libinput: Switches

Switches

libinput supports a couple of switches.

Unlike button events that come in press and release pairs, switches are usually toggled once and left at the setting for an extended period of time.

Only some switches are handled by libinput, see libinput_switch for a list of supported switches. Switch events are exposed to the caller, but libinput may handle some switch events internally and enable or disable specific features based on a switch state.

The order of switch events is guaranteed to be correct, i.e., a switch will never send consecutive switch on, or switch off, events.

# Lid switch handling

Where available, libinput listens to devices providing a lid switch. The evdev event code `EV_SW` `SW_LID` is provided as LIBINPUT_SWITCH_LID. If devices with a lid switch have a touchpad device, the device is disabled while the lid is logically closed. This is to avoid ghost touches that can be caused by interference with touchpads and the closed lid. The touchpad is automatically re-enabled whenever the lid is openend.

This handling of lid switches is transparent to the user, no notifications are sent and the device appears as enabled at all times.

On some devices, the device's lid state does not always reflect the physical state and the lid state may report as closed even when the lid is physicall open. libinput employs some heuristics to detect user input (specificially typing) to re-enable the touchpad on those devices.

# Tablet mode switch handling

Where available, libinput listens to devices providing a tablet mode switch. This switch is usually triggered on devices that can switch between a normal laptop layout and a tablet-like layout. One example for such a device is the Lenovo Yoga.

The event sent by the kernel is `EV_SW` `SW_TABLET_MODE` and is provided as LIBINPUT_SWITCH_TABLET_MODE. When the device switches to tablet mode, the touchpad and internal keyboard are disabled. If a trackpoint exists, it is disabled too. The input devices are automatically re-enabled whenever tablet mode is disengaged.

This handling of tablet mode switches is transparent to the user, no notifications are sent and the device appears as enabled at all times.