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I've been trying to implement Roco C. Buljan's JS Spinning Wheel in React and I'm completely stuck at this particular point. The intended behavior is that the wheel spins once and after stopping displays the pointed sector.
Here's what my code looks like:
import React, { useEffect, useRef } from "react";
import "./SpinWheel.css";
function SpinWheel() {
const sectors = [
{ color: "#f82", label: "Stack" },
{ color: "#0bf", label: "10" },
{ color: "#fb0", label: "200" },
{ color: "#0fb", label: "50" },
{ color: "#b0f", label: "100" },
{ color: "#f0b", label: "5" },
];
// Generate random float in range min-max:
const rand = (m, M) => Math.random() * (M - m) + m;
const tot = sectors.length;
const wheel = useRef(null);
const spin = useRef(null);
useEffect(() => {
const ctx = wheel.current.getContext("2d");
const elSpin = spin.current;
spinWheel(ctx, elSpin);
}, []);
function spinWheel(ctx, elSpin) {
const dia = ctx.canvas.width;
const rad = dia / 2;
const PI = Math.PI;
const TAU = 2 * PI;
const arc = TAU / sectors.length;
const friction = 0.991; // 0.995=soft, 0.99=mid, 0.98=hard
const angVelMin = 0.002; // Below that number will be treated as a stop
let angVelMax = 0; // Random ang.vel. to acceletare to
let angVel = 0; // Current angular velocity
let ang = 0; // Angle rotation in radians
let isSpinning = false;
let isAccelerating = false;
//* Get index of current sector */
const getIndex = () => Math.floor(tot - (ang / TAU) * tot) % tot;
//* Draw sectors and prizes texts to canvas */
const drawSector = (sector, i) => {
const ang = arc * i;
ctx.save();
// COLOR
ctx.beginPath();
ctx.fillStyle = sector.color;
ctx.moveTo(rad, rad);
ctx.arc(rad, rad, rad, ang, ang + arc);
ctx.lineTo(rad, rad);
ctx.fill();
// TEXT
ctx.translate(rad, rad);
ctx.rotate(ang + arc / 2);
ctx.textAlign = "right";
ctx.fillStyle = "#fff";
ctx.font = "bold 30px sans-serif";
ctx.fillText(sector.label, rad - 10, 10);
//
ctx.restore();
};
//* CSS rotate CANVAS Element */
const rotate = () => {
const sector = sectors[getIndex()];
ctx.canvas.style.transform = `rotate(${ang - PI / 2}rad)`;
elSpin.textContent = !angVel ? sector.label : "SPIN";
elSpin.style.background = sector.color;
};
const frame = () => {
if (!isSpinning) return;
if (angVel >= angVelMax) isAccelerating = false;
// Accelerate
if (isAccelerating) {
angVel ||= angVelMin; // Initial velocity kick
angVel *= 1.06; // Accelerate
}
// Decelerate
else {
isAccelerating = false;
angVel *= friction; // Decelerate by friction
// SPIN END:
if (angVel < angVelMin) {
isSpinning = false;
angVel = 0;
}
}
ang += angVel; // Update angle
ang %= TAU; // Normalize angle
rotate(); // CSS rotate!
};
const engine = () => {
frame();
requestAnimationFrame(engine);
};
elSpin.addEventListener("click", () => {
if (isSpinning) return;
isSpinning = true;
isAccelerating = true;
angVelMax = rand(0.25, 0.4);
});
// INIT!
sectors.forEach(drawSector);
rotate(); // Initial rotation
engine(); // Start engine!
}
return (
<div id="wheelOfFortune">
<canvas id="wheel" ref={wheel} width="300" height="300"></canvas>
<div id="spin" ref={spin}>
SPIN asd asd asd as dasd as dasd asd asd as d
</div>
</div>
);
}
export default SpinWheel;
And here's the sandbox link
The issue is that if I console.log the useEffect block, I can see that it executes twice at the start which is not what I intend. I tried putting an empty array as the dependency array but it still doesn't work for me. The second issue is that the wheel supposedly stops and then spins a small amount yet again, resulting in two final sector outputs. Again, not what I intend. I can only guess that it is rendering more than once but I'm not sure. Any ideas what I'm doing wrong?
There are a couple things you need to do to get this working in a react context:
The spinWheel method should return start/stop/cleanup methods for controlling the wheel. The cleanup method should clean up any artifacts such as event handlers and whatnot.
const startSpin = () => {
if (isSpinning) return;
isSpinning = true;
isAccelerating = true;
angVelMax = rand(0.25, 0.4);
};
const stopSpin = () => {
isSpinning = false;
isAccelerating = false;
}
elSpin.addEventListener("click", startSpin);
const cleanup = () => {
elSpin.removeEventListener("click", startSpin);
};
...
return { startSpin, stopSpin, cleanup };
As mentioned in a comment, you need to make sure your effect has a "cleanup" function which stops the wheel (see this link). This is necessary so that the setup → cleanup → setup sequence works in development as described on that page.
useEffect(() => {
const ctx = wheel.current.getContext("2d");
const elSpin = spin.current;
const { startSpin, stopSpin, cleanup } = spinWheel(ctx, elSpin);
startSpin();
return () => {
stopSpin();
cleanup();
}
}, []);
Here's a link to a working sandbox: https://codesandbox.io/s/spin-wheel-forked-tb42zf?file=/src/components/SpinWheel/SpinWheel.js:546-826
I have a function that craeates divs with a circle.
Now they are all created and appear at the beginning of the page and go further in order.
Next, I need each circle to appear in a random place. I did this.
