wl_tablet specification draft
spitzak at gmail.com
Fri Jun 27 13:04:59 PDT 2014
On 06/26/2014 09:38 PM, Ping Cheng wrote:
> With my experience, mapping whole tablet to a window or a
> specific display area is preferred. That is how mapping works on Windows
> and Mac too.
First this is *only* when the drawing program wants it to happen. There
is some kind of mode switch so the user can use the pen to do things
outside the drawing area. When the drawing program is not controlling it
the user wants to be able to use the pen instead of the mouse for all
I would also love to see addressed the ability to get "square" movement
out of the pad, and to automatically switch to "mouse mode" if the
outputs are a significantly different shape than the tablet. Though
Linux was by far the worst, all three systems (OS/X and Windows) fell
down badly here, mostly by making it impossible to mode-switch between
mouse and tablet mode, and on Windows it is impossible to change the
scale of mouse mode. None of them would change how the mapping is done
when outputs are added/removed. I believe "limit to one monitor" is not
necessary and is only being provided as a work-around for the non-square
mappings that should be avoided in a different way.
Even though it sounds like it is disagreeing with me, there is no need
for "mouse emulations". Wayland clients should all be written to know
that they could get pen events just like mouse events and to handle them
the same if they don't want to do anything smarter with the pen.
Vaguely thinking of this from a Wayland client's pov it seems like what
should happen is this:
- The pen moves the seat's mouse cursor, always. If more than one cursor
is wanted the pen should be in a different seat. The user is not
manipulating more than one device at a time and does not want to see two
- By default the pen can move the cursor anywhere the mouse could move
it. A configuration option sets the "scale" (possibly a range) between
pen movements and cursor motion. If mapping the tablet to the bounding
box of all the outputs exceeds this scale then it automatically switches
to "mouse mode" (ie relative movement, possibly with acceleration).
Conversely if it is too small, or the aspect is sufficiently different,
then only a centered rectangle of the tablet is used. The setting is
automatically updated when the outputs or configuration changes as long
as no pen buttons are held down. It may be useful to have horizontal and
vertical enter "mouse mode" independently, but somebody needs to try that.
- Clients can request that the tablet be mapped to a rectangle in a
particular surface. They must have the seat mouse focus for this to
happen. Unless some extra api is used for force the mapping, the
built-in rules are applied to determine the scale and whether mouse-mode
is used, based on the size and aspect of this rectangle.
- If this mapping is happening, other devices (ie the mouse) can still
move the cursor outside the rectangle. It will jump back in when pen is
moved in proximity.
- This does not "grab" the mouse/pen. If other surfaces are visible
inside the rectangle (either because it is larger than the surface or
because of an overlapping surface) then clicks go to the client the
surface belongs to.
- A client can request the default mode be restored, even if they did
not set the rectangle, as long as it has seat mouse focus. This is so an
overlapping dialog can decide whether it should exit the mode. I think
this will be better than any built-in rules for relinquishing the mode.
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