input View {
  mat4 mvp,
  mat4 proj,
  mat4 proj_inverse,
  mat4 view,
  mat4 world, //geometry.world atm
  float2 fov, //fov.x, fov.y
  float2 resolution,
  float4 target_region,
  float4 target_region_size
}

input Font {
  image2D pages[8]
}

input FUI {
  float2 canvas_size,
  #0 image2D tex_mask
}

stage vertex vert(
    input { View view },
    vertex in {
        #0 float4 pos,
        #1 float4 color,
        #2 float2 uv,
        #3 float4 data
    },
    fragment out {
        float4 color,
        float2 uv,
        float2 mask_uv,
        float clip
    })
{
    out.uv = in.uv;
    out.color = in.color;
    out.clip = in.data.x;
    out.mask_uv = float2(in.data.y, 1.0 - in.data.z);

    stage.pos = input.view.mvp * float4(in.pos.xyz, 1.0);
}

stage fragment frag(
    input { FUI ui, Font font },
    fragment in {
        float4 color,
        float2 uv,
        float2 mask_uv,
        float clip,
        float page
    })
{
    //outside mask uvs?
    bool outside_mask = in.mask_uv.x < 0.0 || 
                        in.mask_uv.x > 1.0 ||
                        in.mask_uv.y < 0.0 ||
                        in.mask_uv.y > 1.0;
                        
    if(outside_mask) {
        discard;
        // stage.color[0] = float4(1,0.2,0.3,1);
        return;
    }

    float4 mask = texture(input.ui.tex_mask, in.mask_uv);

    //16 bit mask
        // float mask_clip = round(mask.r * 65535.0);
    //8 bit mask
        int lsb = int(round(mask.r * 255.0));
        int msb = int(round(mask.g * 255.0)) * 256; //<< 8;
        int mask_clip = lsb | msb;
        // int mask_clip = lsb + msb; //webgl1

        //outside our clipping bounds?
    int my_clip = int(in.clip);
    if(my_clip != 0 && mask_clip < my_clip) {
        discard;
        // stage.color[0] = float4(0,1,1,0.2);
        return;
    }

    int page = int(in.page);
    float4 msdf_sample = texture(input.font.pages[0], in.uv.xy);
    if(page == 1) { msdf_sample = texture(input.font.pages[1], in.uv.xy); }
    if(page == 2) { msdf_sample = texture(input.font.pages[2], in.uv.xy); }
    if(page == 3) { msdf_sample = texture(input.font.pages[3], in.uv.xy); }
    if(page == 4) { msdf_sample = texture(input.font.pages[4], in.uv.xy); }
    if(page == 5) { msdf_sample = texture(input.font.pages[5], in.uv.xy); }
    if(page == 6) { msdf_sample = texture(input.font.pages[6], in.uv.xy); }
    if(page == 7) { msdf_sample = texture(input.font.pages[7], in.uv.xy); }

    float r = msdf_sample.r;
    float g = msdf_sample.g;
    float b = msdf_sample.b;
    float median = max(min(r, g), min(max(r, g), b));
    float opacity = float(median > 0.5);

    stage.color[0] = float4(in.color.rgb, in.color.a * opacity * mask.a);

}