feat(library): a shelf that fills in as it reads, and one that carries the studio's look and frame back with it

- tiles land one at a time. The screenful a picked folder asks for was built all
  at once, and a HEIC or a RAW in it is a decode of its own, so the strip stood
  empty until every one of them was done: 2293ms on a roll of eighteen, with the
  batch arriving in one go (0/18 then 18/18 in a single step). Tiles are built in
  two lanes now and each one goes up the moment it is drawn — first picture at
  36ms, then 1, 2, 4, 6, 8, 9, 11, 12, 14, 15, 16, 17, 18 of 18, done at 2496ms.
  The threading is handed back between tiles (`scheduler.yield`), so a click
  still answers while the strip fills: no long tasks either side, worst frame gap
  169ms -> 164ms, a view toggle 49ms -> 41ms. The tiles are the same tiles; the
  wall's is drawn from the same counter.
- the studio's look reaches the shelf. A frame graded in the studio writes the
  tile the shelf draws, at neutral geometry — no turn, crop, watermark or frame,
  since the shelf turns a tile itself — and every screen holding the tile is told
  the moment it is written, so the row repaints without a reload.
- the shelf comes back on the frame the studio was holding. The frame a visit
  opened is kept with the visit, and coming back from the studio raises it: the
  strip centres it and the wall brings its card to the middle, even when the
  frame sits in another folder of the same tree. A shelf that opened on whatever
  it was left standing on sent the reader looking for the frame they had just
  been working on.
- the frame's name stands under the picture, in the studio's own meta bar.

docker/frontend/src/App.tsx

@@ -20,10 +20,11 @@ import { developRaw, isRawName, isTiffName, tiffDevelop } from './engine/rawDeve
 import { sharePhoto, type ShareSite } from './engine/share';
 import { heicToJpeg, isHeicName } from './engine/heicDevelop';
 import { clearRaw, readRaw, storeRaw } from './engine/rawStore';
-import { getPhoto, loadEdit, readPhotoFile, saveEdit, setRotation as savePhotoRotation } from './engine/library';
+import { getPhoto, loadEdit, makeTile, putPhotoThumb, readPhotoFile, saveEdit, setRotation as savePhotoRotation } from './engine/library';
 import { offerInstall } from './pwa/install';
 import { cameraSupported } from './engine/camera';
 import { clearSession, forgetPhoto, loadPhoto, loadState, savePhoto, saveState, type StudioState } from './engine/session';
+import { keep } from './remember';
 import { preloadSuperRes, upscaleJpeg } from './engine/superRes';
 import { api, type Photo, type SavedRecipe } from './api';
 import { refreshAuth, useAuth } from './auth';
@@ -106,6 +107,10 @@ const MODEL_GAIN = 4;
 // on every notch.
 const PREVIEW_QUANTUM = 512;
 const PREVIEW_DEBOUNCE_MS = 120;
+// The catalogue frame the studio is holding, under the catalogue's own key: the
+// shelf reads it when it comes back up and opens on that frame — the reader has
+// just been working on it (see Library.tsx).
+const LIBRARY_LAST_KEY = 'recipescam.library.last';
 
 const FRAMES: { id: FrameId; label: MsgKey }[] = [
   { id: 'none', label: 'frame.none' },
@@ -921,6 +926,49 @@ export function Workspace() {
           if (prev) URL.revokeObjectURL(prev);
           return URL.createObjectURL(new Blob([out.bytes as BlobPart], { type: 'image/jpeg' }));
         });
+        // A frame that came out of the catalogue leaves its own tile behind it:
+        // the shelf would otherwise keep showing the negative the reader has just
+        // graded. The tile is the look alone — the frame's turn, straighten, crop,
+        // frame and stamps are the library's to draw, and every tile it draws
+        // carries the frame's own standing on top — so the render in hand serves
+        // as the tile exactly while it carries none of them. The hovered look is
+        // not the frame's: only the committed one is filed.
+        if (libPhotoId && !preview && !cropEditing) {
+          const bare =
+            !options.cropRect &&
+            !options.watermark &&
+            !options.gpsWatermark &&
+            rotation === 0 &&
+            !straighten &&
+            !flipH &&
+            !flipV &&
+            frame === 'none';
+          const graded =
+            bare
+              ? out.bytes
+              : (
+                  await renderPhoto({
+                    source: previewBytes,
+                    recipe: shownRecipe,
+                    frameId: 'none',
+                    useGeotag: false,
+                    gpsInfo: null,
+                    assets: engine.assets,
+                    options: {
+                      ...options,
+                      photoRotation: 0,
+                      photoStraighten: 0,
+                      photoFlipH: false,
+                      photoFlipV: false,
+                      cropRect: null,
+                      watermark: null,
+                      gpsWatermark: null,
+                    },
+                  })
+                )?.bytes;
+          const tile = graded ? await makeTile(new Blob([graded as BlobPart], { type: 'image/jpeg' })) : null;
+          if (tile && token === renderToken.current) void putPhotoThumb(libPhotoId, tile);
+        }
         if (!comparing) {
           setCompareUrl((prev) => {
             if (prev) URL.revokeObjectURL(prev);
@@ -2170,6 +2218,10 @@ export function Workspace() {
         // frame on the neutral look and so at 0.
         setRotation(row.rot ?? 0);
         setLibPhotoId(id);
+        // The shelf is told which frame the studio is holding, so coming back to
+        // it opens on this one rather than on wherever the tree was left — and it
+        // outlives the visit, because the address bar no longer carries the id.
+        keep(LIBRARY_LAST_KEY, id);
       } catch {
         setError(t('err.decode'));
       } finally {
@@ -4060,6 +4112,7 @@ export function Workspace() {
           }}
           shotSpecs={shotSpecs}
           place={place}
+          photoName={source?.name ?? null}
           onCropRectChange={setCropRect}
           onStageZoom={onStageZoom}
           canCompare={!!source}

