From 9e52dc03556e9fb33150c450b7fed2ea7ead6b64 Mon Sep 17 00:00:00 2001
From: Greg Pomerantz <gmp@wow.st>
Date: Mon, 2 Nov 2026 00:02:48 -0500
Subject: [PATCH] gtauri: MediaStore fast path + js-ready handshake +
 virtualized grid
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- MediaStore fast path: Kotlin's ContentObserver queries MediaStore
  for images added in the last 120s and writes path|added|size lines
  to .ms_recent, then wakes Rust via the proven zero-arg
  nativeFsChange() JNI. Rust upserts those rows and emits
  immediately — a camera photo appears in ~1s without waiting for
  the ~10s FUSE re-read of a 10,000-file directory. (Direct
  Kotlin->Rust JNI string passing and Rust->Java calls crash under
  the emulator's x86_64->arm64 native bridge; file handoff plus
  zero-arg JNI is the only reliable channel.)
- js-ready handshake: the first gallery-files emit fires ~30 ms
  after process start, before the WebView's JS exists (Tauri events
  are fire-and-forget, so it was lost). JS now signals
  'gtauri-js-ready'; Rust re-emits the current state.
- Virtualized grid: the document is ONE spacer (full scroll height)
  plus ONE band of recycled cells pinned by transform — ~80 DOM
  nodes total for a 10,000-photo library. Launch cost no longer
  scales with library size; the first screen renders as soon as
  the WebView boots and the first thumbs arrive.
- 'Missing photos' report resolved: the full walk of the 9,961-file
  Camera dir enumerates exactly 8,438 images with no guard firing;
  the difference is videos, which a photo gallery correctly
  excludes.
---
 harnesses/gtauri/frontend/dist/index.html     | 296 ++++++++++--------
 .../android/app/src/main/AndroidManifest.xml  |   3 +
 .../main/java/wow/gmp/gallery/MainActivity.kt |  87 +++++
 harnesses/gtauri/src/db.rs                    |  42 +++
 harnesses/gtauri/src/lib.rs                   | 109 ++++++-
 harnesses/gtauri/src/scan.rs                  |  46 ++-
 6 files changed, 449 insertions(+), 134 deletions(-)

diff --git a/harnesses/gtauri/frontend/dist/index.html b/harnesses/gtauri/frontend/dist/index.html
index 52ea4a8..e54f0f3 100644
--- a/harnesses/gtauri/frontend/dist/index.html
+++ b/harnesses/gtauri/frontend/dist/index.html
@@ -5,9 +5,17 @@
 <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
 <title>Gallery</title>
 <style>
-  /* Chromium owns: layout, compositor-driven scroll, lazy fetch+decode,
-     image cache/eviction, viewer compositing. Rust owns: scan, SQLite,
-     on-disk thumbnail cache behind gallery://. */
+  /* Chromium owns: layout, compositor-driven scroll, image cache,
+     viewer compositing. Rust owns: scan, SQLite, thumbnail decode and
+     the on-disk cache behind gallery://. */
+  /*
+     VIRTUALIZED GRID
+     The document contains ONE spacer div (full scroll height) and ONE
+     band of recycled cells (~2.5 screens + buffer). Total DOM nodes:
+     ~80 for a 10,000-photo library — layout cost is independent of
+     library size, so launch renders the first screen as soon as the
+     WebView boots + the first thumbnails arrive.
+  */
   html, body {
     margin: 0; padding: 0;
     background: #0a0a0c;
@@ -24,19 +32,22 @@
     z-index: 10;
   }
 
-  #grid {
+  #grid { position: relative; }
+  #spacer { /* scroll length driver — no content */ }
+
+  #band {
+    position: absolute; left: 0; right: 0; top: 0;
     display: grid;
     grid-template-columns: repeat(3, 1fr);
     gap: 4px;
     padding: 4px;
+    will-change: transform; /* compositor-positioned, zero layout */
   }
   .cell {
-    aspect-ratio: 1 / 1;
     overflow: hidden;
     background: #1c1c22;
     border-radius: 2px;
   }
-  /* explicit 1:1 box via aspect-ratio → zero layout shift on arrival */
   .cell img {
     width: 100%; height: 100%;
     object-fit: cover;
@@ -79,7 +90,10 @@
 </head>
 <body>
 <div id="status"><span id="stext">starting…</span></div>
-<div id="grid"></div>
+<div id="grid">
+  <div id="spacer"></div>
+  <div id="band"></div>
+</div>
 <div id="viewer">
   <div id="vload"></div>
   <img id="vimg" alt="">
@@ -89,143 +103,174 @@
 "use strict";
 
 const grid = document.getElementById("grid");
+const spacer = document.getElementById("spacer");
+const band = document.getElementById("band");
 const stext = document.getElementById("stext");
 const viewer = document.getElementById("viewer");
 const vimg = document.getElementById("vimg");
 const vload = document.getElementById("vload");
 
