#version 110

/*
    zfast_crt_nogeo - A simple, fast CRT shader.

    Copyright (C) 2017 Greg Hogan (SoltanGris42)
    Copyright (C) 2023 Jose Linares (Dogway)

    This program is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by the Free
    Software Foundation; either version 2 of the License, or (at your option)
    any later version.


Notes:  This shader does scaling with a weighted linear filter
        based on the algorithm by Iñigo Quilez here:
        https://iquilezles.org/articles/texture/
        but modified to be somewhat sharper. Then a scanline effect that varies
        based on pixel brightness is applied along with a monochrome aperture mask.
        This shader runs at ~60fps on the Chromecast HD (10GFlops) on a 1080p display.
        (https://forums.libretro.com/t/android-googletv-compatible-shaders-nitpicky)

Dogway: This is the same as zfast_crt_geo but without the screen curvature for extra
        performance, specially for (320x240) "widescreen" games like Sega Genesis, NeoGeo, etc.

*/


// Parameter lines go here:
#pragma parameter SCANLINE_WEIGHT "Scanline Amount"     9.0 0.0 15.0 0.5
#pragma parameter MASK_DARK       "Mask Effect Amount"  0.4 0.0 1.0 0.05

#if defined(VERTEX)

#if __VERSION__ >= 130
#define COMPAT_VARYING out
#define COMPAT_ATTRIBUTE in
#define COMPAT_TEXTURE texture
#else
#define COMPAT_VARYING varying
#define COMPAT_ATTRIBUTE attribute
#define COMPAT_TEXTURE texture2D
#endif

#ifdef GL_ES
#define COMPAT_PRECISION mediump
#else
#define COMPAT_PRECISION
#endif

COMPAT_ATTRIBUTE vec4 VertexCoord;
COMPAT_ATTRIBUTE vec4 COLOR;
COMPAT_ATTRIBUTE vec4 TexCoord;
COMPAT_VARYING vec4 COL0;
COMPAT_VARYING vec4 TEX0;
COMPAT_VARYING vec2 invDims;
COMPAT_VARYING vec2 scale;

vec4 _oPosition1;
uniform mat4 MVPMatrix;
uniform COMPAT_PRECISION int FrameDirection;
uniform COMPAT_PRECISION int FrameCount;
uniform COMPAT_PRECISION vec2 OutputSize;
uniform COMPAT_PRECISION vec2 TextureSize;
uniform COMPAT_PRECISION vec2 InputSize;

// compatibility #defines
#define vTexCoord TEX0.xy

#ifdef PARAMETER_UNIFORM
// All parameter floats need to have COMPAT_PRECISION in front of them
uniform COMPAT_PRECISION float SCANLINE_WEIGHT;
uniform COMPAT_PRECISION float MASK_DARK;
#else
#define SCANLINE_WEIGHT 9.0
#define MASK_DARK 0.4
#endif

void main()
{
    gl_Position = MVPMatrix * VertexCoord;

    TEX0.xy = TexCoord.xy*1.00001;
    invDims = 1.0/TextureSize.xy;
}

#elif defined(FRAGMENT)

#ifdef GL_ES
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif
#ifdef GL_FRAGMENT_PRECISION_HIGH
#define COMPAT_PRECISION highp
#else 
#define COMPAT_PRECISION mediump
#endif
#else
#define COMPAT_PRECISION
#endif

#if __VERSION__ >= 130
#define COMPAT_VARYING in
#define COMPAT_TEXTURE texture
out COMPAT_PRECISION vec4 FragColor;
#else
#define COMPAT_VARYING varying
#define FragColor gl_FragColor
#define COMPAT_TEXTURE texture2D
#endif

uniform COMPAT_PRECISION int FrameDirection;
uniform COMPAT_PRECISION int FrameCount;
uniform COMPAT_PRECISION vec2 OutputSize;
uniform COMPAT_PRECISION vec2 TextureSize;
uniform COMPAT_PRECISION vec2 InputSize;
uniform sampler2D Texture;
COMPAT_VARYING vec4 TEX0;
COMPAT_VARYING vec2 invDims;

// compatibility #defines
#define Source Texture
#define vTexCoord TEX0.xy
#define scale vec2(TextureSize.xy/InputSize.xy)

#ifdef PARAMETER_UNIFORM
// All parameter floats need to have COMPAT_PRECISION in front of them
uniform COMPAT_PRECISION float SCANLINE_WEIGHT;
uniform COMPAT_PRECISION float MASK_DARK;
#else
#define SCANLINE_WEIGHT 9.0
#define MASK_DARK 0.4
#endif

#define MSCL (OutputSize.y > 1499.0 ? 0.3333 : 0.5)
// This compensates the scanline+mask embedded gamma from the beam dynamics
#define pwr vec3(1.0/((-0.0325*SCANLINE_WEIGHT+1.0)*(-0.311*MASK_DARK+1.0))-1.2)



// NTSC-J (D93) -> Rec709 D65 Joint Matrix (with D93 simulation)
// This is compensated for a linearization hack (RGB*RGB and then sqrt())
const mat3 P22D93 = mat3(
     1.00000, 0.00000, -0.06173,
     0.07111, 0.96887, -0.01136,
     0.00000, 0.08197,  1.07280);


// Returns gamma corrected output, compensated for scanline+mask embedded gamma
vec3 inv_gamma(vec3 col, vec3 power)
{
    vec3 cir  = col-1.0;
         cir *= cir;
         col  = mix(sqrt(col),sqrt(1.0-cir),power);
    return col;
}


void main()
{
    vec2 vpos   = vTexCoord*scale;

    vpos  *= (1.0 - vpos.xy);
    float vig = vpos.x * vpos.y * 46.0;
          vig = min(sqrt(vig), 1.0);


    // This is just like "Quilez Scaling" but sharper
    COMPAT_PRECISION float p = vTexCoord.y * TextureSize.y;
    // Snap to the center of the underlying texel.
    COMPAT_PRECISION float i = floor(p) + 0.5;
    COMPAT_PRECISION float f = p - i;
    COMPAT_PRECISION float Y = f*f;
    p = (i + 4.0*Y*f)*invDims.y;

    COMPAT_PRECISION float whichmask = floor(vTexCoord.x*scale.x*OutputSize.x)*-MSCL;
    COMPAT_PRECISION float mask = 1.0 + float(fract(whichmask) < MSCL)    *-MASK_DARK;
    COMPAT_PRECISION vec3 colour = COMPAT_TEXTURE(Source, vec2(vTexCoord.x,p)).rgb;

    colour = max((colour*colour) * (P22D93 * vig), 0.0);

    COMPAT_PRECISION float scanLineWeight = (1.5 - SCANLINE_WEIGHT*(Y - Y*Y));

    FragColor.rgba = vec4(inv_gamma(colour.rgb*mix(scanLineWeight*mask, 1.0, colour.r*0.26667+colour.g*0.26667+colour.b*0.26667),pwr),1.0);

}
#endif
