How to drag images / objects within Canvas after zooming / scaling them? - javascript

Following is my Complete code. Which is edited as per this link How to drag images / objects within Canvas?.
Requirement :
Basically what I am doing is, First I am drawing SVG file on canvas with drawSvg with the help of canvg.
On this file I am plotting images(green1.png and orange1.png) through JSON which is present in markers.js.
Scenario 1:
If I pan without Zooming/scaling then able to drag those images(green1.png, orange1.png) and able to pan canvas properly.
But If I zoom after panning then images are not translating on proper position because of panX and panY points. But panX and panY are point we want for panning.
Scenario 2: :
If I scale/zoom first and then if I pan then images(orange1.png, green1.png) are changing their position and not able to drag images (orange1.png, green1.png).
What can be done in these scenarios?
HTML Code :
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<script src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
<style>
canvas {
border:1px solid #000
}
.tooltip{
*position:fixed;
position:absolute;
*background:#ff7;
background:green;
border:1px solid #000;
padding:7px;
font-family:sans-serif;
font-size:12px;
}
.tooltip2 {
*position:fixed;
position:absolute;
background:pink;
border:1px solid #000;
padding:7px;
font-family:sans-serif;
font-size:12px;
}
</style>
</head>
<body>
<script src="http://canvg.googlecode.com/svn/trunk/rgbcolor.js"></script>
<script src="http://canvg.googlecode.com/svn/trunk/StackBlur.js"></script>
<script src="http://canvg.googlecode.com/svn/trunk/canvg.js"></script>
<canvas id="myCanvas" width="800" height="700" style="border: 1px solid;margin-top: 10px;"></canvas>
<div id="buttonWrapper">
<input type="button" id="plus" value="+">
<input type="button" id="minus" value="-">
<input type="button" id="original_size" value="100%">
</div>
<script src="/static/js/markers.js"></script>
<script src="/static/js/draw.js"></script>
</body>
</html>
draw.js:
var dataJSON = data || [];
var dataJSON2 = data2 || [];
window.onload = function(){
//$(function(){
var canvas=document.getElementById("myCanvas");
var ctx=canvas.getContext("2d");
var canvasOffset=$("#myCanvas").offset();
var offsetX=canvasOffset.left;
var offsetY=canvasOffset.top;
var lastX=0;
var lastY=0;
var panX=0;
var panY=0;
var dragging=[];
var dragging2=[];
var isDown=false;
function loadImages(sources, callback){
var images = {};
var loadImages = 0;
var numImages = 0;
//get num of sources
for(var i in sources){
numImages++;
}
for(var i in sources){
images[i] = new Image();
images[i].onload = function(){
if(++loadImages >= numImages){
callback(images);
}
};
images[i].src = sources[i];
}
}
var sources = {orange : '/static/images/orange1.png', green : '/static/images/green1.png'};
// load the tiger image
var svgfiles = ["/static/images/awesome_tiger.svg"];
/*var tiger=new Image();
tiger.onload=function(){
draw();
}
tiger.src="tiger.png";*/
function draw(scaleValue){
ctx.clearRect(0,0,canvas.width,canvas.height);
ctx.save();
ctx.drawSvg(svgfiles[0],panX,panY,400*scaleValue, 400*scaleValue);
//ctx.drawImage(tiger,panX,panY,tiger.width,tiger.height);
//ctx.scale(scaleValue, scaleValue);
loadImages(sources, function(images){
ctx.scale(scaleValue, scaleValue);
for(var i = 0, pos; pos = dataJSON[i]; i++) {
ctx.drawImage(images.orange, parseInt(parseInt(pos.x) + parseInt(panX)), parseInt(parseInt(pos.y) + parseInt(panY)), 20/scaleValue, 20/scaleValue);
}
for(var i = 0, pos; pos = dataJSON2[i]; i++) {
ctx.drawImage(images.green, parseInt(parseInt(pos.x) + parseInt(panX)), parseInt(parseInt(pos.y) + parseInt(panY)), 20/scaleValue, 20/scaleValue);
}
ctx.restore();
});
};
var scaleValue = 1;
var scaleMultiplier = 0.8;
draw(scaleValue);
var startDragOffset = {};
var mouseDown = false;
// add button event listeners
document.getElementById("plus").addEventListener("click", function(){
scaleValue /= scaleMultiplier;
//checkboxZoomPan();
draw(scaleValue);
}, false);
document.getElementById("minus").addEventListener("click", function(){
scaleValue *= scaleMultiplier;
//checkboxZoomPan();
draw(scaleValue);
}, false);
document.getElementById("original_size").addEventListener("click", function(){
scaleValue = 1;
//checkboxZoomPan();
draw(scaleValue);
}, false);
// create an array of any "hit" colored-images
function imagesHitTests(x,y){
// adjust for panning
x-=panX;
y-=panY;
