2019js13k/js/Camera.js

class Camera {
	constructor() {
		this.position = { x: -100, y: -100 };
		this.viewBox = { x: 100, y: 100, width: 600, height: 400 };
	}

	init(canvas) {
		this.viewBox.x = canvas.width / 3;
		this.viewBox.y = canvas.height / 3;
		this.viewBox.width = canvas.width - 2 * this.viewBox.x;
		this.viewBox.height = canvas.height - 2 * this.viewBox.y;

		this.position = { x: canvas.width / 2, y: canvas.height / 2 };
	}

	update(canvas, player, delta) {
		this.followPlayer(player, delta);
	}

	handleResize(canvas) {
		this.viewBox.x = canvas.width / 3;
		this.viewBox.y = canvas.height / 3;
		this.viewBox.width = canvas.width - 2 * this.viewBox.x;
		this.viewBox.height = canvas.height - 2 * this.viewBox.y;
	}

	followPlayer(player) {
		var truePos = { x: 0, y: 0 };
		truePos.x = this.position.x + player.position.x;
		truePos.y = this.position.y + player.position.y;

		if (truePos.x <= this.viewBox.x) {
			this.position.x -= truePos.x - this.viewBox.x;
		}

		if (player.position.x + this.position.x >= this.viewBox.x + this.viewBox.width) {
			this.position.x += (this.viewBox.x + this.viewBox.width) - truePos.x;
		}

		if (truePos.y <= this.viewBox.y) {
			this.position.y -= truePos.y - this.viewBox.y;
		}

		if (player.position.y + this.position.y >= this.viewBox.y + this.viewBox.height) {
			this.position.y += (this.viewBox.y + this.viewBox.height) - truePos.y;
		}
	}
}