---
title: "splitView(_:effectiveRect:forDrawnRect:ofDividerAt:)"
framework: appkit
role: symbol
role_heading: Instance Method
path: "appkit/nssplitviewdelegate/splitview(_:effectiverect:fordrawnrect:ofdividerat:)"
---

# splitView(_:effectiveRect:forDrawnRect:ofDividerAt:)

Allows the delegate to modify the rectangle where mouse clicks initiate divider dragging.

## Declaration

```swift
@MainActor optional func splitView(_ splitView: NSSplitView, effectiveRect proposedEffectiveRect: NSRect, forDrawnRect drawnRect: NSRect, ofDividerAt dividerIndex: Int) -> NSRect
```

## Parameters

- `splitView`: The split view that sends the message.
- `proposedEffectiveRect`: The proposed rectangle where mouse clicks initiate divider dragging. The rectangle uses the coordinate system that splitView defines.
- `drawnRect`: The frame of the divider in the coordinate system that splitView defines.
- `dividerIndex`: The index of the divider.

## Return Value

Return Value A rectangle, in the coordinate system that splitView defines, where mouse clicks initiate divider dragging.

## Discussion

Discussion A split view with thick dividers proposes the drawn frame as the effective frame. A split view with thin dividers proposes an effective frame that’s a little larger than the drawn frame to make it easier for the user to grab the divider. If a split view has no delegate, or if its delegate doesn’t respond to this message, the split view behaves as if it has a delegate that returns proposedEffectiveRect when it receives this message.

## See Also

### Configuring and Drawing View Dividers

- [splitView(_:shouldHideDividerAt:)](appkit/nssplitviewdelegate/splitview(_:shouldhidedividerat:).md)
- [splitView(_:additionalEffectiveRectOfDividerAt:)](appkit/nssplitviewdelegate/splitview(_:additionaleffectiverectofdividerat:).md)