-let total = 0, loaded = 0, lastSig = "", scanning = false;
-const imgById = new Map(); // id -> <img> (for thumb-ready re-requests)
+const COLS = 3, GAP = 4, PAD = 4, BUFFER_ROWS = 12;
+
+let ids = [];          // display order (mtime desc)
+let total = 0, scanning = false, lastSig = "";
+let cellW = 0, rowH = 0, rows = 0;
+const loadedSet = new Set(); // ids whose real thumb has rendered
+const imgById = new Map();   // id -> <img> currently bound in the band
+const pool = [];             // recycled .cell elements (band children)
 
 function statusLine() {
   stext.textContent = total + " photos" +
     (scanning ? " • scanning…" : "") +
-    (loaded < total ? " (" + loaded + ")" : "");
+    (loadedSet.size < total ? " (" + loadedSet.size + ")" : "");
 }
 
-let lastIds = [];
-function rebuild(ids, isScanning, found) {
-  const sig = ids.length + ":" + (ids[0] ?? 0) + ":" + (ids[ids.length - 1] ?? 0);
-  if (sig === lastSig && scanning === isScanning) return;
-  lastSig = sig;
-  scanning = isScanning;
-  total = ids.length; loaded = 0;
-  // Live rescan (a photo just landed) inserts at the top and would
-  // shift everything — pin the viewport to the cell that was on top.
-  let keepId = null;
-  if (lastIds.length > 0 && rowH > 0) {
-    const topIdx = Math.min(lastIds.length - 1, Math.floor(window.scrollY / rowH) * 3);
-    keepId = lastIds[topIdx];
-  }
-  grid.replaceChildren();
-  imgById.clear();
-  const frag = document.createDocumentFragment();
-  for (const id of ids) {
+/* ---------------- layout metrics (uniform 3-col squares) ------------- */
+function layoutMetrics() {
+  const w = grid.clientWidth || innerWidth;
+  cellW = Math.floor((w - PAD * 2 - GAP * (COLS - 1)) / COLS);
+  if (cellW < 10) cellW = 10;
+  rowH = cellW + GAP;
+  rows = Math.ceil(total / COLS);
+  for (const c of pool) c.style.height = cellW + "px";
+  spacer.style.height = (rows * rowH - (rows ? GAP : 0) + PAD * 2) + "px";
+}
+
+/* ---------------- band recycling -------------------------------------- */
+function cellAt(i) { // create pool cells on demand
+  while (pool.length <= i) {
     const c = document.createElement("div");
     c.className = "cell";
     const im = new Image();
-    im.loading = "lazy";
     im.decoding = "async";
-    im.dataset.url = "http://gallery.localhost/thumb/" + id;
-    im.__ph = false, im.__retry = 0, im.__lazy = true;
-    im.src = im.dataset.url;
-    imgById.set(id, im);
+    im.__retry = 0;
     im.addEventListener("load", () => {
-      // naturalWidth 1 => the Rust placeholder, not a real thumb
-      if (im.naturalWidth > 2) { loaded++; statusLine(); }
-      else if (im.__retry < 4) {
+      // im.__id = the id this img was last requested for (a stale
+      // load event from a previous assignment must not be credited
+      // to the recycled cell's new id).
+      const id = im.__id;
+      if (im.naturalWidth > 2) {
+        if (id !== undefined && !loadedSet.has(id)) { loadedSet.add(id); statusLine(); }
+      } else if (im.__retry < 4) {
         im.__retry++;
-        jlog("js ph-load id=" + id + " retry=" + im.__retry);
-        // safety net in case thumb-ready was lost (page rebuild race)
-        setTimeout(() => {
-          if (!im.complete || im.naturalWidth <= 2) {
-            // Skip cells far outside the viewport — a fast scroll pass
-            // leaves hundreds of cold cells behind; re-requesting them
-            // all would flood the queue with junk the user cannot see.
-            const r = im.getBoundingClientRect();
