Method drawRect

src/openlayers/core/StyleUtils.js:802–840

* 绘制矩形边框背景 * @param ctx * @param style * @param textArray * @param lineHeight * @param canvas * @returns {{width: number, height: number}}

(ctx, style, textArray, lineHeight, canvas)

   * @returns {{width: number, height: number}}
   */
  static drawRect(ctx, style, textArray, lineHeight, canvas) {
    let backgroundFill = style.backgroundFill, maxWidth = style.maxWidth - doublePadding;
    let width, height = 0, lineCount = 0, lineWidths = [];
    //100的宽度，去掉左右两边3padding
    textArray.forEach(function (arrText) {
      let line = '', isOverMax;
      lineCount++;
      for (var n = 0; n < arrText.length; n++) {
        let textLine = line + arrText[n];
        let metrics = ctx.measureText(textLine);
        let textWidth = metrics.width;
        if ((textWidth > maxWidth && n > 0) || arrText[n] === '\n') {
          line = arrText[n];
          lineCount++;
          //有换行，记录当前换行的width
          isOverMax = true;
        } else {
          line = textLine;
          width = textWidth;
        }
      }
      if (isOverMax) {
        lineWidths.push(maxWidth);
      } else {
        lineWidths.push(width);
      }
    }, this);
    width = this.getCanvasWidth(lineWidths, maxWidth);
    height = lineCount * lineHeight;
    height += doublePadding;
    canvas.width = width;
    canvas.height = height;
    ctx.fillStyle = backgroundFill;
    ctx.fillRect(0, 0, width, height);
    return {
      width: width,
      height: height
    }
  }
  /**
   * 获取自适应的宽度（如果没有超过最大宽度，就用文字的宽度）
   * @param lineWidths