// create var to hold any hits
var hits=[];
// hit-test each image
// add hits to hits[]
loadImages(sources, function(images){
for(var i = 0, pos; pos = dataJSON[i]; i++) {
if(x >= parseInt(pos.x * scaleValue) && x <= parseInt((pos.x * scaleValue) + 20) && y >= parseInt(pos.y * scaleValue) && y <= parseInt((pos.y * scaleValue) + 20)){
hits.push(i);
}
}
});
return(hits);
}
function imagesHitTests2(x,y){
// adjust for panning
//x-=panX;
//x = parseInt(x) - parseInt(panX);
// y-=panY;
x-=panX;
y-=panY;
// create var to hold any hits
var hits2=[];
// hit-test each image
// add hits to hits[]
loadImages(sources, function(images){
for(var i = 0, pos; pos = dataJSON2[i]; i++) {
//if(x > pos.x && x < parseInt(parseInt(pos.x) + parseInt(20)) && y > pos.y && y < parseInt(parseInt(pos.y) + parseInt(20))){
if(x >= parseInt(pos.x * scaleValue) && x <= parseInt((pos.x * scaleValue) + 20) && y >= parseInt(pos.y * scaleValue) && y <= parseInt((pos.y * scaleValue) + 20)){
hits2.push(i);
}
}
});
return(hits2);
}
function handleMouseDown(e){
// get mouse coordinates
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// set the starting drag position
lastX=mouseX;
lastY=mouseY;
// test if we're over any of the images
dragging=imagesHitTests(mouseX,mouseY);
dragging2=imagesHitTests2(mouseX,mouseY);
// set the dragging flag
isDown=true;
}
function handleMouseUp(e){
// clear the dragging flag
isDown=false;
}
function handleMouseMove(e){
// if we're not dragging, exit
if(!isDown){
return;
}
//get mouse coordinates
mouseX=parseInt(e.clientX-offsetX);
mouseY=parseInt(e.clientY-offsetY);
// calc how much the mouse has moved since we were last here
var dx=mouseX-lastX;
var dy=mouseY-lastY;
// set the lastXY for next time we're here
lastX=mouseX;
lastY=mouseY;
// handle drags/pans
if(dragging.length>0){
// we're dragging images
// move all affected images by how much the mouse has moved
for(var i = 0, pos; pos = dataJSON[dragging[i]]; i++) {
pos.x = parseInt(pos.x) + parseInt(dx);
pos.y = parseInt(pos.y) + parseInt(dy);
}
}
else if(dragging2.length>0){
for(var i = 0, pos1; pos1 = dataJSON2[dragging2[i]]; i++) {
pos1.x = parseInt(pos1.x) + parseInt(dx);
pos1.y = parseInt(pos1.y) + parseInt(dy);
}
}
else{
// we're panning the tiger
// set the panXY by how much the mouse has moved
panX+=dx;
panY+=dy;
}
draw(scaleValue);
}
// use jQuery to handle mouse events
$("#myCanvas").mousedown(function(e){handleMouseDown(e);});
$("#myCanvas").mousemove(function(e){handleMouseMove(e);});
$("#myCanvas").mouseup(function(e){handleMouseUp(e);});
// }); // end $(function(){});
}
markers.js:
data = [
{ "id" :["first"],
"x": ["195"],
"y": ["150"],
"tooltiptxt": ["Region 1"]
},
{
"id" :["second"],
"x": ["255"],
"y": ["180"],
"tooltiptxt": ["Region 2"]
},
{
"id" :["third"],
"x": ["200"],
"y": ["240"],
"tooltiptxt": ["Region 3"]
}
];
data2 = [
{ "id" :["first2"],
"x": ["225"],
"y": ["150"],
"tooltiptxt": ["Region 21"]
},
{
"id" :["second2"],
"x": ["275"],
"y": ["180"],
"tooltiptxt": ["Region 22"]
},
{
"id" :["third3"],
"x": ["300"],
"y": ["240"],
"tooltiptxt": ["Region 23"]
}
];

1.)
positionX * xScale and positionY * yScale
2.)
try this code in draw function
ctx.drawImage(images.orange, parseInt(parseInt(pos.x) + parseInt(panX / scaleValue)), parseInt(parseInt(pos.y) + parseInt(panY / scaleValue)), 20/scaleValue, 20/scaleValue);

Related

How do i Make a sprite change with keyboard input i'm using vanilla JS

so ive been testing out HTML canvas. im trying to get a sprite to change on keyboard input.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<canvas id='Game' width='200' height='200' style='border: 2px solid #000000;'></canvas>
<script>
window.onload = function(){
var Game = document.getElementById('Game');
var context = Game.getContext('2d')
var room = new Image();
var lx = 0;
var ly = 0;
var li = 0;
var lo = 0;
var lwidth = 100;
var lheight = 100;
room.onload = function(){
context.drawImage(room,lx,ly,lwidth,lheight,li,lo,200,200);
}
room.src = 'https://i.ibb.co/D7fL7yN/Room.png';
var sprite = new Image();
var cx = 0;
var cy = 125;
var sy = 0;
var sx = 0;
var swidth = 35;
var sheight = 34;
sprite.onload = function(){
context.drawImage(sprite,sx,sy,swidth,sheight,cx,cy,50,50);
}
sprite.src = 'https://i.ibb.co/7VhjqPr/John-Sheet.png';
}
</script>
</body>
</html>
ive been searching on how to change the SX with Keyboard input so my character changes sprites. can you help me? a code example would be best!
