can-insert? (augments, and augmentable only) in mode:host-text-mixin

Called before items are inserted into the editor. If the return value is #f, then the insert will be aborted.

The editor is internally locked for writing during a call to this method (see also Locks). Use after-insert to modify the editor, if necessary.

See also on-insert, after-insert, and on-edit-sequence.

• (send a-mode:host-text-mixin can-insert? orig super-call start len ???
     orig : ???
     super-call : (??? -> ???)
     start : ??
     len : ??

  If a surrogate is set, calls the surrogate with the arguments it was passed, plus this and a function that calls the super method.

  if a surrogate is not set, calls the super method and returns that result.