From 177ffdd7a986208a6ff041b6d7b50c81abc56cf2 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson@vistahigherlearning.com>
Date: Thu, 20 Jun 2019 07:52:23 -0400
Subject: node: Add pause/resume feature.

---
 starling/node.scm | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

(limited to 'starling/node.scm')

diff --git a/starling/node.scm b/starling/node.scm
index dbfc702..ee4fbb8 100644
--- a/starling/node.scm
+++ b/starling/node.scm
@@ -33,6 +33,7 @@
             booted?
             active?
             visible?
+            paused?
             on-boot
             on-enter
             on-exit
@@ -40,6 +41,8 @@
             deactivate
             show
             hide
+            pause
+            resume
             update
             update-tree
             render
@@ -50,7 +53,8 @@
             detach
             run-script
             stop-scripts
-            blink))
+            blink)
+  #:replace (pause))
 
 (define-class <node> ()
   ;; Symbolic name.  Used for easy lookup of children within a parent.
@@ -74,6 +78,8 @@
   ;; Determines whether or not the node and all of its children are
   ;; rendered.
   (visible? #:accessor visible? #:init-form #t #:init-keyword #:visible?)
+  ;; Determines whether or not updates happen.
+  (paused? #:accessor paused? #:init-form #f #:init-keyword #:paused?)
   ;; Use redefinable classes when in dev mode.
   #:metaclass (if developer-mode?
                   <redefinable-class>
@@ -94,13 +100,13 @@
 (define-method (update-tree (node <node>) dt)
   "Update NODE and all of its children.  DT is the amount of time
 passed since the last update, in milliseconds."
-  ;; Update children first, recursively.
-  (for-each-child (lambda (child) (update-tree child dt)) node)
-  ;; Update script, then "physics" (or whatever the update method is
-  ;; doing).
-  (with-agenda (agenda node)
-    (update-agenda 1)
-    (update node dt)))
+  (unless (paused? node)
+    ;; Update children first, recursively.
+    (for-each-child (lambda (child) (update-tree child dt)) node)
+    ;; Scripts take precedence over the update method.
+    (with-agenda (agenda node)
+                 (update-agenda 1)
+                 (update node dt))))
 
 (define-method (render (node <node>) alpha)
   "Render NODE.  ALPHA is the distance between the previous update and
@@ -161,6 +167,12 @@ represented as a ratio in the range [0, 1]."
   "Mark NODE as invisible."
   (set! (visible? node) #f))
 
+(define-method (pause (node <node>))
+  (set! (paused? node) #t))
+
+(define-method (resume (node <node>))
+  (set! (paused? node) #f))
+
 
 ;;;
 ;;; Child management
-- 
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