Base shape of every cancelable BEFORE event raised by WhiteboardState (and by
the components layered on top of it). Handlers run SYNCHRONOUSLY during the emit; any
handler may set Cancel to true and the operation is aborted before it touches
the board (no undo snapshot, no journal entry, no WhiteboardState.Changed$
emission). The matching AFTER event then never fires.
Base shape of every cancelable BEFORE event raised by WhiteboardState (and by the components layered on top of it). Handlers run SYNCHRONOUSLY during the emit; any handler may set Cancel to
trueand the operation is aborted before it touches the board (no undo snapshot, no journal entry, no WhiteboardState.Changed$ emission). The matching AFTER event then never fires.