gdk:event-scroll-direction (instance)

instance -- a gdk:event-scroll instance
direction -- a value of the gdk:scroll-direction enumeration

Accessor of the direction slot of the gdk:event-scroll structure. The gdk:scroll-direction function extracts the scroll direction from a scroll event.

If you wish to handle both discrete and smooth scrolling, you should check the return value of this function, or of the gdk:event-scroll-deltas function. 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;
  }