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pdf_single_page_viewer.js
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pdf_single_page_viewer.js
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/* Copyright 2017 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 { BaseViewer } from './base_viewer';
import { shadow } from 'pdfjs-lib';
class PDFSinglePageViewer extends BaseViewer {
constructor(options) {
super(options);
this.eventBus.on('pagesinit', (evt) => {
// Since the pages are placed in a `DocumentFragment`, make sure that
// the current page becomes visible upon loading of the document.
this._ensurePageViewVisible();
});
}
get _setDocumentViewerElement() {
// Since we only want to display *one* page at a time when using the
// `PDFSinglePageViewer`, we cannot append them to the `viewer` DOM element.
// Instead, they are placed in a `DocumentFragment`, and only the current
// page is displayed in the viewer (refer to `this._ensurePageViewVisible`).
return shadow(this, '_setDocumentViewerElement', this._shadowViewer);
}
_resetView() {
super._resetView();
this._previousPageNumber = 1;
this._shadowViewer = document.createDocumentFragment();
this._updateScrollDown = null;
}
_ensurePageViewVisible() {
let pageView = this._pages[this._currentPageNumber - 1];
let previousPageView = this._pages[this._previousPageNumber - 1];
let viewerNodes = this.viewer.childNodes;
switch (viewerNodes.length) {
case 0: // Should *only* occur on initial loading.
this.viewer.appendChild(pageView.div);
break;
case 1: // The normal page-switching case.
if (viewerNodes[0] !== previousPageView.div) {
throw new Error(
'_ensurePageViewVisible: Unexpected previously visible page.');
}
if (pageView === previousPageView) {
break; // The correct page is already visible.
}
// Switch visible pages, and reset the viewerContainer scroll position.
this._shadowViewer.appendChild(previousPageView.div);
this.viewer.appendChild(pageView.div);
this.container.scrollTop = 0;
break;
default:
throw new Error(
'_ensurePageViewVisible: Only one page should be visible at a time.');
}
this._previousPageNumber = this._currentPageNumber;
}
_scrollUpdate() {
if (this._updateScrollDown) {
this._updateScrollDown();
}
super._scrollUpdate();
}
_scrollIntoView({ pageDiv, pageSpot = null, pageNumber = null, }) {
if (pageNumber) { // Ensure that `this._currentPageNumber` is correct.
this._setCurrentPageNumber(pageNumber);
}
const scrolledDown = this._currentPageNumber >= this._previousPageNumber;
this._ensurePageViewVisible();
// Ensure that rendering always occurs, to avoid showing a blank page,
// even if the current position doesn't change when the page is scrolled.
this.update();
super._scrollIntoView({ pageDiv, pageSpot, pageNumber, });
// Since scrolling is tracked using `requestAnimationFrame`, update the
// scroll direction during the next `this._scrollUpdate` invocation.
this._updateScrollDown = () => {
this.scroll.down = scrolledDown;
this._updateScrollDown = null;
};
}
_getVisiblePages() {
return this._getCurrentVisiblePage();
}
_updateHelper(visiblePages) { }
get _isScrollModeHorizontal() {
// The Scroll/Spread modes are never used in `PDFSinglePageViewer`.
return shadow(this, '_isScrollModeHorizontal', false);
}
_updateScrollMode() { }
_updateSpreadMode() { }
}
export {
PDFSinglePageViewer,
};