[oden] Writable Textures and re-work TS API

Now we return Texture objects to make things a little bit more
type-safe, at the cost of a small allocation (I hope!)

game/main.ts

@@ -1,26 +1,48 @@
-import { cls, print, spr, use_texture } from "./graphics";
+import { cls, print, spr, use_texture, Texture } from "./graphics";
 import { load_texture } from "./assets";
 import { since_start } from "./time";
 import { btn, Button } from "./input";
+// import { load_string } from "./io";
 import { new_v2, vadd, vmul, vnorm } from "./vector";
 
+/// TODO: Support reload by saving and restoring state from init/update/restore.
+
 /// A nice looping frame counter.
 let clock = 0;
 
-let bot_sprite: number | undefined = undefined;
+let bot_sprite: Texture | undefined = undefined;
 
 // Note zelda overworld is 16x8 screens
 //      zelda screen is 16x11 tiles
 // from a feeling point of view this is sufficient, apparently :D
 
-export function init() {
-  print("Hello world!");
+let loaded = false;
 
+async function load_map(path: string) {
+  // print("Loading map:", path);
+  // const blob = await load_string(path);
+  // const map = JSON.parse(blob);
+  // print("Loaded map:", map);
+}
+
+function load_assets() {
   // Start this load, but then...
-  load_texture("./bot.png").then((n) => {
+  let texture_load = load_texture("./bot.png").then((n) => {
     print("Bot loaded at", since_start());
     bot_sprite = n;
   });
+
+  let map_load = load_map("./overworld.ldtk");
+
+  Promise.all([texture_load, map_load]).then(() => {
+    loaded = true;
+    print("All are loaded.");
+  });
+}
+
+export function init() {
+  print("Hello world!");
+  load_assets();
 }
 
 const friction = 0.6;
@@ -80,6 +102,10 @@ const robo_info = {
 
 export function draw() {
   cls(0.1, 0.2, 0.3);
+  if (!loaded) {
+    return;
+  }
+
   if (bot_sprite != undefined) {
     // ...it gets resolved here?
     use_texture(bot_sprite);