| Button | The button was released to cause the event. The Button argument is a bit field with bits corresponding to the left button (bit 0), right button (bit 1), and middle button (bit 2)values 1, 2, and 4, respectively. Only one of the bits is set, indicating which button caused the event. |
| Shift | The state of the Shift, Ctrl and Alt keys when the button specified in the Button argument was pressed or released. A bit is set if the key is down. The Shift argument is a bit field, with the least-significant bits corresponding to the Shift key (bit 0), the Ctrl key (bit 1), and the Alt key (bit 2 ). These bits correspond to the values 1, 2, and 4, respectively. Shift indicates the state of these keys. Some, all, or none of the bits can be set, indicating that some, all, or none of the keys is pressed. For example, if both Ctrl and Alt were pressed, the value of Shift would be 6. |
| x | The current X location, in drawing units, of the mouse pointer. |
| y | The current Y location, in drawing units, of the mouse pointer. |