Now I need all of them to move randomly across the entire page, I have difficulties with this.
Here is an example of how everything works for one element that is already on the page.
https://jsfiddle.net/quej8wko/
But when I add this code, all my created circles don't move.
I get an error:
"message": "Uncaught TypeError: Cannot set properties of null (setting 'willChange')",
This is probably due to the fact that initially there are no circles on the page. How can I connect the code so that all created circles move?
//creating circles
var widthHeight = 40; // <-- circle width
var margin = 20; // <-- margin - is it necessary ?
var delta = widthHeight + margin;
function createDiv(id, color) {
let div = document.createElement('div');
var currentTop = 0;
var documentHeight = document.documentElement.clientHeight;
var documentWidth = document.documentElement.clientWidth;
div.setAttribute('class', id);
if (color === undefined) {
let colors = ['#35def2', '#35f242', '#b2f235', '#f2ad35', '#f24735', '#3554f2', '#8535f2', '#eb35f2', '#f2359b', '#f23547'];
div.style.backgroundColor = colors[Math.floor(Math.random() * colors.length)];
}
else {
div.style.backgroundColor = color;
}
div.classList.add("circle");
div.classList.add("animation");
// Get the random positions minus the delta
currentTop = Math.floor(Math.random() * documentHeight) - delta;
currentLeft = Math.floor(Math.random() * documentWidth) - delta;
// Keep the positions between -20px and the current positions
var limitedTop = Math.max(margin * -1, currentTop);
var limitedLeft = Math.max(margin * -1, currentLeft);
div.style.top = limitedTop + "px";
div.style.left = limitedLeft + "px";
document.body.appendChild(div);
}
let i = 0;
const oneSecond = 1000;
setInterval(() => {
i += 1;
createDiv(`circle${i}`)
}, oneSecond);
//move circles
function RandomObjectMover(obj, container) {
this.$object = obj;
this.$container = container;
this.container_is_window = container === window;
this.pixels_per_second = 250;
this.current_position = { x: 0, y: 0 };
this.is_running = false;
}
// Set the speed of movement in Pixels per Second.
RandomObjectMover.prototype.setSpeed = function(pxPerSec) {
this.pixels_per_second = pxPerSec;
}
RandomObjectMover.prototype._getContainerDimensions = function() {
if (this.$container === window) {
return { 'height' : this.$container.innerHeight, 'width' : this.$container.innerWidth };
} else {
return { 'height' : this.$container.clientHeight, 'width' : this.$container.clientWidth };
}
}
RandomObjectMover.prototype._generateNewPosition = function() {
// Get container dimensions minus div size
var containerSize = this._getContainerDimensions();
var availableHeight = containerSize.height - this.$object.clientHeight;
var availableWidth = containerSize.width - this.$object.clientHeight;
// Pick a random place in the space
var y = Math.floor(Math.random() * availableHeight);
var x = Math.floor(Math.random() * availableWidth);
return { x: x, y: y };
}
RandomObjectMover.prototype._calcDelta = function(a, b) {
var dx = a.x - b.x;
var dy = a.y - b.y;
var dist = Math.sqrt( dx*dx + dy*dy );
return dist;
}
RandomObjectMover.prototype._moveOnce = function() {
// Pick a new spot on the page
var next = this._generateNewPosition();
// How far do we have to move?
var delta = this._calcDelta(this.current_position, next);
// Speed of this transition, rounded to 2DP
var speed = Math.round((delta / this.pixels_per_second) * 100) / 100;
//console.log(this.current_position, next, delta, speed);
this.$object.style.transition='transform '+speed+'s linear';
this.$object.style.transform='translate3d('+next.x+'px, '+next.y+'px, 0)';
// Save this new position ready for the next call.
this.current_position = next;
};
RandomObjectMover.prototype.start = function() {
if (this.is_running) {
return;
}
// Make sure our object has the right css set
this.$object.willChange = 'transform';
this.$object.pointerEvents = 'auto';
this.boundEvent = this._moveOnce.bind(this)
// Bind callback to keep things moving
this.$object.addEventListener('transitionend', this.boundEvent);
// Start it moving
this._moveOnce();
this.is_running = true;
}
RandomObjectMover.prototype.stop = function() {
if (!this.is_running) {
return;
}
this.$object.removeEventListener('transitionend', this.boundEvent);
this.is_running = false;
}
// Init it
var x = new RandomObjectMover(document.querySelector(".circle"), window);
// Start it off
x.start();
.circle {
clip-path: circle(50%);
height: 40px;
width: 40px;
margin: 20px;
position: absolute;
}
I have modified the snippet which works as you expected.
There was a mistake where you were initializing and creating the object instance only once and none of the div elements that you created inside the setInterval function never got Instantiated.
I think you are just starting out with JavaScript with this sample project.
Below are few suggestions:
Learn to debug the code. You should be using dev tools by making use of debugger statement where it takes you to the source code to analyze the variable scope and stack during the runtime. console.log also helps in few situations.
