z-bar-qt/assets/shaders/geminiglow.frag

#version 440

layout(location = 0) in vec2 qt_TexCoord0;
layout(location = 0) out vec4 fragColor;

layout(std140, binding = 0) uniform buf {
    mat4  qt_Matrix;
    float qt_Opacity;
    vec2  itemSize;
    vec2  rectSize;
    float radius;
    float glowSize;
    float innerGlow;
    float lineWidth;
    float phase;
    float intensity;
    vec4  color1;
    vec4  color2;
    vec4  color3;
    vec4  color4;
};

const float TAU = 6.28318530718;

float sdRoundBox(vec2 p, vec2 halfSize, float r)
{
    vec2 q = abs(p) - (halfSize - r);
    return length(max(q, 0.0)) + min(max(q.x, q.y), 0.0) - r;
}

vec3 palette(float t)
{
    t = fract(t) * 4.0;
    float f = smoothstep(0.0, 1.0, fract(t));
    if (t < 1.0) return mix(color1.rgb, color2.rgb, f);
    if (t < 2.0) return mix(color2.rgb, color3.rgb, f);
    if (t < 3.0) return mix(color3.rgb, color4.rgb, f);
    return mix(color4.rgb, color1.rgb, f);
}

float hash(vec2 p)
{
    return fract(sin(dot(p, vec2(12.9898, 78.233))) * 43758.5453);
}

void main()
{
    vec2 p = (qt_TexCoord0 - 0.5) * itemSize;

    float r = clamp(radius, 0.0, min(rectSize.x, rectSize.y) * 0.5);
    float d = sdRoundBox(p, rectSize * 0.5, r);

    // ~1px antialiasing width
    float aa = max(fwidth(d), 0.75);

    // Coverage of the shape: 1 inside, 0 outside, soft across the edge
    float inside = 1.0 - smoothstep(-aa, aa, d);

    // Only skip work when clearly outside and there's no outer glow
    if (glowSize <= 0.0 && d > aa) {
        fragColor = vec4(0.0);
        return;
    }

    float ang = atan(p.y, p.x);
    float a2  = phase * TAU;
    float u = ang / TAU + 0.5 + phase;
    u += 0.07 * sin(ang * 2.0 + a2) + 0.04 * sin(ang * 3.0 - a2 * 2.0);
    vec3 col = palette(u);

    float g = 0.0;
    if (d > 0.0) {
        float t = clamp(d / max(glowSize, 0.001), 0.0, 1.0);
        g = (glowSize > 0.0) ? pow(1.0 - t, 3.0) : 0.0;
    } else if (innerGlow > 0.0) {
        float t = clamp(-d / innerGlow, 0.0, 1.0);
        g = pow(1.0 - t, 3.0);
    }

    float pulse = 0.9 + 0.1 * sin(a2 * 2.0 + ang);
    g *= pulse;

    // Line: inside only, with a soft inner edge AND a soft outer edge
    float line = 0.0;
    if (lineWidth > 0.0) {
        float inner = 1.0 - smoothstep(lineWidth - aa, lineWidth + aa, -d);
        line = inner * inside;
    }

    float a = clamp(g * intensity + line * 0.9, 0.0, 1.0);

    // Antialias the outer silhouette when there is no outer glow
    if (glowSize <= 0.0)
        a *= inside;

    col = mix(col, vec3(1.0), line * 0.25);

    a += (hash(gl_FragCoord.xy) - 0.5) / 255.0;
    a = clamp(a, 0.0, 1.0);

    fragColor = vec4(col * a, a) * qt_Opacity;
}