From 84840ede6646ed793b61cdd889d3f57ab05e9311 Mon Sep 17 00:00:00 2001
From: Gene Pasquet <dev@etenil.net>
Date: Wed, 8 Apr 2026 01:32:55 +0100
Subject: Refactor to be functional

---
 world.scm | 43 ++++++++++++++++++++-----------------------
 1 file changed, 20 insertions(+), 23 deletions(-)

(limited to 'world.scm')

diff --git a/world.scm b/world.scm
index e637e90..14840c8 100644
--- a/world.scm
+++ b/world.scm
@@ -42,31 +42,29 @@
     background)       ; #f or (r g b) / (r g b a) for framebuffer clear
 
   (define (scene-add-entity scene entity)
-    (scene-entities-set! scene (append (scene-entities scene) (list entity)))
-    scene)
+    (update-scene scene
+      entities: (append (scene-entities scene) (list entity))))
 
   (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)
+    "Apply each proc in sequence to the scene's entities; returns a new scene."
+    (update-scene scene
+      entities: (fold (lambda (proc es) (map proc es))
+                      (scene-entities scene)
+                      procs)))
 
   (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)
+    "Keep only entities satisfying pred; returns a new scene."
+    (update-scene scene
+      entities: (filter pred (scene-entities 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)
+  ;; Returns a new camera struct.
+  (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))))))))
+      (update-camera camera
+        x: (inexact->exact (floor (max 0 (- entity-x (/ viewport-w 2)))))
+        y: (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)
@@ -107,11 +105,10 @@
                                (entity-ref e #:group-local-y 0))))
           e)))
 
-  ;; Snap member #:x/#:y to origin + #:group-local-x/y. Call after moving origins (tweens, etc.).
-  (define (scene-sync-groups! scene)
+  ;; Snap member #:x/#:y to origin + #:group-local-x/y. Returns a new scene.
+  (define (scene-sync-groups scene)
     (let ((origins (group-origin-alist (scene-entities scene))))
-      (scene-entities-set! scene
-        (map (lambda (e) (sync-member-to-origin e origins))
-             (scene-entities scene)))
-      scene))
+      (update-scene scene
+        entities: (map (cut sync-member-to-origin <> origins)
+                       (scene-entities scene)))))
 )
-- 
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