add tanks_emit example

jbakse · Jan 12, 2022 · bbb8916 · bbb8916
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diff --git a/public/examples/tanks_emit/README.md b/public/examples/tanks_emit/README.md
@@ -0,0 +1,6 @@
+# tanks
+
+- **asdw** move tank
+- **space** to fire
+
+> Open this example in two browser windows at once!
diff --git a/public/examples/tanks_emit/index.html b/public/examples/tanks_emit/index.html
@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <link rel="stylesheet" href="../sketch.css" />
+    <style>
+      body {
+        display: flex;
+      }
+      #create {
+        padding: 10px;
+      }
+      #shared {
+        background: #eee;
+        white-space: pre;
+      }
+    </style>
+  </head>
+  <body>
+    <div id="canvas-wrap"></div>
+    <div id="shared"></div>
+    <script src="https://unpkg.com/uuid@latest/dist/umd/uuidv4.min.js"></script>
+
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.0.0/p5.min.js"></script>
+
+    <script src="/dist/p5.party.js"></script>
+
+    <script src="index.js"></script>
+  </body>
+</html>
diff --git a/public/examples/tanks_emit/index.js b/public/examples/tanks_emit/index.js
@@ -0,0 +1,133 @@
+/* global uuidv4 */
+/* global partyEmit partySubscribe*/
+
+class Rect {
+  constructor(l = 0, t = 0, w = 0, h = 0) {
+    this.l = l;
+    this.t = t;
+    this.w = w;
+    this.h = h;
+  }
+}
+
+class Point {
+  constructor(x = 0, y = 0) {
+    this.x = x;
+    this.y = y;
+  }
+}
+
+function pointInRect(p, r) {
+  return p.x > r.l && p.x < r.l + r.w && p.y > r.t && p.y < r.t + r.h;
+}
+
+const bounds = new Rect(0, 0, 400, 400);
+
+let shared, me, participants;
+
+function preload() {
+  partyConnect("wss://deepstream-server-1.herokuapp.com", "tanks", "main");
+  shared = partyLoadShared("shared");
+  me = partyLoadMyShared();
+  participants = partyLoadParticipantShareds();
+}
+
+function setup() {
+  createCanvas(400, 400).parent("canvas-wrap");
+
+  noStroke();
+
+  if (partyIsHost()) {
+    shared.bullets = [];
+  }
+  me.tank = { x: 100, y: 100, a: 0 };
+
+  // hosting can change mid-game so every client subscribes, and then checks if it is host on every event
+
+  partySubscribe("createBullet", createBullet);
+}
+
+function draw() {
+  checkKeys();
+  showData();
+  if (partyIsHost()) stepGame();
+  drawScene();
+}
+
+function stepGame() {
+  // step bullets
+  shared.bullets.forEach(stepBullet);
+}
+
+function showData() {
+  document.getElementById("shared").innerText = JSON.stringify(
+    shared,
+    null,
+    "\t"
+  );
+}
+function drawScene() {
+  background("#cc6666");
+  shared.bullets.forEach(drawBullet);
+  for (const p of participants) {
+    if (p.tank) drawTank(p.tank);
+  }
+}
+
+function drawTank(tank) {
+  push();
+  rectMode(CENTER);
+  translate(tank.x, tank.y);
+  rotate(tank.a);
+  rect(0, 0, 30, 30);
+  rect(0, -20, 5, 5);
+  pop();
+}
+
+function createBullet(b) {
+  if (partyIsHost()) shared.bullets.push(b);
+}
+
+function stepBullet(b) {
+  b.x += b.dX;
+  b.y += b.dY;
+  if (!pointInRect(b, bounds)) {
+    const i = shared.bullets.indexOf(b);
+    shared.bullets.splice(i, 1);
+  }
+}
+
+function drawBullet(b) {
+  push();
+  ellipse(b.x, b.y, 10, 10);
+  pop();
+}
+
+function keyPressed() {
+  if (key === " ") {
+    partyEmit("createBullet", {
+      x: me.tank.x,
+      y: me.tank.y,
+      dX: sin(me.tank.a) * 6,
+      dY: -cos(me.tank.a) * 6,
+    });
+  }
+
+  return false;
+}
+function checkKeys() {
+  // forward
+  if (keyIsDown(87) /*w*/) {
+    me.tank.x += sin(me.tank.a) * 3;
+    me.tank.y -= cos(me.tank.a) * 3;
+  }
+
+  // backward
+  if (keyIsDown(83) /*s*/) {
+    me.tank.x += sin(me.tank.a) * -1;
+    me.tank.y -= cos(me.tank.a) * -1;
+  }
+
+  if (keyIsDown(65) /*a*/) me.tank.a -= radians(2);
+  if (keyIsDown(68) /*d*/) me.tank.a += radians(2);
+}
diff --git a/public/examples/tanks_emit/notes.md b/public/examples/tanks_emit/notes.md
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+when two players try to alter the same share object at the same time, one or the other share object "wins"
+
+even if the changes are to different properties of the shared object, one change is lost
+
+this commonly happens when the host is trying to animate some data in a shared object (like moving a bullet) and another player tires to change _anything_ in the same shared object
+
+i just tried working around this by having players add bullets in their own shared object and the host moves them over into the main shared.
+
+this way the players don't write to shared at all
+
+it partly worked but...
+
+now the player writes new bullets to its own participant share + the host removes bullets from that share so they are both writing to the same share. If the player is writing to it a lot (like the player is turning when the shot is fired) we end up with the same kind of problem.
+
+possible solution:
+create a second global shared
+all particpants write new bullets there
+host consumes them
+now we have multiple players + hosts writing to the same record, but not rapidly.
+
+This is starting to look a lot like a message sending or event scheme. And deepstream does have Event stuff built in, and maybe that should be exposed by p5.party?
+
+https://deepstream.io/tutorials/core/pubsub/
+
+con - more complixty to the API
+pro - maybe less complexity/workarounds in sketch code