From 9b5d364add330fc18100491bf3c57316a27183f5 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 27 Aug 2021 16:07:38 -0400
Subject: graphics: path: Separate fill/stroke into different shaders.

---
 data/shaders/path-stroke-frag.glsl | 77 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 data/shaders/path-stroke-frag.glsl

(limited to 'data/shaders/path-stroke-frag.glsl')

diff --git a/data/shaders/path-stroke-frag.glsl b/data/shaders/path-stroke-frag.glsl
new file mode 100644
index 0000000..9682c8f
--- /dev/null
+++ b/data/shaders/path-stroke-frag.glsl
@@ -0,0 +1,77 @@
+// -*- mode: c -*-
+
+#ifdef GLSL330
+out vec4 fragColor;
+#else
+#define fragColor gl_FragColor
+#endif
+
+#ifdef GLSL120
+varying vec2 fragTex;
+varying float fragStrokeLength;
+#else
+in vec2 fragTex;
+in float fragStrokeLength;
+#endif
+
+uniform vec4 color;
+uniform float feather;
+uniform int strokeClosed;
+uniform float strokeWidth;
+uniform int strokeCap;
+uniform int strokeMiterStyle;
+uniform float strokeMiterLimit;
+
+float infinity = 1.0 / 0.0;
+
+void main(void) {
+  if (color.a <= 0.0) {
+    discard;
+  }
+
+  float hw = strokeWidth / 2.0;
+  float u = fragTex.x;
+  float v = fragTex.y;
+  float dx;
+  float dy;
+  float d;
+
+  // Stroke caps.
+  if (u < 0 || u > fragStrokeLength) {
+    if (u < 0) {
+      dx = abs(u);
+    } else {
+      dx = u - fragStrokeLength;
+    }
+    dy = abs(v);
+
+    if (strokeCap == 0) { // none
+      d = infinity;
+    } else if (strokeCap == 1) { // butt
+      d = max(dx + hw - 2 * feather, dy);
+    } else if (strokeCap == 2) { // square
+      d = max(dx, dy);
+    } else if (strokeCap == 3) { // round
+      d = sqrt(dx * dx + dy * dy);
+    } else if (strokeCap == 4) { // triangle out
+      d = dx + dy;
+    } else if (strokeCap == 5) { // triangle in
+      d = max(dy, hw - feather + dx - dy);
+    }
+    // Stroke inner/join
+  } else {
+    d = abs(v);
+  }
+
+  if(d <= hw) {
+    fragColor = color;
+  } else {
+    vec4 c = vec4(color.rgb, color.a * (1.0 - ((d - hw) / feather)));
+
+    if (c.a <= 0.0) {
+      discard;
+    }
+
+    fragColor = c;
+  }
+}
-- 
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