Tracking keyboard state.
You can create an object that hold the state of the keyboard, specifically the keys you are interested in reacting to. Use the "keydown" and "keyup" KeyboardEvent to update the keyboard state as the events fire. Use the KeyboardEvent property code to workout which key is changing. DO NOT use keyCode as that has depreciated and is Non Standard
You also want to prevent the default behaviour of keys. Eg prevent arrow keys scrolling the page. This is done by calling the event preventDefault function
const keys = {
ArrowRight: false,
ArrowLeft: false,
ArrowUp: false,
ArrowDown: false,
}
addEventListener("keydown", keyEvent);
addEventListener("keyup", keyEvent);
function keyEvent(event) {
if (keys[event.code] !== undefined) {
keys[event.code] = event.type === "keydown";
event.preventDefault();
}
}
Then in the game you need only check the keyboard state
if (keys.ArrowRight) { moveRight() }
if (keys.ArrowLeft) { moveLeft() }
// and so on
In the demo below the keys are binded to game actions, meaning that what and how many keys are used are independent of the action. The are also set via configuration, so that key binding can be changed without changing game code. You can also bind other inputs as in example
Animation
To animate you should use the timer function requestAnimationFrame as it is specifically designed to give the best animation results. It will call your rendering function, you can consider the rendering function like a loop, that is call every time you step forward in animation time.
Putting it together
The demo below use the above (modified) methods to get keyboard input and render the scene via animation frame requests.
It also uses some techniques (simple versions of) that help make your game a better product.
Encapsulates the player as an object
Maintains game state by holding the current rendering function in currentRenderState
Has configuration config so all important values are in one place, and could be loaded (from JSON file) to easily change the game without changing code.
Has configurable keyboard binding, Note more than one key can be bound to a game action. In example movement is via WASD or arrow keys.
All text is configurable (making it language independent)
Passes the 2D context to all rendering code.
Separates the game from the rendering. This makes it easier to port the game to low end or high end devices or even move it to a server where ctx is replaced with coms and the game can be broadcast . The game does not change only how it is rendered
var currentRenderState = getFocus; // current game state
const config = {
player: {
start: {x: 100, y:100},
speed: 2,
imageURL: "https://i.stack.imgur.com/C7qq2.png?s=64&g=1",
},
keys: { // link key code to game action
up: ["ArrowUp", "KeyW"],
down: ["ArrowDown", "KeyS"],
left: ["ArrowLeft", "KeyA"],
right: ["ArrowRight", "KeyD"],
},
touchableTime: 140, // in ms. Set to 0 or remove to deactivate
text: {
focus: "Click canvas to get focus",
loading: "Just a moment still loading media!",
instruct: "Use arrow keys or WASD to move",
}
};
requestAnimationFrame(mainLoop); // request first frame
const ctx = gameCanvas.getContext("2d");
const w = gameCanvas.width, h = gameCanvas.height;
const player = {
image: (()=> {
const img = new Image;
img.src = config.player.imageURL;
img.addEventListener("load", () => player.size = img.width, {once: true});
return img;
})(),
x: config.player.start.x,
y: config.player.start.y,
size: 0,
speed: config.player.speed,
direction: 0,
update() {
var oldX = this.x, oldY = this.y;
if (actions.left) { this.x -= this.speed }
if (actions.right) { this.x += this.speed }
if (actions.up) { this.y -= this.speed }
if (actions.down) { this.y += this.speed }
if (this.x < 0) { this.x = 0 }
else if (this.x > w - this.size) { this.x = w - this.size }
if (this.y < 0) { this.y = 0 }
else if (this.y > h - this.size) { this.y = h - this.size }
const mx = this.x - oldX, my = this.y - oldY;
if (mx !== 0 || my !== 0) { this.direction = Math.atan2(my, mx) }
},
draw(ctx) {
if (ctx) {
ctx.setTransform(1, 0, 0, 1, this.x + this.size / 2, this.y + this.size / 2);
ctx.rotate(this.direction + Math.PI / 2); // rotate 90 deg as image points up
ctx.drawImage(this.image,-this.size / 2, -this.size / 2, this.size, this.size);
}
}
}
function drawText(ctx, text, size, color) {
if (ctx) {
ctx.fillStyle = color;
ctx.font = size + "px Arial";
ctx.textAlign = "center";
ctx.fillText(text, w / 2, h * (1/4));
}
}
function getFocus(ctx) {
drawText(ctx, config.text.focus, 24, "black");
}
function drawScene(ctx) {
if (!player.size === 0) {
drawText(ctx, config.text.loading, 16, "blue")
actions.hasInput = false; // ensure instruction are up when ready
} else {
if (!actions.hasInput) { drawText(ctx, config.text.instruct, 16, "blue") }
player.update();
player.draw(ctx);
}
}