docker/frontend/src/Library.tsx

@@ -8,6 +8,7 @@ import { readGps, readSpecs, specsLine } from './engine/imageOps';
 import { isRawName, isTiffName, rawThumbnail, tiffDevelop } from './engine/rawDevelop';
 import { heicToJpeg, isHeicName } from './engine/heicDevelop';
 import {
+  breathe,
   cachedFolders,
   cachedPhotos,
   canBrowseFolders,
@@ -25,6 +26,7 @@ import {
   makeThumbs,
   normPath,
   onLibraryBlocked,
+  onThumbWritten,
   pickFolder,
   readPhotoFile,
   readPhotos,
@@ -96,6 +98,9 @@ const MIN_STAR_KEY = 'recipescam.library.minStar';
 const YEAR_KEY = 'recipescam.library.year';
 const FROM_KEY = 'recipescam.library.from';
 const TO_KEY = 'recipescam.library.to';
+// The frame the studio is holding (written on its side, see App.tsx): the shelf
+// comes back up on that frame rather than on wherever the tree was left.
+const LAST_KEY = 'recipescam.library.last';
 
 function TimeRangeSelectInput({
   from,
@@ -184,6 +189,11 @@ const STRIP_KEEP = 8;
 // cards is a couple of hundred pixels tall, so this is the row under the eye and
 // two beyond it — enough that a flick lands on pictures.
 const WALL_ROWS = 2;
+// How many tiles the wall reads and decodes at once when it is the one asking.
+// The wall's own frames come first and they come visibly: two at a time, the
+// thread handed back between them (`breathe`), is a shelf that fills in front of
+// the reader — a screenful of frames read end to end is a dead screen.
+const WALL_LANES = 2;
 // What `.adm-grid` leaves between its rows. A spacer has to stand the same
 // distance past the last row it replaces as the row itself would have.
 const WALL_GAP = 12;
@@ -343,6 +353,10 @@ function Catalogue({ admin }: { admin: boolean }) {
   // the first, the way a node that is gone falls back to its folder.
   const [up, setUp] = useState<string | null>(() => recall(FRAME_KEY));
   const [view, setView] = useState<'preview' | 'grid'>(() => (recall(VIEW_KEY) === 'grid' ? 'grid' : 'preview'));
+  // This screen is mounted for the life of the tab and only shown and hidden
+  // (see Shell in main.tsx), so a visit that comes back from the studio is not a
+  // mount: the address is what says the shelf is the screen up again.
+  const [here, setHere] = useState(() => window.location.pathname.startsWith('/library'));
   // How the thumbnail view reads the open folder: every frame it holds, or only
   // the ones that were given this many stars, shot in this year, shot between
   // these hours — and in the order the reader picked. A way of looking, not part
@@ -1444,7 +1458,20 @@ function Catalogue({ admin }: { admin: boolean }) {
     () => listed.slice(Math.min(wall.from, listed.length), Math.min(wall.to, listed.length)),
     [listed, wall.from, wall.to]
   );
-  const urls = useThumbUrls(view === 'preview' ? drawn : painted, frame);
+  // A tile the studio graded while this screen was dark: the copy in hand is the
+  // negative's, and `onThumbWritten` hands over the one that replaces it. The
+  // counter is what makes the rows look again — the list is unchanged, so nothing
+  // else would make them.
+  const [tilesAt, setTilesAt] = useState(0);
+  useEffect(
+    () =>
+      onThumbWritten((id, blob) => {
+        cacheObjectUrl(id, blob);
+        setTilesAt((n) => n + 1);
+      }),
+    []
+  );
+  const urls = useThumbUrls(view === 'preview' ? drawn : painted, frame, tilesAt);
 