I could see a lot of confusing naming convention (You have named the create div parameter as id but creating a div class using that id)
Try using ES6 features (class syntax is really good when writing OOP in JS although it's just a syntactic sugar for prototype)
//creating circles
var widthHeight = 40; // <-- circle width
var margin = 20; // <-- margin - is it necessary ?
var delta = widthHeight + margin;
function createAndInitializeDivObject(id, color) {
let div = document.createElement('div');
var currentTop = 0;
var documentHeight = document.documentElement.clientHeight;
var documentWidth = document.documentElement.clientWidth;
div.setAttribute('class', id);
if (color === undefined) {
let colors = ['#35def2', '#35f242', '#b2f235', '#f2ad35', '#f24735', '#3554f2', '#8535f2', '#eb35f2', '#f2359b', '#f23547'];
div.style.backgroundColor = colors[Math.floor(Math.random() * colors.length)];
}
else {
div.style.backgroundColor = color;
}
div.classList.add("circle");
div.classList.add("animation");
// Get the random positions minus the delta
currentTop = Math.floor(Math.random() * documentHeight) - delta;
currentLeft = Math.floor(Math.random() * documentWidth) - delta;
// Keep the positions between -20px and the current positions
var limitedTop = Math.max(margin * -1, currentTop);
var limitedLeft = Math.max(margin * -1, currentLeft);
div.style.top = limitedTop + "px";
div.style.left = limitedLeft + "px";
document.body.appendChild(div);
var x = new RandomObjectMover(document.querySelector(`.${id}`), window);
x.start();
}
let i = 0;
const oneSecond = 1000;
setInterval(() => {
i += 1;
createAndInitializeDivObject(`circle${i}`)
}, oneSecond);
//move circles
function RandomObjectMover(obj, container) {
this.$object = obj;
this.$container = container;
this.container_is_window = container === window;
this.pixels_per_second = 250;
this.current_position = { x: 0, y: 0 };
this.is_running = false;
}
// Set the speed of movement in Pixels per Second.
RandomObjectMover.prototype.setSpeed = function(pxPerSec) {
this.pixels_per_second = pxPerSec;
}
RandomObjectMover.prototype._getContainerDimensions = function() {
if (this.$container === window) {
return { 'height' : this.$container.innerHeight, 'width' : this.$container.innerWidth };
} else {
return { 'height' : this.$container.clientHeight, 'width' : this.$container.clientWidth };
}
}
RandomObjectMover.prototype._generateNewPosition = function() {
// Get container dimensions minus div size
var containerSize = this._getContainerDimensions();
var availableHeight = containerSize.height - this.$object.clientHeight;
var availableWidth = containerSize.width - this.$object.clientHeight;
// Pick a random place in the space
var y = Math.floor(Math.random() * availableHeight);
var x = Math.floor(Math.random() * availableWidth);
return { x: x, y: y };
}
RandomObjectMover.prototype._calcDelta = function(a, b) {
var dx = a.x - b.x;
var dy = a.y - b.y;
var dist = Math.sqrt( dx*dx + dy*dy );
return dist;
}
RandomObjectMover.prototype._moveOnce = function() {
// Pick a new spot on the page
var next = this._generateNewPosition();
// How far do we have to move?
var delta = this._calcDelta(this.current_position, next);
// Speed of this transition, rounded to 2DP
var speed = Math.round((delta / this.pixels_per_second) * 100) / 100;
//console.log(this.current_position, next, delta, speed);
this.$object.style.transition='transform '+speed+'s linear';
this.$object.style.transform='translate3d('+next.x+'px, '+next.y+'px, 0)';
// Save this new position ready for the next call.
this.current_position = next;
};
RandomObjectMover.prototype.start = function() {
if (this.is_running) {
return;
}
// Make sure our object has the right css set
this.$object.willChange = 'transform';
this.$object.pointerEvents = 'auto';
this.boundEvent = this._moveOnce.bind(this)
// Bind callback to keep things moving
this.$object.addEventListener('transitionend', this.boundEvent);
// Start it moving
this._moveOnce();
this.is_running = true;
}
RandomObjectMover.prototype.stop = function() {
if (!this.is_running) {
return;
}
this.$object.removeEventListener('transitionend', this.boundEvent);
this.is_running = false;
}
// Init it
var x = new RandomObjectMover(document.querySelector(".circle"), window);
// Start it off
x.start();
.circle {
width: 35px;
height: 35px;
border-radius: 35px;
background-color: #ffffff;
border: 3px solid purple;
position: absolute;
}
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="style.css">
</head>
<body>
<div class="circle"></div>
<script src="app.js"></script>
</body>
</html>
I'm working on a small flappy-bird-like-game demo. Everthing seems fine, but I have a small problem/question.
I setup a collider function, and the callback works as expected, when the "two" objects collide, but there is a strange behavior:
the white-square (the bird) can fly through the obstacles, when coming from the side
but cannot passthrough when coming from below or on above
BUT the callback is execute always.
blue arrow marks where the square passes through
green arrows mark where the square doesn't passthrough
I'm not sure if this is, because I'm using rectangles (they sometimes) cause problems, or because of my nested physics setup. I even tried to replaced the white rectangel with a sprite, but this still produces the same result/error.
For my demo: I could probablly just destroy the object and restart the level on collision, but I still would like to understand why this is happening? And how I can prevent this, inconsistant behavior.
I'm probably missing something, but couldn't find it, and I don't want to rebuild the application again.
So my question is: why is this happening? And How can I prevent this?
