Description
This event is reported when the user touches two fingers on an object and moves them apart or towards each other.
The event message reported as the result of ⎕DQ, or supplied as the right argument to your callback function, is a 5-element vector as follows :
| [1] | Object | ref or character vector |
| [2] | Event | 'GestureZoom' or 493 |
| [3] | Flags | integer which reports the state of the gesture |
| [4] | Location | 2-element integer vector containing the y and x-position respectively of the centre point of the zoom (the point midway between the two fingers). These are reported in pixel coordinates relative to the origin (top-left corner) of the object reporting the event. |
| [5] | Distance | 2-element integer vector containing the high and low parts (words) of a 64-bit integer that indicates the distance between the two fingers. |
The Flags parameter [3] which reports the state of the Gesture, is an integer with the value 0, 1 (GF_BEGIN),or 4 (GF_END) with the following meanings:
| Name | Value | Description |
| 0 | A gesture is in progress | |
| GF_BEGIN | 1 | A gesture is starting. |
| GF_END | 4 | A gesture has finished. |
When the user first touches two fingers on an object and begins to move them apart or towards each other, the object generates a GestureZoom event with a Flags parameter of 1 (GF_BEGIN). As the user continues to moves the fingers apart or towards each other, the object generates a series of GestureZoom events with a Flags parameter of 0. When the user lifts one or both fingers away, the object generates it generates a final GestureZoom event, with a Flags parameter of 4 (GF_END).
No other event will be reported between the start and end of a series of GestureZoom events.
The associated callback is run immediately while the windows notification is still on the stack. See High-Priority Callback Functions.
Returning zero from the callback disables any default handling by the operating system.