under control of the compositor, which is well aware of the size
of the outputs, or any api by clients to restrict the tablet to an area.

3. (this is my only real proposal that would differ from existing systems):
I think the system could automatically switch to relative mode if the
absolute area exceeds the relative area by too large a factor. In my
experience this is as small as 1, but it is possible other users would
disagree. At least use this to initialize a new device before the user
customizes it.
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