dirty-draw.toit

// ESC := "^"
ESC := "\x1b"
WIDTH := 33
HEIGHT := 32
FPS := 120
SIZE := WIDTH * HEIGHT
pixels := ByteArray(SIZE)

dirty_x1 := 0
dirty_y1 := 0
dirty_x2 := WIDTH - 1
dirty_y2 := HEIGHT - 1


clear:
  SIZE.repeat: pixels[it] = 0
  dirty_x1 = 0
  dirty_y1 = 0
  dirty_x2 = WIDTH - 1
  dirty_y2 = HEIGHT - 1

set x y c:
  pixels[x + y * WIDTH] = c
  if x < dirty_x1: dirty_x1 = x
  if x > dirty_x2: dirty_x2 = x
  if y < dirty_y1: dirty_y1 = y
  if y > dirty_y2: dirty_y2 = y


main:
  print "$(ESC)[2J$(ESC)[?25l"
  period := Duration --ms=(1000/FPS)
  while true:
    start := Time.now
    render
    draw
    extra := Duration.until start + period
    sleep extra

o := 0
sx := 0
sy := 0
mx := 1
my := 1
render:
  o = (o + 1) % 256
  set sx sy o
  sx += mx
  sy += my
  if sx >= WIDTH:
    sx = WIDTH - 1
    mx = -mx
  else if sx < 0:
    sx = 0
    mx = -mx
  if sy >= HEIGHT:
    sy = HEIGHT - 1
    my = -my
  else if sy < 0:
    sy = 0
    my = -my
  // clear
  // o += 2
  // HEIGHT.repeat: |y|
  //   WIDTH.repeat: |x|
  //     pixels[y * WIDTH + x] = (o + x + y) % 256 


draw:
  // print [sx, sy, dirty_x1, dirty_y1, dirty_x2, dirty_y2]
  image := ""
  odd := dirty_y1 % 2
  for y := dirty_y1 - odd; y <= dirty_y2; y += 2:
    // print "y=$(y) y>>1=$(y>>1) y1=$(dirty_y1) y2=$(dirty_y2)"
    old_top := -1
    old_bottom := -1
    image += "$(ESC)[$((y>>1)+1);$(dirty_x1+1)H"
    for x := dirty_x1; x <= dirty_x2; x += 1:
      i := x + y * WIDTH
      top := pixels[i]
      bottom := pixels[i + WIDTH]
      if top != old_top:
        old_top = top
        image += "$(ESC)[38;5;$(top)m"
      if bottom != old_bottom:
        old_bottom = bottom
        image += "$(ESC)[48;5;$(bottom)m"
      image += "▀"
  image += "$(ESC)[0m"
  print(image)
  dirty_x1 = WIDTH
  dirty_y1 = HEIGHT
  dirty_x2 = -1
  dirty_y2 = -1