Function getSymbol

src/mapboxgl/overlay/symbol/MapExtendSymbol.js:309–342

* @function WebSymbol.prototype.getSymbol * @param {string} id - 符号ID。 * @description 获取符号信息。 * @returns {object} 符号信息。 * @private

(id, map)

   * @private
   */
  async function getSymbol(id, map) {
    let url = `${map.basePath}/${id}/${id}`;
    if (process.env.NODE_ENV === 'development') {
      url = `../../dist/resources/symbols/${id}/${id}`;
    }

    const value = await FetchRequest.get(`${url}.json`).then(response => {
      if (!response.ok) {
        return null;
      }
      return response.json();
    })
      .catch(() => null);
    if (!value) {
      return null;
    }
    const paint = value.paint || {};
    const layout = value.layout || {};
    const hasImage = paint['fill-pattern'] || paint['line-pattern'] || layout['icon-image'];
    const image = hasImage && await new Promise((resolve) => {
      const image = new Image();
      image.src = `${url}.png`;
      image.onload = (content) => {
        resolve(content ? image : null);
      };
      image.onerror = () => {
        resolve(null);
      };
    });
    return {
      value,
      image
    }
  }

  /**
   * 加载单个Web符号