touchZoom
Touch zoom event.
[event]
touchZoom([in] int status, [in] int winX, [in] int winY, [in] int distance)
This event is fired when the user performs a touch zoom, i.e., a
two-finger "pinch" gesture.
The status argument is:
- 0 for the first
touchZoomevent, when the user first touches the screen with two fingers - 1 for intermediate events, when the user moves their fingers
- 2 for the last event, when the user lifts their fingers
The winX, winY arguments are the coordinates
of one of the touch points, in window coordinates.
The distance argument is the distance between the two
touch points.
This event is only called if enableTouchZoom is set to true.
IMPORTANT: Setting enableTouchZoom to true only enables the
events; it does not perform any zooming. The touchZoom
event must be implemented to handle zooming.
The purpose is to allow the application code to update the user interface (e.g., a "current zoom" display), limit the minimum/maximum zoom level, etc. The standard approach is to zoom based on the ratio of the current distance to the previous distance. See the sample code below.
VB:
Private touchZoomPrevDist As Long
...
viewer.enableTouchZoom = True
...
Private Sub viewer_touchZoom(status As Long, winX As Long, winY As Long, distance As Long) _
Handles viewer.touchZoom
' on the first touchZoom event (status = 0), just save the distance
' for use in subsequent events
If status <> 0 Then
' compute the new zoom level
z = (viewer.zoomPercent * distance) / touchZoomPrevDist
' don't go below 10% or above 800%
If z < 10 Then
z = 10
ElseIf z > 800 Then
z = 800
End If
' set the new zoom level
viewer.zoomCentered(z)
End If
' save the distance - this will be used in the next touchZoom event
touchZoomPrevDist = distance
End Sub