The type of scroll this is (e.g. line, page, etc.).
This indicates the intent of the scroll, not necessarily the size. Not all scrollable areas will have the concept of a "line" or "page", but they can respond to the different standard key bindings that cause scrolling, which are bound to keys that people use to indicate a "line" scroll (e.g. control-arrowDown keys) or a "page" scroll (e.g. pageDown key). It is recommended that at least the relative magnitudes of the scrolls match expectations.
final ScrollIncrementType type