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Pre-render *one* additional page when spreadModes are enabled

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Please note that we (obviously) don't want to unconditionally pre-render more than one page all the time, since that could very easily lead to overall worse performance in some documents.[1]
However, when spreadModes are enabled it does make sense to attempt to pre-render both of the pages of the next/previous spread.

---
[1] Since it may cause pre-rendering to unnecessarily compete for parsing resources, on the worker-thread, with "regular" rendering.
This commit is contained in:
Jonas Jenwald 2021-10-02 11:43:58 +02:00
parent fb6c807ba2
commit e4794a678a
2 changed files with 19 additions and 6 deletions
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8
web/base_viewer.js
View File

@ -1250,10 +1250,16 @@ class BaseViewer {
const scrollAhead = this._isScrollModeHorizontal
? this.scroll.right
: this.scroll.down;
const preRenderExtra =
this._scrollMode === ScrollMode.VERTICAL &&
this._spreadMode !== SpreadMode.NONE &&
!this.isInPresentationMode;
const pageView = this.renderingQueue.getHighestPriority(
visiblePages,
this._pages,
scrollAhead
scrollAhead,
preRenderExtra
);
if (pageView) {
this._ensurePdfPageLoaded(pageView).then(() => {

17
web/pdf_rendering_queue.js
View File

@ -102,8 +102,9 @@ class PDFRenderingQueue {
* @param {Object} visible
* @param {Array} views
* @param {boolean} scrolledDown
* @param {boolean} [preRenderExtra]
*/
getHighestPriority(visible, views, scrolledDown) {
getHighestPriority(visible, views, scrolledDown, preRenderExtra = false) {
/**
* The state has changed. Figure out which page has the highest priority to
* render next (if any).
@ -128,14 +129,20 @@ class PDFRenderingQueue {
// All the visible views have rendered; try to render next/previous page.
// (IDs start at 1, so no need to add 1 when `scrolledDown === true`.)
const preRenderIndex = scrolledDown
? visible.last.id
: visible.first.id - 2;
const preRenderView = views[preRenderIndex];
let preRenderIndex = scrolledDown ? visible.last.id : visible.first.id - 2;
let preRenderView = views[preRenderIndex];
if (preRenderView && !this.isViewFinished(preRenderView)) {
return preRenderView;
}
if (preRenderExtra) {
preRenderIndex += scrolledDown ? 1 : -1;
preRenderView = views[preRenderIndex];
if (preRenderView && !this.isViewFinished(preRenderView)) {
return preRenderView;
}
}
// Everything that needs to be rendered has been.
return null;
}