From a8ad9034fc9b11cc6ccc52f6a92fd5ce0f2d63e7 Mon Sep 17 00:00:00 2001
From: Youwes09 <yuvi.shen@outlook.com>
Date: Tue, 9 Jun 2026 22:52:11 -0500
Subject: [PATCH] Fix: Reader Longstrip Bookmark + ProgressBar

---
 src/lib/components/reader/PageView.svelte     | 273 +++++++++++++-----
 src/lib/components/reader/Reader.svelte       |  71 +++--
 .../components/reader/ReaderControls.svelte   |  15 +-
 .../components/reader/ReaderOverlay.svelte    |  20 +-
 .../reader/ReaderProgressBar.svelte           |  37 ++-
 .../components/reader/lib/chapterLoader.ts    |  17 +-
 src/lib/components/reader/lib/navigation.ts   |  26 +-
 .../components/reader/lib/scrollHandler.ts    |  75 +++--
 src/lib/components/series/SeriesHeader.svelte |  15 +-
 .../shared/manga/MangaPreview.svelte          |   2 +-
 10 files changed, 407 insertions(+), 144 deletions(-)

diff --git a/src/lib/components/reader/PageView.svelte b/src/lib/components/reader/PageView.svelte
index 2f0163d..2b28c57 100644
--- a/src/lib/components/reader/PageView.svelte
+++ b/src/lib/components/reader/PageView.svelte
@@ -1,10 +1,11 @@
 <script lang="ts">
+  import { tick }               from "svelte";
   import { readerState }        from "$lib/state/reader.svelte";
   import { settingsState }      from "$lib/state/settings.svelte";
   import { createPinchTracker } from "$lib/components/reader/lib/pinchZoom";
   import type { PinchTracker }  from "$lib/components/reader/lib/pinchZoom";
   import type { StripChapter }  from "$lib/components/reader/lib/scrollHandler";
-  
+
   interface Props {
     style:            string;
     imgCls:           string;
@@ -54,11 +55,51 @@
   let resolvedSrc = $state<Record<number, string>>({});
   let revokeQueue: string[] = [];
 
-  let observer: IntersectionObserver | null = null;
-  const elementIndex = new Map<Element, number>();
+  // Aspect ratios (w/h) keyed by flat index, written by the img onload handler.
+  // Retained as a fallback for scrollToFlatIndex when a slot is not yet in DOM.
+  const aspectMap = new Map<number, number>();
 
-  let viewportCenter = $state(0);
+  let currentSrc        = $state<string | null>(null);
+  let currentGroupSrcs  = $state<(string | null)[]>([]);
 
+  let centerIdx = $state(0);
+
+  // ── Non-longstrip page src resolution ────────────────────────────────────
+  $effect(() => {
+    if (style === "longstrip" || !pageReady) return;
+    const pageNum = readerState.pageNumber;
+    const urls    = readerState.pageUrls;
+    const group   = currentGroup;
+    currentSrc       = null;
+    currentGroupSrcs = group.map(() => null);
+    let cancelled = false;
+    if (style === "double") {
+      group.forEach((pg, i) => {
+        const url = urls[pg - 1];
+        if (!url) return;
+        resolveUrl(url, 999).then(src => {
+          if (cancelled) return;
+          currentGroupSrcs = currentGroupSrcs.map((s, j) => j === i ? src : s);
+        });
+      });
+    } else {
+      const url = urls[pageNum - 1];
+      if (url) resolveUrl(url, 999).then(src => { if (!cancelled) currentSrc = src; });
+    }
+    return () => { cancelled = true; };
+  });
+
+  // ── Non-longstrip: scroll to top on every page change ────────────────────
+  // Ported from Suwayomi's useReaderScrollToStartOnPageChange.
+  // Prevents stale pan position carrying over when flipping pages.
+  $effect(() => {
+    void readerState.pageNumber;
+    if (style !== "longstrip" && containerEl) {
+      containerEl.scrollTo(0, 0);
+    }
+  });
+
+  // ── Blob URL revocation ───────────────────────────────────────────────────
   function scheduleRevoke(src: string) {
     if (!src || !src.startsWith("blob:")) return;
     revokeQueue.push(src);
@@ -68,6 +109,7 @@
     });
   }
 
+  // ── Load window management ────────────────────────────────────────────────
   function loadPage(idx: number) {
     if (loadedSet.has(idx)) return;
     const page = flatPages[idx];
@@ -99,62 +141,162 @@
     }
   }
 
-  function recalcWindow() {
-    const center = viewportCenter;
-    const lo     = center - LOAD_RADIUS;
-    const hi     = center + LOAD_RADIUS;
+  function recalcWindow(center: number) {
+    const lo      = center - LOAD_RADIUS;
+    const hi      = center + LOAD_RADIUS;
     const evictLo = center - UNLOAD_RADIUS;
     const evictHi = center + UNLOAD_RADIUS;
     for (let i = 0; i < flatPages.length; i++) {
-      if (i >= lo && i <= hi)           loadPage(i);
-      else if (i < evictLo || i > evictHi) unloadPage(i);
+      if (i >= lo && i <= hi)               loadPage(i);
+      else if (i < evictLo || i > evictHi)  unloadPage(i);
     }
   }
 
-  $effect(() => { void viewportCenter; recalcWindow(); });
-  $effect(() => { void flatPages.length; recalcWindow(); });
+  $effect(() => { recalcWindow(centerIdx); });
+  $effect(() => { void flatPages.length; recalcWindow(centerIdx); });
 
