here_be_dragons/demo/www/index.js

import {Cell, World} from "mapgen-demo";
import { memory } from "mapgen-demo/mapgen_demo_bg";

const CELL_SIZE = 15;
const GRID_COLOR = "#CCCCCC";
const DEAD_COLOR = "#FFFFFF";
const ALIVE_COLOR = "#000000";
const TILE_SIZE = 39;

var world = null;
const width = 80;
const height = 50;

const infoDiv = document.getElementById('map-info');
// Give the canvas room for all of our cells and a 1px border
// around each of them.
const canvas = document.getElementById("mapgen-canvas");
canvas.height = CELL_SIZE * height;
canvas.width = CELL_SIZE * width;
// Load tiles bitmap
let tiles_image = new Image();
tiles_image.src = 'assets/tiles.png';

const ctx = canvas.getContext('2d');

function get_seed() {
    var seed_text = document.getElementById("seed").value;
    if( seed_text.length > 0) {
        return Number(seed_text);
    } 
    return Date.now();
}

// Map generators
function newCellularAutomata() {
    world = World.new_cellular_automata(width, height, get_seed());
    requestAnimationFrame(renderLoop);
}

function newSimpleRooms() {
    var seed = Date.now();
    world = World.new_simple_rooms(width, height, get_seed());
    requestAnimationFrame(renderLoop);
}

function newBspInterior() {
    var seed = Date.now();
    world = World.new_bsp_interior(width, height, get_seed());
    requestAnimationFrame(renderLoop);
}

function newDrunkard() {
    var seed = Date.now();
    world = World.new_drunkard(width, height, get_seed());
    requestAnimationFrame(renderLoop);
}

function newRandomGen() {
    var seed = Date.now();
    world = World.new_random(width, height, get_seed());
    requestAnimationFrame(renderLoop);
}

const renderLoop = () => {
    // universe.tick();

    drawCells();

    requestAnimationFrame(renderLoop);
};

const getIndex = (row, column) => {
    return row * width + column;
};

const is_inner_wall = (tiles, col, row) => {
    for (let c = Math.max(col-1, 0); c < Math.min(col+2, width); c++) {
        for (let r = Math.max(row-1, 0); r < Math.min(row+2, height); r++) {
            if ((c != col || r != row) && tiles[getIndex(r, c)] == Cell.Floor) {
                return false;
            }
        }
    }

    return true;
}

const draw_tile = (ctx, row, col, tile_type) => {
    var tile_x = 0;
    var tile_y = 0;
    if (tile_type == "floor") {
        tile_x = 3;
        tile_y = 2;
    } else if (tile_type == "inner_wall") {
        tile_x = 18;
        tile_y = 0;
    } else {
        tile_x = 0;
        tile_y = 3;
    }
    ctx.drawImage(
        tiles_image,
        tile_x * TILE_SIZE + 3,
        tile_y * TILE_SIZE + 3,
        TILE_SIZE - 3,
        TILE_SIZE - 3,
        col * CELL_SIZE,
        row * CELL_SIZE,
        CELL_SIZE,
        CELL_SIZE);

}

const drawCells = () => {
    const tilesPtr = world.tiles();
    const tiles = new Uint8Array(memory.buffer, tilesPtr, width * height);

    ctx.beginPath();

    for (let row = 0; row < height; row++) {
        for (let col = 0; col < width; col++) {
            const idx = getIndex(row, col);
            if (tiles[idx] == Cell.Floor) {
                draw_tile(ctx, row, col, "floor");
            } else if (is_inner_wall(tiles, col, row)){
                draw_tile(ctx, row, col, "inner-wall");
            } else {
                draw_tile(ctx, row, col, "wall");
            }
        }
    }

    ctx.stroke();
};

newRandomGen();

// Connect UI element
document.getElementById('cellular-automata-option').addEventListener('click', newCellularAutomata);
document.getElementById('simple-rooms-option').addEventListener('click', newSimpleRooms);
document.getElementById('bsp-interior-option').addEventListener('click', newBspInterior);
document.getElementById('drunkard-option').addEventListener('click', newDrunkard);
document.getElementById('random-option').addEventListener('click', newRandomGen);