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CALayoutManager Protocol Reference

Overview

CALayoutManager is an informal protocol implemented by Core Animation layout managers. If a layer’s sublayers require custom layout you create a class that implements this protocol and set it as the layer’s layout manager using the CALayer method setLayoutManager:. Your custom layout manager is then used when the layer invokes setNeedsLayout or layoutSublayers.

Tasks

Layout Layers

• – invalidateLayoutOfLayer:
• – layoutSublayersOfLayer:

Calculate Layer Size

• – preferredSizeOfLayer:

Instance Methods

invalidateLayoutOfLayer:

Invalidates the layout of the specified layer.

- (void)invalidateLayoutOfLayer:(CALayer *)layer

Parameters

layer

The layer that requires layout.

Discussion

This method is called when the preferred size of the specified layer may have changed. The receiver should invalidate any cached state.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

CALayer.h

layoutSublayersOfLayer:

Layout each of the sublayers in the specified layer.

- (void)layoutSublayersOfLayer:(CALayer *)layer

Parameters

layer

The layer that requires layout of its sublayers.

Discussion

This method is called when the sublayers of the layer may need rearranging, and is typically called when a sublayer has changed its size. The receiver is responsible for changing the frame of each sublayer that requires layout.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

CALayer.h

preferredSizeOfLayer:

Returns the preferred size of the specified layer in its coordinate system.

- (CGSize)preferredSizeOfLayer:(CALayer *)layer

Parameters

layer

The layer that requires layout.

Return Value

The preferred size of the layer in the coordinate space of layer.

Discussion

This method is called when the preferred size of the specified layer may have changed. The receiver is responsible for recomputing the preferred size and returning it. If this method is not implemented the preferred size is assumed to be the size of the bounds of layer.

Availability

• Available in Mac OS X v10.5 and later.

Declared In

CALayer.h

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