Documentation for reference

View2D is a way of describing viewport in 2D. Commonly used with ARegion (area region or active region). Used for view panning and scrolling purposes. The scrolling operations are present in view2D_ops.c file. Similar to other operations like subdivide in Edit Mode.

Scroll by a length of one "page" happens when we click on an empty space outside the size of the scrollbar. The scrollbar moves down by a fixed amount called a page.

Lukas Tonne worked on a similar Edge Panning structure.