Fix infinite scroll open previous/next chapter

Regression 53c24280c3

CHANGELOG.md

@@ -51,7 +51,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 - (**Reader**) Fix mobile progress bar previous/next chapter button visibility on hover and while disabled
 - (**Reader**) Fix jumping back to the first page on window resize
 - (**Reader**) Fix chapter not getting marked as read in continuous reading mode in case the last page is not big enough to get marked as the current page
-- (**Reader**) Fix infinite scrolling with disabled transition page
+- (**Reader**) Fix infinite scrolling sometimes not opening previous/next chapter
 - (**Browse**) Fix showing only nsfw sources in the browse source page when the "show nsfw" setting is disabled
 
 ## [20260509.01] (r3147) - 2026-05-09

src/features/reader/infinite-scroll/useReaderInfiniteScrollUpdateChapter.ts

@@ -271,13 +271,19 @@ export const useReaderInfiniteScrollUpdateChapter = (
         }
 
         const onScroll = () => {
+            const THRESHOLD = 2;
+
             const isAtStartX = scrollElement.scrollLeft === 0;
-            const isAtEndX =
-                Math.ceil(scrollElement.scrollLeft) === scrollElement.scrollWidth - scrollElement.clientWidth;
+            const distanceEndX = Math.abs(
+                Math.abs(scrollElement.scrollLeft) - (scrollElement.scrollWidth - scrollElement.clientWidth),
+            );
+            const isAtEndX = distanceEndX >= 0 && distanceEndX <= THRESHOLD;
 
             const isAtStartY = scrollElement.scrollTop === 0;
-            const isAtEndY =
-                Math.ceil(scrollElement.scrollTop) === scrollElement.scrollHeight - scrollElement.clientHeight;
+            const distanceStartY = Math.abs(
+                Math.abs(scrollElement.scrollTop) - (scrollElement.scrollHeight - scrollElement.clientHeight),
+            );
+            const isAtEndY = distanceStartY >= 0 && distanceStartY <= THRESHOLD;
 
             const isAtStart = isContinuousVerticalReadingModeActive ? isAtStartY : isAtStartX;
             const isAtEnd = isContinuousVerticalReadingModeActive ? isAtEndY : isAtEndX;