Here is the code:
const width = 400;
const height = 200;
const spacing = width / 4;
const levelSpeed = width / 4;
const flySpeed = width / 4;
var GameScene = {
create (){
let player = this.add.rectangle(width / 4, height / 2, 20, 20, 0xffffff);
this.physics.add.existing(player);
this.input.keyboard.on('keydown-SPACE', (event) => {
if(player.body.velocity.y >= -flySpeed/2){
player.body.setVelocityY(-flySpeed);
}
});
player.body.onWorldBounds = true;
player.body.setCollideWorldBounds(true );
this.physics.world.on("worldbounds", function (body) {
console.info('GAME OVER');
player.y = height / 2;
player.body.setVelocity(0);
});
this.pipes = [];
for(let idx = 1; idx <= 10; idx++) {
let obstacle = this.createObstacle(spacing * idx, Phaser.Math.Between(-height/3, 0));
this.add.existing(obstacle);
this.pipes.push(obstacle);
this.physics.add.collider(obstacle.list[0], player)
this.physics.add.collider(obstacle.list[1], player, _ => console.info(2))
}
},
update(){
this.pipes.forEach((item) => {
if(item.x <= 0){
item.body.x = spacing * 10;
}
})
},
extend: {
createObstacle (x, y){
let topPipe = (new Phaser.GameObjects.Rectangle(this, 0, 0 , 20 , height / 2 ,0xff0000)).setOrigin(0);
let bottomPipe = (new Phaser.GameObjects.Rectangle(this, 0, height/2 + 75, 20 , height / 2 ,0xff0000)).setOrigin(0);
this.physics.add.existing(topPipe);
this.physics.add.existing(bottomPipe);
topPipe.body.setImmovable(true);
topPipe.body.allowGravity = false;
bottomPipe.body.setImmovable(true);
bottomPipe.body.allowGravity = false;
let obstacle = new Phaser.GameObjects.Container(this, x, y, [
topPipe,
bottomPipe
]);
this.physics.add.existing(obstacle);
obstacle.body.velocity.x = - levelSpeed;
obstacle.body.allowGravity = false;
return obstacle;
}
}
};
var config = {
type: Phaser.AUTO,
parent: 'phaser-example',
width,
height,
scene: [GameScene],
physics: {
default: 'arcade',
arcade: {
gravity: { y: flySpeed },
debug: true
},
}
};
var game = new Phaser.Game(config);
<script src="https://cdn.jsdelivr.net/npm/phaser#3.55.2/dist/phaser.js"></script>
Currently I just can assume, that the physics objects don't seem to work correct, when physics objects are nested.
Maybe I'm wrong, but since I rewrote the code again without nested physics - objects and it seems to work, I think my assumption Is correct. I shouldn't have tried to over engineer my code.
If someone has more insides, please let me know/share. I still not 100% sure, if this is the real reason, for the strange behavior.
Here the rewriten code:
const width = 400;
const height = 200;
const spacing = width / 4;
const levelSpeed = width / 4;
const flySpeed = width / 4;
var GameScene = {
create (){
let player = this.add.rectangle(width / 4, height / 2, 20, 20, 0xffffff);
this.physics.add.existing(player);
this.input.keyboard.on('keydown-SPACE', (event) => {
if(player.body.velocity.y >= -flySpeed/2){
player.body.setVelocityY(-flySpeed);
}
});
player.body.onWorldBounds = true;
player.body.setCollideWorldBounds(true );
this.physics.world.on("worldbounds", function (body) {
console.info('GAME OVER');
player.x = width / 4;
player.y = height / 2;
player.body.setVelocity(0);
});
this.pipes = [];
for(let idx = 1; idx <= 10; idx++) {
let obstacle = this.createObstacle(spacing * idx, Phaser.Math.Between(-height/3, 0));
this.add.existing(obstacle[0]);
this.add.existing(obstacle[1]);
this.pipes.push(...obstacle);
this.physics.add.collider(obstacle[0], player)
this.physics.add.collider(obstacle[1], player, _ => console.info(2))
}
},
update(){
this.pipes.forEach((item) => {
if(item.x <= 0){
item.body.x = spacing * 10;
}
item.body.velocity.x = - levelSpeed;
})
},
extend: {
createObstacle (x, y){
let topPipe = (new Phaser.GameObjects.Rectangle(this, x, -20 , 20 , height / 2 ,0xff0000)).setOrigin(0);
let bottomPipe = (new Phaser.GameObjects.Rectangle(this, x, height/2 + 75, 20 , height / 2 ,0xff0000)).setOrigin(0);
this.physics.add.existing(topPipe);
this.physics.add.existing(bottomPipe);
topPipe.body.setImmovable(true);
topPipe.body.allowGravity = false;
topPipe.body.velocity.x = - levelSpeed;
bottomPipe.body.setImmovable(true);
bottomPipe.body.allowGravity = false;
bottomPipe.body.velocity.x = - levelSpeed;
return [topPipe, bottomPipe];
}
}
};
var config = {
type: Phaser.AUTO,
parent: 'phaser-example',
width,
height,
scene: [GameScene],
physics: {
default: 'arcade',
arcade: {
gravity: { y: flySpeed },
debug: true
},
}
};
var game = new Phaser.Game(config);
<script src="https://cdn.jsdelivr.net/npm/phaser#3.55.2/dist/phaser.js"></script>
I'm trying to get a nice knob/dial that can be rotated to send a value back to the server via websockets.
The basic premise works well, I got the code from the web.
I am trying to modify the code so that I get a prettier knob. I've been successful by placing the canvas inside a couple of divs which display static images, while the canvas rotates a translucent image in response to mouse/touch events.
The additions that I made to the code work well on the desktop (I'm running Firefox 45.0.2) but do not work at all on an iPad (Safari, iOS 9.3.5) and only partially on an iPhone (iOS 10.2.1)
On the iPhone, the knob rotates in the opposite direction to that expected, and often only horizontal movement will start the knob rotating.
I'm not using (nor do I want to use) any libraries such as jquery.
The code below will work as is. However, removing the comment marks in the body section will cause the problems I indicated.
(Oh and to forestall any comments, the black background and odd text colour is just there to so that you can see the translucent element without the static backgrounds)
I'm not at all experienced with jscript and can only just manage to follow what the code is doing at the moment. (one of the reasons I don't want to use additional libraries)
I suspect that the problem lies with how the touch event coordinates are interpreted, but I can't test them in any way.
