Hi Florian,
I have a touch screen which generates a plethora of event types
according to libinput-debug-events (including what seems to be
multi-touch events). I can even see distinct events for the digitizer
pen.
However, further up the stack, all this is gone. I don't get any
two-finger scrolling, for instance. There is no right-button
emulation in Firefox, either. I can still generate primary button
click events and (single-finger) drag events, but that's about it.
Handling of touch events is up to the application. Besides the minimal single-touch to
pointer event emulation (which only applies to X11/Xwayland) there are no emulation layers
making this up for applications that don't know about touch events themselves.
GTK+3 provides built-in support for 1 finger touch scrolling, text edition popovers, text
selection handles and other touch features. App can nonetheless be developed in touch
unfriendly ways, so some some attention is needed throughout the stack. For example the
gnome HIG largely avoids popup menus, even more for stuff that is inaccessible otherwise.
Other apps/toolkits/etc have to actively take care of touch support themselves. Firefox,
despite "using" GTK+, implements itself large parts of their UI, if they
don't observe touch input, it's pretty much for them to make use of it too.
It's worth pointing out that, at least as far as gtk3 is concerned, you are expecting
the wrong gestures, scrolling happens on 1 finger input, the "long press"
gesture doesn't necessarily map to "right click", etc.
With Wayland, the pen appears to be completely dead. With X, I get
Can you interact with gnome-shell with it? or is it entirely dead?
some reaction to the pen in Xournal (some pointer indication moves),
but Xournal does not put any ink on the screen.
Not entirely sure what's up with X. As xournal is a GTK+2 application it requires
Xwayland support for it on wayland. There are already patches in Xorg patchwork adding
this missing bridging for tablet events.
How can I help to improve matters in this area?
You should perhaps file/ping bugs regarding touch support in your favorite apps, and/or
wait for ports to GTK+3.
Cheers,
Carlos