libinput is done

Don't panic. Of course it isn't. Stop typing that angry letter to the editor and read on. I just picked that title because it's clickbait and these days that's all that matters, right?

With the release of libinput 1.4 and the newest feature to add tablet pad mode switching, we've now finished the TODO list we had when libinput was first conceived. Let's see what we have in libinput right now:

• keyboard support (actually quite boring)
• touchscreen support (actually quite boring too)
• support for mice, including middle button emulation where needed
• support for trackballs including the ability to use them rotated and to use button-based scrolling
• touchpad support, most notably:
  • proper multitouch support on touchpads [1]
  • two-finger scrolling and edge scrolling
  • tapping, tap-to-drag and drag-lock (all configurable)
  • pinch and swipe gestures
  • built-in palm and thumb detection
  • smart disable-while-typing without the need for an external process like syndaemon
  • more predictable touchpad behaviours because everything is based on physical units [2]
  • a proper API to allow for kinetic scrolling on a per-widget basis
• tracksticks work with middle button scrolling and communicate with the touchpad where needed
• tablet support, most notably:
  • each tool is a separate entity with its own capabilities
  • the pad itself is a separate entity with its own capabilities and events
  • mode switching is exported by the libinput API and should work consistently across callers
• a way to identify if multiple kernel devices belong to the same physical device (libinput device groups)
• a reliable test suite
• Documentation!

The side-effect of libinput is that we are also trying to fix the rest of the stack where appropriate. Mostly this meant pushing stuff into systemd/udev so far, with the odd kernel fix as well. Specifically the udev bits means we

• know the DPI density of a mouse
• know whether a touchpad is internal or external
• fix up incorrect axis ranges on absolute devices (mostly touchpads)
• try to set the trackstick sensitivity to something sensible
• know when the wheel click is less/more than the default 15 degrees

And of course, the whole point of libinput is that it can be used from any Wayland compositor and take away most of the effort of implementing an input stack. GNOME, KDE and enlightenment already uses libinput, and so does Canonical's Mir. And some distribution use libinput as the default driver in X through xf86-input-libinput (Fedora 22 was the first to do this). So overall libinput is already quite a success.

The hard work doesn't stop of course, there are still plenty of areas where we need to be better. And of course, new features come as HW manufacturers bring out new hardware. I already have touch arbitration on my todo list. But it's nice to wave at this big milestone as we pass it into the way to the glorious future of perfect, bug-free input. At this point, I'd like to extend my thanks to all our contributors: Andreas Pokorny, Benjamin Tissoires, Caibin Chen, Carlos Garnacho, Carlos Olmedo Escobar, David Herrmann, Derek Foreman, Eric Engestrom, Friedrich Schöller, Gilles Dartiguelongue, Hans de Goede, Jackie Huang, Jan Alexander Steffens (heftig), Jan Engelhardt, Jason Gerecke, Jasper St. Pierre, Jon A. Cruz, Jonas Ådahl, JoonCheol Park, Kristian Høgsberg, Krzysztof A. Sobiecki, Marek Chalupa, Olivier Blin, Olivier Fourdan, Peter Frühberger, Peter Hutterer, Peter Korsgaard, Stephen Chandler Paul, Thomas Hindoe Paaboel Andersen, Tomi Leppänen, U. Artie Eoff, Velimir Lisec.

Finally: libinput was started by Jonas Ådahl in late 2013, so it's already over 2.5 years old. And the git log shows we're approaching 2000 commits and a simple LOCC says over 60000 lines of code. I would also like to point out that the vast majority of commits were done by Red Hat employees, I've been working on it pretty much full-time since 2014 [3]. libinput is another example of Red Hat putting money, time and effort into the less press-worthy plumbing layers that keep our systems running. [4]

[1] Ironically, that's also the biggest cause of bugs because touchpads are terrible. synaptics still only does single-finger with a bit of icing and on bad touchpads that often papers over hardware issues. We now do that in libinput for affected hardware too.
[2] The synaptics driver uses absolute numbers, mostly based on the axis ranges for Synaptics touchpads making them unpredictable or at least different on other touchpads.
[3] Coincidentally, if you see someone suggesting that input is easy and you can "just do $foo", their assumptions may not match reality
[4] No, Red Hat did not require me to add this. I can pretty much write what I want in this blog and these opinions are my own anyway and don't necessary reflect Red Hat yadi yadi ya. The fact that I felt I had to add this footnote to counteract whatever wild conspiracy comes up next is depressing enough.