Any help or suggestions would be appreciated.
HTML Code:
<!DOCTYPE html>
<html>
<head>
<title>Stepper example</title>
<meta name="viewport" content="width=device-width, initial-scale=0.7">
<style>
body {
text-align: center; background-color: black;
color: red
}
.container{
position: relative;
background: url(step_background.png);
width: 480px;
height: 480px;
margin: auto;
z-index:1;
}
.knob{
position: relative;
top: 59px;
background: url(knob_bg.png);
width: 362px;
height:362px;
margin:auto;
z-index:2;
}
#stepper{
position: relative;
}
</style>
<script>
var MIN_TOUCH_RADIUS = 20;
var MAX_TOUCH_RADIUS = 200;
var CANVAS_WIDTH = 362, CANVAS_HEIGHT = 362;
var PIVOT_X = 181, PIVOT_Y = 181;
var plate_angle = 0;
var plate_img = new Image();
var click_state = 0;
var last_angle_pos = 0;
var mouse_xyra = {x:0, y:0, r:0.0, a:0.0};
var ws;
plate_img.src = "knob_fg.png";
function init() {
var stepper = document.getElementById("stepper");
var ctx = stepper.getContext("2d");
stepper.width = CANVAS_WIDTH;
stepper.height = CANVAS_HEIGHT;
stepper.addEventListener("touchstart", mouse_down);
stepper.addEventListener("touchend", mouse_up);
stepper.addEventListener("touchmove", mouse_move);
stepper.addEventListener("mousedown", mouse_down);
stepper.addEventListener("mouseup", mouse_up);
stepper.addEventListener("mousemove", mouse_move);
ctx.translate(PIVOT_X, PIVOT_Y);
rotate_plate(plate_angle);
}
function connect_onclick() {
if(ws == null) {
ws = new WebSocket('ws://'+ window.location.hostname + ':81/', ['arduino']);
document.getElementById("ws_state").innerHTML = "CONNECTING";
ws.onopen = ws_onopen;
ws.onclose = ws_onclose;
ws.onmessage = ws_onmessage;
ws.onerror = function(){ alert("websocket error " + this.url) };
}
else
ws.close();
}
function ws_onopen() {
document.getElementById("ws_state").innerHTML = "<font color='blue'>CONNECTED</font>";
document.getElementById("bt_connect").innerHTML = "Disconnect";
rotate_plate(plate_angle);
}
function ws_onclose() {
document.getElementById("ws_state").innerHTML = "<font color='gray'>CLOSED</font>";
document.getElementById("bt_connect").innerHTML = "Connect";
ws.onopen = null;
ws.onclose = null;
ws.onmessage = null;
ws = null;
rotate_plate(plate_angle);
}
function ws_onmessage(e_msg) {
e_msg = e_msg || window.event; // MessageEvent
plate_angle = Number(e_msg.data);
rotate_plate(plate_angle);
//alert("msg : " + e_msg.data);
}
function rotate_plate(angle) {
var stepper = document.getElementById("stepper");
var ctx = stepper.getContext("2d");
ctx.clearRect(-PIVOT_X, -PIVOT_Y, CANVAS_WIDTH, CANVAS_HEIGHT);
ctx.rotate(-angle / 180 * Math.PI);
ctx.drawImage(plate_img, -PIVOT_X, -PIVOT_Y);
ctx.rotate(angle / 180 * Math.PI);
/*
Currently, the angle displayed and sent as a message appears to be set such that movement in a clockwise direction
reports a negative number. Needs to be looked at, probably by changing "angle.toFixed" to "-angle.toFixed"
*/
if(ws && (ws.readyState == 1))
ws.send(plate_angle.toFixed(4) + "\r\n");
ws_angle = document.getElementById("ws_angle");
ws_angle.innerHTML = angle.toFixed(1);
}
function check_update_xyra(event, mouse_xyra) {
var x, y, r, a;
var min_r, max_r, width;
if(event.touches) {
var touches = event.touches;
x = (touches[0].pageX - touches[0].target.offsetLeft) - PIVOT_X;
y = PIVOT_Y - (touches[0].pageY - touches[0].target.offsetTop);
}
else {
x = event.offsetX - PIVOT_X;
y = PIVOT_Y - event.offsetY;
}
/* cartesian to polar coordinate conversion */
r = Math.sqrt(x * x + y * y);
a = Math.atan2(y, x);
mouse_xyra.x = x;
mouse_xyra.y = y;
mouse_xyra.r = r;
mouse_xyra.a = a;
if((r >= MIN_TOUCH_RADIUS) && (r <= MAX_TOUCH_RADIUS))
return true;
else
return false;
}
function mouse_down(event) {
if(event.target == stepper)
event.preventDefault();
if(event.touches && (event.touches.length > 1))
click_state = event.touches.length;
if(click_state > 1)
return;
if(check_update_xyra(event, mouse_xyra)) {
click_state = 1;
last_angle_pos = mouse_xyra.a / Math.PI * 180.0;
}
}
function mouse_up() {
click_state = 0;
}
function mouse_move(event) {
var angle_pos, angle_offset;
if(event.touches && (event.touches.length > 1))
click_state = event.touches.length;
if(!click_state || (click_state > 1))
return;
if(!check_update_xyra(event, mouse_xyra)) {
click_state = 0;
return;
}
event.preventDefault();
angle_pos = mouse_xyra.a / Math.PI * 180.0;
if(angle_pos < 0.0)
angle_pos = angle_pos + 360.0;
angle_offset = angle_pos - last_angle_pos;
last_angle_pos = angle_pos;
if(angle_offset > 180.0)
angle_offset = -360.0 + angle_offset;
else
if(angle_offset < -180.0)
angle_offset = 360 + angle_offset;
plate_angle += angle_offset;
rotate_plate(plate_angle);
}
window.onload = init;
</script>
</head>
<body>
<h2>
Smart Expansion / Stepper Motor<br><br>
Angle <font id="ws_angle" color="blue">0</font><br><br>
<!--
<div class="container">
<div class="knob">
-->
<canvas id="stepper"></canvas>
<!--
</div>
</div>
-->
<br><br>
WebSocket <font id="ws_state" color="gray">CLOSED</font>
</h2>
<p><button id="bt_connect" type="button" onclick="connect_onclick();">Connect</button></p>
</body>
</html>
I might need to add an additional comment to give the link to the backgound image
knob_bg.png
knob_fg.png
So, after managing to find out how to debug html on an ios device via firefox on windows, I have managed to find out what was causing my code to fail.
