ScrollUnit

Specifies the unit of scroll deltas.

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