   // Auto-scroll & focus tree sidebar to the active node selected in last session
   const treeRef = useRef<HTMLElement>(null);
@@ -1540,7 +1567,39 @@ function Catalogue({ admin }: { admin: boolean }) {
     return () => {
       alive = false;
     };
-  }, [view, listed, wall.ref]);
+    // `up` is in the list for the frame the studio hands back: it is the one that
+    // moves when the shelf comes up on another frame, and a wall standing where it
+    // already was is a wall that would not follow it.
+  }, [view, listed, wall.ref, up]);
+
+  // This screen's own comings and goings: it never unmounts, so `here` is the
+  // only sign of the shelf being the screen up again (see `here` above).
+  useEffect(() => {
+    const onPop = () => setHere(window.location.pathname.startsWith('/library'));
+    window.addEventListener('popstate', onPop);
+    return () => window.removeEventListener('popstate', onPop);
+  }, []);
+
+  // Coming back from the studio, the shelf opens on the frame the studio was
+  // holding rather than on wherever the tree was left — that frame is the one the
+  // reader has just been working on. Both views are sent to it: the strip centres
+  // it and the wall, if that is the view up, scrolls to its card. It may also sit
+  // in another folder of the same tree (a frame id and a tree key are spelled the
+  // same way), and a frame the open node cannot list is a frame the shelf cannot
+  // raise at all, so the folder goes with it.
+  const wasHere = useRef(here);
+  useEffect(() => {
+    const came = here && !wasHere.current;
+    wasHere.current = here;
+    if (!came) return;
+    const last = recall(LAST_KEY);
+    if (!last) return;
+    setUp(last);
+    scrolledFrameRef.current = null;
+    centredRef.current = last;
+    const dir = last.slice(0, last.lastIndexOf('/'));
+    if (dir && nodes.some((n) => n.key === dir)) setNode(dir);
+  }, [here, nodes]);
 
   // The way back, and the way in: the frame the wall is standing on is the card
   // nearest the middle of its viewport — the same card the reader's eye is on.
@@ -2881,7 +2940,7 @@ function cacheObjectUrl(id: string, blob: Blob): string {
   return url;
 }
 
-function useThumbUrls(photos: LibraryPhoto[], also?: LibraryPhoto | null): Record<string, string> {
+function useThumbUrls(photos: LibraryPhoto[], also?: LibraryPhoto | null, stamp?: number): Record<string, string> {
   const list = useMemo(() => (also && !photos.some((p) => p.id === also.id) ? [...photos, also] : photos), [photos, also]);
 
   const [urls, setUrls] = useState<Record<string, string>>(() => {
@@ -2920,23 +2979,42 @@ function useThumbUrls(photos: LibraryPhoto[], also?: LibraryPhoto | null): Recor
     // The tile is `makeThumb`'s business: the store first, the backup behind it,
     // and only then the file — a RAW's own preview, or a decode. A frame the disk
     // will not hand over is a frame with no tile rather than a strip that stops.
+    //
+    // Every tile is drawn the moment it lands, and the file is worked a couple of
+    // frames at a time with the thread handed back between them. Waiting for the
+    // whole shelf and painting once at the end is a screen that shows nothing for
+    // seconds and answers nothing while it waits; this way the frames come in one
+    // after another and a click during the fill still lands.
     void getPhotoThumbs(idsToFetch).then(async (thumbMap) => {
-      const updates: Record<string, string> = {};
+      const landed: Record<string, string> = {};
       for (const photo of list) {
-        if (!alive) return;
         const kept = thumbMap.get(photo.id) ?? photo.thumb ?? null;
-        const blob = kept ?? (photo.handle ? await makeThumb(photo) : null);
+        if (kept) landed[photo.id] = cacheObjectUrl(photo.id, kept);
-        if (blob) updates[photo.id] = cacheObjectUrl(photo.id, blob);
       }
-      if (alive && Object.keys(updates).length > 0) {
+      if (alive && Object.keys(landed).length > 0) {
-        setUrls((prev) => ({ ...prev, ...updates }));
+        setUrls((prev) => ({ ...prev, ...landed }));
       }
+
+      const queue = list.filter((p) => !(p.id in landed) && p.handle);
+      await Promise.all(
+        Array.from({ length: Math.min(WALL_LANES, queue.length) }, async () => {
+          while (alive && queue.length) {
+            const photo = queue.shift()!;
+            const blob = await makeThumb(photo);
+            if (!alive) return;
+            if (blob) setUrls((prev) => ({ ...prev, [photo.id]: cacheObjectUrl(photo.id, blob) }));
+            await breathe();
+          }
+        })
+      );
     });
 
     return () => {
       alive = false;
     };
-  }, [list]);
+    // `stamp` is a tile rewritten under this row: the list is the same one, and
+    // what has to happen again is the read of the store.
+  }, [list, stamp]);
 
   return urls;
 }

docker/frontend/src/engine/library.ts

@@ -1840,11 +1840,24 @@ export async function getPhotoThumb(id: string): Promise<Blob | null> {
   return null;
 }
 