The problem was in the function check_update_xyra(event, mouse_xyra)
Specifically the lines :
x = (touches[0].pageX - touches[0].target.offsetLeft) - PIVOT_X;
y = PIVOT_Y - (touches[0].pageY - touches[0].target.offsetTop);
The target.offsetxxx was returning a value of 0. This made the radian value (r) to be out of bounds which caused the function to return false, or in the case of the iPhone caused the touch event to behave strangely.
The reason for for the offsets coming back as 0 was because I did not factor in the fact that they provided the offset from the targets parent only, not the document as a whole.
I managed to fix this by adding some code to add the offsets for all parent elements then used that sum to calculate new x and y coordinates.
My code change follows.
However, if anyone has a more elegant method of calculating the offsets, I would appreciate it.
Cheers...
function check_update_xyra(event, mouse_xyra) {
var x, y, r, a;
var tgtoffleft = 0;
var tgtofftop = 0;
var min_r, max_r, width;
if(event.touches) {
var touches = event.touches;
// Bit of code to calculate the actual Left and Top offsets by adding offsets
// of each parent back through the hierarchy
var tgt = event.touches[0].target;
while (tgt) {
tgtoffleft = tgtoffleft + tgt.offsetLeft;
tgtofftop = tgtofftop + tgt.offsetTop;
tgt = tgt.offsetParent;
}
// x = (touches[0].pageX - touches[0].target.offsetLeft) - PIVOT_X;
// y = PIVOT_Y - (touches[0].pageY - touches[0].target.offsetTop);
x = (touches[0].pageX - tgtoffleft) - PIVOT_X;
y = PIVOT_Y - (touches[0].pageY - tgtofftop);
}
else {
x = event.offsetX - PIVOT_X;
y = PIVOT_Y - event.offsetY;
}
/* cartesian to polar coordinate conversion */
r = Math.sqrt(x * x + y * y);
a = Math.atan2(y, x);
mouse_xyra.x = x;
mouse_xyra.y = y;
mouse_xyra.r = r;
mouse_xyra.a = a;
if((r >= MIN_TOUCH_RADIUS) && (r <= MAX_TOUCH_RADIUS))
return true;
else
return false;
}
We're working with the HTML5 canvas, displaying lots of images at one time.
This is working pretty well but recently we've had a problem with chrome.
When drawing images on to a canvas you seem to reach a certain point where the performance degrades very quickly.
It's not a slow effect, it seems that you go right from 60fps to 2-4fps.
Here's some reproduction code:
// Helpers
// https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Math/random
function getRandomInt(min, max) { return Math.floor(Math.random() * (max - min + 1)) + min; }
// http://www.paulirish.com/2011/requestanimationframe-for-smart-animating/
window.requestAnimFrame = (function () { return window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || function (callback) { window.setTimeout(callback, 1000 / 60); }; })();
// https://github.com/mrdoob/stats.js
var Stats = function () { var e = Date.now(), t = e; var n = 0, r = Infinity, i = 0; var s = 0, o = Infinity, u = 0; var a = 0, f = 0; var l = document.createElement("div"); l.id = "stats"; l.addEventListener("mousedown", function (e) { e.preventDefault(); y(++f % 2) }, false); l.style.cssText = "width:80px;opacity:0.9;cursor:pointer"; var c = document.createElement("div"); c.id = "fps"; c.style.cssText = "padding:0 0 3px 3px;text-align:left;background-color:#002"; l.appendChild(c); var h = document.createElement("div"); h.id = "fpsText"; h.style.cssText = "color:#0ff;font-family:Helvetica,Arial,sans-serif;font-size:9px;font-weight:bold;line-height:15px"; h.innerHTML = "FPS"; c.appendChild(h); var p = document.createElement("div"); p.id = "fpsGraph"; p.style.cssText = "position:relative;width:74px;height:30px;background-color:#0ff"; c.appendChild(p); while (p.children.length < 74) { var d = document.createElement("span"); d.style.cssText = "width:1px;height:30px;float:left;background-color:#113"; p.appendChild(d) } var v = document.createElement("div"); v.id = "ms"; v.style.cssText = "padding:0 0 3px 3px;text-align:left;background-color:#020;display:none"; l.appendChild(v); var m = document.createElement("div"); m.id = "msText"; m.style.cssText = "color:#0f0;font-family:Helvetica,Arial,sans-serif;font-size:9px;font-weight:bold;line-height:15px"; m.innerHTML = "MS"; v.appendChild(m); var g = document.createElement("div"); g.id = "msGraph"; g.style.cssText = "position:relative;width:74px;height:30px;background-color:#0f0"; v.appendChild(g); while (g.children.length < 74) { var d = document.createElement("span"); d.style.cssText = "width:1px;height:30px;float:left;background-color:#131"; g.appendChild(d) } var y = function (e) { f = e; switch (f) { case 0: c.style.display = "block"; v.style.display = "none"; break; case 1: c.style.display = "none"; v.style.display = "block"; break } }; var b = function (e, t) { var n = e.appendChild(e.firstChild); n.style.height = t + "px" }; return { REVISION: 11, domElement: l, setMode: y, begin: function () { e = Date.now() }, end: function () { var f = Date.now(); n = f - e; r = Math.min(r, n); i = Math.max(i, n); m.textContent = n + " MS (" + r + "-" + i + ")"; b(g, Math.min(30, 30 - n / 200 * 30)); a++; if (f > t + 1e3) { s = Math.round(a * 1e3 / (f - t)); o = Math.min(o, s); u = Math.max(u, s); h.textContent = s + " FPS (" + o + "-" + u + ")"; b(p, Math.min(30, 30 - s / 100 * 30)); t = f; a = 0 } return f }, update: function () { e = this.end() } } }
