miniprogram/ec-canvas/wx-canvas.js

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export default class WxCanvas {
  constructor(ctx, canvasId, isNew, canvasNode) {
    this.ctx = ctx;
    this.canvasId = canvasId;
    this.chart = null;
    this.isNew = isNew
    if (isNew) {
      this.canvasNode = canvasNode;
    }
    else {
      this._initStyle(ctx);
    }

    // this._initCanvas(zrender, ctx);

    this._initEvent();
  }

  getContext(contextType) {
    if (contextType === '2d') {
      return this.ctx;
    }
  }

  // canvasToTempFilePath(opt) {
  //   if (!opt.canvasId) {
  //     opt.canvasId = this.canvasId;
  //   }
  //   return wx.canvasToTempFilePath(opt, this);
  // }

  setChart(chart) {
    this.chart = chart;
  }

  attachEvent() {
    // noop
  }

  detachEvent() {
    // noop
  }

  _initCanvas(zrender, ctx) {
    zrender.util.getContext = function () {
      return ctx;
    };

    zrender.util.$override('measureText', function (text, font) {
      ctx.font = font || '12px sans-serif';
      return ctx.measureText(text);
    });
  }

  _initStyle(ctx) {
    ctx.createRadialGradient = () => {
      return ctx.createCircularGradient(arguments);
    };
  }