From c1d0b5f7daa3aa2684b8179133790e216c6b82e6 Mon Sep 17 00:00:00 2001
From: elixir <1597046542@qq.com>
Date: Mon, 20 Jul 2026 16:12:22 +0800
Subject: [PATCH 1/2] fix(epubjs): preserve last page at chapter boundaries

---
 packages/epubjs/src/managers/default/index.js | 30 ++++++++++++++-----
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/packages/epubjs/src/managers/default/index.js b/packages/epubjs/src/managers/default/index.js
index cbc0311c..91d20d63 100644
--- a/packages/epubjs/src/managers/default/index.js
+++ b/packages/epubjs/src/managers/default/index.js
@@ -481,13 +481,24 @@ class DefaultViewManager {
     ) {
       this.scrollLeft = this.container.scrollLeft
 
-      left =
-        this.container.scrollLeft +
-        this.container.offsetWidth +
-        this.layout.delta
-
-      if (left <= this.container.scrollWidth) {
-        this.scrollBy(this.layout.delta, 0, true)
+      // `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
+
+      if (this.container.scrollLeft < maxScrollLeft - epsilon) {
+        this.scrollTo(
+          Math.min(
+            this.container.scrollLeft + this.layout.delta,
+            maxScrollLeft,
+          ),
+          0,
+          true,
+        )
       } else {
         next = this.views.last().section.next()
       }
@@ -675,7 +686,10 @@ class DefaultViewManager {
                 }
               } else {
                 this.scrollTo(
-                  this.container.scrollWidth - this.layout.delta,
+                  Math.max(
+                    0,
+                    this.container.scrollWidth - this.container.clientWidth,
+                  ),
                   0,
                   true,
                 )

From 78054c59cec79ff0d658249983be614ca4d47817 Mon Sep 17 00:00:00 2001
From: elixir <1597046542@qq.com>
Date: Mon, 20 Jul 2026 16:34:14 +0800
Subject: [PATCH 2/2] fix(epubjs): snap paginated navigation to page boundaries

---
 packages/epubjs/src/managers/default/index.js | 21 ++++++++++++-------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/packages/epubjs/src/managers/default/index.js b/packages/epubjs/src/managers/default/index.js
index 91d20d63..6406c560 100644
--- a/packages/epubjs/src/managers/default/index.js
+++ b/packages/epubjs/src/managers/default/index.js
@@ -489,13 +489,13 @@ class DefaultViewManager {
         this.container.scrollWidth - this.container.clientWidth,
       )
       const epsilon = 1
+      const currentPage = Math.round(
+        this.container.scrollLeft / this.layout.delta,
+      )
 
       if (this.container.scrollLeft < maxScrollLeft - epsilon) {
         this.scrollTo(
-          Math.min(
-            this.container.scrollLeft + this.layout.delta,
-            maxScrollLeft,
-          ),
+          Math.min((currentPage + 1) * this.layout.delta, maxScrollLeft),
           0,
           true,
         )
@@ -596,8 +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()
       }
@@ -853,9 +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) {