// Bloom: the brightest ink glows, a little. The glow itself is made by the
// shell at half resolution and below (bloom-down, bloom-up: a dual Kawase
// filter over a bright pass, in linear light) and arrives here in
// pardesBloom; this pass adds it to the frame. Only true highlights pass
// the threshold, and the strength stays in §8.2's budget (at most 5%) and
// under pardesCap, so no text or selection loses contrast below its own or
// 4.5. Tags, grips, notices and the cursor are left alone (pardesSpare).
// It is a Shadertoy file: pardes puts its prefix before it.

layout(set = 2, binding = 1) uniform sampler2D pardesBloom;

float strength() { return min(pardesByLevel(0.02, 0.035, 0.05), pardesCap); }

vec3 toLinear(vec3 c) {
    return mix(pow((c + 0.055) / 1.055, vec3(2.4)), c / 12.92, lessThanEqual(c, vec3(0.04045)));
}

vec3 toSrgb(vec3 c) {
    c = max(c, vec3(0.0));
    return mix(1.055 * pow(c, vec3(1.0 / 2.4)) - 0.055, c * 12.92, lessThanEqual(c, vec3(0.0031308)));
}

float ign(vec2 p) {
    return fract(52.9829189 * fract(dot(p, vec2(0.06711056, 0.00583715))));
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 uv = fragCoord / iResolution.xy;
    vec4 frame = texture(iChannel0, uv);
    if (pardesSpared(fragCoord)) {
        fragColor = frame;
        return;
    }
    vec3 glow = texture(pardesBloom, uv).rgb;
    vec3 col = toLinear(frame.rgb) + glow * strength();
    vec3 srgb = toSrgb(col);
    // Dithered: a glow's long falloff never bands.
    srgb += (ign(fragCoord) - 0.5) / 255.0 * step(1e-4, dot(glow, vec3(1.0)));
    fragColor = vec4(clamp(srgb, 0.0, 1.0), frame.a);
}