#version 410

uniform sampler2D fontTexture;
uniform sampler2D termTexture;
uniform vec2 termSize;


in vec3 colV;
in vec3 worldPos;
in vec2 uvV; // 0..1 across the terminal window

out vec4 fragColor;


vec3 mf(vec3 x)
{
    return x - floor(x);
}
void main (void)
{
    vec2 uv = uvV.xy;
    
    // termTexture has the character data as ascii/255 in red, termSize grid

    uv.y = 1.0 - uv.y;
    uv *= termSize;
    vec2 charPart = fract(uv);
    uv = (floor(uv) + vec2(0.5, 0.5)) / termSize;
    float charF = texture(termTexture, uv).r;
    charF *= 255.0;

    // textureFont is a 16 x 6 of char pictures, 0x20..0x7f
    float charLeft = mod(charF , 16.0) / 16.0;
    float charWidth = 1.0 / 16.0;
    float charTop = float(floor(charF / 16.0) - 2.0) / 6.0;
    float charHeight = 1.0 / 6.0;

    vec2 charSpot = vec2(charLeft, charTop) + charPart * vec2(charWidth, charHeight);
    float charVal = texture(fontTexture, charSpot).r;
    charVal = 1.0 - charVal;
    vec4 c = vec4(charVal, charVal, charVal, charVal * 3.0);
    
    c = max(c, vec4(.1,.1,.5,.5));
    if(charF < 1.0)
        discard;
    
    fragColor = c;
}