A positive integer that identifies the drawable.
- iOS 10.3+
- macOS 10.15.4+
- Mac Catalyst 13.4+
- tvOS 10.3+
Drawable objects are usually owned by some other object, such as a
CAMetal. The owning object gives the first drawable it creates an ID of
0, and it increments the ID by
1 for each additional drawable it creates.