splatjs/lib/camera.js

"use strict";

var Entity = require("./entity");

/**
 * A basic camera. It's really an {@link Splat.Entity}, so you can control it in the same way.
 * By changing {@link Splat.Entity#x} and {@link Splat.Entity#y} you control what portion of the canvas is viewable.
 * For example, if the Camera is at 50,50, and you draw a rectangle at 200,200,
 * it will appear on the screen at 150,150.
 * @constructor
 * @augments Splat.Entity
 * @alias Splat.Camera
 * @param {number} x The top-left x coordinate
 * @param {number} y The top-left y coordinate
 * @param {number} width The width on the x-axis. Currently doesn't do anything.
 * @param {number} height The height on the y-axis. Currently doesn't do anything.
 */
function Camera(x, y, width, height) {
	Entity.call(this, x, y, width, height);
}
Camera.prototype = Object.create(Entity.prototype);
/**
 * Offset all following draw operations on the canvas.
 * This is automatically called for you by {@link Splat.Scene}.
 * @param {external:CanvasRendingContext2D} context The context to offset
 */
Camera.prototype.draw = function(context) {
	context.translate(-(this.x|0), -(this.y|0));
};
/**
 * Draw on the canvas at not-offset coordinates.
 * For example, if the camera is at 50,50 and you draw a rectangle at 200,200
 * it will appear on the screen at 200,200.
 * @param {external:CanvasRendingContext2D} context The context to offset
 * @param {drawCallback} drawFunc The callback the performs the non-offset drawing.
 */
Camera.prototype.drawAbsolute = function(context, drawFunc) {
	context.save();
	context.translate(this.x|0, this.y|0);
	drawFunc();
	context.restore();
};

module.exports = Camera;