Allows the delegate to return an additional rectangle in which mouse clicks will initiate divider dragging.
- macOS 10.5+
The split view that sent the message.
The index of the divider.
An additional rectangle in which mouse clicks should initiate divider dragging. The rectangle should be expressed in the coordinate system defined by
NSZero indicates no additional dragging rectangle is desired.
If a split view has no delegate, or if its delegate does not respond to this message, only mouse clicks within the effective frame of a divider initiate divider dragging.