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  "title" : "splitView(_:additionalEffectiveRectOfDividerAt:)"
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# splitView(_:additionalEffectiveRectOfDividerAt:)

Allows the delegate to return an additional rectangle where mouse clicks can initiate divider dragging.

```
@MainActor optional func splitView(_ splitView: NSSplitView, additionalEffectiveRectOfDividerAt dividerIndex: Int) -> NSRect
```

## Parameters

`splitView`

The split view that sends the message.

`dividerIndex`

The index of the divider.

## Return Value

An additional rectangle, in the coordinate system that `splitView` defines, where mouse clicks can initiate divider dragging. Returning <doc://com.apple.documentation/documentation/Foundation/NSZeroRect> indicates no additional dragging rectangle is necessary.

## Discussion

If a split view has no delegate, or if its delegate doesn’t respond to this message, only mouse clicks within the effective frame of a divider initiate divider dragging.

---

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