A layer that provides a way to asynchronously provide tiles of the layer's content, potentially cached at multiple levels of detail.
- iOS 2.0+
- macOS 10.5+
- tvOS 9.0+
As more data is required by the renderer, the layer's
draw(_: method is called on one or more background threads to supply the drawing operations to fill in one tile of data. The clip bounds and current transformation matrix (CTM) of the drawing context can be used to determine the bounds and resolution of the tile being requested.
Regions of the layer may be invalidated using the
set method however the update will be asynchronous. While the next display update will most likely not contain the updated content, a future update will.