-  function setupObserver(containerEl: HTMLElement) {
-    observer?.disconnect();
-    elementIndex.clear();
-    observer = new IntersectionObserver(
-      (entries) => {
-        let best = -1;
-        let bestRatio = -1;
-        for (const entry of entries) {
-          const idx = elementIndex.get(entry.target);
-          if (idx === undefined) continue;
-          if (entry.isIntersecting && entry.intersectionRatio > bestRatio) {
-            bestRatio = entry.intersectionRatio;
-            best = idx;
-          }
-        }
-        if (best >= 0 && best !== viewportCenter) viewportCenter = best;
-      },
-      { root: containerEl, rootMargin: "0px", threshold: [0, 0.1, 0.5, 1.0] },
-    );
-  }
+  // ── Scroll position preservation on image resize above viewport ───────────
+  // Ported from Suwayomi's usePreserveOnLeadingPageRender.
+  //
+  // Problem: when a placeholder above the current scroll position loads its
+  // real image and changes height, the browser shifts the scroll position
+  // relative to the viewport (layout shift). This corrects for that by:
+  //   1. Tracking the first visible image and its offsetTop at last scroll.
+  //   2. On every ResizeObserver entry for an image above scrollTop, computing
+  //      the delta and applying it as a scroll correction.
+  //
+  // MutationObserver watches for images being added/removed so the
+  // ResizeObserver stays in sync with the actual DOM without needing
+  // querySelectorAll on every scroll tick.
+  $effect(() => {
+    if (style !== "longstrip" || !containerEl) return;
 
-  function observePage(el: HTMLDivElement, idx: number) {
-    elementIndex.set(el, idx);
-    observer?.observe(el);
-    return {
-      update(newIdx: number) { elementIndex.set(el, newIdx); },
-      destroy() { observer?.unobserve(el); elementIndex.delete(el); },
+    let visibleImg: HTMLElement | undefined;
+    let visibleImgTop = 0;
+    let lastScrollTop = 0;
+
+    const onScroll = () => {
+      lastScrollTop = containerEl.scrollTop;
+      if (visibleImg) {
+        visibleImgTop = visibleImg.offsetTop;
+      }
     };
+    containerEl.addEventListener("scroll", onScroll, { passive: true });
+
+    const intersectionObs = new IntersectionObserver((entries) => {
+      const first = entries.find(e => e.isIntersecting);
+      if (first?.target instanceof HTMLElement) {
+        visibleImg    = first.target;
+        visibleImgTop = first.target.offsetTop;
+      }
+    });
+
+    const resizeObs = new ResizeObserver((entries) => {
+      if (!visibleImg) return;
+      const hasEntryBeforeScroll = entries.some(e => {
+        if (!(e.target instanceof HTMLElement)) return false;
+        // Skip zero-size preload placeholders (they are outside the load window)
+        if (!e.target.clientWidth && !e.target.clientHeight) return false;
+        return e.target.offsetTop < lastScrollTop;
+      });
+      if (!hasEntryBeforeScroll) return;
+      const newTop = lastScrollTop - visibleImgTop + visibleImg.offsetTop;
+      containerEl.scrollTo({ top: newTop, behavior: "instant" } as ScrollToOptions);
+    });
+
+    const observe   = (el: Element) => { intersectionObs.observe(el); resizeObs.observe(el); };
+    const unobserve = (el: Element) => { intersectionObs.unobserve(el); resizeObs.unobserve(el); };
+
+    const mutationObs = new MutationObserver((mutations) => {
+      for (const m of mutations) {
+        m.addedNodes.forEach(n => {
+          if (!(n instanceof HTMLElement)) return;
+          const imgs = n instanceof HTMLImageElement ? [n] : Array.from(n.querySelectorAll("img"));
+          imgs.forEach(observe);
+        });
+        m.removedNodes.forEach(n => {
+          if (!(n instanceof HTMLElement)) return;
+          const imgs = n instanceof HTMLImageElement ? [n] : Array.from(n.querySelectorAll("img"));
+          imgs.forEach(unobserve);
+        });
+      }
+    });
+    mutationObs.observe(containerEl, { childList: true, subtree: true });
+
+    // Observe images already in the DOM at setup time
+    containerEl.querySelectorAll("img").forEach(observe);
+
+    return () => {
+      containerEl.removeEventListener("scroll", onScroll);
+      mutationObs.disconnect();
+      resizeObs.disconnect();
+      intersectionObs.disconnect();
+    };
+  });
+
+  // ── Cursor hide on inactivity (longstrip) ─────────────────────────────────
+  // Ported from Suwayomi's useReaderHideCursorOnInactivity.
+  // Hides the cursor after 5 s of mouse inactivity, restores on movement.
+  $effect(() => {
+    if (style !== "longstrip" || !containerEl) return;
+
+    const HIDE_AFTER_MS = 5_000;
+    let timer: ReturnType<typeof setTimeout> | null = null;
+
+    const show = () => {
+      containerEl.style.cursor = "";
+      if (timer) clearTimeout(timer);
+      timer = setTimeout(() => { containerEl.style.cursor = "none"; }, HIDE_AFTER_MS);
+    };
+
+    show(); // start the timer immediately
+    window.addEventListener("mousemove", show, { passive: true });
+
+    return () => {
+      containerEl.style.cursor = "";
+      window.removeEventListener("mousemove", show);
+      if (timer) clearTimeout(timer);
+    };
+  });
+
+  // ── Scroll to target flat index ───────────────────────────────────────────
+  export function notifyScrollCenter(idx: number) {
+    centerIdx = idx;
   }
 
+  export async function scrollToFlatIndex(idx: number) {
+    if (!containerEl || !flatPages.length) return;
+    centerIdx = idx;
+    recalcWindow(idx);
+    // Wait for Svelte to render any newly-in-window slots.
+    await tick();
+    if (!containerEl) return;
+    // Use scrollIntoView — the browser knows the exact element position
+    // regardless of image load state or aspect ratio. This is the same approach
+    // used by Suwayomi's useReaderHandlePageSelection (imageRef.scrollIntoView).
+    const slots = containerEl.querySelectorAll<HTMLElement>(".strip-slot");
+    const slot  = slots[idx];
+    if (slot) {
+      slot.scrollIntoView({ block: "start", behavior: "instant" });
+    } else {
+      // Slot not in DOM — proportional fallback (very unlikely after tick).
+      containerEl.scrollTop = (idx / flatPages.length) * containerEl.scrollHeight;
+    }
+  }
+
+  // ── Reset on chapter change ───────────────────────────────────────────────
   let lastChapterId = 0;
   $effect(() => {
     const chapterId = readerState.activeChapter?.id ?? 0;
     if (chapterId === lastChapterId) return;
     lastChapterId = chapterId;
-    loadedSet      = new Set<number>();
-    resolvedSrc    = {};
-    const resume   = readerState.resumePage;
-    viewportCenter = resume > 1 ? resume - 1 : 0;
+    loadedSet   = new Set<number>();
+    resolvedSrc = {};
+    centerIdx   = 0;
+    aspectMap.clear();
   });
 
