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).
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_xor down if it'sdelta_y. This is the same logic for negative values but you have to scroll left instead of right if it'sdelta_xand up instead of down if it'sdelta_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).