Multi-finger and path gestures need a single-pointer alternative
Aliases: pointer gestures · single-point alternative · WCAG 2.5.1
What it is
Pinch, two-finger rotate, multi-finger swipe, a circle, or any stroke that must follow a path is unusable for someone who can keep only one contact. The WCAG pointer-gestures criterion requires that anything done with a path or multiple points also be doable with a single pointer—a tap, a click, or a drag to a target. The alternative is the operation, not a larger drawing of the same complex stroke.
Why it happens
Motor impairment, missing digits, a head stick or switch, and a hand already holding the device all prevent a stable second contact or a curved path. Recognizers want relative motion (span, angle) or a shape, quantities that are undefined under one point. Kane, Wobbrock, and Ladner’s work on touch gestures for blind users also shows path error growing without visual correction. A single-pointer alternative rewrites the command from geometry into activation: a button, a stepper, or “zoom to this stop.” Move-up for reorder is one case; this leaf covers every multipoint and path command.
Studying it
Recruit people who can stably use only one point (including motor-impaired and switch users). Tasks should cover zoom, rotate, and multi-finger shortcuts. Compare gesture-only versus gesture-plus-button on independent completion, time, and need for a helper. A WCAG checklist is a start, not a substitute: a button that cannot take focus still fails.
Where it stops holding
Content that follows a one-finger pan is not a path gesture and does not need “tap instead of drag.” A game that uses two fingers as the skill itself is a different case, but menus, settings, and purchases still need a single point. If the system pinch already has button zoom, the app need not duplicate it; app-private two-finger commands must. Single-pointer alternatives address motor feasibility, not duration thresholds, and not gestures swallowed by a screen reader.
Applying it
- Give pinch plus/minus buttons or a slider; give rotate angle steppers or a 90° button; give multi-finger shortcuts a menu item.
- Turn path gestures (checkmark, circle) into select-then-choose-from-menu.
- Complete primary tasks with one finger, using a split-finger constraint glove if needed; any step that requires a second finger or a prescribed path is a defect.