function mainLoop() {
ctx.setTransform(1, 0, 0, 1, 0, 0);
ctx.clearRect(0, 0, w, h);
currentRenderState(ctx);
requestAnimationFrame(mainLoop); // request next frame
}
// keys holds action name for each named key. eg for up action ArrowUp: "up", KeyW: "up",
const keys = Object.entries(config.keys)
.reduce((keys, [action,codes]) =>
codes.reduce((keys, code) => (keys[code] = action, keys), keys), {});
// actions are set true when key down. NOTE first up key for action cancels action
const actions = Object.keys(config.keys)
.reduce((actions,action) => (actions[action] = false, actions),{});
addEventListener("keydown", keyEvent);
addEventListener("keyup", keyEvent);
function keyEvent(event) {
if (keys[event.code] !== undefined) {
actions[keys[event.code]] = event.type === "keydown";
event.preventDefault();
actions.hasInput = true;
}
}
if (config.touchableTime) {
const actionTimers = {};
touchable.addEventListener("click", (e) => {
if (e.target.dataset.action) {
actions[e.target.dataset.action] = true;
clearTimeout(actionTimers[e.target.dataset.action]);
actionTimers[e.target.dataset.action] = setTimeout(() => actions[e.target.dataset.action] = false, config.touchableTime);
actions.hasInput=true;
if (currentRenderState !== drawScene) {
window.focus();
currentRenderState = drawScene;
}
}
});
} else {
touchable.classList.add("hide");
}
gameCanvas.addEventListener("click", () => currentRenderState = drawScene, {once: true});
canvas {border: 1px solid black}
#game {
width:402px;
height:182px;
font-size: 24px;
user-select: none;
}
.left {
position: absolute;
top: 160px;
left: 10px;
cursor: pointer;
}
.right {
position: absolute;
top: 160px;
left: 355px;
cursor: pointer;
}
#touchable span:hover {color: red}
.hide { display: none }
<div id="game">
<canvas id="gameCanvas" width="400" height="180"></canvas>
<div id="touchable">
<div class="left">
<span data-action="up">▲</span>
<span data-action="down">▼</span>
</div>
<div class="right">
<span data-action="left">◄</span>
<span data-action="right">►</span>
</div>
</div>
</div>
Click to snippet frame area for focusing keyboard events
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<canvas id='Game' width='200' height='200' style='border: 2px solid #000000;'></canvas>
<script>
window.onload = function(){
// Keyboard collect
const keys = [];
document.onkeydown = e => {
var code = e.which;
if(keys.indexOf(code) < 0){
keys.push(code);
}
};
document.onkeyup = e => keys.splice(keys.indexOf(e.which),1);
// constants
const Game = document.getElementById('Game');
const context = Game.getContext('2d')
const room = new Image();
const lx = 0;
const ly = 0;
const li = 0;
const lo = 0;
const lwidth = 100;
const lheight = 100;
room.onload = function(){
context.drawImage(room,lx,ly,lwidth,lheight,li,lo,200,200);
}
room.src = 'https://i.ibb.co/D7fL7yN/Room.png';
const sprite = new Image();
const swidth = 35;
const sheight = 34;
const sy = 0;
sprite.onload = function(){
context.drawImage(sprite,0,sy,swidth,sheight,0,cy,50,50);
}
sprite.src = 'https://i.ibb.co/7VhjqPr/John-Sheet.png';
// variables
let cx = 0;
let cy = 125;
let sx = 0;
// new variables
const frames_per_step = 20;
let moving = false; // moving flag
let step = 0; // frame counter (for steps)
// main loop function
function tick() {
// keyboard process
if (keys.length) {
keys.forEach(item => {
switch(item){
case 68:case 39://D and right arrow
cx += 1; // move right
// change sprite
if (step++ < frames_per_step / 2) {
sx = 35; // leg up
} else {
sx = 70; // leg down
if(step > frames_per_step) step = 0;
}
moving = true;
break;
case 65:case 37://A and left arrow
cx -= 1; // move left
// change sprite
if (step++ < frames_per_step / 2) {
sx = 105;
} else {
sx = 140;
if(step > frames_per_step) step = 0;
}
moving = true;
break;
// no sprite mechanics here, just move
case 87:case 38://W adn arrow up
cy -= 1;
break;
case 83:case 40://S adn arrow down
cy += 1;
break;
}
});
// render
context.drawImage(room,lx,ly,lwidth,lheight,li,lo,200,200);
context.drawImage(sprite,sx,sy,swidth,sheight,cx,cy,50,50);
} else if(moving) { // return sprite to stay position
sx = 0;
context.drawImage(room,lx,ly,lwidth,lheight,li,lo,200,200);
context.drawImage(sprite,sx,sy,swidth,sheight,cx,cy,50,50);
moving = false;
} // else do nothing
requestAnimationFrame(tick);
}
tick();
}
</script>
</body>
</html>

The old elements of canvas reappears after clearing the canvas using clearRect(...)

Whenever I try to clear the canvas using clearRect(), at first it is cleared. But as soon as I start redrawing the old elements reappear. I even tried
context.width = context.width
but nothing seems to be working. The canvas is getting cleared initially but on clicking the clear button, it clears at first, but everything reappears. Please help me in debugging this error. The clearRect method is in the end of the code.
