From 027671d62f3453eca3fde5fb46d5270a075121d7 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Thu, 12 Jan 2017 20:07:37 -0500
Subject: render: sprite: Implement dynamic sprite batch resizing.

---
 chickadee/render/sprite.scm | 45 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 36 insertions(+), 9 deletions(-)

diff --git a/chickadee/render/sprite.scm b/chickadee/render/sprite.scm
index f85ae93..bc2ac1d 100644
--- a/chickadee/render/sprite.scm
+++ b/chickadee/render/sprite.scm
@@ -16,6 +16,7 @@
 ;;; <http://www.gnu.org/licenses/>.
 
 (define-module (chickadee render sprite)
+  #:use-module (rnrs bytevectors)
   #:use-module (srfi srfi-4)
   #:use-module (srfi srfi-9)
   #:use-module (srfi srfi-11)
@@ -126,25 +127,51 @@ void main (void) {
   (blend-mode sprite-batch-blend-mode set-sprite-batch-blend-mode!)
   (shader sprite-batch-shader set-sprite-batch-shader!)
   (size sprite-batch-size set-sprite-batch-size!)
-  (capacity sprite-batch-capacity)
-  (index-buffer sprite-batch-index-buffer)
-  (position-buffer sprite-batch-position-buffer)
-  (texture-buffer sprite-batch-texture-buffer)
-  (vertex-array sprite-batch-vertex-array))
+  (capacity sprite-batch-capacity set-sprite-batch-capacity!)
+  (index-buffer sprite-batch-index-buffer set-sprite-batch-index-buffer!)
+  (position-buffer sprite-batch-position-buffer set-sprite-batch-position-buffer!)
+  (texture-buffer sprite-batch-texture-buffer set-sprite-batch-texture-buffer!)
+  (vertex-array sprite-batch-vertex-array set-sprite-batch-vertex-array!))
 
-(define (make-sprite-batch capacity)
-  "Make a sprite batch that can hold CAPACITY sprites."
+(define (init-sprite-batch batch capacity)
   (let* ((index (make-streaming-vertex-buffer 'index (* capacity 6)))
          (pos (make-streaming-vertex-buffer 'vec2  (* capacity 4)))
          (tex (make-streaming-vertex-buffer 'vec2  (* capacity 4)))
          (va (make-vertex-array index pos tex)))
-    (%make-sprite-batch #f #f #f 0 capacity index pos tex va)))
+    (set-sprite-batch-capacity! batch capacity)
+    (set-sprite-batch-index-buffer! batch index)
+    (set-sprite-batch-position-buffer! batch pos)
+    (set-sprite-batch-texture-buffer! batch tex)
+    (set-sprite-batch-vertex-array! batch va)))
+
+(define (make-sprite-batch capacity)
+  "Make a sprite batch that can hold CAPACITY sprites."
+  (let ((batch (%make-sprite-batch #f #f #f 0 0 #f #f #f #f)))
+    (init-sprite-batch batch capacity)
+    batch))
 
 (define (sprite-batch-full? batch)
   (= (sprite-batch-capacity batch) (sprite-batch-size batch)))
 
 (define (double-sprite-batch-size! batch)
-  #f)
+  (let ((old-index (sprite-batch-index-buffer batch))
+        (old-verts (sprite-batch-position-buffer batch))
+        (old-tex (sprite-batch-texture-buffer batch)))
+    (unmap-vertex-buffer! old-index)
+    (unmap-vertex-buffer! old-verts)
+    (unmap-vertex-buffer! old-tex)
+    (init-sprite-batch batch (* (sprite-batch-capacity batch) 2))
+    (sprite-batch-begin! batch)
+    (let ((new-index (sprite-batch-index-buffer batch))
+          (new-verts (sprite-batch-position-buffer batch))
+          (new-tex (sprite-batch-texture-buffer batch)))
+      (define (copy from to)
+        (bytevector-copy! (vertex-buffer-data from) 0
+                          (vertex-buffer-data to) 0
+                          (bytevector-length (vertex-buffer-data from))))
+      (copy old-index new-index)
+      (copy old-verts new-verts)
+      (copy old-tex new-tex))))
 
 (define (sprite-batch-reset! batch)
   "Reset BATCH to size 0."
-- 
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