(gobject:define-genum "GdkScrollUnit" scroll-unit
  (:export t
   :type-initializer "gdk_scroll_unit_get_type")
  :wheel
  :surface)  

:wheel

The delta is in number of wheel clicks.

:surface

The delta is in surface pixels to scroll directly on screen.

Specifies the unit of scroll deltas. When you get the :wheel value, a delta of 1.0 means 1 wheel detent click in the south direction, 2.0 means 2 wheel detent clicks in the south direction. This is the same logic for negative values but in the north direction.

If you get the :surface value, are managing a scrollable view and get a value of 123, you have to scroll 123 surface logical pixels right if it is delta_x or down if it is delta_y. This is the same logic for negative values but you have to scroll left instead of right if it is delta_x and up instead of down if it is delta_y.

1 surface logical pixel is equal to 1 real screen pixel multiplied by the final scale factor of your graphical interface, the product of the desktop scale factor and eventually a custom scale factor in your application.

Since 4.8