A move drag works from the notes as they were when it began, so each update re-applies one delta rather than accumulating rounding. The session holds that snapshot: say when the drag starts, how far it has moved, and whether it ended or was cancelled.

cancelDrag

open override fun cancelDrag()

commit

open override fun commit(app: AppModel): Boolean

Writes the session back to the clip, through the undo history.

createNote

open override fun createNote(startSeconds: Double, durationSeconds: Double, note: Int, velocity: Float)

deleteNote

open override fun deleteNote(index: Int)

finishDrag

open override fun finishDrag(index: Int, originalStart: Double, originalEnd: Double, originalNote: Int)

isNoteSelected

open override fun isNoteSelected(index: Int): Boolean

loadNotes

open override fun loadNotes(snapshot: PianoRollSnapshot?)

matchesSource

open override fun matchesSource(snapshot: PianoRollSnapshot): Boolean

Whether this session was built from that snapshot's UMP stream. False means the clip changed underneath and the session must be reloaded — which is what stops an edit being applied to a clip it was not made against.

moveSelection

open override fun moveSelection(timeDeltaSeconds: Double, pitchDelta: Int)

performAction

open override fun performAction(action: PianoRollAction, pasteSeconds: Double = 0.0)

resizeNote

open override fun resizeNote(index: Int, startSeconds: Double, durationSeconds: Double, note: Int)

selectNote

open override fun selectNote(index: Int, additive: Boolean = false, toggle: Boolean = false)

index -1 clears the selection.