can-delete? (augments, and augmentable only) in text:file-mixin

Called before a range is deleted from the editor. If the return value is #f, then the delete will be aborted.

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

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

• (send a-text:file-mixin can-delete? start len boolean
     start : number
     len : number

  Returns false if the result of get-read-write? is true, otherwise returns the result of calling inner.