Function Layer

libs/echarts/echarts.simple.js:7294–7352

(id, painter, dpr)

 * @param {number} [dpr]
 */
var Layer = function (id, painter, dpr) {
    var dom;
    dpr = dpr || devicePixelRatio;
    if (typeof id === 'string') {
        dom = createDom(id, painter, dpr);
    }
    // Not using isDom because in node it will return false
    else if (isObject$1(id)) {
        dom = id;
        id = dom.id;
    }
    this.id = id;
    this.dom = dom;

    var domStyle = dom.style;
    if (domStyle) { // Not in node
        dom.onselectstart = returnFalse; // 避免页面选中的尴尬
        domStyle['-webkit-user-select'] = 'none';
        domStyle['user-select'] = 'none';
        domStyle['-webkit-touch-callout'] = 'none';
        domStyle['-webkit-tap-highlight-color'] = 'rgba(0,0,0,0)';
        domStyle['padding'] = 0; // eslint-disable-line dot-notation
        domStyle['margin'] = 0; // eslint-disable-line dot-notation
        domStyle['border-width'] = 0;
    }

    this.domBack = null;
    this.ctxBack = null;

    this.painter = painter;

    this.config = null;

    // Configs
    /**
     * 每次清空画布的颜色
     * @type {string}
     * @default 0
     */
    this.clearColor = 0;
    /**
     * 是否开启动态模糊
     * @type {boolean}
     * @default false
     */
    this.motionBlur = false;
    /**
     * 在开启动态模糊的时候使用，与上一帧混合的alpha值，值越大尾迹越明显
     * @type {number}
     * @default 0.7
     */
    this.lastFrameAlpha = 0.7;

    /**
     * Layer dpr
     * @type {number}
     */
    this.dpr = dpr;