input device support in xserver

[Keith Packard]

Around 12 o'clock on Feb 14, Warren Turkal wrote:

>    HAL<->mouse reader/dbus sender<->dbus<-> dbus
>    receiver<->xserver<->xapp

That's a lot of context switches for mouse events, which will introduce
significant additional latency into a system which is already slow enough. 
It concerns me.

Oh, one extra twist here though -- the Composite mechanism doesn't (yet) 
provide any way to let an external agent manipulate the translation from 
physical motion to both hierarchy and logical position, we may want to 
figure out how this works at the same time, as one option would be to 
actually use this mechanism and pass the translated events to the server 
via dbus.  I don't know.

>    1. how to notify apps of input device changes

That seems pretty straightforward; RandR sends a single "hey, something 
changed" event and leaves most of the complicated information to a 
separate request/reply.

>    2. how to retain backward compatibility while moving forward
>       gracefully

To some extent, it is impossible to be perfectly compatible and still gain 
the ability to remove devices (adding seems pretty easy).  Applications 
are going to break, let's focus on making things right before we try to 
kludge them so that the huge set of existing Xinput using applications can 
work in all situations without trouble.

-keith