CODEWITHSUNDEEP
javascripthtmlhtml5-canvas
Oliver Kucharzewski
Oliver Kucharzewski

Reputation: 2665

Check when object collides with border of canvas

I'm fairly new to Canvas HTML5 and was curious to know how to check if the 'Hero' in my game has collided with the border of the canvas as I would like to give it an alert or something if it did.

Here is my current code:

// Create the canvas
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = 512;
canvas.height = 480;
document.body.appendChild(canvas);

// Background image
var bgReady = false;
var bgImage = new Image();
bgImage.onload = function () {
    bgReady = true;
};
bgImage.src = "images/background.png";

// Hero image
var heroReady = false;
var heroImage = new Image();
heroImage.onload = function () {
    heroReady = true;
};
heroImage.src = "images/hero.png";

// Monster image
var monsterReady = false;
var monsterImage = new Image();
monsterImage.onload = function () {
    monsterReady = true;
};
monsterImage.src = "images/flamingo.png";

// Game objects
var hero = {
    speed: 256 // movement in pixels per second
};
var monster = {};
var monstersCaught = 0;

// Handle keyboard controls
var keysDown = {};

addEventListener("keydown", function (e) {
    keysDown[e.keyCode] = true;
}, false);

addEventListener("keyup", function (e) {
    delete keysDown[e.keyCode];
}, false);

// Reset the game when the player catches a monster
var reset = function () {
    hero.x = canvas.width / 2;
    hero.y = canvas.height / 2;

    // Throw the monster somewhere on the screen randomly
    monster.x = 32 + (Math.random() * (canvas.width - 64));
    monster.y = 32 + (Math.random() * (canvas.height - 64));
};

// Update game objects
var update = function (modifier) {
    if (38 in keysDown) { // Player holding up
        hero.y -= hero.speed * modifier;
    }
    if (40 in keysDown) { // Player holding down
        hero.y += hero.speed * modifier;
    }
    if (37 in keysDown) { // Player holding left
        hero.x -= hero.speed * modifier;
    }
    if (39 in keysDown) { // Player holding right
        hero.x += hero.speed * modifier;
    }

    // Are they touching?
    if (
        hero.x <= (monster.x + 32)
        && monster.x <= (hero.x + 32)
        && hero.y <= (monster.y + 32)
        && monster.y <= (hero.y + 32)
    ) 
    {
        ++monstersCaught;
        reset();
    }


};

// Draw everything
var render = function () {
    if (bgReady) {
        ctx.drawImage(bgImage, 0, 0);
    }

    if (heroReady) {
        ctx.drawImage(heroImage, hero.x, hero.y);
    }

    if (monsterReady) {
        ctx.drawImage(monsterImage, monster.x, monster.y);
    }

    // Score
    ctx.fillStyle = "rgb(250, 250, 250)";
    ctx.font = "24px Helvetica";
    ctx.textAlign = "left";
    ctx.textBaseline = "top";
    ctx.fillText("Flamingos slaughtered: " + monstersCaught, 32, 32);

};

// The main game loop
var main = function () {
    var now = Date.now();
    var delta = now - then;

    update(delta / 1000);
    render();

    then = now;
};

// Let's play this game!
reset();
var then = Date.now();
setInterval(main, 1); // Execute as fast as possible

Upvotes: 0

Views: 1725

Answers (2)

benef
benef

Reputation: 1

I fixed this : 

var update = function (modifier) {
    if (38 in keysDown) { // Player holding up
        hero.y -= hero.speed * modifier;
    }
    if (40 in keysDown) { // Player holding down
        hero.y += hero.speed * modifier;
    }
    if (37 in keysDown) { // Player holding left
        hero.x -= hero.speed * modifier;
    }
    if (39 in keysDown) { // Player holding right
        hero.x += hero.speed * modifier;
    }

    // Are they touching?
    if (
        hero.x <= (monster.x + 32)
        && monster.x <= (hero.x + 32)
        && hero.y <= (monster.y + 32)
        && monster.y <= (hero.y + 32)
    ) {
        ++monstersCaught;
        reset();
    }
    if(hero.x <= 0){
        hero.x = 0;
    }
    else if(isMaxWidth()){
        hero.x = canvas.width -32
    }
    if(hero.y <= 0){
        hero.y = 0;
    }
    else if(isMaxHeight()){
        hero.y = canvas.height -32
    }

};

var isMaxWidth = function(){
    return hero.x >= canvas.width - 32;
};

var isMaxHeight = function(){
    return hero.y >= canvas.height - 32;
};

Regards.

Upvotes: 0

Nevin
Nevin

Reputation: 3306

Basically what GameAlchemist has told ,should work.

But if the screen is resized or something similar.

You should go for 

0 <= x < window.innerWidth

and 

0 <= x < window.innerHeight

Condition: Windows size and canvas size should be equal

Upvotes: 1

Related Questions