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(module downstroke/scene-loader *
(import scheme
(chicken base)
(only srfi-1 filter-map)
(srfi 69)
(prefix sdl2 "sdl2:")
(prefix sdl2-ttf "ttf:")
defstruct
downstroke/tilemap
downstroke/world
downstroke/engine)
;; Create a prefab registry from alternating symbol/constructor pairs.
;; Returns a srfi-69 hash-table mapping symbols to constructor functions.
(define (make-prefab-registry . pairs)
(let ((ht (make-hash-table)))
(let loop ((p pairs))
(if (null? p) ht
(begin
(hash-table-set! ht (car p) (cadr p))
(loop (cddr p)))))))
;; Instantiate a prefab by type from the registry.
;; Returns the entity plist if type exists, #f otherwise.
(define (instantiate-prefab registry type x y w h)
(let ((ctor (hash-table-ref/default registry type #f)))
(and ctor (ctor x y w h))))
;; Convert TMX object list to entities.
;; Object types are strings from XML; convert to symbols before instantiating.
;; Filters out #f results (objects without registered prefabs).
(define (tilemap-objects->entities tilemap instantiate-fn)
(filter-map
(lambda (obj)
(instantiate-fn (string->symbol (object-type obj))
(object-x obj) (object-y obj)
(object-width obj) (object-height obj)))
(tilemap-objects tilemap)))
;; Create an SDL2 texture from the tileset image embedded in a tilemap.
(define (create-tileset-texture renderer tilemap)
(sdl2:create-texture-from-surface
renderer
(tileset-image (tilemap-tileset tilemap))))
;; Load a TMX tilemap file and store it in the game asset registry.
;; Returns the loaded tilemap struct.
(define (game-load-tilemap! game key filename)
(let ((tm (load-tilemap filename)))
(game-asset-set! game key tm)
tm))
;; Load a TSX tileset file and store it in the game asset registry.
;; Returns the loaded tileset struct.
(define (game-load-tileset! game key filename)
(let ((ts (load-tileset filename)))
(game-asset-set! game key ts)
ts))
;; Load a TTF font file and store it in the game asset registry.
;; size is the point size. Returns the loaded font.
(define (game-load-font! game key filename size)
(let ((font (ttf:open-font filename size)))
(game-asset-set! game key font)
font))
;; Load a scene from a TMX tilemap file.
;; 1. Loads the tilemap from the file (and stores in assets)
;; 2. Creates a texture from the tilemap's tileset image
;; 3. Creates a scene with empty entities list
;; 4. Sets the scene on the game
;; Returns the scene.
(define (game-load-scene! game filename)
(let* ((tm (game-load-tilemap! game 'tilemap filename))
(tex (create-tileset-texture (game-renderer game) tm))
(scene (make-scene
entities: '()
tilemap: tm
camera: (make-camera x: 0 y: 0)
tileset-texture: tex
camera-target: #f)))
(game-scene-set! game scene)
scene))
) ;; end module
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