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# CGMouseButton

Constants that specify buttons on a one, two, or three-button mouse.

```
enum CGMouseButton
```

## Overview

Quartz supports up to 32 mouse buttons. The first three buttons are specified using these three constants. Additional buttons are specified in USB order using the integers 3 to 31.

These constants are used:

- In the function [`init(mouseEventSource:mouseType:mouseCursorPosition:mouseButton:)`](/documentation/CoreGraphics/CGEvent/init(mouseEventSource:mouseType:mouseCursorPosition:mouseButton:)) to specify the button that’s changing state.
- In the function [`buttonState(_:button:)`](/documentation/CoreGraphics/CGEventSource/buttonState(_:button:)) to specify the button that’s being tested.
- To specify the value of the `kCGMouseEventButtonNumber` event field when modifying an event.

## Topics

### Constants

[`CGMouseButton.left`](/documentation/CoreGraphics/CGMouseButton/left)

[`CGMouseButton.right`](/documentation/CoreGraphics/CGMouseButton/right)

[`CGMouseButton.center`](/documentation/CoreGraphics/CGMouseButton/center)


---

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