Wednesday, July 28, 2021

It's templates all the way down - part 4

Part 1, Part 2, Part 3

After getting thouroughly nerd-sniped a few weeks back, we now have FreeBSD support through qemu in the ci-templates. This is possible through the qemu image generation we have had for quite a while now. So let's see how we can easily add a FreeBSD VM (or other distributions) to our gitlab CI pipeline:

     FDO_DISTRIBUTION_TAG: 'freebsd.0' # some value for humans to read
     - .freebsd
     - .fdo.qemu-build@freebsd
Now, so far this may all seem quite familiar. And indeed, this is almost exactly the same process as for normal containers (see Part 1), the only difference is the .fdo.qemu-build base template. Using this template means we build an image babushka: our desired BSD image is actual a QEMU RAW image sitting inside another generic container image. That latter image only exists to start the QEMU image and set up the environment if need be, you don't need to care what distribution it runs out (Fedora for now).

Because of the nesting, we need to handle this accordingly in our script: tag for the actual test job - we need to start the image and make sure our jobs are actually built within. The templates set up an ssh alias "vm" for this and the vmctl script helps to do things on the vm:

    - .freebsd
    - .fdo.distribution-image@freebsd
    # start our QEMU image
    - /app/vmctl start
    # copy our current working directory to the VM
    # (this is a yaml multiline command to work around the colon)
    - |
      scp -r $PWD vm:
    # Run the build commands on the VM and if they succeed, create a .success file
    - /app/vmctl exec "cd $CI_PROJECT_NAME; meson builddir; ninja -C builddir" && touch .success || true
    # Copy results back to our run container so we can include them in artifacts:
    - |
      scp -r vm:$CI_PROJECT_NAME/builddir .
    # kill the VM
    - /app/vmctl stop
    # Now that we have cleaned up: if our build job before
    # failed, exit with an error
    - [[ -e .success ]] || exit 1
Now, there's a bit to unpack but with the comments above it should be fairly obvious what is happening. We start the VM, copy our working directory over and then run a command on the VM before cleaning up. The reason we use touch .success is simple: it allows us to copy things out and clean up before actually failing the job.

Obviously, if you want to build any other distribution you just swap the freebsd out for fedora or whatever - the process is the same. libinput has been using fedora qemu images for ages now.

Tuesday, July 27, 2021

libinput and hold gestures

Thanks to the work done by Josè Expòsito, libinput 1.19 will ship with a new type of gesture: Hold Gestures. So far libinput supported swipe (moving multiple fingers in the same direction) and pinch (moving fingers towards each other or away from each other). These gestures are well-known, commonly used, and familiar to most users. For example, GNOME 40 recently has increased its use of touchpad gestures to switch between workspaces, etc. Swipe and pinch gestures require movement, it was not possible (for callers) to detect fingers on the touchpad that don't move.

This gap is now filled by Hold gestures. These are triggered when a user puts fingers down on the touchpad, without moving the fingers. This allows for some new interactions and we had two specific ones in mind: hold-to-click, a common interaction on older touchscreen interfaces where holding a finger in place eventually triggers the context menu. On a touchpad, a three-finger hold could zoom in, or do dictionary lookups, or kill a kitten. Whatever matches your user interface most, I guess.

The second interaction was the ability to stop kinetic scrolling. libinput does not actually provide kinetic scrolling, it merely provides the information needed in the client to do it there: specifically, it tells the caller when a finger was lifted off a touchpad at the end of a scroll movement. It's up to the caller (usually: the toolkit) to implement the kinetic scrolling effects. One missing piece was that while libinput provided information about lifting the fingers, it didn't provide information about putting fingers down again later - a common way to stop scrolling on other systems.

Hold gestures are intended to address this: a hold gesture triggered after a flick with two fingers can now be used by callers (read: toolkits) to stop scrolling.

Now, one important thing about hold gestures is that they will generate a lot of false positives, so be careful how you implement them. The vast majority of interactions with the touchpad will trigger some movement - once that movement hits a certain threshold the hold gesture will be cancelled and libinput sends out the movement events. Those events may be tiny (depending on touchpad sensitivity) so getting the balance right for the aforementioned hold-to-click gesture is up to the caller.

As usual, the required bits to get hold gestures into the wayland protocol are either in the works, mid-flight or merge-ready so expect this to hit the various repositories over the medium-term future.