#version 440

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

layout(std140, binding = 0) uniform buf {
    // qt_Matrix and qt_Opacity must always be both present
    // if the built-in vertex shader is used.
    mat4 qt_Matrix;
    float qt_Opacity;
    vec4 color;
    float relativeSizeX;
    float relativeSizeY;
    float spread;
};

float linearstep(float e0, float e1, float x)
{
    return clamp((x - e0) / (e1 - e0), 0.0, 1.0);
}

void main()
{
    float alpha =
        smoothstep(0.0, relativeSizeX, 0.5 - abs(0.5 - qt_TexCoord0.x)) *
        smoothstep(0.0, relativeSizeY, 0.5 - abs(0.5 - qt_TexCoord0.y));

    float spreadMultiplier = linearstep(spread, 1.0 - spread, alpha);
    fragColor = color * qt_Opacity * spreadMultiplier * spreadMultiplier;
}