+  // ── Inspect / zoom helpers ────────────────────────────────────────────────
   const INSPECT_ZOOM_STEP = 0.15;
   const INSPECT_ZOOM_MAX  = 8;
 
@@ -238,6 +380,11 @@
     return () => cancelAnimationFrame(rafId);
   });
 
+  $effect(() => {
+    if (style !== "longstrip") stopMidScroll();
+  });
+
+  // ── Pinch zoom ────────────────────────────────────────────────────────────
   let pinch: PinchTracker | null = null;
 
   $effect(() => {
@@ -255,6 +402,7 @@
     }
   });
 
+  // ── Pointer / mouse / wheel event handlers ────────────────────────────────
   export function onInspectMouseDown(e: MouseEvent) {
     if ((e.target as Element).closest(".bar")) return;
     if (e.button === 1 && style === "longstrip") {
@@ -388,18 +536,7 @@
   function setContainer(el: HTMLDivElement) {
     containerEl = el;
     bindContainer(el);
-    if (style === "longstrip") setupObserver(el);
   }
-
-  $effect(() => {
-    if (style === "longstrip" && containerEl) {
-      setupObserver(containerEl);
-    } else if (style !== "longstrip") {
-      observer?.disconnect();
-      observer = null;
-      stopMidScroll();
-    }
-  });
 </script>
 
 <div
@@ -459,7 +596,7 @@
     {#each flatPages as page, gi (page.chapterId + ":" + page.localIndex)}
       {@const src = resolvedSrc[gi]}
       {@const isLoaded = loadedSet.has(gi)}
-      <div class="strip-slot" use:observePage={gi}>
+      <div class="strip-slot" data-local-page={page.localIndex + 1} data-chapter={page.chapterId}>
         {#if isLoaded && src}
           <img
             {src}
@@ -475,7 +612,9 @@
               const img  = e.currentTarget as HTMLImageElement;
               const slot = img.closest<HTMLElement>(".strip-slot");
               if (slot && img.naturalWidth > 0) {
-                slot.style.setProperty("--aspect", String(img.naturalWidth / img.naturalHeight));
+                const aspect = img.naturalWidth / img.naturalHeight;
+                slot.style.setProperty("--aspect", String(aspect));
+                aspectMap.set(gi, aspect);
               }
             }}
           />
@@ -490,11 +629,11 @@
 
   {:else if style === "fade" && pageReady}
     <div class="inspect-wrap" style="transform:scale({readerState.inspectScale}) translate({readerState.inspectPanX / readerState.inspectScale}px,{readerState.inspectPanY / readerState.inspectScale}px)">
-      {#await resolveUrl(readerState.pageUrls[readerState.pageNumber - 1], 999)}
+      {#if currentSrc}
+        <img src={currentSrc} alt="Page {readerState.pageNumber}" class={imgCls} decoding="async" style="opacity:{fadingOut ? 0 : 1};transition:opacity 0.1s ease" draggable="false" />
+      {:else}
         <div class="page-loader page-loader-single" aria-hidden="true">{@render skeleton()}</div>
-      {:then src}
-        <img {src} alt="Page {readerState.pageNumber}" class={imgCls} decoding="async" style="opacity:{fadingOut ? 0 : 1};transition:opacity 0.1s ease" draggable="false" />
-      {/await}
+      {/if}
     </div>
 
   {:else if style === "double" && pageReady}
@@ -502,11 +641,11 @@
       {#if pageGroups.length}
         <div class="double-wrap">
           {#each currentGroup as pg, i (pg)}
-            {#await resolveUrl(readerState.pageUrls[pg - 1], 999)}
+            {#if currentGroupSrcs[i]}
+              <img src={currentGroupSrcs[i]} alt="Page {pg}" class="{imgCls} page-half {i === 0 ? 'gap-left' : 'gap-right'}" decoding="async" draggable="false" />
+            {:else}
               <div class="page-loader page-half {i === 0 ? 'gap-left' : 'gap-right'}" aria-hidden="true">{@render skeleton()}</div>
-            {:then src}
-              <img {src} alt="Page {pg}" class="{imgCls} page-half {i === 0 ? 'gap-left' : 'gap-right'}" decoding="async" draggable="false" />
-            {/await}
+            {/if}
           {/each}
         </div>
       {:else}
@@ -518,11 +657,11 @@
 
