1 files changed, 41 insertions, 0 deletions
diff --git a/gfx/wr/webrender/res/sample_color0.glsl b/gfx/wr/webrender/res/sample_color0.glsl
new file mode 100644
index 0000000000..fa8d85961d
--- /dev/null
+++ b/gfx/wr/webrender/res/sample_color0.glsl
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/// This file provides the boilerplate for sampling from sColor0 with strict sample bounds.
+
+#include shared
+
+flat varying mediump vec4 v_uv0_sample_bounds;
+varying highp vec2 v_uv0;
+
+#ifdef WR_VERTEX_SHADER
+
+/// sample_pos is in 0..1 normalized coordinates
+/// uv_rect is in pixel.
+void vs_init_sample_color0(vec2 sample_pos, RectWithEndpoint uv_rect) {
+    vec2 uv = mix(uv_rect.p0, uv_rect.p1, sample_pos);
+
+    vec2 texture_size = vec2(TEX_SIZE(sColor0));
+
+    v_uv0 = uv / texture_size;
+
+    v_uv0_sample_bounds = vec4(
+        uv_rect.p0 + vec2(0.5),
+        uv_rect.p1 - vec2(0.5)
+    ) / texture_size.xyxy;
+}
+
+#endif
+
+#ifdef WR_FRAGMENT_SHADER
+
+/// The vertex shader must have called vs_init_sample_color0
+vec4 fs_sample_color0() {
+    vec2 uv = clamp(v_uv0, v_uv0_sample_bounds.xy, v_uv0_sample_bounds.zw);
+    vec4 texel = TEX_SAMPLE(sColor0, uv);
+
+    return texel;
+}
+
+#endif