Progress

1 files changed, 19 insertions, 0 deletions

diff --git a/world.scm b/world.scm
index 2cd0feb..8e1651a 100644
--- a/world.scm
+++ b/world.scm
@@ -56,4 +56,23 @@
     (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)
+    (camera-x-set! camera (max 0 (- (entity-ref entity #:x 0) (/ viewport-w 2))))
+    (camera-y-set! camera (max 0 (- (entity-ref entity #:y 0) (/ 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)))
 )