   {:else if pageReady}
     <div class="inspect-wrap" style="transform:scale({readerState.inspectScale}) translate({readerState.inspectPanX / readerState.inspectScale}px,{readerState.inspectPanY / readerState.inspectScale}px)">
-      {#await resolveUrl(readerState.pageUrls[readerState.pageNumber - 1], 999)}
+      {#if currentSrc}
+        <img src={currentSrc} alt="Page {readerState.pageNumber}" class={imgCls} decoding="async" draggable="false" />
+      {:else}
         <div class="page-loader page-loader-single" aria-hidden="true">{@render skeleton()}</div>
-      {:then src}
-        <img {src} alt="Page {readerState.pageNumber}" class={imgCls} decoding="async" draggable="false" />
-      {/await}
+      {/if}
     </div>
   {/if}
 </div>
diff --git a/src/lib/components/reader/Reader.svelte b/src/lib/components/reader/Reader.svelte
index c697ea8..8dfaccb 100644
--- a/src/lib/components/reader/Reader.svelte
+++ b/src/lib/components/reader/Reader.svelte
@@ -12,9 +12,10 @@
   import { clampZoom, captureZoomAnchor, restoreZoomAnchor } from "$lib/components/reader/lib/zoomHelpers";
   import { loadChapter, scheduleResumeDismiss }              from "$lib/components/reader/lib/chapterLoader";
   import { historyState }                                    from "$lib/state/history.svelte";
+  import { setPreviewManga }                                 from "$lib/state/series.svelte";
   import { getAdapter }                                      from "$lib/request-manager";
   import { setReading, clearReading }                        from "$lib/core/discord";
-  import { revokeBlobUrl }                                   from "$lib/core/cache/imageCache";
+  import { revokeBlobUrl, cancelQueuedFetches, preloadBlobUrls } from "$lib/core/cache/imageCache";
   import type { ReaderSettings }                             from "$lib/state/reader.svelte";
   import ReaderControls                                      from "$lib/components/reader/ReaderControls.svelte";
   import PageView                                            from "$lib/components/reader/PageView.svelte";
@@ -211,6 +212,36 @@
 
   const startAtLast = () => { startAtLastPageRef.current = true; };
 
+  function flatIndexForPage(page: number): number {
+    const chId = readerState.visibleChapterId ?? readerState.activeChapter?.id;
+    const chunks = readerState.stripChapters;
+    let offset = 0;
+    for (const chunk of chunks) {
+      if (chunk.chapterId === chId) return offset + Math.max(0, page - 1);
+      offset += chunk.urls.length;
+    }
+    return Math.max(0, page - 1);
+  }
+
+  function primedJump(page: number, commit = true) {
+    if (useBlob && commit && style !== "longstrip") {
+      cancelQueuedFetches();
+      const urls = readerState.pageUrls;
+      const lo   = Math.max(0, page - 2);
+      const hi   = Math.min(urls.length, page + 4);
+      preloadBlobUrls(urls.slice(lo, hi), 999);
+    }
+    jumpToPage(
+      page,
+      style,
+      lastPage,
+      style === "longstrip" ? (idx) => pageViewRef.scrollToFlatIndex(idx) : null,
+      stripToRender.reduce((s, c) => s + c.urls.length, 0),
+      readerState.visibleChapterId ?? readerState.activeChapter?.id ?? 0,
+      readerState.stripChapters,
+    );
+  }
+
   const goNext = $derived(rtl
     ? () => goBack(style, adjacent, startAtLast)
     : () => goForward(style, adjacent, lastPage, maybeMarkCurrentRead, startAtLast));
@@ -218,7 +249,6 @@
     ? () => goForward(style, adjacent, lastPage, maybeMarkCurrentRead, startAtLast)
     : () => goBack(style, adjacent, startAtLast));
 
-  // clear Discord presence and free page blob textures before closing
   function handleCloseReader() {
     clearReading().catch(() => {});
     for (const url of readerState.pageUrls) revokeBlobUrl(url);
@@ -232,13 +262,13 @@
     goNext:           () => goNext(),
     goPrev:           () => goPrev(),
     closeReader:      () => handleCloseReader(),
-    goToPage:         (p) => jumpToPage(p, style, lastPage, containerEl),
+    goToPage:         (p) => primedJump(p),
     lastPage:         () => lastPage,
     adjustZoom:       (d) => { captureZoomAnchor(containerEl, style, zoomAnchor); applySettings({ readerZoom: clampZoom(zoom + d) }); restoreZoomAnchor(containerEl, zoomAnchor); },
     resetZoom:        () => { captureZoomAnchor(containerEl, style, zoomAnchor); applySettings({ readerZoom: 1.0 }); restoreZoomAnchor(containerEl, zoomAnchor); },
     cycleStyle:       () => { const idx = PAGE_STYLES.indexOf(style); applySettings({ pageStyle: PAGE_STYLES[(idx + 1) % PAGE_STYLES.length] }); },
     toggleDirection:  () => applySettings({ readingDirection: rtl ? "ltr" : "rtl" }),
-    openSettings: () => { app.setSettingsOpen(true); },
+    openSettings:     () => { app.setSettingsOpen(true); },
     toggleBookmark:   () => toggleBookmark(displayChapter, readerState.pageNumber),
     toggleAutoScroll: () => { if (style === "longstrip") updateSettings({ autoScroll: !(settingsState.settings.autoScroll ?? false) }); },
     toggleMarker:     () => {
@@ -325,7 +355,6 @@
     }
   });
 
