physarum/vendor/gioui.org/shader/gio/zstencil.frag.0.glsl100es

#version 100
precision mediump float;
precision highp int;

varying highp vec2 vTo;
varying highp vec2 vFrom;
varying highp vec2 vCtrl;

void main()
{
    float dx = vTo.x - vFrom.x;
    bool increasing = vTo.x >= vFrom.x;
    bvec2 _35 = bvec2(increasing);
    vec2 left = vec2(_35.x ? vFrom.x : vTo.x, _35.y ? vFrom.y : vTo.y);
    bvec2 _41 = bvec2(increasing);
    vec2 right = vec2(_41.x ? vTo.x : vFrom.x, _41.y ? vTo.y : vFrom.y);
    vec2 extent = clamp(vec2(vFrom.x, vTo.x), vec2(-0.5), vec2(0.5));
    float midx = mix(extent.x, extent.y, 0.5);
    float x0 = midx - left.x;
    vec2 p1 = vCtrl - left;
    vec2 v = right - vCtrl;
    float t = x0 / (p1.x + sqrt((p1.x * p1.x) + ((v.x - p1.x) * x0)));
    float y = mix(mix(left.y, vCtrl.y, t), mix(vCtrl.y, right.y, t), t);
    vec2 d_half = mix(p1, v, vec2(t));
    float dy = d_half.y / d_half.x;
    float width = extent.y - extent.x;
    dy = abs(dy * width);
    vec4 sides = vec4((dy * 0.5) + y, (dy * (-0.5)) + y, (0.5 - y) / dy, ((-0.5) - y) / dy);
    sides = clamp(sides + vec4(0.5), vec4(0.0), vec4(1.0));
    float area = 0.5 * ((((sides.z - (sides.z * sides.y)) + 1.0) - sides.x) + (sides.x * sides.w));
    area *= width;
    if (width == 0.0)
    {
        area = 0.0;
    }
    gl_FragData[0].x = area;
}