From c6c63425f42a44e483b8676f562fa960e59c8777 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Tue, 18 Apr 2023 07:44:23 -0400
Subject: region: Use pushdown state.

---
 catbird/region.scm | 31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/catbird/region.scm b/catbird/region.scm
index f1cc306..f42532a 100644
--- a/catbird/region.scm
+++ b/catbird/region.scm
@@ -25,6 +25,7 @@
   #:use-module (catbird config)
   #:use-module (catbird mixins)
   #:use-module (catbird node)
+  #:use-module (catbird pushdown)
   #:use-module (catbird scene)
   #:use-module (chickadee)
   #:use-module (chickadee data array-list)
@@ -53,8 +54,7 @@
 (define-root-class <region> (<renderable> <updatable> <nameable> <rankable>)
   (area #:accessor area #:init-keyword #:area)
   (camera #:accessor camera #:init-keyword #:camera #:init-value #f)
-  (scene #:accessor scene #:init-keyword #:scene #:init-value #f)
-  (scene-stack #:getter scene-stack #:init-thunk make-array-list)
+  (scene-state #:accessor scene-state #:init-thunk make-pushdown-state)
   (viewport #:accessor viewport))
 
 (define-method (area-x (region <region>))
@@ -99,23 +99,32 @@
        (make-exception-with-message "region area exceeds window area")))
     (make <region> #:area area #:name name #:rank rank)))
 
-(define-method (replace-scene (r <region>) (new-scene <scene>))
-  (let ((old-scene (scene r)))
+(define-method (scene (region <region>))
+  (state-current (scene-state region)))
+
+(define-method (replace-scene (region <region>) (new-scene <scene>))
+  (let ((old-scene (scene region)))
     (when old-scene (on-exit old-scene))
-    (set! (scene r) new-scene)
-    (set! (regions new-scene) (cons r (regions new-scene)))
+    (state-push! (scene-state region) new-scene)
+    (set! (regions new-scene) (cons region (regions new-scene)))
     (on-enter new-scene)))
 
 (define-method (push-scene (region <region>) (new-scene <scene>))
   (let ((old-scene (scene region)))
     (when old-scene
-      (array-list-push! (scene-stack region) old-scene))
-    (replace-scene region new-scene)))
+      (on-exit old-scene))
+    (state-push! (scene-state region))
+    (set! (regions new-scene) (cons region (regions new-scene)))
+    (on-enter new-scene)))
 
 (define-method (pop-scene (region <region>))
-  (let ((stack (scene-stack region)))
-    (unless (array-list-empty? stack)
-      (replace-scene (array-list-pop! stack)))))
+  (let ((old-scene (state-pop! (scene-state region))))
+    (on-exit old-scene)
+    (set! (regions old-scene)
+          (delq region (regions old-scene))))
+  (let ((restored-scene (scene region)))
+    (when restored-scene
+      (on-enter restored-scene))))
 
 (define-method (update (region <region>) dt)
   (let ((s (scene region)))
-- 
cgit v1.2.3