Pixel Touchpad

A minimal Android app that turns a phone's display into a virtual touchpad for controlling the cursor on an external monitor (desktop mode).

Features

• Cursor movement – one finger, relative movement like a laptop touchpad
• Click – short one-finger tap
• Scroll – two-finger vertical drag

Requirements

• Android 9+ (Pixel 8 with Android 15/16/17 ideal)
• Shizuku installed and running
• External display connected via USB-C
• "Universal cursor" turned OFF — Settings → Connected devices → External displays → (built-in display) → this toggle only appears when "Mirror built-in display" is off. With it on, Android lets the system cursor roam across both the phone screen and the external display, which fights with this app (the phone screen is a touch surface only — there's nothing useful for a cursor to do there). Leave it off so the cursor stays reliably on the external display.

How it works

1. The app connects to Shizuku and starts a privileged service
2. The service uses InputManager.injectInputEvent() to inject mouse events on the secondary display
3. TouchpadView on the phone captures touch gestures and translates them into cursor movement

Local build

To build directly on your own x86_64 Linux machine (no waiting on CI), see BUILD.md.

Build via GitHub Actions

1. Create a repository on GitHub

Go to github.com/new and create a new repository (e.g. PixelTouchpad).

2. Push the code

cd PixelTouchpad
git init
git add .
git commit -m "Initial commit"
git branch -M main
git remote add origin https://github.com/YOUR_USERNAME/PixelTouchpad.git
git push -u origin main

3. Wait for the build

• Go to the Actions tab in the repository
• The build starts automatically on push
• Once done (about 3-5 minutes), click the run → Artifacts → download PixelTouchpad-debug.zip

4. Install on the phone

• Unzip the ZIP – it contains an .apk file
• Transfer it to the phone and install it (allow installs from unknown sources)

Usage

1. Start Shizuku and activate the service (Wireless debugging)
2. Connect the monitor via a USB-C cable
3. Turn on desktop mode in Developer options
4. Open Pixel Touchpad
5. Tap Connect – the app connects to Shizuku and finds the external display
6. The touchpad activates – move your finger across the phone's display

Customization

Touchpad sensitivity

In TouchpadView.kt:

var sensitivity = 2.5f        // cursor speed
var scrollSensitivity = 0.03f // scroll speed

Click detection

In TouchpadView.kt:

private val tapMaxDuration = 200L   // max touch duration for a click (ms)
private val tapMaxDistance = 30f     // max finger movement for a click (px)

Known limitations

• The cursor resets to the middle of the display after an app restart
• Requires restarting Shizuku after a phone restart

License

MIT – do whatever you want with it.