ludic/examples/library/sprite_atlas.ludic

# sprite_atlas.ludic — the engine sprite-render system draws atlas ids (#90).
# `Sprite { id, atlas: 1 }` marks `id` as a Sprite.cell / Sprite.cell_span sprite
# (any size, here a 16x32 two-cell character) and esys_sprite routes it through
# atlas_draw_ex with scale / flip / tint, so the #81 atlas API and the #85 engine
# sprite system compose. atlas: 0 (the default) keeps `id` a 16x16 table sprite.
# Verified by pixel readback after one frame.
#
# Driven headless by one stdin key ('q' quits after the frame renders).
#   printf 'q' | LUDIC_MODULES=packages bin/ludic examples/library/sprite_atlas.ludic  ->  32 1 1 1 0
program SpriteAtlas {
  import "ludic.core/components.ludic"

  state SpriteAtlasState {
    TALL: int = 0
  }

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

  @OnStart handler Boot(sprite_atlas_st: mut SpriteAtlasState) {
    let sheet = Sprite.sheet("assets/kenney/tiny-dungeon/Tilemap/tilemap_packed.png", 16, 16)
    sprite_atlas_st.TALL = Sprite.cell_span(sheet, 0, 0, 1, 2)                       # a 16x32 sprite: two cells tall
    spawn Tall   { Position { x: 40, y: 40 },  Sprite { id: sprite_atlas_st.TALL, atlas: 1 } }
    spawn Tinted { Position { x: 100, y: 40 }, Sprite { id: sprite_atlas_st.TALL, atlas: 1, tint: 0xff0000 } }
    spawn Table  { Position { x: 160, y: 40 }, Sprite { id: sprite_atlas_st.TALL } }   # atlas: 0 -> the (empty) 16x16 table
  }

  # An empty Render handler: the engine sprite system draws the Sprite entities.
  handler Draw phase Render { }

  @OnQuit handler Report(sprite_atlas_st: SpriteAtlasState) {
    print(Sprite.height(sprite_atlas_st.TALL))           # 32 — the span is two cells tall

    var top = 0
    for yy in 40 .. 56 { for xx in 40 .. 56 { if Screen.pixel(xx, yy) != 0 { top = 1 } } }
    print(top)                           # 1 — the upper cell drew

    var bottom = 0
    for yy in 56 .. 72 { for xx in 40 .. 56 { if Screen.pixel(xx, yy) != 0 { bottom = 1 } } }
    print(bottom)                        # 1 — the lower cell drew too (a table sprite stops at 16px)

    var tinted = 1
    var seen = 0
    for yy in 40 .. 72 { for xx in 100 .. 116 {
      let c = Screen.pixel(xx, yy)
      if c != 0 { seen = 1;  if c != 0xff0000 { tinted = 0 } }
    } }
    print(bi((seen == 1) and (tinted == 1)))   # 1 — every opaque pixel took the tint

    var table = 0
    for yy in 40 .. 72 { for xx in 160 .. 176 { if Screen.pixel(xx, yy) != 0 { table = 1 } } }
    print(table)                         # 0 — without atlas: 1 the id is a table id (nothing loaded there)
  }
}