PgUp / PgDown navigation does not change current selection

[dmaevsky]

It scrolls the viewport, but does not perform the actual "navigation": the selected cell stays the same, which means that a further arrow key press would scroll the viewport back to the original position. Hope this is not intended behavior.

[joneit]

In general apps do not usually change the selection on PgUp/PgDn.

Excel did not at first implement PgUp/PgDn, perhaps for this reason.... But it does seem to support it now and inasmuch as Hypergrid is modeled to some degree on Excel, we could consider adding this as an option (that is, tied to an option flag).

Excel's precise behavior when a single cell is selected is straight-forward. But when Excel has a range of cells selected or multiple selections, it first reduces the selection to the last single cell selected or the primary cell of the most recently selected range.

This is all just to treat the selection as a cursor concept, an apparent legacy of dumb terminals of the VisiCalc era.