-            if (r.bottom < -innerHeight || r.top > 2 * innerHeight) return;
-            jlog("js retry id=" + id + " v=" + im.__retry);
-            im.src = im.dataset.url + "?v=" + im.__retry;
-          }
-        }, 1500);
+        // Cold cell: Rust served the 1x1 placeholder and queued the
+        // decode. Only bother re-requesting if the cell is still in
+        // (or near) the band — far cells will be re-requested when they
+        // cycle in, or via the thumb-ready event.
+        const r = im.getBoundingClientRect();
+        if (r.bottom < -2 * innerHeight || r.top > 3 * innerHeight) return;
+        jlog("js retry id=" + id + " v=" + im.__retry);
+        im.src = "http://gallery.localhost/thumb/" + id + "?v=" + im.__retry;
       }
     });
-    im.addEventListener("click", () => openViewer(id));
+    im.addEventListener("click", () => {
+      const id = +c.dataset.id;
+      if (id) openViewer(id);
+    });
     c.appendChild(im);
-    frag.appendChild(c);
+    band.appendChild(c);
+    pool.push(c);
   }
-  grid.appendChild(frag);
-  lastIds = ids.slice();
+  return pool[i];
+}
+
+let bandDirty = true;
+function markBand() { bandDirty = true; }
+
+function updateBand() {
+  if (total === 0 || rowH === 0) return;
+  const y = window.scrollY;
+  const r0 = Math.max(0, Math.floor(y / rowH) - BUFFER_ROWS);
+  const r1 = Math.min(rows, Math.ceil((y + innerHeight) / rowH) + BUFFER_ROWS);
+  const i0 = r0 * COLS, i1 = r1 * COLS;
+  band.style.transform = "translateY(" + (r0 * rowH) + "px)";
+  const need = i1 - i0;
+  while (pool.length < need) cellAt(pool.length);
+  for (let s = 0; s < pool.length; s++) {
+    const c = pool[s];
+    if (s >= need) { c.style.display = "none"; continue; }
+    const idx = i0 + s;
+    const id = ids[idx];
+    if (id === undefined) { c.style.display = "none"; continue; }
+    c.style.display = "";
+    if (+c.dataset.idx !== idx) {
+      c.dataset.idx = idx;
+      c.dataset.id = id;
+      const im = c.firstElementChild;
+      im.__retry = 0;
+      im.__id = id;
+      // swap tracking: this id is now bound to this img
+      const old = +c.dataset.idold || 0;
+      if (old && imgById.get(old) === im) imgById.delete(old);
+      c.dataset.idold = id;
+      imgById.set(id, im);
+      im.src = "http://gallery.localhost/thumb/" + id;
+    }
+  }
+}
+
+function bandLoop() {
+  if (bandDirty) { bandDirty = false; updateBand(); }
+  requestAnimationFrame(bandLoop);
+}
+requestAnimationFrame(bandLoop);
+addEventListener("scroll", () => {
+  markBand();
+  sendAnchor(false);
+}, { passive: true });
+addEventListener("resize", () => { layoutMetrics(); markBand(); });
+
+/* -------- rebuild (initial list + live rescan) ------------------------ */
+function rebuild(newIds, isScanning, found) {
+  const sig = newIds.length + ":" + (newIds[0] ?? 0) + ":" + (newIds[newIds.length - 1] ?? 0);
+  if (sig === lastSig && scanning === isScanning) return;
+  // pin the viewport: the cell currently on top keeps its screen slot
+  const keepId = (ids.length > 0 && rowH > 0)
+    ? ids[Math.min(ids.length - 1, Math.floor(window.scrollY / rowH) * COLS)]
+    : null;
+  ids = newIds;
+  lastSig = sig;
+  scanning = isScanning;
+  total = ids.length;
+  layoutMetrics();
+  bandDirty = true;
   statusLine();
-  eagerBand();
-  if (keepId !== null) {
+  if (keepId !== null && !scanning) {
     const i = ids.indexOf(keepId);
     if (i >= 0) {
-      requestAnimationFrame(() => scrollTo(0, Math.floor(i / 3) * rowH));
+      requestAnimationFrame(() => scrollTo(0, PAD + Math.floor(i / COLS) * rowH));
     }
   }
 }
 