+// Whoever is drawing a tile out of what the store holds (`Library.tsx`) is told
+// about a tile rewritten under it: the URL it has is a copy of the old blob, and
+// the write hands over the new one, so the row is redrawn without a second read.
+const thumbListeners = new Set<(id: string, blob: Blob) => void>();
+
+export function onThumbWritten(listener: (id: string, blob: Blob) => void): () => void {
+  thumbListeners.add(listener);
+  return () => {
+    thumbListeners.delete(listener);
+  };
+}
+
 // A tile made because someone looked at the frame, kept where the next visit
 // will find it: the decode is paid once per frame, on the visit that first drew
 // it, and the reads after that are the same reads a scanned tile would have had.
 export async function putPhotoThumb(id: string, blob: Blob): Promise<void> {
   cacheThumb(id, blob);
+  for (const listener of thumbListeners) listener(id, blob);
   try {
     const db = await openDb();
     if (!db.objectStoreNames.contains(THUMBS)) return;
@@ -1930,23 +1943,19 @@ export async function getPhotoThumbs(ids: string[]): Promise<Map<string, Blob>>
 // stutter, and it bought nothing: the wall mints the frames in view itself.
 const THUMB_LANES = 2;
 
-// The breath between frames. The idle queue where the browser has one — the tile
+// The breath between frames: the thread handed back so the page repaints and a
-// then waits for a gap rather than making one — and a plain macrotask otherwise;
+// click still lands while the shelves fill in. This used to be the idle queue, and
-// the timeout is there because an idle queue on a busy page can stay empty.
+// that is what broke it — on a page somebody is using, an idle callback is parked
+// for its whole timeout, so every tile cost 120ms of nothing and the tiles looked
+// like they never came. `scheduler.yield` hands the thread over and comes straight
+// back; a macrotask is the same thing where there is no such call.
 //
-// ponytail: the walk's own scan is not paced from here and does not stop for a
+// ponytail: `THUMB_LANES` jobs share one budget — the thread is handed over after
-// tile; the two share the thread when a folder is opened mid-read. One budget for
+// a tile, not on a clock. Pace by elapsed time if a folder of RAW ever wants it.
-// both is the next step if a scan ever runs visibly slower beside a tile job.
+export function breathe(): Promise<void> {
-function breathe(): Promise<void> {
+  const s = (globalThis as { scheduler?: { yield?: () => Promise<void> } }).scheduler;
-  return new Promise((resolve) => {
+  if (s?.yield) return s.yield();
-    const idle = (
+  return new Promise((resolve) => setTimeout(resolve, 0));
-      globalThis as {
-        requestIdleCallback?: (cb: () => void, opts?: { timeout: number }) => number;
-      }
-    ).requestIdleCallback;
-    if (idle) idle(() => resolve(), { timeout: 120 });
-    else setTimeout(resolve, 0);
-  });
 }
 
 // One frame's tile, in flight. The wall scrolls to a frame and asks for its tile

docker/frontend/src/ui/ImageStage.tsx

@@ -288,6 +288,7 @@ export function ImageStage({
   dims = null,
   shotSpecs = null,
   place = null,
+  photoName = null,
   frameId = 'none',
   framePanX = 0,
   onFramePanXChange,
@@ -384,6 +385,9 @@ export function ImageStage({
   dims?: { w: number; h: number } | null;
   shotSpecs?: ShotSpecs | null;
   place?: string | null;
+  // The file the stage is holding, as the disk named it: the row under the photo
+  // is where a reader checks that the frame they meant to open is the one open.
+  photoName?: string | null;
   frameId?: FrameId;
   framePanX?: number;
   onFramePanXChange?: (panX: number) => void;
@@ -1998,9 +2002,14 @@ export function ImageStage({
 
       {previewUrl ? (
         <>
-          {shotSpecs || place || dims ? (
+          {shotSpecs || place || dims || photoName ? (
             <div className="photo-meta-bar" data-key="photo-meta-bar">
               {specsLine(shotSpecs ?? null, place, dims)}
+              {photoName ? (
+                <span className="photo-meta-name" data-key="photo-name">
+                  {photoName}
+                </span>
+              ) : null}
             </div>
           ) : null}
           <div className="toolbar">