Implement gradient borders

1 files changed, 46 insertions, 0 deletions

diff --git a/src/render_helpers/shaders/gradient_border.frag b/src/render_helpers/shaders/gradient_border.frag
new file mode 100644
index 00000000..354968cf
--- /dev/null
+++ b/src/render_helpers/shaders/gradient_border.frag
@@ -0,0 +1,46 @@
+precision mediump float;
+uniform float alpha;
+#if defined(DEBUG_FLAGS)
+uniform float tint;
+#endif
+uniform vec2 size;
+varying vec2 v_coords;
+
+uniform vec4 color_from;
+uniform vec4 color_to;
+uniform float angle;
+uniform vec2 gradient_offset;
+uniform float gradient_width;
+uniform float gradient_total;
+
+#define FRAC_PI_2   1.57079632679
+#define PI          3.14159265359
+#define FRAC_3_PI_2 4.71238898038
+#define TAU         6.28318530718
+
+void main() {
+    vec2 coords = v_coords * size + gradient_offset;
+
+    if ((FRAC_PI_2 <= angle && angle < PI) || (FRAC_3_PI_2 <= angle && angle < TAU))
+        coords.x -= gradient_width;
+
+    float frag_angle = FRAC_PI_2;
+    if (coords.x != 0.0)
+        frag_angle = atan(coords.y, coords.x);
+
+    float angle_frag_to_grad = frag_angle - angle;
+
+    float frac = cos(angle_frag_to_grad) * length(coords) / gradient_total;
+    if (PI <= angle)
+        frac += 1.0;
+    frac = clamp(frac, 0.0, 1.0);
+
+    vec4 out_color = mix(color_from, color_to, frac);
+
+#if defined(DEBUG_FLAGS)
+    if (tint == 1.0)
+        out_color = vec4(0.0, 0.3, 0.0, 0.2) + out_color * 0.8;
+#endif
+
+    gl_FragColor = out_color;
+}