1 files changed, 90 insertions, 0 deletions
diff --git a/gfx/wr/webrender/res/ps_quad_conic_gradient.glsl b/gfx/wr/webrender/res/ps_quad_conic_gradient.glsl
new file mode 100644
index 0000000000..afd02b2776
--- /dev/null
+++ b/gfx/wr/webrender/res/ps_quad_conic_gradient.glsl
@@ -0,0 +1,90 @@
+/* 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 shader renders radial graidents in a color or alpha target.
+
+#include ps_quad,gradient
+
+#define PI                  3.141592653589793
+
+// x: start offset, y: offset scale, z: angle
+// Packed in to a vector to work around bug 1630356.
+flat varying highp vec3 v_start_offset_offset_scale_angle_vec;
+#define v_start_offset v_start_offset_offset_scale_angle_vec.x
+#define v_offset_scale v_start_offset_offset_scale_angle_vec.y
+#define v_angle v_start_offset_offset_scale_angle_vec.z
+
+varying highp vec2 v_dir;
+
+#ifdef WR_VERTEX_SHADER
+struct ConicGradient {
+    vec2 center;
+    vec2 scale;
+    float start_offset;
+    float end_offset;
+    float angle;
+    // 1.0 if the gradient should be repeated, 0.0 otherwise.
+    float repeat;
+};
+
+ConicGradient fetch_conic_gradient(int address) {
+    vec4[2] data = fetch_from_gpu_buffer_2f(address);
+
+    return ConicGradient(
+        data[0].xy,
+        data[0].zw,
+        data[1].x,
+        data[1].y,
+        data[1].z,
+        data[1].w
+    );
+}
+
+void pattern_vertex(PrimitiveInfo info) {
+    ConicGradient gradient = fetch_conic_gradient(info.pattern_input.x);
+    v_gradient_address.x = info.pattern_input.y;
+    v_gradient_repeat.x = gradient.repeat;
+
+    // Store 1/d where d = end_offset - start_offset
+    // If d = 0, we can't get its reciprocal. Instead, just use a zero scale.
+    float d = gradient.end_offset - gradient.start_offset;
+    v_offset_scale = d != 0.0 ? 1.0 / d : 0.0;
+
+    v_angle = PI / 2.0 - gradient.angle;
+    v_start_offset = gradient.start_offset * v_offset_scale;
+    v_dir = ((info.local_pos - info.local_prim_rect.p0) * gradient.scale - gradient.center);
+}
+
+#endif
+
+
+#ifdef WR_FRAGMENT_SHADER
+
+// From https://math.stackexchange.com/questions/1098487/atan2-faster-approximation
+float approx_atan2(float y, float x) {
+    vec2 a = abs(vec2(x, y));
+    float slope = min(a.x, a.y) / max(a.x, a.y);
+    float s2 = slope * slope;
+    float r = ((-0.0464964749 * s2 + 0.15931422) * s2 - 0.327622764) * s2 * slope + slope;
+
+    r = if_then_else(float(a.y > a.x), 1.57079637 - r, r);
+    r = if_then_else(float(x < 0.0),   3.14159274 - r, r);
+    // To match atan2's behavior, -0.0 should count as negative and flip the sign of r.
+    // Does this matter in practice in the context of conic gradients?
+    r = r * sign(y);
+
+    return r;
+}
+
+vec4 pattern_fragment(vec4 color) {
+    // Use inverse trig to find the angle offset from the relative position.
+    vec2 current_dir = v_dir;
+    float current_angle = approx_atan2(current_dir.y, current_dir.x) + v_angle;
+    float offset = fract(current_angle / (2.0 * PI)) * v_offset_scale - v_start_offset;
+
+    color *= sample_gradient(offset);
+    return color;
+}
+
+#endif