ShellIdleRegistrar typedef
ShellIdleRegistrar =
VoidCallback Function(bool delete())
Registers the shell's idle probe with its host (host embedding API spec S-4): true while no tool is part-way through a shape, so the host's own Undo and Redo wait as the shell's do. Returns the withdrawal, which the shell calls on dispose, as ShellSettleRegistrar's.
Implementation
typedef ShellIdleRegistrar = VoidCallback Function(bool Function() idle);