pdf.js/src/display/base_factory.js

/* Copyright 2015 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { CMapCompressionType, unreachable } from "../shared/util.js";

class BaseCanvasFactory {
  constructor() {
    if (this.constructor === BaseCanvasFactory) {
      unreachable("Cannot initialize BaseCanvasFactory.");
    }
  }

  create(width, height) {
    if (width <= 0 || height <= 0) {
      throw new Error("Invalid canvas size");
    }
    const canvas = this._createCanvas(width, height);
    return {
      canvas,
      context: canvas.getContext("2d"),
    };
  }

  reset(canvasAndContext, width, height) {
    if (!canvasAndContext.canvas) {
      throw new Error("Canvas is not specified");
    }
    if (width <= 0 || height <= 0) {
      throw new Error("Invalid canvas size");
    }
    canvasAndContext.canvas.width = width;
    canvasAndContext.canvas.height = height;
  }

  destroy(canvasAndContext) {
    if (!canvasAndContext.canvas) {
      throw new Error("Canvas is not specified");
    }
    // Zeroing the width and height cause Firefox to release graphics
    // resources immediately, which can greatly reduce memory consumption.
    canvasAndContext.canvas.width = 0;
    canvasAndContext.canvas.height = 0;
    canvasAndContext.canvas = null;
    canvasAndContext.context = null;
  }

  /**
   * @private
   */
  _createCanvas(width, height) {
    unreachable("Abstract method `_createCanvas` called.");
  }
}

class BaseCMapReaderFactory {
  constructor({ baseUrl = null, isCompressed = false }) {
    if (this.constructor === BaseCMapReaderFactory) {
      unreachable("Cannot initialize BaseCMapReaderFactory.");
    }
    this.baseUrl = baseUrl;
    this.isCompressed = isCompressed;
  }

  async fetch({ name }) {
    if (!this.baseUrl) {
      throw new Error(
        'The CMap "baseUrl" parameter must be specified, ensure that ' +
          'the "cMapUrl" and "cMapPacked" API parameters are provided.'
      );
    }
    if (!name) {
      throw new Error("CMap name must be specified.");
    }
    const url = this.baseUrl + name + (this.isCompressed ? ".bcmap" : "");
    const compressionType = this.isCompressed
      ? CMapCompressionType.BINARY
      : CMapCompressionType.NONE;

    return this._fetchData(url, compressionType).catch(reason => {
      throw new Error(
        `Unable to load ${this.isCompressed ? "binary " : ""}CMap at: ${url}`
      );
    });
  }

  /**
   * @private
   */
  _fetchData(url, compressionType) {
    unreachable("Abstract method `_fetchData` called.");
  }
}

class BaseStandardFontDataFactory {
  constructor({ baseUrl = null }) {
    if (this.constructor === BaseStandardFontDataFactory) {
      unreachable("Cannot initialize BaseStandardFontDataFactory.");
    }
    this.baseUrl = baseUrl;
  }

  async fetch({ filename }) {
    if (!this.baseUrl) {
      throw new Error(
        'The standard font "baseUrl" parameter must be specified, ensure that ' +
          'the "standardFontDataUrl" API parameter is provided.'
      );
    }
    if (!filename) {
      throw new Error("Font filename must be specified.");
    }
    const url = `${this.baseUrl}${filename}`;

    return this._fetchData(url).catch(reason => {
      throw new Error(`Unable to load font data at: ${url}`);
    });
  }

  /**
   * @private
   */
  _fetchData(url) {
    unreachable("Abstract method `_fetchData` called.");
  }
}

class BaseSVGFactory {
  constructor() {
    if (this.constructor === BaseSVGFactory) {
      unreachable("Cannot initialize BaseSVGFactory.");
    }
  }

  create(width, height) {
    if (width <= 0 || height <= 0) {
      throw new Error("Invalid SVG dimensions");
    }
    const svg = this._createSVG("svg:svg");
    svg.setAttribute("version", "1.1");
    svg.setAttribute("width", `${width}px`);
    svg.setAttribute("height", `${height}px`);
    svg.setAttribute("preserveAspectRatio", "none");
    svg.setAttribute("viewBox", `0 0 ${width} ${height}`);

    return svg;
  }

  createElement(type) {
    if (typeof type !== "string") {
      throw new Error("Invalid SVG element type");
    }
    return this._createSVG(type);
  }

  /**
   * @private
   */
  _createSVG(type) {
    unreachable("Abstract method `_createSVG` called.");
  }
}

export {
  BaseCanvasFactory,
  BaseCMapReaderFactory,
  BaseStandardFontDataFactory,
  BaseSVGFactory,
};