Sounds like a reasonable request.
As a matter of purity Mir has tried to hide compositor information like
screen position from clients, which is otherwise a good idea.
Until now we've dithered between two approaches:
(a) Support arbitrary 3D transformations but only support input
correctly when surfaces are flat (2D).
(b) Support arbitrary 3D transformations and support accurate
coordinate transformation for correct input even when a surface is not
"flat".
I think we're more going down the road of (b) now -- anpok touched it
last. In that case you would get a function:
Point client_coord_to_screen_coord(Point local);
This supports the generalised case where under transformation, a button
rectangle may in fact no be a rectangle on the screen.
But it's also kind of OK if we just want to assume transformations
always settle back to 2D and appear flat on the screen for the sake of
simplified input handling.
- Daniel
On 22/07/14 07:42, Gerry Boland wrote:
Hey folks,
in working on QtCompositor, I stumbled across a problem ([1]).
Autopilot needs to know the position of items in an application
(buttons, etc) in screen coordinates - not surface. It needs that as it
generates inputs via uevent, which are defined in screen coordinates.
To calculate absolute item position, it must know the position of the
application surface in screen coordinates.
However Mir does not give applications this information.
But Autopilot has this requirement, so how can we satisfy it?
Thomi and I chewed this over a bit, and the ideas we had were:
1. unity8 exposes a DBus API which
a) allows AP to ask "what are the coordinates of the surface with
PID x
b) emit signals when surface position changes
This isn't ideal, as it requires punching holes in client appArmor
confinements just for testing, and would also require a lot of work in
Autopilot to be able to listen to those DBus signals.
2. AP injects events directly into Qt/unity8
Requires unity8 to be in a "testing" mode. Qt would need lots of work
for it to handle relative coordinates being injected.
3. Mir let the clients find their surface's screen position
But I don't think the Mir team like that final idea (I'm not a fan either).
So I'd like to open this discussion up, and see if the Mir team have
considered this issue and have suggestions/plans.
Thanks!
-Gerry
P.S. for now I've written a hack to fix AP tests with qtComp, so this is
not an urgent topic.
[1] https://bugs.launchpad.net/mir/+bug/1346633
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