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Editorial Team
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Asked: 2026-05-28T06:19:11+00:00

I understand that this response clearly states that this is not possible without a

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I understand that this response clearly states that this is not possible without a private function call. Therefore, according to Apple’s terms, this approach cannot be used on an App Store app.

However, some apps already seem to use this function call:

  • Penultimate for actual palm rejection without a predefined rejection area like in Note Taker HD
  • Virtuoso for pressure sensitivity, which they call “TrueVelocity 2”
  • GarageBand also for pressure sensitivity

Clearly, this approach is already widely used in App Store apps despite Apple’s restrictions.

tl;dr What is the private function call on iOS to get touch size?

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1 Answer

  1. Editorial Team

    Size and pressure are two different animals. Penultimate most likely tests for a large amount of touches in a certain area (palms have a large area after all, generate tons of touches).

    Touch “size” does not exist. IOS touch events are generated when a finger contacts the screen. The OS then takes a center point from the touch and that’s what you get. It’s not a CGRect, it’s a CGPoint.

    Pressure is ‘easier’ though. see here for a workaround: Tap pressure strength detection using accelerometer

    And while I see you’re in the market for private API’s, github hosts a number of class dumps: http://github.com/kennytm/iphone-private-frameworks and https://github.com/nst/iOS-Runtime-Headers

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