 /* -------- scroll anchor for Rust-side thumbnail prefetch --------------
-   Tell Rust where the viewport is (throttled to ~7 Hz); the Rust worker
-   pre-decodes the rows ahead of us so fast scrolls hit a warm cache. */
-let rowH = 0, lastAnchor = 0, anchorSent = false, anchorTrail = null;
+   `a` = index of the first visible grid cell. Rust pre-decodes rows
+   ahead of the viewport so fast scrolls hit a warm mem cache. */
+let lastAnchor = 0, anchorTrail = null;
 function sendAnchor(force) {
   const now = performance.now();
   if (!force && now - lastAnchor < 150) {
-    // Throttled tick: schedule a TRAILING send so the final scroll
-    // position is never left unreported (a stale anchor makes Rust
-    // drop fresh urgent work as "off-screen").
     if (!anchorTrail) {
-      anchorTrail = setTimeout(() => {
-        anchorTrail = null;
-        sendAnchor(true);
-      }, 160);
+      anchorTrail = setTimeout(() => { anchorTrail = null; sendAnchor(true); }, 160);
     }
     return;
   }
   lastAnchor = now;
-  if (rowH === 0) {
-    const c = grid.querySelector(".cell");
-    if (c) rowH = c.getBoundingClientRect().height + 4; // + grid gap
-  }
-  if (rowH > 0) {
-    const a = Math.floor(window.scrollY / rowH) * 3;
-    anchorSent = true;
+  if (rowH > 0 && total > 0) {
+    const a = Math.min(total - 1, Math.floor(window.scrollY / rowH) * COLS);
     try {
-      window.__TAURI__.event.emit("gtauri-scroll", { a: a });
-      window.__TAURI__.event.emit("gtauri-log", "js anchor a=" + a + " y=" + Math.round(window.scrollY));
+      window.__TAURI__.event.emit("gtauri-scroll", { a: Math.max(0, a) });
+      window.__TAURI__.event.emit("gtauri-log", "js anchor a=" + Math.max(0, a) + " y=" + Math.round(window.scrollY));
     } catch (e) {}
-    eagerBand();
   }
 }
-
-/* Force the visible band + next screen to load NOW (bypass Chromium's
-   lazy-loader intersection delay after a fast jump). Far cells stay lazy. */
-function eagerBand() {
-  if (rowH === 0) return;
-  const i0 = Math.max(0, Math.floor((window.scrollY - innerHeight) / rowH) * 3 - 3);
-  const i1 = Math.min(total, Math.ceil((window.scrollY + 2.2 * innerHeight) / rowH) * 3 + 3);
-  const kids = grid.children;
-  let forced = 0;
-  for (let i = i0; i < i1; i++) {
-    const im = kids[i] && kids[i].firstElementChild;
-    if (im && !im.complete) {
-      im.loading = "eager";
-      if (im.__lazy) { im.__lazy = false; forced++; }
-    }
-  }
-  if (forced > 0) jlog("js eager forced=" + forced + " range=[" + i0 + "," + i1 + "]");
-}
 function jlog(s) {
   try { window.__TAURI__.event.emit("gtauri-log", s); } catch (e) {}
 }
-addEventListener("scroll", () => sendAnchor(false), { passive: true });
 
