lib/web/pdf_rendering_queue.js

/**
 * @licstart The following is the entire license notice for the
 * Javascript code in this page
 *
 * Copyright 2020 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.
 *
 * @licend The above is the entire license notice for the
 * Javascript code in this page
 */
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.PDFRenderingQueue = exports.RenderingStates = void 0;
const CLEANUP_TIMEOUT = 30000;
const RenderingStates = {
  INITIAL: 0,
  RUNNING: 1,
  PAUSED: 2,
  FINISHED: 3
};
exports.RenderingStates = RenderingStates;

class PDFRenderingQueue {
  constructor() {
    this.pdfViewer = null;
    this.pdfThumbnailViewer = null;
    this.onIdle = null;
    this.highestPriorityPage = null;
    this.idleTimeout = null;
    this.printing = false;
    this.isThumbnailViewEnabled = false;
  }

  setViewer(pdfViewer) {
    this.pdfViewer = pdfViewer;
  }

  setThumbnailViewer(pdfThumbnailViewer) {
    this.pdfThumbnailViewer = pdfThumbnailViewer;
  }

  isHighestPriority(view) {
    return this.highestPriorityPage === view.renderingId;
  }

  renderHighestPriority(currentlyVisiblePages) {
    if (this.idleTimeout) {
      clearTimeout(this.idleTimeout);
      this.idleTimeout = null;
    }

    if (this.pdfViewer.forceRendering(currentlyVisiblePages)) {
      return;
    }

    if (this.pdfThumbnailViewer && this.isThumbnailViewEnabled) {
      if (this.pdfThumbnailViewer.forceRendering()) {
        return;
      }
    }

    if (this.printing) {
      return;
    }

    if (this.onIdle) {
      this.idleTimeout = setTimeout(this.onIdle.bind(this), CLEANUP_TIMEOUT);
    }
  }

  getHighestPriority(visible, views, scrolledDown) {
    const visibleViews = visible.views;
    const numVisible = visibleViews.length;

    if (numVisible === 0) {
      return null;
    }

    for (let i = 0; i < numVisible; ++i) {
      const view = visibleViews[i].view;

      if (!this.isViewFinished(view)) {
        return view;
      }
    }

    if (scrolledDown) {
      const nextPageIndex = visible.last.id;

      if (views[nextPageIndex] && !this.isViewFinished(views[nextPageIndex])) {
        return views[nextPageIndex];
      }
    } else {
      const previousPageIndex = visible.first.id - 2;

      if (views[previousPageIndex] && !this.isViewFinished(views[previousPageIndex])) {
        return views[previousPageIndex];
      }
    }

    return null;
  }

  isViewFinished(view) {
    return view.renderingState === RenderingStates.FINISHED;
  }

  renderView(view) {
    switch (view.renderingState) {
      case RenderingStates.FINISHED:
        return false;

      case RenderingStates.PAUSED:
        this.highestPriorityPage = view.renderingId;
        view.resume();
        break;

      case RenderingStates.RUNNING:
        this.highestPriorityPage = view.renderingId;
        break;

      case RenderingStates.INITIAL:
        this.highestPriorityPage = view.renderingId;
        view.draw().finally(() => {
          this.renderHighestPriority();
        }).catch(reason => {
          console.error(`renderView: "${reason}"`);
        });
        break;
    }

    return true;
  }

}

exports.PDFRenderingQueue = PDFRenderingQueue;