-  // Separate from chapter load: also re-fires when idle splash dismisses so presence is restored.
   $effect(() => {
     const ch    = readerState.activeChapter;
     const manga = readerState.activeManga;
@@ -361,26 +390,18 @@
     if (style === "longstrip" && readerState.pageUrls.length && readerState.activeChapter) {
       const ch       = readerState.activeChapter;
       const urls     = readerState.pageUrls;
-      const targetPg = untrack(() => readerState.resumePage);
+      const resumeTo = untrack(() => readerState.resumePage);
       appending                    = false;
       readerState.stripChapters    = [{ chapterId: ch.id, chapterName: ch.name, urls }];
       readerState.visibleChapterId = ch.id;
       tick().then(() => {
         if (!containerEl) return;
-        if (targetPg > 1) {
-          const chId = ch.id;
-          const scrollToResumePage = () => {
-            const target = containerEl!.querySelector<HTMLImageElement>(`img[data-local-page="${targetPg}"][data-chapter="${chId}"]`);
-            if (!target) { requestAnimationFrame(scrollToResumePage); return; }
-            containerEl!.querySelectorAll<HTMLImageElement>(`img[data-chapter="${chId}"]`).forEach((img, i) => { if (i < targetPg) img.loading = "eager"; });
-            const doScroll = () => { target.scrollIntoView({ block: "start" }); readerState.stripResumeReady = true; };
-            if (target.complete && target.naturalHeight > 0) doScroll();
-            else { target.loading = "eager"; target.addEventListener("load", doScroll, { once: true }); }
-          };
-          scrollToResumePage();
+        if (resumeTo > 1) {
+          pageViewRef.scrollToFlatIndex(resumeTo - 1);
+          readerState.stripResumeReady = true;
           return;
         }
-        containerEl!.scrollTop = 0;
+        containerEl.scrollTop = 0;
       });
     }
   });
@@ -430,10 +451,11 @@
     untrack(() => {
       cleanupScroll();
       cleanupScroll = setupScrollTracking(containerEl!, {
-        onPageChange:    (p) => { readerState.pageNumber = p; },
-        onChapterChange: (id) => { readerState.visibleChapterId = id; },
-        onMarkRead:      (id) => markChapterRead(id, markedRead),
-        onAppend:        () => {
+        onPageChange:      (p)   => { readerState.pageNumber = p; },
+        onChapterChange:   (id)  => { readerState.visibleChapterId = id; },
+        onCenterIdxChange: (idx) => { pageViewRef?.notifyScrollCenter(idx); },
+        onMarkRead:        (id)  => markChapterRead(id, markedRead),
+        onAppend: () => {
           if (appending || !readerState.stripChapters.length) return;
           appending = true;
           appendNextChapter(
@@ -628,6 +650,7 @@
     onClampZoom={clampZoom}
     onApplySettings={applySettings}
     onSettingsOpen={() => { app.setSettingsOpen(true); }}
+    onOpenPreview={() => { if (readerState.activeManga) setPreviewManga(readerState.activeManga); }}
     {perMangaEnabled}
   />
 
@@ -688,7 +711,7 @@
       {barPosition}
       onGoPrev={goPrev}
       onGoNext={goNext}
-      onJumpToPage={(p) => jumpToPage(p, style, lastPage, containerEl)}
+      onJumpToPage={(p, commit) => primedJump(p, commit)}
     />
   {/snippet}
 
@@ -702,7 +725,7 @@
       {barPosition}
       onGoPrev={goPrev}
       onGoNext={goNext}
-      onJumpToPage={(p) => jumpToPage(p, style, lastPage, containerEl)}
+      onJumpToPage={(p, commit) => primedJump(p, commit)}
     />
   {/if}
 </div>
diff --git a/src/lib/components/reader/ReaderControls.svelte b/src/lib/components/reader/ReaderControls.svelte
index db500dd..523e984 100644
--- a/src/lib/components/reader/ReaderControls.svelte
+++ b/src/lib/components/reader/ReaderControls.svelte
@@ -36,6 +36,7 @@
     onClampZoom:          (z: number) => number;
     onApplySettings:      (patch: Partial<ReaderSettings>) => void;
     onSettingsOpen:       () => void;
+    onOpenPreview:        () => void;
     perMangaEnabled:      boolean;
   }
 
@@ -47,7 +48,7 @@
     barPosition, progressBar,
     onCaptureZoomAnchor, onRestoreZoomAnchor,
     onMaybeMarkRead, onToggleBookmark, onCommitMarker, onDeleteMarker,
-    onClampZoom, onApplySettings, onSettingsOpen,
+    onClampZoom, onApplySettings, onSettingsOpen, onOpenPreview,
     perMangaEnabled,
   }: Props = $props();
 
@@ -155,12 +156,12 @@
           <span class="ch-info">&#xE2CE;</span>
         {:else}
           <span class="ch-marquee-track" onwheel={(e) => { e.stopPropagation(); (e.currentTarget as HTMLElement).scrollLeft += e.deltaY; }}>
-            <span class="ch-marquee-content">
-              <span class="ch-title">{readerState.activeManga?.title}</span>
-              <span class="ch-sep">/</span>
-              <span class="ch-name">{displayChapter?.name}</span>
+              <button class="ch-marquee-content ch-preview-btn" onclick={onOpenPreview}>
+                <span class="ch-title">{readerState.activeManga?.title}</span>
+                <span class="ch-sep">/</span>
+                <span class="ch-name">{displayChapter?.name}</span>
+              </button>
             </span>
-          </span>
         {/if}
       </div>
       {#if !isVertical}
@@ -494,6 +495,8 @@
   .ch-marquee-track { overflow-x: auto; min-width: 0; flex: 1; scrollbar-width: none; }
   .ch-marquee-track::-webkit-scrollbar { display: none; }
   .ch-marquee-content { display: inline-flex; align-items: center; gap: var(--sp-2); white-space: nowrap; }
+  .ch-preview-btn { background: none; border: none; cursor: pointer; padding: 0; font-size: inherit; font-family: inherit; border-radius: var(--radius-sm); transition: opacity var(--t-fast); }
+  .ch-preview-btn:hover { opacity: 0.7; }
   .ch-title { color: var(--text-secondary); font-weight: var(--weight-medium); }
   .ch-sep   { color: var(--text-faint); flex-shrink: 0; }
   .ch-name  { color: var(--text-muted); }
diff --git a/src/lib/components/reader/ReaderOverlay.svelte b/src/lib/components/reader/ReaderOverlay.svelte
index 8328ba8..aef7c93 100644
--- a/src/lib/components/reader/ReaderOverlay.svelte
+++ b/src/lib/components/reader/ReaderOverlay.svelte
@@ -21,11 +21,27 @@
     readerState.dlOpen = false;
   }
 
+  let bannerMounted = $state(false);
+  let bannerFading  = $state(false);
+
+  $effect(() => {
+    if (showResumeBanner) {
+      bannerMounted = true;
+      bannerFading  = false;
+    } else if (bannerMounted) {
+      bannerFading = true;
+    }
+  });
+
   const queueable = $derived(adjacent.remaining.filter(c => !c.downloaded));
+
+  function onBannerAnimationEnd() {
+    if (bannerFading) { bannerMounted = false; bannerFading = false; }
+  }
 </script>
 
