also, added key codes from launchpad sources.
thus, a few constants change their names.
These are the current keys:
PGFWD = next page
PGBCK = previous page
SHIFT+PGFWD = zoom in
SHIFT+PGBCK = zoom out
A = fit to page
S = fit to page width
D = fit to page height
SHIFT+A = fit to page content
SHIFT+S = fit to page content width
SHIFT+D = fit to page content height
SHIFT+FW_UP = Gamma + 0.2
SHIFT+FW_DOWN = Gamma - 0.2
in order to use the tile cache for variable zoomed tiles, we need more
flexibility. thus, now cache tiles are hashed (well, in fact it's a
concatenation) of their metadata.
also, we close pages right after opening them - there was no re-use
before and now we have opening and closing at one place. this should
also make it easier for the garbage collector.
This exposed small bug in checkcache which checked just page no
which didn't get invalidated when closing page, so we now check if page
is also not nil
