libinput update

libinput is a shared input stack for Wayland compositors

libinput update

Features added since XDC 2014:

edge scrolling, middle button scrolling, natural scrolling, scroll sources, configurable pointer speed, per-device acceleration methods, unaccelerated motion events, hovering fingers on touchpads, click method configuration, device capability queries, device groups, touchpad gestures, touchpad size required, disable-while-typing, tap drag-lock, thumb detection, usec timestamps

libinput and udev

We're trying to use the stack below us, and fix it where needed.

The udev hwdb is a hard requirement.

libinput and udev

udev decides the type of device

• ID_INPUT_MOUSE, ID_INPUT_TOUCHPAD

→ A single place in the system where device types are assigned.

libinput and udev

Pointer acceleration constants

• MOUSE_DPI for hardware-resolution settings
• POINTINGSTICK_SENSITIVITY adjusts kernel driver sensitivity
• POINTINGSTICK_CONST_ACCEL applies a base factor

libinput and udev

Device models and attributes

• LIBINPUT_MODEL_LENOVO_X230
• LIBINPUT_MODEL_SYNAPTICS_SERIAL_TOUCHPAD
• LIBINPUT_MODEL_ATTR_SIZE_HINT
• LIBINPUT_MODEL_ATTR_RESOLUTION_HINT

These are internal API, udev is only used as storage facility

Device groups

Some devices have multiple kernel devices

libinput assigns a single struct libinput_device_group

struct libinput_device_group *g1, *g2;

g1 = libinput_device_get_device_group(dev1);
g2 = libinput_device_get_device_group(dev2);

if (g1 == g2)
    printf("Same physical device\n");

Touchpad size

All of libinput's internal handling is in mm

Touchpads must have x/y resolutions

Pointer acceleration

Tuning the algorithm

• slow motions are decelerated, up to 70%
• "normal" movements are 1:1

See the documentation

Pointer acceleration

Different algorithms for different devices

• Lenovo x230 has a custom accel method
• Touchpad accel != pointer accel
• low-dpi mice != high-dpi mice

Pointer acceleration

A "flat" pointer acceleration profile

• for high-dpi/switchable-dpi mice

• no acceleration but a constant factor

dx/dy = dx/dx * factor

• coming up in libinput 1.1

Touchpad gestures

Swipe:

• dx/dy of the logical center (no abs coordinates)
• number of fingers

Touchpad gestures

Pinch:

• dx/dy of the logical center (no abs coordinates)
• number of fingers
• rotation in degrees
• finger spread factor

Touchpad gestures

• 2mm dead zone before we can decide whether a 2fg gesture is a gesture
• Slight bias towards scrolling
• disabled on some touchpads

Thumb detection

Click a button with a thumb while using the index

• Area and pressure-based (in theory)

Touchpads don't provide enough information, pressure is surface size and doesn't work well at the edges

Scroll sources

libinput's pointer axis events include a source

• LIBINPUT_POINTER_AXIS_SOURCE_WHEEL
• LIBINPUT_POINTER_AXIS_SOURCE_FINGER
• LIBINPUT_POINTER_AXIS_SOURCE_CONTINUOUS

No kinetic scrolling in libinput!

xf86-input-libinput

xf86-input-libinput is the X driver wrapper around libinput

A thin wrapper with almost no logic

Button drag lock

Button logically down, when physically released

• Accessibility
• identical to evdev, mouse
• should be in the compositor, but this is X...

Horizontal scrolling

• libinput always provides horizontal scroll data
• scroll events should be handled at the widget level
• Option to discard events

Future plans

• Wacom tablet support (for real!)
• "buttonset" interface
• Pointer acceleration improvements for touchpads and trackpoints
• Extended touch information (patch on list)