OptionalchildrenDrawn first in the control, so it hides with the handles and paints under them: the rotate handle.
OptionalcontextDraw the control as context: the frame of a group a selected member is inside, as Excel draws it (a dotted outline and hollow neutral handles). Its handles still resize that group.
Compass names of the handles to draw (nw, n, … se).
How the frame is mirrored: the gesture's while one is in flight, else the movable's.
OptionalisFade the control, as during a gesture. It stays mounted: the handle being dragged holds the pointer capture.
OptionalonA press on the move grip a frame too small for its handles shows in their place. Omit when the frame cannot be moved.
The pointer moved. delta is how far it is from the press, in screen pixels; keepAspect is
whether Shift is held.
The gesture was lost (pointercancel).
The pointer was released.
A press on a handle. Return false to refuse the gesture.
Degrees clockwise the frame is turned; only the cursors use it, the box turns itself.
Props of a control a content kind registers in place of the generic one (see
registerMovableRenderer): the generic control's, and what a control of its own needs.