status argument is:
- 0 for the first touch zoom event, 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
winY arguments are the coordinates
of one of the touch points, in window coordinates.
distance argument is the distance between the two
This callback is only called if
pdfEnableTouchZoom has been called
pdfEnableTouchZoom with true only
enables the callbacks; it does not perform any zooming.
pdfSetTouchZoomCbk callback must be implemented to
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.