circulartrackpad

A small userspace daemon that makes the circular ring gesture on the Panasonic Let's Note trackpad work as a scroll wheel under Wayland.

Panasonic Let's Note laptops ship with a distinctive round trackpad whose outer ring is meant to be used as a rotary scroll control. Under X11 this was handled by the old xf86-input-synaptics driver (CircularScrolling option). libinput — which every Wayland compositor uses — dropped circular scroll support, so on Wayland the ring zone just moves the pointer like any other spot on the pad.

circulartrackpad restores the feature in userspace:

1. Grabs the real trackpad's evdev node exclusively.
2. Creates a virtual pointer device via uinput.
3. Classifies each touch: the inner disc becomes pointer motion, the outer ring becomes REL_WHEEL ticks based on angular movement.

The compositor sees a plain mouse-like device, so it works in GNOME, KDE, Sway, or anything else — no extensions or plugins needed.

Hardware

Developed and tested on a Panasonic Let's Note with a Synaptics TM3562-003 touchpad (HID 06cb:cdea). Other Let's Note models with a different touchpad controller will need the vendor/product IDs in install.sh and the coordinate range in src/main.rs adjusted — see Porting below.

Install

Requires Rust (stable) and a Linux system with udev and uinput.

git clone https://github.com/mikiobraun/circulartrackpad
cd circulartrackpad
./install.sh

The installer:

• builds the release binary
• copies it to /usr/local/bin/circulartrackpad
• writes a udev rule to /etc/udev/rules.d/70-circulartrackpad.rules that grants the active local-seat user access to the trackpad and /dev/uinput via POSIX ACLs (systemd uaccess)
• reloads udev

Log out and back in once after install so the ACLs apply, then run:

circulartrackpad --help

No sudo, no input group membership needed — only the user currently logged in at the physical seat can access the devices, and access is revoked on logout.

Usage

circulartrackpad [OPTIONS]

  -d, --device <DEVICE>    Input device path [default: auto-detect]
  -p, --pointer <POINTER>  Pointer sensitivity multiplier [default: 1.5]
  -s, --scroll <SCROLL>    Scroll ticks per radian of ring rotation [default: 5]
  -r, --ring <RING>        Ring threshold as fraction of max radius [default: 0.65]
  -i, --invert-scroll      Invert scroll direction
      --no-tap             Disable tap-to-click
      --tap-timeout <MS>   Tap timeout in milliseconds [default: 180]
      --tap-move-threshold <UNITS>
                           Tap movement threshold in raw coordinate units [default: 20]

By default the daemon auto-detects the Panasonic trackpad by its reported name (Synaptics TM3562-003). You only need -d if your trackpad shows up under a different name or you want to use an explicit event node.

Touch the inner area to move the pointer; slide your finger around the outer ring to scroll. Lower --ring values make the ring zone wider (easier to stay in while scrolling); higher values make it thinner.

Tap-to-click is enabled by default: a quick, single-finger tap in the inner zone emits a left button click, and a quick two-finger tap emits a right button click. Use --no-tap to disable this, or adjust the --tap-timeout and --tap-move-threshold if you find taps are being missed or triggered accidentally.

Running at login

Once you're happy with the options, run:

./enable-autostart.sh -p 1.5 -s 5 -r 0.65

Any arguments you pass to the script are baked into the systemd user unit's ExecStart. It writes ~/.config/systemd/user/circulartrackpad.service, reloads the user daemon, and enables + starts the service. To change the options later either re-run the script or edit the unit file directly and systemctl --user daemon-reload && systemctl --user restart circulartrackpad.

Porting to other hardware

If your trackpad reports different HID IDs or a different coordinate range, two spots need updating:

1. install.sh — change VENDOR_ID / PRODUCT_ID to match your device (find them with cat /proc/bus/input/devices).
2. src/main.rs — the PAD_MAX constant assumes ABS_X/ABS_Y go from 0 to 528. Check your device with sudo evtest and adjust if different. The classifier assumes a square, circular pad centered on the origin of the coordinate space.

How it works

The daemon reads multitouch events (ABS_MT_SLOT, ABS_MT_POSITION_X/Y, ABS_MT_TRACKING_ID) and on each SYN_REPORT inspects slot 0 (the primary finger):

• If the finger is within ring of the max radius from center, it's in the ring zone: compute the polar angle, take the delta from the previous frame (with wraparound handling), accumulate fractional scroll ticks, and emit REL_WHEEL.
• Otherwise it's in the inner zone: emit REL_X / REL_Y deltas.

Physical button events (BTN_LEFT, BTN_RIGHT) are forwarded unchanged. In addition, because the daemon exclusively grabs the real touchpad, tap-to-click is implemented in userspace: a short, single-finger touch in the inner zone synthesizes BTN_LEFT, and a short two-finger touch synthesizes BTN_RIGHT.

License

MIT — see LICENSE.