122 lines
4.0 KiB
JavaScript
122 lines
4.0 KiB
JavaScript
/* Copyright 2017 Mozilla Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { BaseViewer } from './base_viewer';
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import { shadow } from 'pdfjs-lib';
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class PDFSinglePageViewer extends BaseViewer {
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constructor(options) {
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super(options);
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this.eventBus.on('pagesinit', (evt) => {
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// Since the pages are placed in a `DocumentFragment`, make sure that
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// the current page becomes visible upon loading of the document.
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this._ensurePageViewVisible();
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});
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}
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get _setDocumentViewerElement() {
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// Since we only want to display *one* page at a time when using the
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// `PDFSinglePageViewer`, we cannot append them to the `viewer` DOM element.
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// Instead, they are placed in a `DocumentFragment`, and only the current
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// page is displayed in the viewer (refer to `this._ensurePageViewVisible`).
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return shadow(this, '_setDocumentViewerElement', this._shadowViewer);
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}
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_resetView() {
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super._resetView();
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this._previousPageNumber = 1;
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this._shadowViewer = document.createDocumentFragment();
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this._updateScrollDown = null;
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}
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_ensurePageViewVisible() {
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let pageView = this._pages[this._currentPageNumber - 1];
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let previousPageView = this._pages[this._previousPageNumber - 1];
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let viewerNodes = this.viewer.childNodes;
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switch (viewerNodes.length) {
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case 0: // Should *only* occur on initial loading.
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this.viewer.appendChild(pageView.div);
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break;
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case 1: // The normal page-switching case.
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if (viewerNodes[0] !== previousPageView.div) {
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throw new Error(
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'_ensurePageViewVisible: Unexpected previously visible page.');
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}
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if (pageView === previousPageView) {
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break; // The correct page is already visible.
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}
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// Switch visible pages, and reset the viewerContainer scroll position.
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this._shadowViewer.appendChild(previousPageView.div);
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this.viewer.appendChild(pageView.div);
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this.container.scrollTop = 0;
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break;
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default:
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throw new Error(
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'_ensurePageViewVisible: Only one page should be visible at a time.');
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}
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this._previousPageNumber = this._currentPageNumber;
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}
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_scrollUpdate() {
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if (this._updateScrollDown) {
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this._updateScrollDown();
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}
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super._scrollUpdate();
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}
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_scrollIntoView({ pageDiv, pageSpot = null, pageNumber = null, }) {
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if (pageNumber) { // Ensure that `this._currentPageNumber` is correct.
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this._setCurrentPageNumber(pageNumber);
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}
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const scrolledDown = this._currentPageNumber >= this._previousPageNumber;
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this._ensurePageViewVisible();
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// Ensure that rendering always occurs, to avoid showing a blank page,
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// even if the current position doesn't change when the page is scrolled.
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this.update();
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super._scrollIntoView({ pageDiv, pageSpot, pageNumber, });
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// Since scrolling is tracked using `requestAnimationFrame`, update the
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// scroll direction during the next `this._scrollUpdate` invocation.
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this._updateScrollDown = () => {
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this.scroll.down = scrolledDown;
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this._updateScrollDown = null;
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};
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}
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_getVisiblePages() {
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return this._getCurrentVisiblePage();
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}
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_updateHelper(visiblePages) { }
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get _isScrollModeHorizontal() {
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// The Scroll/Spread modes are never used in `PDFSinglePageViewer`.
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return shadow(this, '_isScrollModeHorizontal', false);
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}
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_updateScrollMode() { }
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_updateSpreadMode() { }
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}
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export {
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PDFSinglePageViewer,
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};
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