checkerboard.zig

const std = @import("std");

extern fn consoleLog(arg: u32) void;

const checkerboard_size: usize = 8;

// checkerboard_size * 2, where each pixel is 4 bytes (rgba)
var checkerboard_buffer = std.mem.zeroes(
    [checkerboard_size][checkerboard_size][4]u8,
);

// The returned pointer will be used as an offset integer to the wasm memory
export fn getCheckerboardBufferPointer() [*]u8 {
    return @ptrCast(&checkerboard_buffer);
}

export fn getCheckerboardSize() usize {
    return checkerboard_size;
}

export fn colorCheckerboard(
    dark_value_red: u8,
    dark_value_green: u8,
    dark_value_blue: u8,
    light_value_red: u8,
    light_value_green: u8,
    light_value_blue: u8,
) void {
    for (&checkerboard_buffer, 0..) |*row, y| {
        for (row, 0..) |*square, x| {
            var is_dark_square = true;

            if ((y % 2) == 0) {
                is_dark_square = false;
            }

            if ((x % 2) == 0) {
                is_dark_square = !is_dark_square;
            }

            var square_value_red = dark_value_red;
            var square_value_green = dark_value_green;
            var square_value_blue = dark_value_blue;
            if (!is_dark_square) {
                square_value_red = light_value_red;
                square_value_green = light_value_green;
                square_value_blue = light_value_blue;
            }

            square.*[0] = square_value_red;
            square.*[1] = square_value_green;
            square.*[2] = square_value_blue;
            square.*[3] = 255;
        }
    }
}