#version 300 es

precision mediump float;
precision mediump sampler2DArray;

// (x offset, y offset, zoom)
uniform vec3 transform;
// (window width, window height, _)
uniform vec3 window;

in vec4 pass_style;
out vec4 f_color;

void main() {
    // See actually_upload in drawing.rs to understand the different things encoded.
    if (pass_style[0] == 100.0) {
        // The hatching should be done in map-space, so panning/zooming doesn't move the stripes.
        // This is screen_to_map, also accounting for the y-inversion done by the vertex shader.
        float map_x = (gl_FragCoord.x + transform[0]) / transform[2];
        float map_y = (window[1] - gl_FragCoord.y + transform[1]) / transform[2];
        if (mod(map_x + map_y, 2.0) <= 0.1) {
            f_color = vec4(0.0, 1.0, 1.0, 1.0);
        } else if (mod(map_x - map_y, 2.0) <= 0.1) {
            f_color = vec4(0.0, 1.0, 1.0, 1.0);
        } else {
            // Let the polygon with its original colors show instead.
            discard;
	}
    } else if (pass_style[0] == 101.0) {
        float map_x = (gl_FragCoord.x + transform[0]) / transform[2];
        float map_y = (window[1] - gl_FragCoord.y + transform[1]) / transform[2];
        if (mod(map_x + map_y, 2.0) <= 0.5) {
            f_color = vec4(1.0, 1.0, 1.0, 1.0);
        } else {
            // Let the polygon with its original colors show instead.
            discard;
	}
    } else {
        f_color = pass_style;
    }
}