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        AppBITS: TrackWeight Turns Your Trackpad into a Scale (Sort Of)

   Adam Engst

   At the beloved MacHack conference of yesteryear, the main event was
   always the MacHax Best Hack Contest (don't ask about the different
   spelling). For their contest entries, some of the top Mac programmers
   would stay awake for up to 72 hours straight coding. On the final day
   of the conference, everyone would gather in an auditorium as developer
   after developer showed off their hacks. Audience reaction was
   enthusiastic, with hacks that aimed to improve the overall Mac user
   experience often being met with derisive cries of 'Useful!'

   In 1999, Lisa Lippincott's Unfinder won first place despite facing
   numerous catcalls, since it was the first time we saw Undo available
   for non-destructive actions in the Finder, such as moving files; see
   '[1]The MacHack Hack Contest 1999,' 12 July 1999. (In contrast,
   asciiMac, the 1998 winner from Alexandra Ellwood and Miro Jurisic,
   converted the entire Mac interface to ASCII graphics in real time,
   which no one mocked as useful; see '[2]Moof on the Hoof: MacHack '98,'
   6 July 1998.)

   All that's by way of introducing a new Mac app that would have fit in
   perfectly at MacHack:[3]TrackWeight, which turns the Mac's trackpad
   into a precision scale for weighing small objects. On the face of
   things, this would seem like a handy feature, but the technical
   requirements for implementing TrackWeight make it the perfect MacHack
   novelty app. The problem is that trackpad pressure events are generated
   only when capacitance is detected on the trackpad surface'in other
   words, your finger or another conductive object must be in contact with
   the trackpad. When that's the case, the trackpad's Force Touch sensors
   provide pressure readings that can be calibrated and converted into
   weight measurements.

   It's nearly impossible to rest your finger on the trackpad, press the
   Space bar to calibrate, and then add something else to the trackpad to
   weigh it without changing the pressure applied by your finger. It can
   be done'I glimpsed a few correct weights while testing'but I spent
   vastly more time failing to get accurate measurements than succeeding.
   Neither a pen with a conductive nub nor a plum'both of which could
   control the pointer'provided a stable weight and conductivity.

   I'm rooting for TrackWeight's developers to figure out a workaround for
   the required finger pressure so the app becomes actually useful, but
   until then, it's mostly an inspired hack that would have earned
   applause from the MacHack crowd.

References

   Visible links
   1. https://tidbits.com/1999/07/12/the-machack-hack-contest-1999/
   2. https://tidbits.com/1998/07/06/moof-on-the-hoof-machack-98/
   3. https://github.com/KrishKrosh/TrackWeight

   Hidden links:
   4. https://tidbits.com/uploads/2025/07/TrackWeight.png

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