Shader "UI/SDFOutline"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
        _Outline ("Outline", Color) = (0,0,0,1)
        _SDFOutline("SDF Outline", Range(0, 1)) = 0.5
        _SDFThreshold("SDF Threshold", Range(0, 1)) = 0.6
        _Smoothness("Smoothness", Range(0, 1)) = 0.2
 
        _StencilComp ("Stencil Comparison", Float) = 8
        _Stencil ("Stencil ID", Float) = 0
        _StencilOp ("Stencil Operation", Float) = 0
        _StencilWriteMask ("Stencil Write Mask", Float) = 255
        _StencilReadMask ("Stencil Read Mask", Float) = 255
 
        _ColorMask ("Color Mask", Float) = 15
 
        [Toggle(UNITY_UI_ALPHACLIP)] _UseUIAlphaClip ("Use Alpha Clip", Float) = 0
    }
 
    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }
 
        Stencil
        {
            Ref [_Stencil]
            Comp [_StencilComp]
            Pass [_StencilOp]
            ReadMask [_StencilReadMask]
            WriteMask [_StencilWriteMask]
        }
 
        Cull Off
        Lighting Off
        ZWrite Off
        ZTest [unity_GUIZTestMode]
        Blend SrcAlpha OneMinusSrcAlpha
        ColorMask [_ColorMask]
         
        Pass
        {
            Name "Default"
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 2.0
 
            #include "UnityCG.cginc"
            #include "UnityUI.cginc"
 
            #pragma multi_compile __ UNITY_UI_CLIP_RECT
            #pragma multi_compile __ UNITY_UI_ALPHACLIP
 
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };
 
            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                float2 texcoord  : TEXCOORD0;
                float4 worldPosition : TEXCOORD1;
                UNITY_VERTEX_OUTPUT_STEREO
            };
 
            sampler2D _MainTex;
            fixed4 _Color;
            fixed4 _Outline;
            fixed4 _TextureSampleAdd;
            float4 _ClipRect;
            float4 _MainTex_ST;
            float _SDFOutline;
            float _SDFThreshold;
            float _Smoothness;
 
            v2f vert(appdata_t v)
            {
                v2f OUT;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(OUT);
                OUT.worldPosition = v.vertex;
                OUT.vertex = UnityObjectToClipPos(OUT.worldPosition);
 
                OUT.texcoord = TRANSFORM_TEX(v.texcoord, _MainTex);
 
                OUT.color = v.color * _Color;
                return OUT;
            }
 
            fixed4 frag(v2f IN) : SV_Target
            {
                fixed col = tex2D(_MainTex, IN.texcoord).x;
                half4 color = _TextureSampleAdd + IN.color;

                float distance = smoothstep(_SDFOutline, saturate(_SDFOutline + _Smoothness), col); 
                color.rgb = lerp(_Outline, color, distance);
                
                color.a *= smoothstep(_SDFThreshold, saturate(_SDFThreshold + _Smoothness), col);
                #ifdef UNITY_UI_CLIP_RECT
                color.a *= UnityGet2DClipping(IN.worldPosition.xy, _ClipRect);
                #endif
 
                #ifdef UNITY_UI_ALPHACLIP
                clip (color.a - 0.001);
                #endif
 
                return color;
            }
        ENDCG
        }
    }
}