Lazily create agendas for scripted nodes.

Most nodes do not end up running scripts, so this saves some precious
time and reduces GC pressure.

1 files changed, 17 insertions, 5 deletions

diff --git a/catbird/mixins.scm b/catbird/mixins.scm
index 3945aab..6e1cd4a 100644
--- a/catbird/mixins.scm
+++ b/catbird/mixins.scm
@@ -150,7 +150,16 @@
 
 (define-class <scriptable> (<updatable>)
   (paused? #:accessor paused? #:init-form #f #:init-keyword #:paused?)
-  (agenda #:getter agenda #:init-thunk make-agenda))
+  ;; The agenda gets created lazily when the first script is run.
+  ;; This reduces overhead for scriptable objects that don't end up
+  ;; running any scripts.
+  (agenda #:accessor agenda #:init-value #f))
+
+(define-method (ensure-agenda (obj <scriptable>))
+  (or (agenda obj)
+      (let ((fresh-agenda (make-agenda)))
+        (set! (agenda obj) fresh-agenda)
+        fresh-agenda)))
 
 (define-method (on-pause (obj <scriptable>))
   #t)
@@ -170,15 +179,18 @@
 
 (define-method (update/around (obj <scriptable>) dt)
   (unless (paused? obj)
-    (with-agenda (agenda obj)
-      (update-agenda dt)
+    (let ((agenda (agenda obj)))
+      (when agenda
+        (with-agenda agenda
+          (update-agenda dt)))
       (next-method))))
 
 (define-syntax-rule (run-script obj body ...)
-  (with-agenda (agenda obj) (script body ...)))
+  (with-agenda (ensure-agenda obj) (script body ...)))
 
 (define-method (stop-scripts obj)
-  (with-agenda (agenda obj) (clear-agenda)))
+  (when (agenda obj)
+    (with-agenda (agenda obj) (clear-agenda))))
 
 
 ;;;