struct VSInput {
    float2 position : POSITION;
    float2 uv : TEXCOORD0;
    float4 color : COLOR0;
};

struct PSInput {
    float4 position : SV_Position;
    float2 uv : TEXCOORD0;
    float4 color : COLOR0;
};

struct Constants {
    matrix transform;
};
ParameterBlock<Constants> param_buffer : register(b0);

PSInput vertex_main(VSInput input) {
    PSInput output;
    output.position = mul(float4(input.position, 0.0f, 1.0f), param_buffer.transform);
    output.uv = input.uv;
    output.color = input.color;
    return output;
}

Texture2D sdf_texture : register(t0);
SamplerState sdf_sampler : register(s0);

struct FontParams {
    float smoothing;      // 平滑度
    float thickness;      // 字体粗细
    float outline_width;   // 描边宽度
    float4 outline_color;  // 描边颜色
}
ParameterBlock<FontParams> font_param : register(b1);

float4 pixel_main(PSInput input) : SV_Target {
    // 采样SDF纹理
    float distance = sdf_texture.Sample(sdf_sampler, input.uv).r;
    
    // 计算主要形状
    float alpha = smoothstep(font_param.thickness - font_param.smoothing, 
                           font_param.thickness + font_param.smoothing, 
                           distance);
                           
    // 计算轮廓
    float outline_alpha = smoothstep(font_param.thickness - font_param.outline_width - font_param.smoothing,
                                  font_param.thickness - font_param.outline_width + font_param.smoothing,
                                  distance);
                                  
    // 混合主要颜色和轮廓颜色
    float4 main_color = input.color * alpha;
    float4 outline = font_param.outline_color * (outline_alpha - alpha);
    
    return main_color + outline;
}