An optional gesture boundary hint on a continuous mutation verb (see the undo/redo
spec, "Coalescing"). The web-ui knows exactly where a fader/knob drag starts (pointer
down) and ends (pointer up); end deterministically closes the undo coalescing group so
"drag, pause, drag again" lands as two undo entries. Additive + defaulted-absent — every
existing handler ignores it; only the undo recorder reads it.
An optional gesture boundary hint on a continuous mutation verb (see the undo/redo spec, "Coalescing"). The web-ui knows exactly where a fader/knob drag starts (pointer down) and ends (pointer up);
enddeterministically closes the undo coalescing group so "drag, pause, drag again" lands as two undo entries. Additive + defaulted-absent — every existing handler ignores it; only the undo recorder reads it.