Fix: Respect Page-Order in Loading & Memory Eviction (#61, #63, #68)

src/features/reader/components/PageView.svelte

@@ -19,6 +19,7 @@
     fadingOut:       boolean;
     tapToToggleBar:  boolean;
     pinchZoomEnabled: boolean;
+    chapterEpoch:    number;
     onGetZoom:       () => number;
     onSetZoom:       (z: number) => void;
     resolveUrl:      (url: string, priority?: number) => Promise<string>;
@@ -31,10 +32,152 @@
   const {
     style, imgCls, effectiveWidth, loading, error, pageReady,
     pageGroups, currentGroup, stripToRender, fadingOut,
-    tapToToggleBar, pinchZoomEnabled, onGetZoom, onSetZoom,
+    tapToToggleBar, pinchZoomEnabled, chapterEpoch, onGetZoom, onSetZoom,
     resolveUrl, onTap, onWheel, onToggleUi, bindContainer,
   }: Props = $props();
 
+  const LOAD_RADIUS   = 5;
+  const UNLOAD_RADIUS = 10;
+
+  type FlatPage = { chapterId: number; chapterName: string; localIndex: number; url: string; total: number };
+
+  const flatPages = $derived.by<FlatPage[]>(() => {
+    const out: FlatPage[] = [];
+    for (const chunk of stripToRender) {
+      for (let i = 0; i < chunk.urls.length; i++) {
+        out.push({ chapterId: chunk.chapterId, chapterName: chunk.chapterName, localIndex: i, url: chunk.urls[i], total: chunk.urls.length });
+      }
+    }
+    return out;
+  });
+
+  let loadedSet   = $state(new Set<number>());
+  let resolvedSrc = $state<Record<number, string>>({});
+  let revokeQueue: string[] = [];
+
+  let observer: IntersectionObserver | null = null;
+  const elementIndex = new Map<Element, number>();
+
+  let viewportCenter = $state(0);
+
+  function scheduleRevoke(src: string) {
+    if (!src || !src.startsWith("blob:")) return;
+    revokeQueue.push(src);
+    requestAnimationFrame(() => {
+      const url = revokeQueue.shift();
+      if (url) {
+        try { URL.revokeObjectURL(url); } catch { }
+      }
+    });
+  }
+
+  function loadPage(idx: number) {
+    if (loadedSet.has(idx)) return;
+    const page = flatPages[idx];
+    if (!page) return;
+    const newSet = new Set(loadedSet);
+    newSet.add(idx);
+    loadedSet = newSet;
+    const priority = (page.localIndex < 8 && page.chapterId === flatPages[0]?.chapterId) ? 8 - page.localIndex : 0;
+    resolveUrl(page.url, priority).then(src => {
+      if (loadedSet.has(idx)) {
+        resolvedSrc = { ...resolvedSrc, [idx]: src };
+      } else {
+        scheduleRevoke(src);
+      }
+    });
+  }
+
+  function unloadPage(idx: number) {
+    if (!loadedSet.has(idx)) return;
+    const newSet = new Set(loadedSet);
+    newSet.delete(idx);
+    loadedSet = newSet;
+    const oldSrc = resolvedSrc[idx];
+    if (oldSrc) {
+      const next = { ...resolvedSrc };
+      delete next[idx];
+      resolvedSrc = next;
+      scheduleRevoke(oldSrc);
+    }
+  }
+
+  function recalcWindow() {
+    const center = viewportCenter;
+    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);
+      }
+    }
+  }
+
+  $effect(() => {
+    void viewportCenter;
+    recalcWindow();
+  });
+
+  $effect(() => {
+    void flatPages.length;
+    recalcWindow();
+  });
+
+  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],
+      }
+    );
+  }
+
+  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);
+      }
+    };
+  }
+
+  $effect(() => {
+    void chapterEpoch;
+    loadedSet   = new Set<number>();
+    resolvedSrc = {};
+    const resume = readerState.resumePage;
+    viewportCenter = resume > 1 ? resume - 1 : 0;
+  });
+
   const INSPECT_ZOOM_STEP = 0.15;
   const INSPECT_ZOOM_MAX  = 8;
 
@@ -194,7 +337,17 @@
   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;
+    }
+  });
 </script>
 
 <div
@@ -221,61 +374,77 @@
     <div class="center-overlay"><p class="error-msg">{error}</p></div>
   {/if}
 
