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Center pages vertically in PresentationMode (issue 10906)

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*This patch can be tested e.g. with the `sizes.pdf` document in the test-suite.*

While this patch isn't necessarily the best solution, e.g. it might be possible to solve this with *only* CSS, it's what I was able to come up with to address an old issue.
The solution here re-uses the `spread`-class in PresentationMode, since that one already takes care of centering pages *vertically*, together with a dummy-page that takes up the entire height of the window.

Finally, some PresentationMode-related CSS-rules are also simplified slightly, since the changes in PR 14112 (using Page-scrolling) allows some clean-up here.
This commit is contained in:
Jonas Jenwald 2021-11-23 13:29:00 +01:00
parent 70fc30d97c
commit f7b1da418f
3 changed files with 60 additions and 34 deletions
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64
web/base_viewer.js
View file

@ -159,24 +159,14 @@ class PDFPageViewBuffer {
}
}
function isSameScale(oldScale, newScale) {
if (newScale === oldScale) {
return true;
}
if (Math.abs(newScale - oldScale) < 1e-15) {
// Prevent unnecessary re-rendering of all pages when the scale
// changes only because of limited numerical precision.
return true;
}
return false;
}
/**
* Simple viewer control to display PDF content/pages.
*/
class BaseViewer {
#buffer = null;
#previousContainerHeight = 0;
#scrollModePageState = null;
/**
@ -751,7 +741,20 @@ class BaseViewer {
if (this._spreadMode === SpreadMode.NONE) {
// Finally, append the new page to the viewer.
const pageView = this._pages[pageNumber - 1];
viewer.appendChild(pageView.div);
if (this.isInPresentationMode) {
const spread = document.createElement("div");
spread.className = "spread";
const dummyPage = document.createElement("div");
dummyPage.className = "dummyPage";
dummyPage.style.height = `${this.container.clientHeight}px`;
spread.appendChild(dummyPage);
spread.appendChild(pageView.div);
viewer.appendChild(spread);
} else {
viewer.appendChild(pageView.div);
}
state.pages.push(pageView);
} else {
@ -828,10 +831,29 @@ class BaseViewer {
scrollIntoView(pageDiv, pageSpot);
}
/**
* Prevent unnecessary re-rendering of all pages when the scale changes
* only because of limited numerical precision.
*/
#isSameScale(newScale) {
if (
this.isInPresentationMode &&
this.container.clientHeight !== this.#previousContainerHeight
) {
// Ensure that the current page remains centered vertically if/when
// the window is resized while PresentationMode is active.
return false;
}
return (
newScale === this._currentScale ||
Math.abs(newScale - this._currentScale) < 1e-15
);
}
_setScaleUpdatePages(newScale, newValue, noScroll = false, preset = false) {
this._currentScaleValue = newValue.toString();
if (isSameScale(this._currentScale, newScale)) {
if (this.#isSameScale(newScale)) {
if (preset) {
this.eventBus.dispatch("scalechanging", {
source: this,
@ -886,6 +908,8 @@ class BaseViewer {
if (this.defaultRenderingQueue) {
this.update();
}
this.#previousContainerHeight = this.container.clientHeight;
}
/**
@ -911,11 +935,15 @@ class BaseViewer {
if (!currentPage) {
return;
}
const noPadding = this.isInPresentationMode || this.removePageBorders;
let hPadding = noPadding ? 0 : SCROLLBAR_PADDING;
let vPadding = noPadding ? 0 : VERTICAL_PADDING;
let hPadding = SCROLLBAR_PADDING,
vPadding = VERTICAL_PADDING;
if (!noPadding && this._scrollMode === ScrollMode.HORIZONTAL) {
if (this.isInPresentationMode) {
hPadding = vPadding = 4;
} else if (this.removePageBorders) {
hPadding = vPadding = 0;
}
if (this._scrollMode === ScrollMode.HORIZONTAL) {
[hPadding, vPadding] = [vPadding, hPadding]; // Swap the padding values.
}
const pageWidthScale =