Locking too early straightens intended diagonals

What it is

Sometimes the path is meant to be diagonal: dragging a photo into a folder on a slant, panning a canvas at 45°, moving a map east and north at once. If direction lock commits in the first few pixels, intentional diagonals are forced straight onto pure X or pure Y, and the destination is unreachable. Earliness is a timing error, not an argument that the lock should not exist.

Why it happens

A lock is an irreversible projection: once the axis is set, orthogonal delta is discarded and later slant cannot restore it. The shorter the window, the less onset noise and true slant can be told apart, so a 40° intent is read as 0°. Pagers like to lock early so the neighbour page never peeks; free canvases need to lock late or never. Premature lock feels like “the hand goes diagonal, the object slides on an axis”—proprioception splits from vision. Speed is irrelevant: a slow 45° drag is sheared the same way.

Studying it

Set drop tasks that can only be finished on a diagonal (the target is off-axis) and vary the pixels required before lock. Measures include arrival rate, heading versus a straight line, and mid-path quits. Plot “failed because locked early” and “failed because unlocked jitter” on one trade-off curve. Do not justify early lock with vertical reading tasks alone.

Where it stops holding

A purely one-dimensional picker (a time wheel) has no legal diagonal, so early lock is almost free. Magnetic alignment and grid snap can hide a straightened path and look like success. In nested orthogonal scroll, locking the axis early is choosing a layer early; the failure is the wrong container. Premature lock does not explain flicker near a velocity threshold.

Applying it

• Turn direction lock off on two-dimensional canvases and lists that accept diagonal drops, or postpone the decision until more travel.
• Pagers may lock early; do not copy that early lock onto a map.
• Place a drop target clearly off-axis: if the object reaches it only after an axis-aligned dogleg, it was straightened.

Related

• Same group: C3.28.1 After drag or scroll starts, direction lock snaps later input to the main axis · C3.28.2 Direction lock removes diagonal drift from natural hand jitter · C3.28.4 The lock window is the angle of the first pixels of travel
• Adjacent: C3.04 Drag · C3.10 Two-finger rotation
• Search: premature lock · diagonal drag · axis snap