-  {#if style === "longstrip"}
-    {#each stripToRender as chunk}
-      {#each chunk.urls as url, i}
-        {#if i < 8}
-          {#await resolveUrl(url, 8 - i)}
-            <img src="" alt="{chunk.chapterName} – Page {i + 1}" data-local-page={i + 1} data-chapter={chunk.chapterId} data-total={chunk.urls.length} class="{imgCls}{store.settings.pageGap ? ' strip-gap' : ''}" loading="eager" decoding="async" />
-          {:then src}
-            <img {src} alt="{chunk.chapterName} – Page {i + 1}" data-local-page={i + 1} data-chapter={chunk.chapterId} data-total={chunk.urls.length} class="{imgCls}{store.settings.pageGap ? ' strip-gap' : ''}" loading="eager" decoding="async" />
-          {/await}
-        {:else}
-          {#await resolveUrl(url, 0)}
-            <img src="" alt="{chunk.chapterName} – Page {i + 1}" data-local-page={i + 1} data-chapter={chunk.chapterId} data-total={chunk.urls.length} class="{imgCls}{store.settings.pageGap ? ' strip-gap' : ''}" loading="lazy" decoding="async" />
-          {:then src}
-            <img {src} alt="{chunk.chapterName} – Page {i + 1}" data-local-page={i + 1} data-chapter={chunk.chapterId} data-total={chunk.urls.length} class="{imgCls}{store.settings.pageGap ? ' strip-gap' : ''}" loading="lazy" decoding="async" />
-          {/await}
-        {/if}
-      {/each}
-    {/each}
-    <div style="height:1px;flex-shrink:0"></div>
-
-  {: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(store.pageUrls[store.pageNumber - 1], 999)}
-        <img src="" alt="Page {store.pageNumber}" class={imgCls} decoding="async" style="opacity:0" />
-      {:then src}
-        <img {src} alt="Page {store.pageNumber}" class={imgCls} decoding="async" style="opacity: {fadingOut ? 0 : 1}; transition: opacity 0.1s ease;" />
-      {/await}
-    </div>
-
-  {:else if style === "double" && pageReady}
-    <div class="inspect-wrap" style="transform:scale({readerState.inspectScale}) translate({readerState.inspectPanX / readerState.inspectScale}px,{readerState.inspectPanY / readerState.inspectScale}px)">
-      {#if pageGroups.length}
-        <div class="double-wrap">
-          {#each currentGroup as pg, i}
-            {#await resolveUrl(store.pageUrls[pg - 1], 999)}
-              <img src="" alt="Page {pg}" class="{imgCls} page-half {i === 0 ? 'gap-left' : 'gap-right'}" decoding="async" />
-            {:then src}
-              <img {src} alt="Page {pg}" class="{imgCls} page-half {i === 0 ? 'gap-left' : 'gap-right'}" decoding="async" />
-            {/await}
-          {/each}
+  {#key chapterEpoch}
+    {#if style === "longstrip"}
+      {#each flatPages as page, gi}
+        {@const src = resolvedSrc[gi]}
+        {@const isLoaded = loadedSet.has(gi)}
+        <div
+          class="strip-slot"
+          use:observePage={gi}
+          data-gi={gi}
+        >
+          {#if isLoaded}
+            <img
+              src={src ?? ""}
+              alt="{page.chapterName} – Page {page.localIndex + 1}"
+              data-local-page={page.localIndex + 1}
+              data-chapter={page.chapterId}
+              data-total={page.total}
+              class="{imgCls}{store.settings.pageGap ? ' strip-gap' : ''}"
+              loading="eager"
+              decoding="async"
+              onload={(e) => {
+                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));
+                }
+              }}
+            />
+          {:else}
+            <div class="strip-placeholder"></div>
+          {/if}
         </div>
-      {:else}
-        <div class="center-overlay"><CircleNotch size={20} weight="light" class="anim-spin" style="color:var(--text-faint)" /></div>
-      {/if}
-    </div>
+      {/each}
+      <div style="height:1px;flex-shrink:0"></div>
 
