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Try to simplify the PDFSinglePageViewer._scrollIntoView method slightly, by unconditionally ensuring that rendering always occurs

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This commit is contained in:
Jonas Jenwald 2019-01-23 09:13:49 +01:00
parent 06cda4c2e7
commit 48e4adf770
1 changed files with 7 additions and 13 deletions
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20
web/pdf_single_page_viewer.js
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@ -39,6 +39,7 @@ class PDFSinglePageViewer extends BaseViewer {
super._resetView(); super._resetView();
this._previousPageNumber = 1; this._previousPageNumber = 1;
this._shadowViewer = document.createDocumentFragment(); this._shadowViewer = document.createDocumentFragment();
this._updateScrollDown = null;
} }
_ensurePageViewVisible() { _ensurePageViewVisible() {
@ -82,9 +83,12 @@ class PDFSinglePageViewer extends BaseViewer {
if (pageNumber) { // Ensure that `this._currentPageNumber` is correct. if (pageNumber) { // Ensure that `this._currentPageNumber` is correct.
this._setCurrentPageNumber(pageNumber); this._setCurrentPageNumber(pageNumber);
} }
let scrolledDown = this._currentPageNumber >= this._previousPageNumber; const scrolledDown = this._currentPageNumber >= this._previousPageNumber;
let previousLocation = this._location;
this._ensurePageViewVisible(); 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, }); super._scrollIntoView({ pageDiv, pageSpot, pageNumber, });
@ -92,18 +96,8 @@ class PDFSinglePageViewer extends BaseViewer {
// scroll direction during the next `this._scrollUpdate` invocation. // scroll direction during the next `this._scrollUpdate` invocation.
this._updateScrollDown = () => { this._updateScrollDown = () => {
this.scroll.down = scrolledDown; this.scroll.down = scrolledDown;
delete this._updateScrollDown; this._updateScrollDown = null;
}; };
// If the scroll position doesn't change as a result of the `scrollIntoView`
// call, ensure that rendering always occurs to avoid showing a blank page.
setTimeout(() => {
if (this._location === previousLocation) {
if (this._updateScrollDown) {
this._updateScrollDown();
}
this.update();
}
}, 0);
} }
_getVisiblePages() { _getVisiblePages() {