Re: Lenovo Yoga 700-11ISK touchscreen

[Alexey Kardashevskiy <aik ozlabs ru>]

On 3/18/18 10:36 PM, Carlos Garnacho wrote:

> > > > 2. the touchscreen seems not to understand multitouch at all so it also
> > > > does not allow scrolling most of the time. If it is firefox or a terminal -
> > > > moving finger over the window selects text. No two finger scrolling is
> > > > possible (enabled and works with the touchpad).
> > >
> > > Ultimately, reaction to (multi)touch is implemented by each specific
> > > application. Any issues there should thus be reported on each
> > > application bug reporting system. NB, such issues are very probably
> > > already filed, so look out for duplicates.
> >
> > Is this different from touchpad? I am asking as the touchpad settings are
> > system wide and it works the same everywhere but there is no such control
> > over the touchscreen behaviour and I wonder why... I expected touchpad and
> > touchscreen to share same settings or each to have own settings and neither
> > seems to be the case.
>
> It is a whole lot different :). From the perspective of the
> application, a touchpad is the essentially same than a mouse, and
> applications have been able to deal with those for many years. As the
> actions apply on a single concrete point (where you see the mouse
> cursor), the windowing (xorg/wayland) is able to send specific events
> of what happened (moved to these coordinates, pressed mouse button,
> scrolled by this much).
>
> Multitouch is peculiar in that the application is made known of basic
> information (new touchpoint at these coordinates, touchpoint moved
> somewhere else, touchpoint was lifted) for *every* touchpoint. The
> application is in charge of seeing where do each apply and giving
> those a meaning, some examples:
> - A touchpoint happening in a browser tab might eventually tap some
> button in the webpage, or be used by the browser to start scrolling if
> it moves past a distance (and effectively cancelling other actions)
> - Say you actually meant to zoom on the page, so a second touchpoint
> on the webpage arrives a couple milliseconds later. All previous
> actions should be rendered ineffective, and the browser should see how
> far away are those touchpoints in order to start zooming based on that
> initial distance, using the center of those 2 points as the zooming
> anchor.
> - But say you missed the webpage in that second touch, and it ends up
> on the location bar. What should the app do in that case? I dunno, but
> what it shouldn't do is zooming :).

Oh. Ok. Seems weird as touchpad seems to have to solve exact same problems
but ok :)


> Toolkits like GTK+ may help to some extent, but nothing enforced apps
> to using that fully/correctly. And in the case of Firefox, I think
> their use of GTK+ is a lot more superficial than that, so there's more
> on their plate to handle.
>
> TL;DR: Touch input is highly location and context dependent, there's
> no way "correct" multitouch-y behavior can be done for free without
> app involvement.

Got it. Thanks for the explanations.


-- 
Alexey