make shader's main function receive normalised co-ordinates

[TodePond]

currently, the second argument gives a positions that's screensize specific. i think it would be more accessible if it passed through 0.0 to 1.0 coordinates of the screen instead

[TristanCacqueray]

Note that it is that way to be compatible with shadertoy, but it's true that it is annoying to do the conversion manually. Perhaps we could have a default template to take care of this:

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = fragCoord/iResolution.xy;

    // Pixel color
    vec3 col = uv.xyx;

    // Output to screen
    fragColor = vec4(col,1.0);
}

[TodePond]

im not so familiar with the shadertoy community, but im looking at whats currently stopping me from messing with it. i guess i would kinda like uv to be a globally accessible variable? i dunno