Touchpad Input (MVP)

New macOS input interface where a keyboard is emulated on the trackpad for silent typing.

MVP Goal

Build a desktop app that converts multi-touch trackpad interactions into text with low noise and fast feedback.

For MVP we will type inside the app first (not system-wide input injection yet).

User Story (MVP)

As a user, I can place multiple fingers on the MacBook trackpad and produce letters/commands without pressing physical keys, so I can type quietly.

MVP Scope

1. Trackpad touch capture
   • Detect individual touches and positions.
   • Support concurrent touches (multi-finger).
2. Touch-to-key mapping
   • Map touch coordinates to a key grid.
   • Emit a character when a touch begins in a region.
3. Text output buffer
   • Show produced characters in an in-app text area.
4. Force Touch hook (experimental)
   • Detect pressure changes where available.
   • Map pressure thresholds to alternate behavior (ex: Shift/delete).
5. Debug visualization
   • Show current touch points and mapped keys for tuning.

Explicitly Out of Scope (for now)

• System-wide keyboard emulation.
• Full keyboard layout parity.
• Predictive text/autocorrect.
• Accessibility/permission polish.
• Production packaging/distribution.

Technical Plan

1. Create a macOS app shell with AppKit touch-capturing view.
2. Implement a simple key grid model (letters + space + delete).
3. Add a session state object to collect emitted characters.
4. Add pressure event handling and simple action mapping.
5. Add metrics logging (touch count, key hit rate) for tuning.

Milestones

1. M1: Input Capture
   • Touch events visible on screen.
2. M2: Character Emission
   • Touch regions emit characters into output.
3. M3: Multi-touch + Pressure
   • Multiple simultaneous touches handled correctly.
   • Pressure action path tested on supported hardware.
4. M4: Stability Pass
   • Reduce accidental hits and improve mapping consistency.

Current Status

• M1: Touch capture working (MultitouchSupport bridge, live finger dots, event log)
• M2: Character emission (QWERTY key grid, output buffer, force-press alt chars, key grid overlay)
• M3: Multi-touch + pressure handling (modifier-hold zones: shift + delete corners)
• M4: Stability pass (contact-size filter, zone cooldown, adjustable pressure floor, settings panel)

Run

Requirements: macOS 11+, Xcode command-line tools or full Xcode.

swift build
swift run

Accessibility permission required: On first launch, macOS will prompt for Accessibility access (needed for the global key monitor that toggles capture). Grant it in System Settings → Privacy & Security → Accessibility.

Once running, double-tap either Control key to start/stop touch capture.