Function Painter

libs/echarts/echarts-en.simple.js:9499–9613

(root, storage, opts)

 * @param {Object} opts
 */
var Painter = function (root, storage, opts) {

    this.type = 'canvas';

    // In node environment using node-canvas
    var singleCanvas = !root.nodeName // In node ?
        || root.nodeName.toUpperCase() === 'CANVAS';

    this._opts = opts = extend({}, opts || {});

    /**
     * @type {number}
     */
    this.dpr = opts.devicePixelRatio || devicePixelRatio;
    /**
     * @type {boolean}
     * @private
     */
    this._singleCanvas = singleCanvas;
    /**
     * 绘图容器
     * @type {HTMLElement}
     */
    this.root = root;

    var rootStyle = root.style;

    if (rootStyle) {
        rootStyle['-webkit-tap-highlight-color'] = 'transparent';
        rootStyle['-webkit-user-select'] =
        rootStyle['user-select'] =
        rootStyle['-webkit-touch-callout'] = 'none';

        root.innerHTML = '';
    }

    /**
     * @type {module:zrender/Storage}
     */
    this.storage = storage;

    /**
     * @type {Array.<number>}
     * @private
     */
    var zlevelList = this._zlevelList = [];

    /**
     * @type {Object.<string, module:zrender/Layer>}
     * @private
     */
    var layers = this._layers = {};

    /**
     * @type {Object.<string, Object>}
     * @private
     */
    this._layerConfig = {};