scroll-related fields into a struct so vertical and horizontal can be
handled by the same code; add to board_zoom out params indicating
whether further zooming is possible.
Includes ability to scroll horizontally by dragging. Board init API
changes to specify board width and max height instead of cell
dimensions, so now board owns task of picking cell size. If the
number of cells does not evenly divide into a board dimension then the
extra pixels are distributed among some columns/rows in a way that
still allows bitblit-based scroll implementations (though horizontal
scrolling at this point always does an invalAll()). Not yet tested
with overlapping tray. And still need to allow rows to be taller than
cols are wide if platform code has given the space. Stream format
changes with this checkin.
access can then be via a ptr, more effecient and faster. The change
seems to save 1K of generated code. No changes to algorithms, only to
field access.