Instance Property

mask

An optional layer whose alpha channel is used to mask the layer’s content.

Declaration

@property(strong) __kindof CALayer *mask;

Discussion

The layer’s alpha channel determines how much of the layer’s content and background shows through. Fully or partially opaque pixels allow the underlying content to show through, but fully transparent pixels block that content.

The default value of this property is nil. When configuring a mask, remember to set the size and position of the mask layer to ensure it is aligned properly with the layer it masks.

Special Considerations

The layer you assign to this property must not have a superlayer. If it does, the behavior is undefined.

See Also

Modifying the Layer’s Appearance

contentsGravity

A constant that specifies how the layer's contents are positioned or scaled within its bounds.

Contents Gravity Values

The contents gravity constants specify the position of the content object when the layer bounds is larger than the bounds of the content object. They are used by the contentsGravity property.

opacity

The opacity of the receiver. Animatable.

hidden

A Boolean indicating whether the layer is displayed. Animatable.

masksToBounds

A Boolean indicating whether sublayers are clipped to the layer’s bounds. Animatable.

doubleSided

A Boolean indicating whether the layer displays its content when facing away from the viewer. Animatable.

cornerRadius

The radius to use when drawing rounded corners for the layer’s background. Animatable.

borderWidth

The width of the layer’s border. Animatable.

borderColor

The color of the layer’s border. Animatable.

backgroundColor

The background color of the receiver. Animatable.

shadowOpacity

The opacity of the layer’s shadow. Animatable.

shadowRadius

The blur radius (in points) used to render the layer’s shadow. Animatable.

shadowOffset

The offset (in points) of the layer’s shadow. Animatable.

shadowColor

The color of the layer’s shadow. Animatable.

shadowPath

The shape of the layer’s shadow. Animatable.

style

An optional dictionary used to store property values that aren't explicitly defined by the layer.

allowsEdgeAntialiasing

A Boolean indicating whether the layer is allowed to perform edge antialiasing.

allowsGroupOpacity

A Boolean indicating whether the layer is allowed to composite itself as a group separate from its parent.