Below is the code
<script>
var canv = document.getElementById('canv'),
ctx = canv.getContext('2d'),
rect = [],
move = false;
var newRect;
var startX, startY, mouseX, mouseY;
var offsetX,offsetY;
function reOffset(){
var bound = canv.getBoundingClientRect();
offsetX = bound.left;
offsetY = bound.top;
}
reOffset();
function movement(){
canv.addEventListener('mousedown', mouseDown, false);
canv.addEventListener('mouseup', mouseUp, false);
canv.addEventListener('mousemove', mouseMove, false);
}
function mouseDown(event){
startX=parseInt(event.clientX-offsetX);
startY=parseInt(event.clientY-offsetY);
move = true;
}
function mouseUp(event){
mouseX=parseInt(event.clientX-offsetX);
mouseY=parseInt(event.clientY-offsetY);
move = false;
if(!overlap(newRect)){
rect.push(newRect);
}
make();
//ctx.fillRect(q.left,q.top,q.right-q.left,q.bottom-q.top);
}
function make(){
for(var i = 0; i < rect.length; i++){
var q = rect[i];
ctx.fillStyle = randomColour();
ctx.fillRect(q.left, q.top, q.right - q.left, q.bottom - q.top);
}
}
function mouseMove(event){
if(move){
mouseX=parseInt(event.clientX - offsetX);
mouseY=parseInt(event.clientY - offsetY);
newRect = {
left : Math.min(startX , mouseX),
right : Math.max(startX , mouseX),
top : Math.min(startY , mouseY),
bottom : Math.max(startY , mouseY),
}
ctx.clearRect(0, 0, canv.width, canv.height);
ctx.strokeRect(startX, startY, mouseX-startX, mouseY-startY);
}
}
function randomColour() {
var colour = [];
for (var i = 0; i < 3; i++) {
colour.push(Math.floor(Math.random() * 256));
}
return 'rgb(' + colour.join(',') + ')';
}
function overlap(newRect){
var q1 = newRect;
//if one rect is completely inside another rect
var inside = function(rectx, recty){
return(recty.left >= rectx.left &&
recty.right <= rectx.right &&
recty.top >= rectx.top &&
recty.bottom <= rectx.bottom);
}
//if the new rect is overlapping any existing rect
var isOverlaping = false;
for(var i = 0; i < rect.length; i++){
var q2 = rect[i];
var isIntersecting = !(q1.left > q2.right ||
q1.right < q2.left ||
q1.top > q2.bottom ||
q1.bottom < q2.top);
var isContain = inside(q2, q1) || inside(q1, q2);
if(isIntersecting || isContain){
isOverlaping=true;
}
}
return(isOverlaping);
}
movement();
//clear the canvas for redrawing
document.getElementById('clear').addEventListener('click', function () {
ctx.clearRect(0, 0, canv.width, canv.height);
}, false);
</script>`
<head>
<title>Simple Paint App</title>
</head>
<body>
<canvas id ="canv" width="1000" height="600" ></canvas>
<div id="button" style="position: absolute;">
<input type="button" id="clear" value="Clear">
</div>
</body>
You need to reset the rect array as well.
Adding this to your clear callback function:
document.getElementById('clear').addEventListener('click', function () {
rect = [];
console.log(rect);
ctx.clearRect(0, 0, canv.width, canv.height);
}, false);
should work, while removing the reset of the rect array (as in your clear callback function), logs the old rectangles as well.

Javascript and jQuery: onclick event listener to increment index in while loop

I have a code which displays a circle and an ellipse when I press "S" (the positions are chosen among 18 possible combinations). Then I have a while loop: I would like that, at every iteration, if the circle is touched a new position is generated right away and, if the circle is NOT touched for 3 consecutive times, a new position is generated.
I have 2 problems: 1) It seems that I cannot put the increment (positions ++) in the if/else statement only. 2) The second iteration does not update the positions of circle and ellipse (I should use a jQuery $ attribute?)
How can I solve this?
