Description
If enabled, this event is reported when the user rotates the mouse wheel.
The event message reported as the result of ⎕DQ, or supplied as the right argument to your callback function, is a 9-element vector as follows :
| [1] | Object | ref or character vector |
| [2] | Event | 'MouseWheel' or 8 |
| [3] | Y | y-position of mouse (number) |
| [4] | X | x-position of mouse (number) |
| [5] | Button | button pressed 1 = left button 2 = right button 4 = middle button |
| [6] | Shift State | sum of shift key codes (number) 1 = Shift key is down 2 = Ctrl key is down |
| [7] | Delta | integer |
| [8] | Lines | integer |
| [9] | Wheel Delta | integer |
The value of Delta indicates the distance that the wheel is rotated, expressed in multiples or divisions of Wheel Delta. A positive value indicates that the wheel was rotated forward, away from the user; a negative value indicates that the wheel was rotated backward, toward the user.
Lines specifies the number of lines to scroll when the wheel is rotated by I Mouse Delta unit. A value of ¯1 indicates that a whole screen is to be scrolled. These values are defined by the user's preferences (Control Panel/Mouse).