node-2d: Fix jittery movement of nodes when paused.

1 files changed, 27 insertions, 2 deletions

diff --git a/starling/node-2d.scm b/starling/node-2d.scm
index 0364a6e..f6fc190 100644
--- a/starling/node-2d.scm
+++ b/starling/node-2d.scm
@@ -277,6 +277,15 @@
                       (loop rest))))))
            (camera-loop rest))))))
 
+(define-method (pause (display <display-2d>))
+  ;; We need to set the last position of all objects in the tree to
+  ;; their current position, otherwise any moving objects will
+  ;; experience this weird jitter while paused because the last
+  ;; position will never be updated during the duration of the pause
+  ;; event.
+  (next-method)
+  (for-each-child remember-position/recursive display))
+
 
 ;;;
 ;;; 2D Scene
@@ -541,8 +550,15 @@
 
 ;; Events
 
+(define-method (remember-position (node <node-2d>))
+  (vec2-copy! (position node) (last-position node)))
+
+(define-method (remember-position/recursive (node <node-2d>))
+  (remember-position node)
+  (for-each-child remember-position/recursive node))
+
 (define-method (update-tree (node <node-2d>) dt)
-  (vec2-copy! (position node) (last-position node))
+  (remember-position node)
   (when (dirty-bounding-box? node)
     (refresh-bounding-box node))
   (next-method))
@@ -575,9 +591,18 @@
   (set! (dirty-matrix? node) #t)
   ;; Set the initial last position to the same as the initial position
   ;; to avoid a brief flash where the node appears at (0, 0).
-  (vec2-copy! (position node) (last-position node))
+  (remember-position node)
   (next-method))
 
+(define-method (pause (node <node-2d>))
+  ;; We need to set the last position of all objects in the tree to
+  ;; their current position, otherwise any moving objects will
+  ;; experience this weird jitter while paused because the last
+  ;; position will never be updated during the duration of the pause
+  ;; event.
+  (next-method)
+  (remember-position/recursive node))
+
 
 ;;;
 ;;; Sprite