A swipe is jointly classified by direction, distance, and velocity

What it is

A swipe (flick) is a short, directed slide that becomes a discrete command at lift: next page, dismiss a card, next story. It is not carrying an object, not 1:1 tracking of content, and not letting a list coast after lift. Direction, distance, and velocity must all qualify. Fail any one, and the motion should fall back to tap, drag, or pan.

Why it happens

A swipe is ballistic: people aim a direction, accelerate, and at lift hand the rest of the intent to the interface. The recognizer reads three quantities at lift—axis angle, path length, terminal speed. Direction alone would promote a slow drag into a page flip. Distance alone would promote a hesitant long pan into a command. Speed alone would promote a jitter spike into a swipe. The three gates together split “I want a command” from “I am still manipulating.” After lift the content may snap to the next detent; it should not inherit a long coast proportional to terminal speed—that is a fling’s job.

Studying it

On a pager and a card stack, collect traces and compare human labels (“meant to flip / meant to pan for a closer look / meant to tap”) with the classifier. Independent variables include velocity threshold, distance threshold, and the allowed direction sector; dependent measures include misses, pans taken as flips, and flips taken as taps. Terminal speed should use a window of tens of milliseconds before lift, not the whole-path average, or a slow-start, fast-finish swipe is averaged away. Portrait phone and landscape tablet should be split: peak wrist speed differs.

Where it stops holding

System gestures that start at the bezel also satisfy the three quantities, but origin is their identity; they are not ordinary swipes. Revealing actions on a list row is one consequence inside the swipe family; classification still uses the three gates, and the revealed actions are a different group. A trackpad two-finger swipe is gained, so desktop pixel speeds are not touchscreen thresholds. A game thumbstick treats sustained direction as an analog value, which is not a discrete swipe.

Applying it

• Give a swipe a direction sector, a minimum displacement, and a lift velocity; fire the command only if all three pass, otherwise hand the pointer to pan or tap.
• After a command swipe, snap to the next detent (one page, one card). Do not slide several more detents in proportion to lift speed.
• Have people do ten of each: a committed flip, a slow nudge of the view, a tap. See which class the classifier gets wrong. Products that tune only one threshold usually break the other two classes suddenly.

Related

• Same group: C3.05.2 Angular tolerance on a swipe sets the misclassification rate · C3.05.3 A swipe-triggered action should be undoable by a reverse swipe · C3.05.4 A swipe leaves no trace and needs a visual hint that it exists
• Adjacent: C3.06 Fling and inertia · C3.07 Pan
• Search: swipe · flick · velocity threshold