circle.lua

io.stdout:setvbuf("no")
if arg[#arg] == "-debug" then require("mobdebug").start() end

window = {}
window.w = 500
window.h = 500
love.window.setMode(window.w,window.h)
love.window.setTitle("Circle Boundaries")

circle = {}
circle.radius = 15
circle.x = circle.radius
circle.y = circle.radius
circle.speed = 20

window.x = {}
window.y = {}
window.x.min = circle.radius
window.x.max = window.w - circle.radius
window.y.min = circle.radius
window.y.max = window.h - circle.radius

function diagnostic()
  print("--------------------------------")
  print(string.format("window.x.min = %d", window.x.min))
  print(string.format("circle.x     = %d", circle.x))
  print(string.format("window.x.max = %d", window.x.max))
  print("              ---               ")
  print(string.format("window.y.min = %d", window.y.min))
  print(string.format("circle.y     = %d", circle.y))
  print(string.format("window.y.max = %d", window.y.max))
end

diagnostic()

circle.move = function(x,y)
  print(string.format("circle.move(%d,%d)", x, y))
  if x > 0 then
    -- Move circle right
    if circle.x + circle.speed < window.x.max then
      print("--------------------------------")
      print(string.format("Adding %d to %d (circle.x)", circle.speed, circle.x))
      circle.x = circle.x + circle.speed
      diagnostic()
    -- Move circle right a remainder
    elseif window.x.max - circle.x < circle.speed and window.x.max - circle.x > 0 then
      print("--------------------------------")
      print(string.format("Adding remainder %d to %d (circle.x)", window.x.max - circle.x, circle.x))
      circle.x = circle.x + (window.x.max - circle.x)
      diagnostic()
    end
  elseif x < 0 then
    -- Move circle left
    if circle.x - circle.speed > window.x.min then
      print("--------------------------------")
      print(string.format("Subtracting %d from %d (circle.x)", circle.speed, circle.x))
      circle.x = circle.x - circle.speed
      diagnostic()
    -- Move circle left a remainder
    elseif circle.x - circle.speed < window.x.min and circle.x - window.x.min < circle.speed and circle.x - window.x.min > 0 then
      print("--------------------------------")
      print(string.format("Subtracting %d from %d (circle.x)", circle.speed, circle.x))
      circle.x = circle.x - (circle.x - window.x.min)
      diagnostic()
    end
  end
end

dtcount = 0
function love.update(dt)
  dtcount = dtcount + dt
  if dtcount > .5 then
    --if( love.keyboard.isDown("w") ) then circle.move(0,-1) end
    if( love.keyboard.isDown("a") ) then circle.move(-1,0) end
    --if( love.keyboard.isDown("s") ) then circle.move(0,1) end
    if( love.keyboard.isDown("d") ) then circle.move(1,0) end
    dtcount = dtcount - .5
  end
end

function love.draw()
  love.graphics.setColor({255,255,255,255})
  love.graphics.circle("fill", circle.x, circle.y, circle.radius, 50);
  love.graphics.setColor({255,0,0,255})
  love.graphics.setPointSize(3)
  love.graphics.point(circle.x,circle.y)
  love.graphics.point(circle.x-circle.radius,circle.y)
  love.graphics.point(circle.x+circle.radius,circle.y)
end