<html>
<head>
</head>
<link rel="stylesheet" href="cssFiles/blackBackground.css">
<script src="jsFiles/drawEllipse.js"></script>
<script src="jsFiles/drawCircle.js"></script>
<script src="jsFiles/newPosition.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.0/jquery.min.js"></script>
<script src='https://code.responsivevoice.org/responsivevoice.js'></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.8/angular.min.js"></script>
<canvas id="myCanvas" width="1260" height="1000" style="border:1px solid red;"></canvas>
<p id="1"></p>
<p id="2"></p>
<script>
var ellipse = [[-150,-300],[-150,0],[-150,300],[150,-300],[150,0],[150,300]];
var circle = [[-350,-300],[-350,0],[-350,300],[350,-300],[350,0],[350,300]];
var radius = 95;
var positions = 0;
var clicks = 0;
var canvas = document.getElementById('myCanvas');
$(document).ready(function() {
document.addEventListener("keydown", function (e) {
if (e.keyCode === 83) { // "Start" is pressed
while (positions<6){
// generate first position
var idx = newPosition(ellipse,circle,radius)
var idx_ellipse = idx[0];
var idx_circle = idx[1];
var xRight = circle[idx_circle][0] + radius + canvas.width/2 ;
var xLeft = circle[idx_circle][0] - radius+ canvas.width/2;
var yTop = circle[idx_circle][1] - radius + canvas.height/2;
var yBottom = circle[idx_circle][1] + radius + canvas.height/2;
document.addEventListener("click", function(e) {
clicks++;
if (e.clientX< xRight && e.clientX> xLeft && e.clientY< yBottom && e.clientY> yTop) { //circle is correctly touched
var idx = newPosition(ellipse,circle,radius) // new position generated
positions++
}
else if (clicks > 3) {
var idx = newPosition(ellipse,circle,radius) // new position generated
positions++
}
}, false); //end of touch listener
} // end of while loop
} // end of "Start" keycode listener
}); //end of keydown listener
}) //end of document function
function newPosition(ellipse,circle,radius){
var idx_ellipse = Math.floor( Math.random() *6);
drawEllipse(ellipse[idx_ellipse][0],ellipse[idx_ellipse][1],radius,2.5,1);
// Check position of ellipse and draw circle on the other side
if (ellipse[idx_ellipse][0] == -150){
var idx_circle = Math.floor(Math.random() * (5 - 3 +1)) + 3;
drawCircle(circle[idx_circle][0],circle[idx_circle][1],radius,2.5,1);
}
else if(ellipse[idx_ellipse][0] == 150) {
var idx_circle = Math.floor(Math.random() * (2 - 0 +1)) + 0;
drawCircle(circle[idx_circle][0],circle[idx_circle][1],radius,2.5,1);
}
return [idx_ellipse,idx_circle];
}
</script>
</body>
</html>

different pages in a canvas game

The Problem
I am creating a game using the HTML5 Canvas, the game has a main menu, the main menu has multiple buttons for you to choose. I am finding it difficult and confusing how I would, for example if the user presses the 'Play' button, to show the game. Here is an image of the main menu:
The Question
The question is how would I get from this page to another in my game?
I think you get the idea. I deliberately created the menu using the canvas, I know I could of made the menu using HTML for example but I cant as this is an example for students of what Canvas can do, whats good and bad etc.
The Code
<html>
<head>
<title>Sean Coyne</title>
</head>
<body onload="start_game()">
<body>
<div style id="canvas">
<canvas id="myCanvas" style="border:5px solid #410b11" height="320" width="480">
<p>Your browser does not support HTML5!</p>
</canvas>
<script type="text/javascript">
//Referencing the canvas
var canvas = document.getElementById("myCanvas");
var context = canvas.getContext("2d");
var width = canvas.getAttribute('width');
var height = canvas.getAttribute('height');
//Finding the position of the mouse
var mouseX;
var mouseY;
//Images
var bgImage = new Image();
var logoImage = new Image();
var playImage = new Image();
var instructImage = new Image();
var settingsImage = new Image();
var aboutImage = new Image();
var peaceImage = new Image();
var backgroundY = 0;
var speed = 1;
//Arrays below used for mouse over function
var buttonX = [130,110,130,160];
var buttonY = [100,140,180,220];
var buttonWidth = [96,260,182,160];
var buttonHeight = [40,40,40,40];
var peaceX = [0,0];
var peaceY = [0,0];
var peaceWidth = 35;
var peaceHeight = 35;
var peaceVisible = false;
var peaceSize = peaceWidth;
var peaceRotate = 0;
var frames = 30;
var timerId = 0;
var fadeId = 0;
var time = 0.0;
peaceImage.src = "Images/peace.png";
bgImage.onload = function(){
context.drawImage(bgImage, 0, backgroundY);
};
bgImage.src = "Images/background.png";
logoImage.onload = function(){
context.drawImage(logoImage, 50, -10);
}
logoImage.src = "Images/logo.png";
playImage.onload = function(){
context.drawImage(playImage, buttonX[0], buttonY[0]);
}
playImage.src = "Images/play.png";
instructImage.onload = function(){
context.drawImage(instructImage, buttonX[1], buttonY[1]);
}
instructImage.src = "Images/instructions.png";
settingsImage.onload = function(){
context.drawImage(settingsImage, buttonX[2], buttonY[2]);
}
settingsImage.src = "Images/settings.png";
aboutImage.onload = function(){
