#version 300 es
// highp is required: the SDF works in absolute pixel coordinates, and mediump loses ~2px of
// precision past x=2000, which eats the 1px feather on a high-DPI phone
precision highp float;
in vec4 vColor;
in highp vec2 vPos;
flat in highp vec4 vSegment;
flat in highp float vHalfWidth;
out vec4 fragColor;
void main() {
    vec2 pa = vPos - vSegment.xy;
    vec2 ba = vSegment.zw - vSegment.xy;
    float h = clamp(dot(pa, ba) / dot(ba, ba), 0.0, 1.0);
    float dist = length(pa - (ba * h));

    float alpha = 1.0 - smoothstep(vHalfWidth - 1.0, vHalfWidth, dist);
    if (alpha <= 0.0)
        discard;

    fragColor = vec4(vColor.rgb, vColor.a * alpha);
}