 try {
   window.__TAURI__.event.listen("gallery-files", (e) => {
     let p = e.payload || {};
-    // On Android the payload can arrive as a JSON *string* — decode it.
     if (typeof p === "string") {
       try { p = JSON.parse(p); } catch (err) { jlog("files parse err: " + err); }
     }
@@ -235,10 +280,13 @@ try {
   });
   // first anchor (top of grid) — Rust also warms 0..36 on its side.
   setTimeout(() => sendAnchor(true), 300);
-  // Cold-miss round-trip: Rust served a 1x1 placeholder and queued the real
-  // decode off the main thread; when it lands, re-request (now a mem hit).
-  // Event payloads arrive as JSON strings on Android (object on some
-  // WebView builds) — normalize both.
+  // READY HANDSHAKE: the initial gallery-files emit can fire before this
+  // page's JS has loaded (small/fast DBs) and be lost (Tauri events are
+  // fire-and-forget). Tell Rust we're listening; it re-emits the state.
+  try { window.__TAURI__.event.emit("gtauri-js-ready"); } catch (e) {}
+  // Rust served a 1x1 placeholder and finished the decode off-main:
+  // re-request (now a mem hit). Payloads arrive as JSON strings on some
+  // WebView builds — normalize both.
   const pid = (e) => {
     const p = e.payload;
     return (typeof p === "string" ? JSON.parse(p) : p) || {};
@@ -246,13 +294,11 @@ try {
   window.__TAURI__.event.listen("thumb-ready", (e) => {
     const id = pid(e).id;
     const im = imgById.get(id);
-    if (!im) return;
-    if (im.naturalWidth <= 2) {
+    if (im && im.naturalWidth <= 2) {
       jlog("js ready id=" + id + " v=" + (im.__retry + 1));
-      im.src = im.dataset.url + "?v=" + (++im.__retry);
+      im.src = "http://gallery.localhost/thumb/" + id + "?v=" + (++im.__retry);
     }
   });
-  // Full-res read finished (worker thread) — re-request; now a mem hit.
   window.__TAURI__.event.listen("full-ready", (e) => {
     const id = pid(e).id;
     if (viewerId === id && !vFullDone) {
@@ -260,14 +306,11 @@ try {
       tryShow(id, "http://gallery.localhost/full/" + id + "?v=f" + (++vFullSeq), true);
     }
   });
-  // Android back: registering ANY "back-button" listener makes Tauri route
-  // the press here instead of finishing the activity (see AppPlugin.kt).
+  // Android back: registering ANY "back-button" listener makes Tauri
+  // route the press here instead of finishing the activity.
   window.__TAURI__.app.onBackButtonPress(() => {
-    if (viewer.classList.contains("open")) {
-      closeViewer();
-    } else {
-      window.__TAURI__.app.exit(0);
-    }
+    if (viewer.classList.contains("open")) closeViewer();
+    else window.__TAURI__.app.exit(0);
   });
 } catch (err) { stext.textContent = "no tauri bridge: " + err; }
 
@@ -275,7 +318,7 @@ try {
 let frLast = performance.now(), frLines = 0, frBatch = [];
 function frFlush() {
   if (frBatch.length === 0) return;
-  frBatch.push("IMG t=" + frLast.toFixed(1) + " loaded=" + loaded + "/" + total +
+  frBatch.push("IMG t=" + frLast.toFixed(1) + " loaded=" + loadedSet.size + "/" + total +
                " scrollY=" + Math.round(window.scrollY));
   const payload = frBatch.join("\n") + "\n";
   frBatch = [];
@@ -301,10 +344,8 @@ function fitScale() {
 }
 
 function vApply() {
-  // Clamp: never zoom out past fit, and pan is limited to the image
-  // edges — the image can never be dragged off-screen leaving blank
-  // space around it. On a letterboxed axis (image smaller than the
-  // viewport in that dimension) panning is locked to centered.
+  // Clamp: never zoom out past fit; pan limited to image edges — no
+  // blank space around the image, letterboxed axes stay centered.
   const s = fitScale();
   if (vScale < s) vScale = s;
   const mx = Math.max(0, (base.w * vScale - innerWidth) / 2);
@@ -327,13 +368,13 @@ function fitViewer(w, h) {
   vApply();
 }
 
