Marks a window context for update.
- iOS 2.0+
- macOS 10.0+
- tvOS 9.0+
- watchOS 2.0+
- Core Graphics
The window context to synchronize. If you pass a PDF context or a bitmap context, this function does nothing.
When you call this function, all drawing operations since the last update are flushed at the next regular opportunity. Under normal conditions, you do not need to call this function.