PICO-8 Button Functions

buttons.p8

-- button functions
--------------------

-- return true if button released since last frame
function btnr(b)
  local bit = shl(1,b)
  return band(bit, pbtn) == bit and btn() == band(bnot(bit), btn())
end

-- return count of frames button has been held down
function btnf(b)
  return (bfr or {})[b+1] or 0
end

-- call this at the end of update
function update_button_state()
  -- track button frames
  bfr = bfr or {}
  for b=0,5 do
    bfr[b+1] = btn(b) and (bfr[b+1] or 0) + 1 or 0
  end

  -- store previous button state
  pbtn = btn()
end