A Boolean value that determines whether the layer presents its content using a Core Animation transaction.
- iOS 8.0+
- macOS 10.11+
- tvOS 9.0+
- Core Animation
By default this value is
CAMetal displays the output of a rendering pass to the display as quickly as possible and asynchronously to any Core Animation transactions. However, if your game or app combines Metal and Core Animation content, it's not guaranteed that your Metal content will arrive in the same frame as your Core Animation content. This could be an issue if, for example, your app draws UIKit content (such as labels with a target position and time) over the top of your
CAMetal and the two domains need to be synchronized.
Setting this value to
true changes this default behavior so that your
CAMetal displays its drawable content synchronously, using whichever Core Animation transaction is current at the time the drawable’s
present() method is called.
However, if you allow Metal to choose when to call the present method (by using the
present(_:) method of a command buffer), the transaction during which you scheduled presentation might end before the drawable is ready to be presented. To avoid this situation, commit the command buffer and call its
wait method to synchronously wait until the drawable is ready, then call the drawable’s
present() method directly.