From a041ba88379729537cf1042d57a6c8bcfc269e5c Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Wed, 14 Dec 2022 12:55:58 -0500
Subject: node-2d: Add centering methods.

---
 catbird/node-2d.scm | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/catbird/node-2d.scm b/catbird/node-2d.scm
index ca5311e..0a1f683 100644
--- a/catbird/node-2d.scm
+++ b/catbird/node-2d.scm
@@ -55,6 +55,9 @@
             align-left
             align-right
             align-top
+            center
+            center-horizontal
+            center-vertical
             default-height
             default-width
             expire-local-matrix
@@ -704,6 +707,24 @@ A."
         (- (local-y a)
            (- (local-y b) (local-origin-y b)))))
 
+(define (center-horizontal a b)
+  "Move the x position of A so that it is centered with B."
+  (set! (position-x b)
+        (+ (local-x a)
+           (/ (- (local-width a) (local-width b)) 2.0)
+           (- (local-x b) (local-origin-x b)))))
+
+(define (center-vertical a b)
+  "Move the y position of A so that it is centered with B."
+  (set! (position-y b)
+        (+ (local-y a)
+           (/ (- (local-height a) (local-height b)) 2.0)
+           (- (local-y b) (local-origin-y b)))))
+
+(define (center a b)
+  "Center B within A."
+  (center-horizontal a b)
+  (center-vertical a b))
 
 
 ;;;
-- 
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