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fix(epubjs): preserve last page at chapter boundaries #202

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fix(epubjs): preserve last page at chapter boundaries #202

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c1d0b5f
fix(epubjs): preserve last page at chapter boundaries
Fall-of-Fall Jul 20, 2026
78054c5
fix(epubjs): snap paginated navigation to page boundaries
Fall-of-Fall Jul 20, 2026
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41 changes: 30 additions & 11 deletions packages/epubjs/src/managers/default/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -481,13 +481,24 @@ class DefaultViewManager {
) {
this.scrollLeft = this.container.scrollLeft

left =
this.container.scrollLeft +
this.container.offsetWidth +
this.layout.delta
// `offsetWidth` includes borders while `scrollWidth` and `clientWidth`
// describe the inner scrollable area. Mixing them can make the last
// page unreachable because of rounding or border-width differences.
const maxScrollLeft = Math.max(
0,
this.container.scrollWidth - this.container.clientWidth,
)
const epsilon = 1
const currentPage = Math.round(
this.container.scrollLeft / this.layout.delta,
)

if (left <= this.container.scrollWidth) {
this.scrollBy(this.layout.delta, 0, true)
if (this.container.scrollLeft < maxScrollLeft - epsilon) {
this.scrollTo(
Math.min((currentPage + 1) * this.layout.delta, maxScrollLeft),
0,
true,
)
} else {
next = this.views.last().section.next()
}
Expand Down Expand Up @@ -585,8 +596,9 @@ class DefaultViewManager {

left = this.container.scrollLeft

if (left > 0) {
this.scrollBy(-this.layout.delta, 0, true)
const currentPage = Math.round(left / this.layout.delta)
if (currentPage > 0) {
this.scrollTo((currentPage - 1) * this.layout.delta, 0, true)
} else {
prev = this.views.first().section.prev()
}
Expand Down Expand Up @@ -675,7 +687,10 @@ class DefaultViewManager {
}
} else {
this.scrollTo(
this.container.scrollWidth - this.layout.delta,
Math.max(
0,
this.container.scrollWidth - this.container.clientWidth,
),
0,
true,
)
Expand Down Expand Up @@ -839,9 +854,13 @@ class DefaultViewManager {
)

let totalPages = this.layout.count(width).pages
let startPage = Math.floor(start / this.layout.pageWidth)
// Treat sub-pixel and border rounding near a page boundary as that page.
const positionEpsilon = 1
let startPage = Math.floor(
(start + positionEpsilon) / this.layout.pageWidth,
)
let pages = []
let endPage = Math.floor(end / this.layout.pageWidth)
let endPage = Math.floor((end + positionEpsilon) / this.layout.pageWidth)

// start page should not be negative
if (startPage < 0) {
Expand Down