#version {{version}}

// pathfinder/resources/shaders/post.fs.glsl
//
// Copyright © 2019 The Pathfinder Project Developers.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// TODO(pcwalton): This could be significantly optimized by operating on a
// sparse per-tile basis.

precision highp float;

uniform sampler2D uSource;
uniform vec2 uFramebufferSize;

in vec2 vTexCoord;

out vec4 oFragColor;

{{{include_post_gamma_correct}}}
{{{include_post_convolve}}}

// Convolve horizontally in this pass.
float sample1Tap(float offset) {
    return texture(uSource, vec2(vTexCoord.x + offset, vTexCoord.y)).r;
}

void main() {
    // Apply defringing if necessary.
    vec4 fgColor = texture(uSource, vTexCoord);
    if (uKernel.w != 0.0) {
        vec4 alphaLeft, alphaRight;
        float alphaCenter;
        sample9Tap(alphaLeft, alphaCenter, alphaRight, 1.0 / uFramebufferSize.x);

        fgColor.rgb =
            vec3(convolve7Tap(alphaLeft, vec3(alphaCenter, alphaRight.xy)),
                 convolve7Tap(vec4(alphaLeft.yzw, alphaCenter), alphaRight.xyz),
                 convolve7Tap(vec4(alphaLeft.zw, alphaCenter, alphaRight.x), alphaRight.yzw));
    }

    // Apply gamma correction if necessary.
    if (uGammaCorrectionBGColor.a > 0.0)
        fgColor.rgb = gammaCorrect(fgColor.rgb);

    // Finish.
    oFragColor = fgColor;
}