Use this protocol to manage scale and contents for a layer hosted in a view. When a window changes its backing resolution, AppKit attempts to automatically update the
contents of all
CALayer objects in the window to match the new resolution. Layers backed by a view are updated automatically. Any layer whose
contents property is set to an
NSImage object is also updated automatically. Based on the
NSImage object’s available representations, AppKit selects an appropriate bitmapped representation, or rasterizes a resolution-independent representation at the appropriate scale factor.
For all other layers, AppKit checks whether the layer has a delegate that implements this protocol. If so, AppKit asks the layer's delegate whether it should automatically update the
contents for that layer to match the new scale factor of the window.