// Firefox events suck
function getOffsetXY(eventArgs) { return { X: eventArgs.offsetX == undefined ? eventArgs.layerX : eventArgs.offsetX, Y: eventArgs.offsetY == undefined ? eventArgs.layerY : eventArgs.offsetY }; }
function getWheelDelta(eventArgs) { if (!eventArgs) eventArgs = event; var w = eventArgs.wheelDelta; var d = eventArgs.detail; if (d) { if (w) { return w / d / 40 * d > 0 ? 1 : -1; } else { return -d / 3; } } else { return w / 120; } }
// Reproduction Code
var stats = new Stats();
document.body.appendChild(stats.domElement);
var masterCanvas = document.getElementById('canvas');
var masterContext = masterCanvas.getContext('2d');
var viewOffsetX = 0;
var viewOffsetY = 0;
var viewScaleFactor = 1;
var viewMinScaleFactor = 0.1;
var viewMaxScaleFactor = 10;
var mouseWheelSensitivity = 10; //Fudge Factor
var isMouseDown = false;
var lastMouseCoords = null;
var imageDimensionPixelCount = 25;
var paddingPixelCount = 2;
var canvasDimensionImageCount = 50;
var totalImageCount = Math.pow(canvasDimensionImageCount, 2);
var images = null;
function init() {
images = createLocalImages(totalImageCount, imageDimensionPixelCount);
initInteraction();
renderLoop();
}
function initInteraction() {
var handleMouseDown = function (eventArgs) {
isMouseDown = true;
var offsetXY = getOffsetXY(eventArgs);
lastMouseCoords = [
offsetXY.X,
offsetXY.Y
];
};
var handleMouseUp = function (eventArgs) {
isMouseDown = false;
lastMouseCoords = null;
}
var handleMouseMove = function (eventArgs) {
if (isMouseDown) {
var offsetXY = getOffsetXY(eventArgs);
var panX = offsetXY.X - lastMouseCoords[0];
var panY = offsetXY.Y - lastMouseCoords[1];
pan(panX, panY);
lastMouseCoords = [
offsetXY.X,
offsetXY.Y
];
}
};
var handleMouseWheel = function (eventArgs) {
var mouseX = eventArgs.pageX - masterCanvas.offsetLeft;
var mouseY = eventArgs.pageY - masterCanvas.offsetTop;
var zoom = 1 + (getWheelDelta(eventArgs) / mouseWheelSensitivity);
zoomAboutPoint(mouseX, mouseY, zoom);
if (eventArgs.preventDefault !== undefined) {
eventArgs.preventDefault();
} else {
return false;
}
}
masterCanvas.addEventListener("mousedown", handleMouseDown, false);
masterCanvas.addEventListener("mouseup", handleMouseUp, false);
masterCanvas.addEventListener("mousemove", handleMouseMove, false);
masterCanvas.addEventListener("mousewheel", handleMouseWheel, false);
masterCanvas.addEventListener("DOMMouseScroll", handleMouseWheel, false);
}
function pan(panX, panY) {
masterContext.translate(panX / viewScaleFactor, panY / viewScaleFactor);
viewOffsetX -= panX / viewScaleFactor;
viewOffsetY -= panY / viewScaleFactor;
}
function zoomAboutPoint(zoomX, zoomY, zoomFactor) {
var newCanvasScale = viewScaleFactor * zoomFactor;
if (newCanvasScale < viewMinScaleFactor) {
zoomFactor = viewMinScaleFactor / viewScaleFactor;
} else if (newCanvasScale > viewMaxScaleFactor) {
zoomFactor = viewMaxScaleFactor / viewScaleFactor;
}
masterContext.translate(viewOffsetX, viewOffsetY);
masterContext.scale(zoomFactor, zoomFactor);
viewOffsetX = ((zoomX / viewScaleFactor) + viewOffsetX) - (zoomX / (viewScaleFactor * zoomFactor));
viewOffsetY = ((zoomY / viewScaleFactor) + viewOffsetY) - (zoomY / (viewScaleFactor * zoomFactor));
viewScaleFactor *= zoomFactor;
masterContext.translate(-viewOffsetX, -viewOffsetY);
}
function renderLoop() {
clearCanvas();
renderCanvas();
stats.update();
requestAnimFrame(renderLoop);
}
function clearCanvas() {
masterContext.clearRect(viewOffsetX, viewOffsetY, masterCanvas.width / viewScaleFactor, masterCanvas.height / viewScaleFactor);
}
function renderCanvas() {
for (var imageY = 0; imageY < canvasDimensionImageCount; imageY++) {
for (var imageX = 0; imageX < canvasDimensionImageCount; imageX++) {
var x = imageX * (imageDimensionPixelCount + paddingPixelCount);
var y = imageY * (imageDimensionPixelCount + paddingPixelCount);
var imageIndex = (imageY * canvasDimensionImageCount) + imageX;
var image = images[imageIndex];
masterContext.drawImage(image, x, y, imageDimensionPixelCount, imageDimensionPixelCount);
}
}
}
function createLocalImages(imageCount, imageDimension) {
var tempCanvas = document.createElement('canvas');
tempCanvas.width = imageDimension;
tempCanvas.height = imageDimension;
var tempContext = tempCanvas.getContext('2d');
var images = new Array();
for (var imageIndex = 0; imageIndex < imageCount; imageIndex++) {
tempContext.clearRect(0, 0, imageDimension, imageDimension);
tempContext.fillStyle = "rgb(" + getRandomInt(0, 255) + ", " + getRandomInt(0, 255) + ", " + getRandomInt(0, 255) + ")";
tempContext.fillRect(0, 0, imageDimension, imageDimension);
var image = new Image();
