# camera_zoom.ludic — the deterministic render-time camera zoom (#78). Zoom is a
# Q16.16 scale applied about the screen centre in the blit path; the world stays
# integer pixels, so lockstep / replay / world_save are untouched. Verified by
# pixel readback (Screen.pixel reads the actual framebuffer, un-transformed).
#
# Deterministic; a full run prints:  1 0 0 1 1
program CameraZoom {
  # a model so the program runs the ECS and links the core runtime (the framebuffer
  # + Screen.* live in runtime/native/core.ludic, spliced for an ECS program).
  property Cam { z: fixed = 1.0 }
  model View { Cam }

  function bi(b: bool) -> int { if b { return 1 };  return 0 }

  entry {
    # A. no zoom: a 4x4 white box drawn at (100,100) lands at (100,100).
    Screen.clear(0)
    Screen.fill_rectangle(100, 100, 4, 4, 0xffffff)
    print(bi(Screen.pixel(101, 101) == 0xffffff))    # 1 — box is here
    print(bi(Screen.pixel(43, 83) == 0xffffff))       # 0 — nothing here yet

    # B. 2x zoom about the screen centre (160,120): (100,100) maps to
    #    ((100-160)*2+160, (100-120)*2+120) = (40, 80), size 4 -> 8, so the box
    #    now covers x 40..48, y 80..88 and has left (101,101).
    Screen.clear(0)
    Camera.zoom(2.0)
    Screen.fill_rectangle(100, 100, 4, 4, 0xffffff)
    print(bi(Screen.pixel(101, 101) == 0xffffff))    # 0 — moved away
    print(bi(Screen.pixel(43, 83) == 0xffffff))       # 1 — scaled to here

    # C. zoom back to 1.0 restores the byte-identical un-zoomed blit.
    Screen.clear(0)
    Camera.zoom(1.0)
    Screen.fill_rectangle(100, 100, 4, 4, 0xffffff)
    print(bi(Screen.pixel(101, 101) == 0xffffff))    # 1 — normal again
  }
}