current_context_usage - Return how many cells the current context has,
and how many of those cells that are currently unused.
total, used
current_context_usage()
This function sweeps the VID pool of the currently active context and
counts O(n) how many of these are in use and subsequently returns how many
slots are available in total, and how many are maked as used. The number of
free slots can be found by subtracting used from total.
function current_context_usage0()
a = fill_surface(32, 32, 0, 0, 0);
print(current_context_usage());
b = fill_surface(32, 32, 0, 0, 0);
print(current_context_usage());
end