Returns whether the marker should be removed.
- macOS 10.0+
The ruler view sending the message.
The marker to be removed.
a can be removed,
Only markers that represent tab stops can be removed. This method returns
a represents an
false otherwise. Because this method can be invoked repeatedly as the user drags a ruler marker, it returns that value immediately. If the change is allowed and the user actually removes the marker, the receiver is also sent a