-  {: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(store.pageUrls[store.pageNumber - 1], 999)}
-        <img src="" alt="Page {store.pageNumber}" class={imgCls} decoding="async" />
-      {:then src}
-        <img {src} alt="Page {store.pageNumber}" class={imgCls} decoding="async" />
-      {/await}
-    </div>
-  {/if}
+    {: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(store.pageUrls[store.pageNumber - 1], 999)}
+          <img src="" alt="Page {store.pageNumber}" class={imgCls} decoding="async" style="opacity:0" />
+        {:then src}
+          <img {src} alt="Page {store.pageNumber}" class={imgCls} decoding="async" style="opacity: {fadingOut ? 0 : 1}; transition: opacity 0.1s ease;" />
+        {/await}
+      </div>
+
+    {:else if style === "double" && pageReady}
+      <div class="inspect-wrap" style="transform:scale({readerState.inspectScale}) translate({readerState.inspectPanX / readerState.inspectScale}px,{readerState.inspectPanY / readerState.inspectScale}px)">
+        {#if pageGroups.length}
+          <div class="double-wrap">
+            {#each currentGroup as pg, i}
+              {#await resolveUrl(store.pageUrls[pg - 1], 999)}
+                <img src="" alt="Page {pg}" class="{imgCls} page-half {i === 0 ? 'gap-left' : 'gap-right'}" decoding="async" />
+              {:then src}
+                <img {src} alt="Page {pg}" class="{imgCls} page-half {i === 0 ? 'gap-left' : 'gap-right'}" decoding="async" />
+              {/await}
+            {/each}
+          </div>
+        {:else}
+          <div class="center-overlay"><CircleNotch size={20} weight="light" class="anim-spin" style="color:var(--text-faint)" /></div>
+        {/if}
+      </div>
+
+    {: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(store.pageUrls[store.pageNumber - 1], 999)}
+          <img src="" alt="Page {store.pageNumber}" class={imgCls} decoding="async" />
+        {:then src}
+          <img {src} alt="Page {store.pageNumber}" class={imgCls} decoding="async" />
+        {/await}
+      </div>
+    {/if}
+  {/key}
 
 </div>
 
@@ -290,6 +459,20 @@
 
   .inspect-wrap { display: flex; align-items: center; justify-content: center; transform-origin: center center; will-change: transform; }
 
+  .strip-slot {
+    width: 100%;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+  }
+
+  .strip-placeholder {
+    width: var(--effective-width, 100%);
+    max-width: var(--effective-width, 100%);
+    aspect-ratio: var(--aspect, 0.667);
+    background: transparent;
+  }
+
   .img { display: block; user-select: none; image-rendering: auto; }
   .img:global(.optimize-contrast) { image-rendering: -webkit-optimize-contrast; }
   :global(.fit-width)    { max-width: var(--effective-width, 100%); width: 100%; height: auto; }

src/features/reader/components/Reader.svelte

@@ -420,23 +420,28 @@
   $effect(() => {
     const ahead   = store.settings.preloadPages ?? 3;
     const current = store.pageUrls[store.pageNumber - 1];
+    const pageNum = store.pageNumber;
+    const urls    = store.pageUrls;
     if (!current) return;
-    if (useBlob) {
-      import("@core/cache/imageCache").then(({ getBlobUrl, preloadBlobUrls }) => {
-        getBlobUrl(current, 999);
-        const upcoming = Array.from({ length: ahead }, (_, i) => store.pageUrls[store.pageNumber + i]).filter(Boolean) as string[];
-        const behind   = store.pageUrls[store.pageNumber - 2];
-        preloadBlobUrls(upcoming, ahead);
-        if (behind) preloadBlobUrls([behind], 0);
-      });
-    } else {
-      for (let i = 1; i <= ahead; i++) {
-        const url = store.pageUrls[store.pageNumber - 1 + i];
-        if (url) preloadImage(url, useBlob);
+    const t = setTimeout(() => {
+      if (useBlob) {
+        import("@core/cache/imageCache").then(({ getBlobUrl, preloadBlobUrls }) => {
+          getBlobUrl(current, 999);
+          const upcoming = Array.from({ length: ahead }, (_, i) => urls[pageNum + i]).filter(Boolean) as string[];
+          const behind   = urls[pageNum - 2];
+          preloadBlobUrls(upcoming, ahead);
+          if (behind) preloadBlobUrls([behind], 0);
+        });
+      } else {
+        for (let i = 1; i <= ahead; i++) {
+          const url = urls[pageNum - 1 + i];
+          if (url) preloadImage(url, useBlob);
+        }
+        const behind = urls[pageNum - 2];
+        if (behind) preloadImage(behind, useBlob);
       }
-      const behind = store.pageUrls[store.pageNumber - 2];
-      if (behind) preloadImage(behind, useBlob);
-    }
+    }, 150);
+    return () => clearTimeout(t);
   });
 