image.src = tempCanvas.toDataURL('image/png');
images.push(image);
}
return images;
}
// Get this party started
init();
And a jsfiddle link for your interactive pleasure:
http://jsfiddle.net/BtyL6/14/
This is drawing 50px x 50px images in a 50 x 50 (2500) grid on the canvas. I've also quickly tried with 25px x 25px and 50 x 50 (2500) images.
We have other local examples that deal with bigger images and larger numbers of images and the other browser start to struggle with these at higher values.
As a quick test I jacked up the code in the js fiddle to 100px x 100px and 100 x 100 (10000) images and that was still running at 16fps when fully zoomed out. (Note: I had to lower the viewMinScaleFactor to 0.01 to fit it all in when zoomed out.)
Chrome on the other hand seems to hit some kind of limit and the FPS drops from 60 to 2-4.
Here's some info about what we've tried and the results:
We've tried using setinterval rather than requestAnimationFrame.
If you load 10 images and draw them 250 times each rather than 2500 images drawn once each then the problem goes away. This seems to indicate that chrome is hitting some kind of limit/trigger as to how much data it's storing about the rendering.
We have culling (not rendering images outside of the visual range) in our more complex examples and while this helps it's not a solution as we need to be able to show all the images at once.
We have the images only being rendered if there have been changes in our local code, against this helps (when nothing changes, obviously) but it isn't a full solution because the canvas should be interactive.
In the example code we're creating the images using a canvas, but the code can also be run hitting a web service to provide the images and the same behaviour (slowness) will be seen.
We've found it very hard to even search for this issue, most results are from a couple of years ago and woefully out of date.
If any more information would be useful then please ask!
EDIT: Changed js fiddle URL to reflect the same code as in the question. The code itself didn't actually change, just the formatting. But I want to be consistent.
EDIT: Updated jsfiddle and and code with css to prevent selection and call requestAnim after the render loop is done.
In Canary this code freezes it on my computer. As to why this happens in Chrome the simple answer is that it uses a different implementation than f.ex. FF. In-depth detail I don't know, but there is obviously room for optimizing the implementation in this area.
I can give some tip however on how you can optimize the given code to make it run in Chrome as well :-)
There are several things here:
You are storing each block of colors as images. This seem to have a huge performance impact on Canary / Chrome.
You are calling requestAnimationFrame at the beginning of the loop
You are clearing and rendering even if there are no changes
Try to (addressing the points):
If you only need solid blocks of colors, draw them directly using fillRect() instead and keep the color indexes in an array (instead of images). Even if you draw them to an off-screen canvas you will only have to do one draw to main canvas instead of multiple image draw operations.
Move requestAnimationFrame to the end of the code block to avoid stacking.
Use dirty flag to prevent unnecessary rendering:
I modified the code a bit - I modified it to use solid colors to demonstrate where the performance impact is in Chrome / Canary.
I set a dirty flag in global scope as true (to render the initial scene) which is set to true each time the mouse move occur:
//global
var isDirty = true;
//mouse move handler
var handleMouseMove = function (eventArgs) {
// other code
isDirty = true;
// other code
};
//render loop
function renderLoop() {
if (isDirty) {
clearCanvas();
renderCanvas();
}
stats.update();
requestAnimFrame(renderLoop);
}
//in renderCanvas at the end:
function renderCanvas() {
// other code
isDirty = false;
}
You will of course need to check for caveats for the isDirty flag elsewhere and also introduce more criteria if it's cleared at the wrong moment. I would store the old position of the mouse and only (in the mouse move) if it changed set the dirty flag - I didn't modify this part though.
As you can see you will be able to run this in Chrome and in FF at a higher FPS.
I also assume (I didn't test) that you can optimize the clearCanvas() function by only drawing the padding/gaps instead of clearing the whole canvas. But that need to be tested.
Added a CSS-rule to prevent the canvas to be selected when using the mouse:
For further optimizing in cases such as this, which is event driven, you don't actually need an animation loop at all. You can just call the redraw when the coords or mouse-wheel changes.
Modification:
http://jsfiddle.net/BtyL6/10/
This was a legitimate bug in chrome.
https://code.google.com/p/chromium/issues/detail?id=247912
It has now been fixed and should be in a chrome mainline release soon.