context.drawImage(aboutImage, buttonX[3], buttonY[3]);
}
aboutImage.src = "Images/about.png";
timerId = setInterval("update()", 1000/frames);
canvas.addEventListener("mousemove", checkPos);
canvas.addEventListener("mouseup", checkClick);
function update() {
clear();
move();
draw();
}
function clear() {
context.clearRect(0, 0, width, height);
}
function move(){
backgroundY -= speed;
if(backgroundY == -1 * height){
backgroundY = 0;
}
if(peaceSize == peaceWidth){
peaceRotate = -1;
}
if(peaceSize == 0){
peaceRotate = 1;
}
peaceSize += peaceRotate;
}
function draw(){
context.drawImage(bgImage, 0, backgroundY);
context.drawImage(logoImage, 50,-10);
context.drawImage(playImage, buttonX[1], buttonY[0]);
context.drawImage(instructImage, buttonX[2], buttonY[1]);
context.drawImage(settingsImage, buttonX[2], buttonY[2]);
context.drawImage(aboutImage, buttonX[3], buttonY[3]);
if(peaceVisible == true){
context.drawImage(peaceImage, peaceX[0] - (peaceSize/2), peaceY[0], peaceSize, peaceHeight);
context.drawImage(peaceImage, peaceX[2] - (peaceSize/2), peaceY[2], peaceSize, peaceHeight);
}
}
function checkPos(mouseEvent){
if(mouseEvent.pageX || mouseEvent.pageY == 0){
mouseX = mouseEvent.pageX - this.offsetLeft;
mouseY = mouseEvent.pageY - this.offsetTop;
}else if(mouseEvent.offsetX || mouseEvent.offsetY == 0){
mouseX = mouseEvent.offsetX;
mouseY = mouseEvent.offsetY;
}
for(i = 0; i < buttonX.length; i++){
if(mouseX > buttonX[i] && mouseX < buttonX[i] + buttonWidth[i]){
if(mouseY > buttonY[i] && mouseY < buttonY[i] + buttonHeight[i]){
peaceVisible = true;
peaceX[0] = buttonX[i] - (peaceWidth/2) - 2;
peaceY[0] = buttonY[i] + 2;
peaceX[1] = buttonX[i] + buttonWidth[i] + (peaceWidth/2);
peaceY[1] = buttonY[i] + 2;
}
}else{
peaceVisible = false;
}
}
}
function checkClick(mouseEvent){
for(i = 0; i < buttonX.length; i++){
if(mouseX > buttonX[i] && mouseX < buttonX[i] + buttonWidth[i]){
if(mouseY > buttonY[i] && mouseY < buttonY[i] + buttonHeight[i]){
fadeId = setInterval("fadeOut()", 1000/frames);
clearInterval(timerId);
canvas.removeEventListener("mousemove", checkPos);
canvas.removeEventListener("mouseup", checkClick);
}
}
}
}
function fadeOut(){
context.fillStyle = "rgba(0,0,0, 0.2)";
context.fillRect (0, 0, width, height);
time += 0.1;
if(time >= 2){
clearInterval(fadeId);
time = 0;
timerId = setInterval("update()", 1000/frames);
canvas.addEventListener("mousemove", checkPos);
canvas.addEventListener("mouseup", checkClick);
}
}
</script>
</body>
</html>
What I usually do is have a switch statement inside the draw loop, and a state variable which holds the current game state (menu, playing, etc...).
Then, based on the current game state you only draw the objects required for the current scene.
Something like this:
var STATES = {
Menu: 0,
PauseMenu: 1,
Playing: 2
};
var currentState = STATES.Menu;
...
function draw() {
switch(currentState) {
case STATES.Menu:
// Draw buttons, etc..
break;
case STATES.Playing:
// Draw the game screen, the player, etc...
break;
}
}
When the user presses the Play button the only thing you have to do is:
function onPlayButtonClick() {
currentState = STATES.Playing;
// Starting the next frame the new state will be "magically" drawn
}
If you don't like the switch statement, you can create a State class that has a draw method. Then you can simply create new states, each with it's own drawing method and in the main draw loop only call the draw method of the current state.
Same goes for the update function, each state has it's own update function (in the main menu you update buttons or animate things, while playing the game you update the game world and run your physics). So, based on the current state your update function is actually different. It's up to you how you structure your code and how you call different functions based on the current state.
In each text option, you should create a smaller Canvas, only with the option text and add a 'click' event with the callbacks.
Tip: You don't need another page, just erase the main canvas and draw what you want.

Javascript addEventListener does it matter what the name of the function is in the second parameter?

Does it matter what the name of the function is in the second parameter of the addEventListern(Parm1, Parm2, Parm3)
I think that the error might have been because not all of the calls were renamed to that specific function name. There are a couple of times when that function is called and I think that would be what probably is causing the errors.
My code works with the below code. You can drag the circle around the canvas.
theCanvas.addEventListener("mousedown", mouseDownListener, false);
But if I change the code to the following.
theCanvas.addEventListener("mousedown", er, false);
And also rename the mouseDownListener method to er I can drag the circle around but when I release the mouse the circle keeps following the mouse pointer around. This seems like an odd behavior and I am not certain as to why this would be.
Question: Does the second parameter function name have to be mouseDownListener exactly or can this be an ad hoc name?
