public interface IViewportListenerRegistered with a text viewer, view port listeners are informed about changes of a text viewer's view port. The view port is that portion of the viewer's document which is visible in the viewer.
Note: This listener will not be notified when the viewer is resized.
Clients may implement this interface.
void viewportChanged(int verticalOffset)Informs that the view port changed. The given vertical position is the new vertical scrolling offset measured in pixels.
Note: This event will not be sent when the viewer is resized.
verticalOffset- the vertical offset measured in pixels