From 4ab7309f45d8297d190e371b3b228451fb51f44e Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Tue, 14 Feb 2023 21:12:01 -0500
Subject: Port 9-patch shader to Seagull.

---
 chickadee/graphics/9-patch.scm | 112 +++++++++++++++++------------------------
 1 file changed, 47 insertions(+), 65 deletions(-)

diff --git a/chickadee/graphics/9-patch.scm b/chickadee/graphics/9-patch.scm
index c023b25..dc14bc7 100644
--- a/chickadee/graphics/9-patch.scm
+++ b/chickadee/graphics/9-patch.scm
@@ -21,6 +21,7 @@
   #:use-module (chickadee graphics blend)
   #:use-module (chickadee graphics color)
   #:use-module (chickadee graphics engine)
+  #:use-module (chickadee graphics seagull)
   #:use-module (chickadee graphics shader)
   #:use-module (chickadee graphics texture)
   #:use-module (chickadee graphics buffer)
@@ -39,72 +40,53 @@
 (define-graphics-variable 9-patch-model-matrix (make-null-matrix4))
 (define-graphics-variable 9-patch-mvp-matrix (make-null-matrix4))
 (define-graphics-variable 9-patch-margins (make-null-rect))
+(define-vertex-shader 9-patch-vertex
+  ((in vec2 position)
+   (in vec2 distance)
+   (out vec2 frag-distance)
+   (uniform mat4 mvp))
+  (outputs
+   (vertex:position (* mvp (vec4 (-> position x) (-> position y) 0.0 1.0)))
+   (frag-distance distance)))
+(define-fragment-shader 9-patch-fragment
+  ((in vec2 frag-distance)
+   (out vec4 frag-color)
+   (uniform vec4 subtexture)
+   (uniform vec4 margins)
+   (uniform float width)
+   (uniform float height)
+   (uniform sampler-2d color-texture)
+   (uniform vec4 tint)
+   (uniform int mode))
+  (let ((patch (lambda (d m0 m1 length tex-length)
+                 (cond
+                  ;; Inside the left/bottom margin.
+                  ((<= d m0)
+                   (* d tex-length))
+                  ;; Inside the right/top margin.
+                  ((>= d (- length m1))
+                   (- tex-length (* (- length d) tex-length)))
+                  ;; In the middle: stretch mode.
+                  ((= mode 0)
+                   (mix m0 (- tex-length m1) (/ (- d m0) (- length m0 m1))))
+                  ;; In the middle: tile mode.
+                  (else
+                   (+ m0 (mod (- d m0) (- tex-length m0 m1))))))))
+    (let ((texcoord (+ (vec2 (-> subtexture x) (-> subtexture y))
+                       (vec2 (patch (-> frag-distance x)
+                                    (-> margins x)
+                                    (-> margins y)
+                                    width
+                                    (-> subtexture z))
+                             (patch (-> frag-distance y)
+                                    (-> margins z)
+                                    (-> margins w)
+                                    height
+                                    (-> subtexture w))))))
+      (outputs
+       (frag-color (* (texture-2d color-texture texcoord) tint))))))
 (define-graphics-variable 9-patch-shader
-  (strings->shader
-   "
-#ifdef GLSL330
-layout (location = 0) in vec2 position;
-layout (location = 1) in vec2 distance;
-#elif defined(GLSL130)
-in vec2 position;
-in vec2 distance;
-#elif defined(GLSL120)
-attribute vec2 position;
-attribute vec2 distance;
-#endif
-#ifdef GLSL120
-varying vec2 fragDistance;
-#else
-out vec2 fragDistance;
-#endif
-uniform mat4 mvp;
-
-void main(void) {
-    fragDistance = distance;
-    gl_Position = mvp * vec4(position.xy, 0.0, 1.0);
-}
-"
-   "
-#ifdef GLSL120
-varying vec2 fragDistance;
-#else
-in vec2 fragDistance;
-#endif
-#ifdef GLSL330
-out vec4 fragColor;
-#endif
-uniform vec4 subtexture;
-uniform vec4 margins;
-uniform float width;
-uniform float height;
-uniform sampler2D colorTexture;
-uniform vec4 tint;
-uniform int mode;
-
-float patch(float d, float m0, float m1, float length, float texLength) {
-    if(d <= m0) { // inside the left/bottom margin.
-        return d * texLength;
-    } else if(d >= length - m1) { // inside the right/top margin.
-        return texLength - ((length - d) * texLength);
-    } else if(mode == 0) { // in the middle, stretch mode.
-        return  mix(m0, texLength - m1, (d - m0) / (length - m0 - m1));
-    } else { // in the middle, tile mode.
-        return m0 + mod((d - m0), texLength - m0 - m1);
-    }
-}
-
-void main (void) {
-    vec2 texcoord = subtexture.xy;
-    texcoord.x += patch(fragDistance.x, margins.x, margins.y, width, subtexture.z);
-    texcoord.y += patch(fragDistance.y, margins.z, margins.w, height, subtexture.w);
-
-#ifdef GLSL330
-    fragColor = texture(colorTexture, texcoord) * tint;
-#else
-    gl_FragColor = texture2D(colorTexture, texcoord) * tint;
-#endif
-}
-"))
+  (compile-shader 9-patch-vertex 9-patch-fragment))
 
 (define* (draw-9-patch* texture
                         rect
-- 
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