calayer 的特殊属性整理

calayer:

An object that manages image-based content and allows you to perform animations on that content.

- (nullable instancetype)presentationLayer;

- (instancetype)modelLayer;

@property(nullable, strong) __kindof CALayer *mask;

@property BOOL masksToBounds;

/* Reload the content of this layer. Calls the -drawInContext: method

 * then updates the `contents' property of the layer. Typically this is

 * not called directly. */

- (void)display;

@property BOOL drawsAsynchronously

@property BOOL allowsEdgeAntialiasing

    API_AVAILABLE(macos(10.10), ios(2.0), watchos(2.0), tvos(9.0));

@property BOOL allowsGroupOpacity

/* When true, the layer is rendered as a bitmap in its local coordinate

 * space ("rasterized"), then the bitmap is composited into the

 * destination 

@property BOOL shouldRasterize;