From f00ab87113842bce26f7022f8d074608c8c140df Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Sat, 2 Jan 2016 07:32:42 -0500
Subject: render: Add render/signal macro.

* sly/render.scm (render/signal): New syntax.
---
 .dir-locals.el |  3 ++-
 sly/render.scm | 10 +++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/.dir-locals.el b/.dir-locals.el
index f8534e6..cd94516 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -21,4 +21,5 @@
    (eval . (put 'with-vertex-buffer 'scheme-indent-function 1))
    (eval . (put 'with-sprite-batch 'scheme-indent-function 2))
    (eval . (put 'uniform-let 'scheme-indent-function 1))
-   (eval . (put 'call-with-surface 'scheme-indent-function 1)))))
+   (eval . (put 'call-with-surface 'scheme-indent-function 1))
+   (eval . (put 'render/signal 'scheme-indent-function 1)))))
diff --git a/sly/render.scm b/sly/render.scm
index 875f7c1..6bc917b 100644
--- a/sly/render.scm
+++ b/sly/render.scm
@@ -31,6 +31,7 @@
   #:use-module (gl)
   #:use-module (gl enums)
   #:use-module (gl low-level)
+  #:use-module (sly signal)
   #:use-module (sly wrappers gl)
   #:use-module ((sly math transform) #:prefix t:)
   #:use-module (sly render color)
@@ -117,7 +118,8 @@
             clear-screen
             uniform-let
             with-color
-            render-mesh))
+            render-mesh
+            render/signal))
 
 ;;;
 ;;; Transformation matrix stack.
@@ -524,3 +526,9 @@ COLOR and applies RENDERER."
             `((mvp ,(graphics-model-view-transform gfx))
               (texture? ,(not (texture-null? (graphics-texture gfx)))))
           draw-graphics-mesh!)))))
+
+(define-syntax-rule (render/signal ((name signal) ...) renderer)
+  "Evaluate RENDERER whenever a bound signal changes."
+  (let ((s (signal-let ((name signal) ...) renderer)))
+    (lambda (gfx)
+      ((signal-ref s) gfx))))
-- 
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