Re: Touchscreen support

[Po Lu <luangruo@yahoo.com>]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Po Lu via "Emacs development discussions." <emacs-devel@gnu.org> writes:
>
>> I implemented the events required for full touchscreen support for
>> XInput 2.  These events are generated only for DirectTouch devices,
>> which means real touchscreens only, no touchpads.
>
> That's fantastic -- proper touchscreen support is something I've been
> wanting to have in Emacs for at least a decade.
>
> One question:
>
>> Please take a look and see if the API I'm exposing is useful, and also
>> easy enough to implement on non-X platforms.
>> +The low-level touchscreen events described below can be used to
>> +implement all the touch sequences described above.  In those events,
>> +each point is represented by a cons of an arbitrary number identifying
>> +the point and a mouse position list (@pxref{Click Events}) specifying
>> +the position of the finger when the event occurred.
>
> What would the implementation of a (for instance) "three finger swipe
> left" event look like based on these primitives?

You would wait for three consecutive `touchscreen-down' events, then
decide if the fingers are in an appropriate location, and then keep
reading for `touchscreen-update' events, calculating their movement.

I can't think of that in any more detail right now, but it should be
similar to how it's implemented on X, whose APIs are paralleled by this
implementation.

Thanks.