Returns the current graphics context.
- iOS 2.0+
- tvOS 9.0+
- watchOS 2.0+
The current graphics context.
The current graphics context is
nil by default. Prior to calling its
draw method, view objects push a valid context onto the stack, making it current. If you are not using a
UIView object to do your drawing, however, you must push a valid context onto the stack manually using the
This function may be called from any thread of your app.