on-change-style (augmentable only) in text%

Called before the style is changed in a given range of the editor, after can-change-style? is called to verify that the change is ok. The after-change-style method is guaranteed to be called after the change has completed.

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

See also on-edit-sequence.

• (send a-text on-change-style start len) -> void
     start : exact non-negative integer
     len : exact non-negative integer