HTML Code:
<!doctype html>
<html lang="en">
<head>
<style type="text/css">
h4 {font-family: sans-serif;}
p {font-family: sans-serif;}
a {font-family: sans-serif; color:#d15423; text-decoration:none;}
</style>
<title>HTML5 Canvas Example - Simple Dragging Objects</title>
<script type="text/javascript">
window.addEventListener("load", canvasApp, false);
var Debugger = function() { };
Debugger.log = function(message) {
try {
console.log(message);
}
catch (exception) {
return;
}
}
function canvasApp() {
var theCanvas = document.getElementById("canvasOne");
var context = theCanvas.getContext("2d");
init();
var numShapes;
var shapes;
var dragIndex;
var dragging;
var mouseX;
var mouseY;
var dragHoldX;
var dragHoldY;
function init() {
numShapes = 1;
shapes = [];
makeShapes();
drawScreen();
theCanvas.addEventListener("mousedown", mouseDownListener, false);
}
function makeShapes() {
var i;
var tempX;
var tempY;
var tempRad;
var tempR;
var tempG;
var tempB;
var tempColor;
for (i=0; i < numShapes; i++) {
tempRad = 10 + Math.floor(Math.random()*25);
tempX = Math.random()*(theCanvas.width - tempRad);
tempY = Math.random()*(theCanvas.height - tempRad);
tempR = Math.floor(Math.random()*255);
tempG = Math.floor(Math.random()*255);
tempB = Math.floor(Math.random()*255);
tempColor = "rgb(" + tempR + "," + tempG + "," + tempB +")";
tempShape = {x:tempX, y:tempY, rad:tempRad, color:tempColor};
shapes.push(tempShape);
}
}
//main function for when the mouse button is clicked -- Once everything is loaded everything depends on this function
function mouseDownListener(evt) {
var i;
var highestIndex = -1;
var bRect = theCanvas.getBoundingClientRect();
mouseX = (evt.clientX - bRect.left)*(theCanvas.width/bRect.width);
mouseY = (evt.clientY - bRect.top)*(theCanvas.height/bRect.height);
//find which shape was clicked
for (i=0; i < numShapes; i++) {
if (hitTest(shapes[i], mouseX, mouseY)) {
dragging = true;
if (i > highestIndex) {
dragHoldX = mouseX - shapes[i].x;
dragHoldY = mouseY - shapes[i].y;
highestIndex = i;
dragIndex = i;
}
}
}
if (dragging) {
window.addEventListener("mousemove", mouseMoveListener, false);
}
theCanvas.removeEventListener("mousedown", mouseDownListener, false);
window.addEventListener("mouseup", mouseUpListener, false);
if (evt.preventDefault) {
evt.preventDefault();
} //standard
else if (evt.returnValue) {
evt.returnValue = false;
} //older IE
return false;
}
function mouseUpListener(evt) {
theCanvas.addEventListener("mousedown", mouseDownListener, false);
window.removeEventListener("mouseup", mouseUpListener, false);
if (dragging) {
dragging = false;
window.removeEventListener("mousemove", mouseMoveListener, false);
}
}
function mouseMoveListener(evt) {
var posX;
var posY;
var shapeRad = shapes[dragIndex].rad;
var minX = shapeRad;
var maxX = theCanvas.width - shapeRad;
var minY = shapeRad;
var maxY = theCanvas.height - shapeRad;
var bRect = theCanvas.getBoundingClientRect();
mouseX = (evt.clientX - bRect.left)*(theCanvas.width/bRect.width);
mouseY = (evt.clientY - bRect.top)*(theCanvas.height/bRect.height);
posX = mouseX - dragHoldX;
posX = (posX < minX) ? minX : ((posX > maxX) ? maxX : posX);
posY = mouseY - dragHoldY;
posY = (posY < minY) ? minY : ((posY > maxY) ? maxY : posY);
shapes[dragIndex].x = posX;
shapes[dragIndex].y = posY;
drawScreen();
}
function hitTest(shape,mx,my) {
var dx;
var dy;
dx = mx - shape.x;
dy = my - shape.y;
return (dx*dx + dy*dy < shape.rad*shape.rad);
}
function drawShapes() {
var i;
for (i=0; i < numShapes; i++) {
context.fillStyle = shapes[i].color;
context.beginPath();
context.arc(shapes[i].x, shapes[i].y, shapes[i].rad, 0, 2*Math.PI, false);
context.closePath();
context.fill();
}
}
function erraseCanvas() {
context.clearRect(0,0,theCanvas.width,theCanvas.height);
}
function clearTheScreenWithRectangle() {
context.fillStyle = "#000000";
context.fillRect(0,0,theCanvas.width,theCanvas.height);
}
function drawScreen() {
//erraseCanvas();
clearTheScreenWithRectangle();
drawShapes();
}
}
</script>
</head>
<body>
<div style="top: 50px; text-align:center">
<canvas id="canvasOne" width="1000" height="500">
Your browser does not support HTML5 canvas.
</canvas>
</div>
</body>
</html>
The second parameter has to be a reference to the function you want called when the event is triggered.
When passing a function, you may call it any, valid javascript identifier.
The second function can be called anything. The behaviour you describe by renaming the function to er could be caused if you forget to rename every occurrence of the function name (especially where it is disabled etc)
No, ceiling cat does not force you to set your function names to anything. You have freedom to name it whatever you like.
The second parameter is just a reference to the function you defined earlier, you can put any function (even anonymous) there.
The second parameter in in this statement can be any valid javascript name.
window.addEventListener("load", canvasApp, false);
Can be any valid name in Javascript that you want it to me.
window.addEventListener("load", ILoveBaseballANDApplePie, false);
window.addEventListener("load", Pizza, false);
window.addEventListener("load", AnyOtherName, false);
function Pizza() {
//do some code here
}
function ILoveBaseballANDApplePie() {
//do some code here
}
For programming purposes I would add the "load" name to the function name some how just so that 2 years later you will remember that that the function has to do with the load parameter. I would purchase a simple book on Javascript and use Notepad++ to go through some simple examples because even after using Javascript for the past 6 months I still find it somewhat of a beast to contend with on some things. With HTML5 you will be using these events probably a lot so I would learn as much as I possibly could about Javascript events.

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