-/// Fetch url and, if it is REAL image bytes (not the 1x1 placeholder),
-/// promote it into the viewer.
+/// Fetch url; promote to the viewer only if REAL image bytes (not the
+/// 1x1 placeholder).
 function tryShow(id, url, isFull) {
   const im = new Image();
   im.addEventListener("load", () => {
     if (viewerId !== id) return;
-    if (im.naturalWidth <= 2) return; // placeholder — wait for the ready event
+    if (im.naturalWidth <= 2) return;
     vimg.src = im.src;
     fitViewer(im.naturalWidth, im.naturalHeight);
     if (isFull) {
@@ -350,11 +391,10 @@ function openViewer(id) {
   vScale = 1; vTx = 0; vTy = 0;
   vload.textContent = "loading…";
   vimg.style.visibility = "hidden";
-  // 1) INSTANT: the grid thumb (served from the Rust mem cache, ~1 ms).
-  //    Same aspect ratio as the full image — the fit stays valid.
+  // 1) INSTANT: the grid thumb (Rust mem cache, ~1 ms).
   tryShow(id, "http://gallery.localhost/thumb/" + id, false);
-  // 2) Full-res: Rust reads the file OFF the main thread; the first
-  //    request gets the placeholder, `full-ready` triggers the swap.
+  // 2) Full-res: Rust reads the file OFF the main thread; first request
+  //    gets the placeholder, `full-ready` triggers the swap.
   tryShow(id, "http://gallery.localhost/full/" + id, true);
   // 3) Safety net in case the ready event is ever lost.
   if (vFullTimer) clearInterval(vFullTimer);
@@ -365,7 +405,6 @@ function openViewer(id) {
     }
     if (++vFullSeq > 10) {
       if (vFullTimer) { clearInterval(vFullTimer); vFullTimer = null; }
-      // Corrupt/unreadable file: stop saying "loading…" forever.
       if (viewerId === id && vimg.naturalWidth <= 2) {
         vload.textContent = "image unavailable";
       }
@@ -386,8 +425,8 @@ function closeViewer() {
 document.getElementById("vclose").addEventListener("click", closeViewer);
 addEventListener("keydown", (e) => { if (e.key === "Escape") closeViewer(); });
 
-/* pointer-based pan + pinch (touch-action:none on #viewer keeps the browser
-   from stealing the gesture) */
+/* pointer-based pan + pinch (touch-action:none keeps the browser from
+   stealing the gesture) */
 const pts = new Map();
 let pinchMid = { x: 0, y: 0 }, pinchDist = 0;
 viewer.addEventListener("pointerdown", (e) => {
@@ -415,8 +454,7 @@ viewer.addEventListener("pointermove", (e) => {
     // The image follows the hand (midpoint drift)...
     vTx += m.x - pinchMid.x;
     vTy += m.y - pinchMid.y;
-    // ...and zooms ABOUT the midpoint: the image point under the
-    // midpoint stays put while the scale changes.
+    // ...and zooms ABOUT the midpoint.
     if (pinchDist > 0 && d > 0) {
       const ratio = d / pinchDist;
       const cx = innerWidth / 2 + vTx, cy = innerHeight / 2 + vTy;
@@ -426,7 +464,7 @@ viewer.addEventListener("pointermove", (e) => {
     }
     pinchMid = m;
     pinchDist = d;
-    vApply(); // also re-clamps (fit min, image-edge pan limits)
+    vApply();
   }
 });
 const endPt = (e) => { pts.delete(e.pointerId); };
diff --git a/harnesses/gtauri/gen/android/app/src/main/AndroidManifest.xml b/harnesses/gtauri/gen/android/app/src/main/AndroidManifest.xml
index 6c5d382..24f1415 100644
--- a/harnesses/gtauri/gen/android/app/src/main/AndroidManifest.xml
+++ b/harnesses/gtauri/gen/android/app/src/main/AndroidManifest.xml
@@ -4,6 +4,9 @@
     <!-- all-files access: the app scans /sdcard/Pictures + /sdcard/DCIM directly
          (same grant the egui gallery already holds for this package). -->
     <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
+    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"
+                     android:maxSdkVersion="32" />
+    <uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />
 
     <!-- AndroidTV support -->
     <uses-feature android:name="android.software.leanback" android:required="false" />
diff --git a/harnesses/gtauri/gen/android/app/src/main/java/wow/gmp/gallery/MainActivity.kt b/harnesses/gtauri/gen/android/app/src/main/java/wow/gmp/gallery/MainActivity.kt
index 44547eb..5bb1178 100644
--- a/harnesses/gtauri/gen/android/app/src/main/java/wow/gmp/gallery/MainActivity.kt
+++ b/harnesses/gtauri/gen/android/app/src/main/java/wow/gmp/gallery/MainActivity.kt
@@ -8,15 +8,96 @@ import android.os.Handler
 import android.os.Looper
 import android.provider.MediaStore
 import androidx.activity.enableEdgeToEdge
+import java.util.concurrent.Executors
 
 class MainActivity : TauriActivity() {
   private var observer: ContentObserver? = null
 
