canvassed/src/create-composite-object.js

'use strict';

const dotty = require("dotty");
const defaultValue = require("default-value");

const createObject = require("./create-object");
const createPropertyMapper = require("./property-mapper");
const requireProperties = require("./require-properties");
const max = require("./util/max");
const min = require("./util/min");

function getPosition(object) {
	return {
		x: defaultValue(object.x, 0),
		y: defaultValue(object.y, 0)
	}
}

module.exports = function createCompositeObject(options) {
	requireProperties(options, ["drawOrder", "objects"]);

	let mapProperties = createPropertyMapper(options.propertyMap);
	let initialPropertySet = mapProperties(options);

	let compositeObject = createObject(Object.assign({
		onSet: function setCompositeProperties(properties) {
			let mappedProperties = mapProperties(properties);

			Object.keys(mappedProperties).forEach((objectName) => {
				if (objectName !== "_") {
					if (this.objects[objectName] != null) {
						this.objects[objectName].set(mappedProperties[objectName]);
					} else {
						throw new Error(`The object specified in the property map as '${objectName}' does not exist`);
					}
				}
			});

			/* We return the `_` object here, which contains all the unmapped
			 * properties - we assume that all unmapped properties are meant to
			 * apply to the composite object rather than its child objects. The
			 * original `.set` method (as defined in createObject) will then use
			 * this result. */
			return defaultValue(mappedProperties._, {});
		},
		onRender: function onRender(context) {
			this.drawOrder.forEach((objectName) => {
				let object = this.objects[objectName];
				let position = getPosition(object);

				object.render(context, {
					x: object.x - this.offsetX,
					y: object.y - this.offsetY
				});
			});
		},
		onRecalculateSize: function onRecalculateSize() {
			let objectMetrics = Object.keys(this.objects).map((objectName) => {
				let object = this.objects[objectName];
				let position = getPosition(object);

				return {
					x1: position.x,
					y1: position.y,
					x2: position.x + object.renderWidth,
					y2: position.y + object.renderHeight
				}
			});

			let x1 = min(objectMetrics.map(object => object.x1));
			let y1 = min(objectMetrics.map(object => object.y1));
			let x2 = max(objectMetrics.map(object => object.x2));
			let y2 = max(objectMetrics.map(object => object.y2));

			this.offsetX = x1;
			this.offsetY = y1;

			return {
				width: x2 - x1,
				height: y2 - y1
			}
		}
	}, initialPropertySet._));

	Object.keys(compositeObject.objects).forEach((objectName) => {
		compositeObject.objects[objectName].on("recalculatedSize", () => {
			compositeObject.recalculateSize();
		});

		compositeObject.objects[objectName].on("bustedCache", () => {
			compositeObject.bustCache();
		});
	});

	compositeObject.set(options);
	return compositeObject;
};