-{#if showResumeBanner}
-  <button class="resume-banner" class:fading={resumeFading} onclick={onDismissResume}>
+{#if bannerMounted}
+  <button class="resume-banner" class:fading={bannerFading} onclick={onDismissResume} onanimationend={onBannerAnimationEnd}>
     Bookmark at page {resumePage}
   </button>
 {/if}
diff --git a/src/lib/components/reader/ReaderProgressBar.svelte b/src/lib/components/reader/ReaderProgressBar.svelte
index b164585..e5eeaaa 100644
--- a/src/lib/components/reader/ReaderProgressBar.svelte
+++ b/src/lib/components/reader/ReaderProgressBar.svelte
@@ -20,7 +20,7 @@
     barPosition:          "top" | "left" | "right";
     onGoPrev:             () => void;
     onGoNext:             () => void;
-    onJumpToPage:         (page: number) => void;
+    onJumpToPage:         (page: number, commit?: boolean) => void;
   }
 
   const {
@@ -32,12 +32,22 @@
 
   const isVertical = $derived(barPosition === "left" || barPosition === "right");
 
-  const hValue = $derived(rtl ? sliderMax - sliderPage + 1 : sliderPage);
-  const hPct   = $derived(`--pct:${sliderPct}%`);
+  const hPct = $derived(`--pct:${sliderPct}%`);
+
+  function sliderValToPage(raw: number): number {
+    return rtl ? sliderMax - raw + 1 : raw;
+  }
+
+  function pageToSliderVal(page: number): number {
+    return rtl ? sliderMax - page + 1 : page;
+  }
 
   function handleH(e: Event) {
-    const raw = Number((e.target as HTMLInputElement).value);
-    onJumpToPage(rtl ? sliderMax - raw + 1 : raw);
+    onJumpToPage(sliderValToPage(Number((e.target as HTMLInputElement).value)), false);
+  }
+
+  function handleHCommit(e: Event) {
+    onJumpToPage(sliderValToPage(Number((e.target as HTMLInputElement).value)), true);
   }
 
   function markerPct(pageNumber: number, forRtl = false): number {
@@ -46,9 +56,9 @@
     return ((ord - 1) / (sliderMax - 1)) * 100;
   }
 
-  // Custom vertical slider
   let trackEl = $state<HTMLDivElement | null>(null);
   let dragging = $state(false);
+  let pendingPage = 0;
 
   function pctFromPointer(clientY: number): number {
     if (!trackEl) return 0;
@@ -64,22 +74,24 @@
     if (e.button !== 0) return;
     e.preventDefault();
     (e.currentTarget as HTMLElement).setPointerCapture(e.pointerId);
-    dragging = true;
+    dragging    = true;
     readerState.sliderDragging = true;
-    const pct  = pctFromPointer(e.clientY);
-    onJumpToPage(pageFromPct(pct));
+    pendingPage = pageFromPct(pctFromPointer(e.clientY));
+    onJumpToPage(pendingPage, false);
   }
 
   function handleTrackPointerMove(e: PointerEvent) {
     if (!dragging) return;
-    const pct = pctFromPointer(e.clientY);
-    onJumpToPage(pageFromPct(pct));
+    pendingPage = pageFromPct(pctFromPointer(e.clientY));
+    onJumpToPage(pendingPage, false);
   }
 
   function handleTrackPointerUp(e: PointerEvent) {
     if (!dragging) return;
     dragging = false;
     readerState.sliderDragging = false;
+    readerState.sliderHover    = false;
+    onJumpToPage(pendingPage, true);
   }
 </script>
 
@@ -102,8 +114,9 @@
           style={hPct}
           min={1}
           max={sliderMax}
-          value={hValue}
+          value={pageToSliderVal(sliderPage)}
           oninput={handleH}
+          onchange={handleHCommit}
           onmousedown={() => readerState.sliderDragging = true}
           onmouseup={() => readerState.sliderDragging = false}
         />
diff --git a/src/lib/components/reader/lib/chapterLoader.ts b/src/lib/components/reader/lib/chapterLoader.ts
index 5634eff..9e2248d 100644
--- a/src/lib/components/reader/lib/chapterLoader.ts
+++ b/src/lib/components/reader/lib/chapterLoader.ts
@@ -1,7 +1,7 @@
-import { readerState }                          from "$lib/state/reader.svelte";
-import { fetchPages }                           from "./pageLoader";
-import { cancelQueuedFetches, revokeBlobUrl }   from "$lib/core/cache/imageCache";
-import { clearResolvedUrlCache, clearPageCache } from "$lib/core/cache/pageCache";
+import { readerState }                                          from "$lib/state/reader.svelte";
+import { fetchPages }                                          from "./pageLoader";
+import { cancelQueuedFetches, revokeBlobUrl, preloadBlobUrls } from "$lib/core/cache/imageCache";
+import { clearResolvedUrlCache, clearPageCache }               from "$lib/core/cache/pageCache";
 
 export function scheduleResumeDismiss() {
   setTimeout(() => { readerState.resumeFading = true; }, 1500);
@@ -46,18 +46,23 @@ export async function loadChapter(
   const resumeTo = bookmark ? bookmark.pageNumber : 0;
   readerState.resumePage      = resumeTo > 1 ? resumeTo : 0;
   readerState.resumeDismissed = false;
-  readerState.resumeVisible   = resumeTo > 1;
-  if (resumeTo > 1) scheduleResumeDismiss();
+  readerState.resumeVisible   = false;
 
