ofxMacTrackpadPressure

macOS trackpad pressure / Force Touch support for openFrameworks.

Files

ofxMacTrackpadPressure/
├── addon_config.mk
├── src/
│   ├── ofxMacTrackpadPressure.h      // C++ header (clean, no Obj-C)
│   └── ofxMacTrackpadPressure.mm     // Objective-C++ implementation
└── example-pressure-drawing/
    └── src/
        ├── main.cpp
        ├── ofApp.h
        └── ofApp.cpp

Installation

1. Copy ofxMacTrackpadPressure/ to your openFrameworks/addons/ folder
2. Generate your project with Project Generator, include this addon
3. Or manually add the .h and .mm files to your Xcode project

Usage

#include "ofxMacTrackpadPressure.h"

ofxMacTrackpadPressure pressure;

void ofApp::setup() {
    pressure.setup();
    pressure.setEnabled(true);
    ofAddListener(pressure.pressureChanged, this, &ofApp::onPressureChanged);
}

void ofApp::onPressureChanged(ofxTrackpadPressureEventArgs& args) {
    float p = args.pressure;  // 1.0 = normal click, up to ~5.0 deep press
}

Key Points

• macOS only — uses NSEvent pressure API
• Force Touch required for variable pressure; normal trackpads return 1.0
• Events fire alongside standard OF mouseDragged — both work simultaneously
• Pressure is accumulated delta from baseline 1.0, not absolute

Controls (example)

• C — clear canvas
• Space — toggle pressure tracking on/off
• Click-and-drag — draw with pressure-sensitive width
• Deep press (Force Touch) — wider strokes