scrolling working!

stuff = image.loadsprite("stuff.png",16,16)
dofile("mapa.txt")

scroll={x=0,y=0,w=16,h=16}

--initx =  x-480/w  -x*w                              math.floor((480-x)/w)
--inity =


function blit_map(x,y,w,h)
x,y,w,h = x or 0, y or 0, w or 16, h or 16
for a = math.max(1,-math.ceil(y/h)), math.min(#mapa,272/h-y/16+1) do
 for b = math.max(1,-math.ceil(x/w)), math.min(#mapa[a],480/w-x/16+1) do
    if tonumber(mapa[a][b]) > 0 then stuff:setframe(tonumber(mapa[a][b])) stuff:resize(w,h) stuff:blit(x+(b-1)*16,y+(a-1)*16) end
 end
 screen.print(5,5,screen.fps().."  "..math.min(#mapa,#mapa+math.ceil(y/h)).."  "..math.min(#mapa[a],#mapa[a]+math.ceil(x/w)))
end


end


while true do
controls.read()

blit_map(scroll.x,scroll.y,scroll.w,scroll.h)

if controls.up() then scroll.y = scroll.y -2 end
if controls.down() then scroll.y = scroll.y +2 end
if controls.right() then scroll.x = scroll.x +2 end
if controls.left() then scroll.x = scroll.x -2 end


if controls.select() then a() end
screen.flip()
end