   readerState.pageNumber = 1;
   try {
     const urls = await fetchPages(id, useBlob, ctrl.signal, resumeTo > 1 ? resumeTo - 1 : 0);
     if (ctrl.signal.aborted) return;
     readerState.pageUrls = urls;
+    if (useBlob && resumeTo > 1) {
+      const lo = Math.max(0, resumeTo - 2);
+      const hi = Math.min(urls.length, resumeTo + 4);
+      preloadBlobUrls(urls.slice(lo, hi), 900);
+    }
     if (startAtLastPage.current)  readerState.pageNumber = urls.length;
     else if (resumeTo > 1)        readerState.pageNumber = Math.min(resumeTo, urls.length || resumeTo);
     readerState.pageReady = true;
     readerState.loading   = false;
+    if (resumeTo > 1) readerState.resumeVisible = true;
     if (adjacent.next) {
       prefetchedChapterId = adjacent.next.id;
       fetchPages(adjacent.next.id, useBlob, ctrl.signal).catch(() => {});
diff --git a/src/lib/components/reader/lib/navigation.ts b/src/lib/components/reader/lib/navigation.ts
index 6f99589..9259f07 100644
--- a/src/lib/components/reader/lib/navigation.ts
+++ b/src/lib/components/reader/lib/navigation.ts
@@ -64,16 +64,32 @@ export function goBack(style: string, adjacent: Adjacent, startAtLastPage: () =>
   } else if (adjacent.prev) { startAtLastPage(); openReader(adjacent.prev, readerState.activeChapterList); }
 }
 
-export function jumpToPage(page: number, style: string, lastPage: number, containerEl: HTMLElement | null) {
+export function jumpToPage(
+  page: number,
+  style: string,
+  lastPage: number,
+  scrollToFlatIndex: ((idx: number) => void) | null,
+  flatPageCount: number,
+  activeChapterId: number,
+  stripChapters: { chapterId: number; urls: string[] }[],
+) {
   if (style === "longstrip") {
-    const chId = readerState.visibleChapterId ?? readerState.activeChapter?.id;
-    containerEl?.querySelector<HTMLImageElement>(`img[data-local-page="${page}"][data-chapter="${chId}"]`)?.scrollIntoView({ block: "start" });
+    if (!scrollToFlatIndex || flatPageCount === 0) return;
+    let offset = 0;
+    for (const chunk of stripChapters) {
+      if (chunk.chapterId === activeChapterId) {
+        scrollToFlatIndex(offset + Math.max(0, page - 1));
+        return;
+      }
+      offset += chunk.urls.length;
+    }
+    scrollToFlatIndex(Math.max(0, page - 1));
     return;
   }
   if (style === "double" && readerState.pageGroups.length) {
-    const group = readerState.pageGroups[page - 1];
+    const group = readerState.pageGroups.find(g => g.includes(page)) ?? readerState.pageGroups.findLast(g => g[0] <= page);
     if (group) readerState.pageNumber = group[0];
   } else {
     readerState.pageNumber = Math.max(1, Math.min(lastPage, page));
   }
-}
+}
\ No newline at end of file
diff --git a/src/lib/components/reader/lib/scrollHandler.ts b/src/lib/components/reader/lib/scrollHandler.ts
index 9a671ec..c3fd3ee 100644
--- a/src/lib/components/reader/lib/scrollHandler.ts
+++ b/src/lib/components/reader/lib/scrollHandler.ts
@@ -7,34 +7,65 @@ export interface StripChapter {
 }
 
 export interface ScrollHandlerCallbacks {
-  onPageChange:     (page: number) => void;
-  onChapterChange:  (chapterId: number) => void;
-  onMarkRead:       (chapterId: number) => void;
-  onAppend:         () => void;
-  getStripChapters: () => StripChapter[];
-  getPageUrls:      () => string[];
-  shouldAutoMark:   () => boolean;
+  onPageChange:        (page: number) => void;
+  onChapterChange:     (chapterId: number) => void;
+  onCenterIdxChange:   (flatIdx: number) => void;
+  onMarkRead:          (chapterId: number) => void;
+  onAppend:            () => void;
+  getStripChapters:    () => StripChapter[];
+  getPageUrls:         () => string[];
+  shouldAutoMark:      () => boolean;
+}
+
+/**
+ * Returns true if the element is considered "at" the read-line.
+ *
+ * Ported from Suwayomi's ReaderPager.utils `isPageInViewport`:
+ *   - If the element's top is above the line AND its bottom is below it → fully covers the line
+ *     (handles a single page that is taller than the viewport).
+ *   - If the element's top is at or below the line AND its bottom is also below it → leading edge
+ *     has crossed the line (normal scroll-past case).
+ *
+ * Using Math.trunc to avoid floating-point jitter from getBoundingClientRect.
+ */
+function isPageAtReadLine(el: HTMLElement, readLineY: number): boolean {
+  const rect   = el.getBoundingClientRect();
+  const top    = Math.trunc(rect.top);
+  const bottom = Math.trunc(rect.bottom);
+  const line   = Math.trunc(readLineY);
+  // Element completely spans the read line (taller than viewport or very tall image)
+  if (top <= line && bottom >= line) return true;
+  // Element's top edge is at or above the line
+  if (top <= line) return true;
+  return false;
 }
 
 export function setupScrollTracking(
   containerEl: HTMLElement,
   callbacks: ScrollHandlerCallbacks,
 ): () => void {
-  const { onPageChange, onChapterChange, onMarkRead, onAppend, getStripChapters, getPageUrls, shouldAutoMark } = callbacks;
+  const {
+    onPageChange, onChapterChange, onCenterIdxChange,
+    onMarkRead, onAppend, getStripChapters, getPageUrls, shouldAutoMark,
+  } = callbacks;
+
   let rafId: number | null = null;
 
   function tick() {
     rafId = null;
     const imgs = containerEl.querySelectorAll<HTMLElement>("img[data-local-page]");
+
     if (!imgs.length) return;
 
-    const containerTop = containerEl.getBoundingClientRect().top;
-    const readLineY    = containerTop + containerEl.clientHeight * READ_LINE_PCT;
+    const containerRect = containerEl.getBoundingClientRect();
+    const readLineY     = containerRect.top + containerEl.clientHeight * READ_LINE_PCT;
 
