Trackpad mapper for Mac

This utility maps finger position on trackpad to curosr coordinate on screen.

• Lightweight
• Does not create window
• Highly configurable
• Status bar app for easy toggling absolute tracking

I personally use this to play Osu! (& Osu!lazer) on Mac with trackpad.

Usage

Open the app, there is a trackpad icon shown on the status bar. By default, mapping was disabled. To toggle mapping, click the icon and choose 'Start absolute tracking' or 'Stop absolute tracking'

Settings

In the preference window, there are three items:

1. • Use settings in header file (settings.h)
2. Trackpad region: [Region]
3. Screen region: [Region]

If you want to use your custom code to map coordinates, enable the first item. (See Modifying rule in header file)

The syntax of [Region] is lowx,lowy,upx,upy, where all numbers are floats in range 0 to 1 inclusively. These numbers are passed as command line arguments to trackpad_mapper_util. Click Apply to update the settings and remember to restart absolute tracking.

Modifying rule in header file

The default settings are stored in settings.def.h. You may want to make a copy of it and rename it to settings.h. This is where all local settings are stored.

Mapping

There is a function map in settings.h that converts normalized finger position on trackpad to absolute coordinate of cursor on Screen. MTPoint map(double, double) must be provided in settings.h as it will be called in trackpad_mapper_util.c.

MTPoint map(double normx, double normy) {
    // whole trackpad to whole screen
    MTPoint point = {
        normx * screenSize.width, normy * screenSize.height
    };
    return point;
}

Use the function rangeRatio() to map custom arrangments.

.x = rangeRatio(normx, lowx, highx),
.y = rangeRatio(normy, lowy, highy),

Set the lowx & highx to a number between 0 & 1, much like a percentage. To map the middle of the trackpad to the whole screen (for x dimension), set lowx to .25 & highx to .75.

Example code to map to top right quarter of trackpad to whole screen

MTPoint map(double normx, double normy) {
    // top right quarter of the area of trackpad to whole screen
    MTPoint point = {
            //the right half (.5 to 1) of the trackpad
            .x = rangeRatio(normx, .5, 1),
            //the top half (0 to 0.5) of the trackpad
            .y = rangeRatio(normy, 0, .5),
        };
    point.x *= screenSize.width;
    point.y *= screenSize.height;
    return point;
}

Remember to rebuild the util everytime you changed map.

Screen Size

extern CGSize screenSize declared in settings.def.h will be initialized in the main program. Do not remove the declaration.

The main program makes sure the mapped cursor coordinate is within screenSize to make the dock appear.

Emitting mouse events

It is possible choose between emitting mouse event or wrapping cursor coordinate (without mouse event). Some programs requires emitting mouse events but enabling it will cause the cursor not to magnify. Set bool emitMouseEvent = true to emit mouse event. The default value is false.

Building

Building the app requires Xcode version >= 11.

To compile, run

make release

The app is located in build/.

You may want to copy the app to the /Applications/ folder or run

make install

to do it for you.

Rebuilding Util

After you modified map, run

make util_release install_util_update

This will compile and update the util binary in the app bundle inside /Applications/

TODO List

• Create an app that can toggle absolute tracking
• Better way to change mapping rule

Reference

Where I got the MultitouchSupport.h header https://gist.github.com/rmhsilva/61cc45587ed34707da34818a76476e11