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(module downstroke-world
*
(import scheme
(chicken base)
(only srfi-1 fold filter)
defstruct
downstroke-tilemap
downstroke-entity)
;; Scene = current level: tilemap (layers, objects) + list of entities.
;; Returns tile-id if the cell at (col, row) in this layer is non-zero, #f otherwise.
(define (layer-tile-at layer col row)
(let ((rows (layer-map layer)))
(and (< row (length rows))
(let ((row-data (list-ref rows row)))
(and (< col (length row-data))
(let ((tile-id (list-ref row-data col)))
(and (not (zero? tile-id)) tile-id)))))))
(define (tilemap-tile-at tilemap col row)
"Get the tile ID at grid position (col, row).
Returns 0 if out of bounds or if all layers have 0 at that cell."
(let ((width (tilemap-width tilemap))
(height (tilemap-height tilemap)))
(if (or (< col 0) (>= col width) (< row 0) (>= row height))
0
(let loop ((layers (tilemap-layers tilemap)))
(if (null? layers)
0
(or (layer-tile-at (car layers) col row)
(loop (cdr layers))))))))
(defstruct camera x y)
(defstruct scene
entities
tilemap
camera
tileset-texture
camera-target) ; symbol tag or #f
(define (scene-add-entity scene entity)
(scene-entities-set! scene (append (scene-entities scene) (list entity)))
scene)
(define (scene-update-entities scene . procs)
"Apply each proc in sequence to the scene's entities; each proc maps over all entities.
The scene's entity list is replaced once with the final result."
(scene-entities-set! scene
(fold (lambda (proc es) (map proc es))
(scene-entities scene)
procs))
scene)
(define (scene-filter-entities scene pred)
"Remove all entities from scene that do not satisfy pred."
(scene-entities-set! scene
(filter pred (scene-entities scene)))
scene)
;; Center camera on entity. Clamps to >= 0 on both axes.
;; viewport-w and viewport-h are the game window dimensions (pixels).
(define (camera-follow! camera entity viewport-w viewport-h)
(let* ((entity-x (entity-ref entity #:x 0))
(entity-y (entity-ref entity #:y 0)))
(camera-x-set! camera (inexact->exact (floor (max 0 (- entity-x (/ viewport-w 2))))))
(camera-y-set! camera (inexact->exact (floor (max 0 (- entity-y (/ viewport-h 2))))))))
;; Returns the first entity in scene whose #:tags list contains tag, or #f.
(define (scene-find-tagged scene tag)
(let loop ((entities (scene-entities scene)))
(cond
((null? entities) #f)
((member tag (entity-ref (car entities) #:tags '())) (car entities))
(else (loop (cdr entities))))))
;; Returns all entities in scene whose #:tags list contains tag.
(define (scene-find-all-tagged scene tag)
(filter (lambda (e) (member tag (entity-ref e #:tags '())))
(scene-entities scene)))
)
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