# trackscreen

Use a laptop touchscreen as a real multitouch **touchpad**. Toggle between
modes with a **five-finger tap**.

* **Touchscreen mode** (the default): nothing changes. trackscreen only reads
  the touchscreen passively, so the desktop keeps native multitouch.
* **Trackpad mode**: trackscreen grabs the touchscreen and re-emits its touches
  through a virtual touchpad ("Trackscreen Virtual Touchpad"). libinput handles
  it like any other touchpad, so you get relative pointer motion with
  acceleration, tap-to-click (1/2/3 fingers = left/right/middle), tap-and-drag,
  two-finger scrolling, pinch zoom, and 3/4-finger swipes. Configure these in
  your desktop's normal touchpad settings (KDE: System Settings -> Touchpad).

The grab exists only in trackpad mode. The kernel releases it if trackscreen
exits or crashes, so the touchscreen can't get stuck. A pen or stylus is a
separate device and is never affected.

## Requirements

Linux with libinput (Wayland or X11), Python 3 and `python-evdev`.

## Install

    ./install.sh            # udev rule (sudo) + systemd user service, starts it now

The udev rule gives the logged-in user access to touchscreens and `/dev/uinput`.
You can join the `input` group instead, but that also exposes every keyboard.

To run it by hand instead: `./trackscreen.py --debug`

## Toggling

* Five-finger tap: fingers down and up within 0.6 s, without moving.
  Tuning: `--toggle-fingers N` (0 disables it), `--tap-time`, `--tap-move`.
* `trackscreen.py --toggle`, or `pkill -USR1 -f trackscreen.py`. Bind either
  to a keyboard shortcut if you like.

A desktop notification shows the new mode (disable with `--no-notify`).

## Other laptops / tuning

* `--list-devices` shows the auto-detected touchscreen; `--device` picks one by
  path or name.
* Physical size comes from the kernel or from udev (`ID_INPUT_WIDTH_MM`), so
  pointer speed is consistent across machines. Override with `--size 307x187`.
* If the built-in display is rotated, use `--rotate 90|180|270`. A
  `LIBINPUT_CALIBRATION_MATRIX` set in udev is applied automatically
  (`--matrix` overrides it).
* `--speed 1.5` scales pointer and gesture speed on top of the desktop settings.
* `--start-mode trackpad` starts in trackpad mode.

## Caveats

* In touchscreen mode the five-finger tap also reaches the desktop as five
  touches. It is usually harmless, but it can tap whatever is under your fingers.
* If "disable touchpad when a mouse is connected" is on, it also applies to
  the virtual touchpad.