Apps should not occupy system-reserved multi-finger gestures

What it is

Even if system gestures are off in some build and the app briefly receives three-finger events, binding a feature to that reserved pose is still wrong. The reserved set is a platform contract: people have learned “three-finger up” as multitasking, not as your canvas tool. Occupying a reserved pose digs a hole in their system model.

Why it happens

Gesture memory is cross-app. People use the same shell gestures to escape on the home screen, in mail, in a game. If an app locally remaps three-finger-up to “draw a line,” that muscle memory will dump them into multitasking in the next app, or turn the escape hatch into line-drawing in this one. Developers who disable system gestures in a simulator get the illusion that “our three-finger works,” then the contract returns on a real device and the feature evaporates. The reserved set also grows with OS versions (a new four-finger pinch to home); a free count today may be claimed tomorrow.

Studying it

List reserved gestures in the target OS docs and intersect with gestures the app registers. For the intersection, run a transfer task: learn the gesture on the system home screen, then do “the same motion” inside the app. Count clashes between expected (system) and app meaning. Treat “we only turned system gestures off in the beta” as a methodological trap and report it separately.

Where it stops holding

A kiosk or exhibit machine you fully control, with no shell gestures, can have an empty reserved set. Enterprise MDM can disable gesture navigation; off those managed devices the contract returns. Two fingers are outside most phone reserved sets, so occupying two fingers is usually legal; copying that policy onto iPad three-finger is not.

Applying it

• Before building, copy the current platform reserved table and subtract it from the app vocabulary. Three- and four-finger swipes and four-finger pinches should not appear outside that difference.
• Accept on a real device with default system gestures, not with a “disable gesture navigation” debug switch as the default.
• Have someone who only knows system gestures, and has not read your help, three-finger-swipe up in the app. They should enter multitasking, not fire a hidden tool. If they fire your tool, you occupied a reserved pose.

Related

• Same group: C3.12.1 System-level multi-finger gestures take priority over app gestures · C3.12.3 System gestures truncate same-shape gestures inside the app
• Adjacent: C3.31 System versus app gesture priority · C3.34 Cultural and regional gesture differences
• Search: reserved gestures · platform convention · do not override