Event.getScrollDirection

Extracts the scroll direction from an event.

If event is not of type gdk.types.EventType.Scroll, the contents of direction are undefined.

If you wish to handle both discrete and smooth scrolling, you should check the return value of this function, or of gdk.event.Event.getScrollDeltas; for instance:

GdkScrollDirection direction;
double vscroll_factor = 0.0;
double x_scroll, y_scroll;

if (gdk_event_get_scroll_direction (event, &direction))
  {
    // Handle discrete scrolling with a known constant delta;
    const double delta = 12.0;

    switch (direction)
      {
      case GDK_SCROLL_UP:
        vscroll_factor = -delta;
        break;
      case GDK_SCROLL_DOWN:
        vscroll_factor = delta;
        break;
      default:
        // no scrolling
        break;
      }
  }
else if (gdk_event_get_scroll_deltas (event, &x_scroll, &y_scroll))
  {
    // Handle smooth scrolling directly
    vscroll_factor = y_scroll;
  }