[SDL] SDL gesture API

Nicholas Rishel rishel.nick at gmail.com
Sun Mar 3 04:08:17 PST 2013

I'm not sure I get your concern. The intent of a gesture library is that it
abstracts away the idea of touch. If you were, for instance, going to use
the system's gesture interface then you can't effectively build your own on
top of it because the touch information you want was hidden in the form of
a simplified set of gesture events instead of touch events.

So, in short, when getting events from the system you would specify whether
you want to receive the OS's gesture events or touch events. If you want to
build your own gesture library, you opt to receive touch events. If you
just want simple, common touch tasks - zoom, scroll, "click" - you opt for
gesture events from the OS.

In SDL I believe that the default is to request touch events, with a flag
to request OS gesture events (someone correct me if I'm wrong!). Once SDL
gets this it is again abstracted to SDL event: either touch events, system
gesture events, or another library gesture events.

Hopefully this clears things up and I haven't provided any misleading
information. <.<''

On Sun, Mar 3, 2013 at 6:47 AM, Sik the hedgehog <sik.the.hedgehog at gmail.com
> wrote:

> I was under the impression they just gave out both of them at the same
> time and it was up to the program to decide what to use. I was talking
> more about whether it's worth using the built-in gesture support
> provided by the operating system or not.
> In any case I imagine that just handling gestures off raw data
> directly may be better in the long term, especially to add support for
> gestures not supported as-is by the operating system. My only worry
> would be any system settings that could tweak said built-in gestures,
> but I could imagine that it still could be faked by retrieving the
> settings and adjusting the gesture processing accordingly.
> 2013/3/3, Nicholas Rishel <rishel.nick at gmail.com>:
> >>
> >> Just a question though: doesn't the operating system handle some
> >> gestures on its own, i.e. it parses the movement and sends an event to
> >> the program with the relevant gesture? Or is that just a
> >> misunderstanding? (or if I'm right, is there any OS where built-in
> >> support for gestures is too lackluster to be worth using?)
> >>
> >> I mention this because if the OS handles gestures then a separate
> >> library may have it hard to reuse that functionality directly. Though
> >> maybe it's better to just do everything manually in the long term and
> >> ignore the OS when it comes to gestures (except maybe for retrieving
> >> user settings, but it wouldn't need SDL for that).
> >>
> >
> > Every operating system I am familiar with that has gestures also has the
> > ability disable them to get raw touch data.
> >
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