[Lazarus] Mouse wheel scroll bar increment size?

[Hans-Peter Diettrich]

Bruce Tulloch schrieb:
> When the mouse wheel is used to change the position of a TScrollBar,
> what determines the size of the increment?
> 
> Empirically it appears to be related to the PageSize property but not in
> an obvious way.

Some time ago I've used a dual definition for the mouse wheel scroll: 
positive values indicate an item count (items=lines...), and negative 
values mean fractions of the page (window) size, e.g. -3 means 1/3 page. 
Such a convention could e.g. replace and extend the SynEdit half-page 
scroll option.

DoDi