macOS Trackpad Pressure Monitor

A Python library for monitoring Force Touch trackpad pressure on macOS.

Overview

This appears to be the first Python package for accessing trackpad pressure on macOS. Before this, you'd need to use Swift/Objective-C or write PyObjC bindings yourself.

For researchers and developers already working in Python, this means pressure data can now integrate directly with existing tools - pandas DataFrames, matplotlib plots, ML models, PsychoPy experiments, audio libraries, whatever you're already using.

Why This Exists

I needed trackpad pressure data for an HCI experiment studying cognitive load during gaming. The experiment setup required collecting pressure alongside eye tracking and EEG data - all using Python APIs.

Couldn't find a Python package for macOS trackpad pressure. Found Swift examples, but I didn't know Swift and had a tight deadline. Used PyObjC to quickly get something working for the experiment.

After finishing, a few other researchers asked for the code for their own projects. Figured I'd clean it up and put it on PyPI in case others need it too.

Installation

pip install macos-trackpad-pressure

Requirements

• macOS 10.11+ with Force Touch trackpad
• Python 3.7+

Quick Start

GUI Monitor

from trackpad_pressure import start_gui_monitor

start_gui_monitor()

A window will open - press on your trackpad with varying pressure to see real-time values (0.0 to 1.0).

With Callback Function

from trackpad_pressure import PressureMonitor

def on_pressure(pressure, stage):
    print(f"Pressure: {pressure:.3f}, Stage: {stage}")

monitor = PressureMonitor(callback=on_pressure)
monitor.start()

Command Line

trackpad-pressure

Use Cases

This library integrates with Python's ecosystem for:

• HCI Research: Collect pressure data alongside other behavioral metrics
• Data Science: Export to pandas DataFrames, visualize with matplotlib/seaborn
• Machine Learning: Training data for gesture recognition models
• Creative Coding: Pressure-sensitive art with Processing/p5
• Music Production: MIDI control via pressure (using mido, python-osc)
• Game Development: Pressure controls in Pygame or Arcade
• Accessibility Tools: Custom input methods for assistive technology
• Education: Teaching input device concepts in Python courses

API Reference

PressureMonitor

PressureMonitor(callback=None)

Parameters:

• callback (callable, optional): Function called when pressure changes. Receives (pressure: float, stage: int).

Methods:

• start(gui=True): Start monitoring. Opens GUI window by default.
• current_pressure: Property returning current pressure value (0.0-1.0)
• current_stage: Property returning Force Touch stage (0, 1, or 2)

start_gui_monitor

start_gui_monitor(monitor=None)

Launch the GUI pressure monitor window.

Parameters:

• monitor (PressureMonitor, optional): Pass a PressureMonitor instance to enable callbacks alongside GUI display.

Examples

Data Collection for Analysis

import time
import pandas as pd
from trackpad_pressure import PressureMonitor

data = []

def collect(pressure, stage):
    data.append({
        'timestamp': time.time(),
        'pressure': pressure,
        'stage': stage
    })

monitor = PressureMonitor(callback=collect)
monitor.start()

# Later: convert to DataFrame
df = pd.DataFrame(data)
df.to_csv('pressure_data.csv')

Real-time Visualization

import matplotlib.pyplot as plt
from trackpad_pressure import PressureMonitor

pressures = []

def update_plot(pressure, stage):
    pressures.append(pressure)
    if len(pressures) % 10 == 0:  # Update every 10 samples
        plt.plot(pressures)
        plt.pause(0.01)

monitor = PressureMonitor(callback=update_plot)
monitor.start()

Pressure-based Thresholds

from trackpad_pressure import PressureMonitor

def on_pressure(pressure, stage):
    if pressure < 0.3:
        print("Light touch")
    elif pressure < 0.7:
        print("Medium pressure")
    else:
        print("Heavy pressure")

monitor = PressureMonitor(callback=on_pressure)
monitor.start()

Troubleshooting

Getting 1.0 for every press?

• Requires a Force Touch trackpad (MacBook 2015+)
• Try pressing and holding with varying pressure, not just clicking
• Check System Preferences → Trackpad to ensure Force Touch is enabled

No pressure values appearing?

• Make sure the window is in focus
• Check terminal for error messages
• Verify you're pressing on the trackpad, not an external mouse

Technical Details

This package uses PyObjC to interface with macOS's Cocoa framework, specifically NSEvent.pressure() for accessing Force Touch sensor data. The API is intentionally simple: pass a callback function, get pressure values. No need to understand NSEvent or Cocoa frameworks unless you want to.

Contributing

Issues and pull requests welcome on GitHub.

License

MIT