   $effect(() => {

src/features/reader/lib/chapterLoader.ts

@@ -1,7 +1,9 @@
-import { store, openReader } from "@store/state.svelte";
-import { readerState }       from "../store/readerState.svelte";
-import { fetchPages }        from "./pageLoader";
-import { trackingState }     from "@features/tracking/store/trackingState.svelte";
+import { store }           from "@store/state.svelte";
+import { readerState }     from "../store/readerState.svelte";
+import { fetchPages }      from "./pageLoader";
+import { trackingState }   from "@features/tracking/store/trackingState.svelte";
+import { cancelQueuedFetches } from "@core/cache/imageCache";
+import { clearResolvedUrlCache } from "@core/cache/pageCache";
 
 export function scheduleResumeDismiss() {
   setTimeout(() => { readerState.resumeFading = true; }, 1500);
@@ -19,6 +21,10 @@ export async function loadChapter(
   abortCtrl.current?.abort();
   const ctrl = new AbortController();
   abortCtrl.current = ctrl;
+
+  cancelQueuedFetches();
+  if (useBlob) clearResolvedUrlCache();
+
   startAtLastPage.current = false;
   markedRead.clear();
   readerState.resetForChapter();
@@ -43,7 +49,7 @@ export async function loadChapter(
     else if (resumeTo > 1)        store.pageNumber = Math.min(resumeTo, urls.length || resumeTo);
     readerState.pageReady = true;
     readerState.loading   = false;
-    if (adjacent.next) fetchPages(adjacent.next.id, useBlob).catch(() => {});
+    if (adjacent.next) fetchPages(adjacent.next.id, useBlob, ctrl.signal).catch(() => {});
   } catch (e: any) {
     if (ctrl.signal.aborted) return;
     readerState.error   = e instanceof Error ? e.message : String(e);

src/features/reader/lib/scrollHandler.ts

@@ -25,57 +25,58 @@ export function setupScrollTracking(
     onAppend, getStripChapters, getPageUrls, shouldAutoMark,
   } = callbacks;
 
-  function onScroll() {
+  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;
 
-    let activePage: number | null = null;
-    let activeChId: number | null = null;
-
-    for (const img of imgs) {
-      if (img.getBoundingClientRect().top <= readLineY) {
-        activePage = Number(img.dataset.localPage);
-        activeChId = Number(img.dataset.chapter);
-      } else break;
+    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; }
+      else hi = mid - 1;
     }
 
-    if (activePage === null) {
-      activePage = Number(imgs[0].dataset.localPage);
-      activeChId = Number(imgs[0].dataset.chapter);
-    }
+    const active   = imgs[best];
+    const activePage = Number(active.dataset.localPage);
+    const activeChId = Number(active.dataset.chapter);
 
-    if (activePage !== null) onPageChange(activePage);
-    if (activeChId)          onChapterChange(activeChId);
+    onPageChange(activePage);
+    if (activeChId) onChapterChange(activeChId);
 
-    if (shouldAutoMark() && activePage !== null && activeChId) {
+    if (shouldAutoMark() && activeChId) {
       const chunks = getStripChapters();
       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;
+      if (atBottom) {
+        const last = chunks[chunks.length - 1];
+        if (last) onMarkRead(last.chapterId);
+      }
     }
 
-    const atBottom = containerEl.scrollTop + containerEl.clientHeight >= containerEl.scrollHeight - 40;
-    if (atBottom && shouldAutoMark()) {
-      const chunks = getStripChapters();
-      const last   = chunks[chunks.length - 1];
-      if (last) onMarkRead(last.chapterId);
-    }
-  }
-
-  function onScrollAppend() {
     const pct = (containerEl.scrollTop + containerEl.clientHeight) / containerEl.scrollHeight;
     if (pct >= 0.80) onAppend();
   }
 
-  containerEl.addEventListener("scroll", onScroll,       { passive: true });
-  containerEl.addEventListener("scroll", onScrollAppend, { passive: true });
+  function onScroll() {
+    if (rafId !== null) return;
+    rafId = requestAnimationFrame(tick);
+  }
+
+  containerEl.addEventListener("scroll", onScroll, { passive: true });
 
   return () => {
     containerEl.removeEventListener("scroll", onScroll);
-    containerEl.removeEventListener("scroll", onScrollAppend);
+    if (rafId !== null) cancelAnimationFrame(rafId);
   };
 }
 
@@ -107,4 +108,4 @@ export function appendNextChapter(
       onDone();
     })
     .catch(() => onDone());
-}
+}