+    // Find the last image whose top is at or above the read line.
+    // Binary search is still valid here since images are ordered top-to-bottom.
     let lo = 0, hi = imgs.length - 1, best = 0;
     while (lo <= hi) {
       const mid = (lo + hi) >>> 1;
-      if (imgs[mid].getBoundingClientRect().top <= readLineY) { best = mid; lo = mid + 1; }
+      if (isPageAtReadLine(imgs[mid], readLineY)) { best = mid; lo = mid + 1; }
       else hi = mid - 1;
     }
 
@@ -45,10 +76,19 @@ export function setupScrollTracking(
     onPageChange(activePage);
     if (activeChId) onChapterChange(activeChId);
 
+    const chunks   = getStripChapters();
+    let flatOffset = 0;
+    for (const chunk of chunks) {
+      if (chunk.chapterId === activeChId) {
+        onCenterIdxChange(flatOffset + activePage - 1);
+        break;
+      }
+      flatOffset += chunk.urls.length;
+    }
+
     if (shouldAutoMark() && activeChId) {
-      const chunks = getStripChapters();
-      const chunk  = chunks.find(c => c.chapterId === activeChId);
-      const total  = chunk ? chunk.urls.length : getPageUrls().length;
+      const chunk = chunks.find(c => c.chapterId === activeChId);
+      const total = chunk ? chunk.urls.length : getPageUrls().length;
       if (total > 0 && activePage >= total) onMarkRead(activeChId);
 
       const atBottom = containerEl.scrollTop + containerEl.clientHeight >= containerEl.scrollHeight - 40;
@@ -58,8 +98,9 @@ export function setupScrollTracking(
       }
     }
 
-    const pct = (containerEl.scrollTop + containerEl.clientHeight) / containerEl.scrollHeight;
-    if (pct >= 0.80) onAppend();
+    if ((containerEl.scrollTop + containerEl.clientHeight) / containerEl.scrollHeight >= 0.80) {
+      onAppend();
+    }
   }
 
   function onScroll() {
@@ -97,4 +138,4 @@ export function appendNextChapter(
       onDone();
     })
     .catch(() => onDone());
-}
+}
\ No newline at end of file
diff --git a/src/lib/components/series/SeriesHeader.svelte b/src/lib/components/series/SeriesHeader.svelte
index ee1b8ce..eaebb81 100644
--- a/src/lib/components/series/SeriesHeader.svelte
+++ b/src/lib/components/series/SeriesHeader.svelte
@@ -9,7 +9,8 @@
   import { get }           from 'svelte/store'
   import Thumbnail         from '$lib/components/shared/manga/Thumbnail.svelte'
   import { resolvedCover } from '$lib/core/cover/coverResolver'
-  import type { MangaPrefs }                                    from '$lib/types/settings'
+  import type { Manga, Chapter, Category } from '$lib/types'
+
   import { seriesState }                                        from '$lib/state/series.svelte'
   import { setPreviewManga }                                    from '$lib/state/series.svelte'
 
@@ -59,6 +60,7 @@
 
   let manageOpen:     boolean = $state(false)
   let genresExpanded: boolean = $state(false)
+  let descExpanded:   boolean = $state(false)
   let altOpen:        boolean = $state(false)
 
   const statusLabel = $derived(
@@ -104,7 +106,7 @@
     </div>
   {:else}
     <div class="meta">
-      <p class="title">{manga?.title}</p>
+      <button class="title" onclick={() => manga && setPreviewManga(manga)} disabled={!manga}>{manga?.title}</button>
 
       {#if manga?.author || manga?.artist}
         <p class="byline">{[manga?.author, manga?.artist].filter(Boolean).filter((v, i, a) => a.indexOf(v) === i).join(' · ')}</p>
@@ -148,8 +150,8 @@
 
       {#if manga?.description}
         <div class="desc-wrap">
-          <p class="desc">{manga.description}</p>
-          <button class="expand-toggle" onclick={() => genresExpanded = !genresExpanded}>Read more</button>
+          <p class="desc" class:desc-open={descExpanded}>{manga.description}</p>
+          <button class="expand-toggle" onclick={() => descExpanded = !descExpanded}>{descExpanded ? 'Show less' : 'Read more'}</button>
         </div>
       {/if}
     </div>
@@ -277,7 +279,11 @@
     font-size: var(--text-base); font-weight: var(--weight-medium);
     color: var(--text-primary); line-height: var(--leading-snug);
     letter-spacing: var(--tracking-tight);
+    background: none; border: none; padding: 0; text-align: left; cursor: pointer;
+    transition: color var(--t-base);
   }
+  .title:hover:not(:disabled) { color: var(--accent-fg); }
+  .title:disabled { cursor: default; }
   .byline { font-size: var(--text-xs); color: var(--text-muted); font-family: var(--font-ui); }
 
   .badges { display: flex; flex-wrap: wrap; gap: var(--sp-1); }
@@ -328,6 +334,7 @@
     font-size: var(--text-xs); color: var(--text-muted); line-height: var(--leading-base);
     display: -webkit-box; -webkit-line-clamp: 4; -webkit-box-orient: vertical; overflow: hidden;
   }
+  .desc.desc-open { display: block; -webkit-line-clamp: unset; overflow: visible; }
   .expand-toggle {
     font-family: var(--font-ui); font-size: var(--text-2xs); color: var(--text-faint);
     letter-spacing: var(--tracking-wide); align-self: flex-start; transition: color var(--t-base);
diff --git a/src/lib/components/shared/manga/MangaPreview.svelte b/src/lib/components/shared/manga/MangaPreview.svelte
index 6ca25f2..d375a32 100644
--- a/src/lib/components/shared/manga/MangaPreview.svelte
+++ b/src/lib/components/shared/manga/MangaPreview.svelte
@@ -259,7 +259,7 @@
   function openSeriesDetail() {
     if (!displayManga) return;
     setActiveManga(displayManga);
-    setNavPage(originNavPage);
+    app.setNavPage(originNavPage);
     close();
   }