+  // MediaStore fast path: when the OS reports a media change (or right
+  // after startup), query MediaStore on a background thread for images
+  // indexed in the last ~2 min and push them to Rust via JNI. This is
+  // what makes a just-taken camera photo appear in ~1 s instead of
+  // waiting for the ~10 s FUSE re-read of a huge directory.
+  private val fsExecutor = Executors.newSingleThreadExecutor()
+  private val mainHandler = Handler(Looper.getMainLooper())
+  private var fsScheduled = false
+
   // Rust side (this app's JNI library, loaded by TauriActivity): wakes
   // the file-watcher thread. One JNI call + one channel send — nothing
   // heavy ever runs on the main thread.
   external fun nativeFsChange()
 
+  // Rust side reads the payload file (getExternalFilesDir/.ms_recent)
+  // when nativeFsChange wakes it. No string crosses JNI.
+
+  /** Query MediaStore for recently-indexed images and push to Rust. */
+  private fun pushRecent() {
+    try {
+      val since = System.currentTimeMillis() / 1000 - 120
+      val sb = StringBuilder()
+      val rows = contentResolver.query(
+        MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
+        arrayOf(
+          MediaStore.Images.Media.DATA,
+          MediaStore.Images.Media.RELATIVE_PATH,
+          MediaStore.Images.Media.SIZE,
+          MediaStore.Images.Media.DATE_ADDED
+        ),
+        "${MediaStore.Images.Media.DATE_ADDED} >= ?",
+        arrayOf(since.toString()),
+        "${MediaStore.Images.Media.DATE_ADDED} DESC"
+      )
+      if (rows == null) {
+        android.util.Log.w("gallery-ms", "MediaStore query returned null (permission?)")
+        return
+      }
+      rows.use { c ->
+        val iData = c.getColumnIndexOrThrow(MediaStore.Images.Media.DATA)
+        val iRel = c.getColumnIndex(MediaStore.Images.Media.RELATIVE_PATH)
+        val iSize = c.getColumnIndexOrThrow(MediaStore.Images.Media.SIZE)
+        val iAdded = c.getColumnIndexOrThrow(MediaStore.Images.Media.DATE_ADDED)
+        while (c.moveToNext()) {
+          var data = c.getString(iData)
+          if (data.isNullOrEmpty() && iRel >= 0) {
+            val rel = c.getString(iRel) ?: continue
+            data = "/storage/emulated/0/" + rel
+          }
+          if (data.isNullOrEmpty()) continue
+          sb.append(data).append('|')
+            .append(c.getLong(iAdded)).append('|')
+            .append(c.getLong(iSize)).append('\n')
+        }
+      }
+      android.util.Log.i("gallery-ms", "pushRecent rows=" + sb.length)
+      if (sb.isNotEmpty()) {
+        // Hand the payload to Rust via a file (robust under the native
+        // bridge; the JNI call stays the proven zero-arg wake).
+        val dir = getExternalFilesDir(null) ?: return
+        val tmp = java.io.File(dir, ".ms_recent.tmp")
+        val fin = java.io.File(dir, ".ms_recent")
+        tmp.writeText(sb.toString())
+        if (!tmp.renameTo(fin)) {
+          tmp.copyTo(fin, overwrite = true)
+          tmp.delete()
+        }
+        nativeFsChange()
+      }
+    } catch (e: Exception) {
+      android.util.Log.w("gallery-ms", "pushRecent failed: " + e)
+    }
+  }
+
+  /** Debounced (800 ms, main thread) schedule of pushRecent on the
+   *  background executor — the observer can fire in bursts. */
+  private fun scheduleFsPush() {
+    if (fsScheduled) return
+    fsScheduled = true
+    mainHandler.postDelayed({
+      fsScheduled = false
+      fsExecutor.execute { pushRecent() }
+    }, 800)
+  }
+
   override fun onCreate(savedInstanceState: Bundle?) {
     enableEdgeToEdge()
     super.onCreate(savedInstanceState)
@@ -27,6 +108,7 @@ class MainActivity : TauriActivity() {
     val obs = object : ContentObserver(Handler(Looper.getMainLooper())) {
       override fun onChange(selfChange: Boolean, uri: Uri?) {
         nativeFsChange()
+        scheduleFsPush()
       }
     }
     observer = obs
@@ -35,10 +117,15 @@ class MainActivity : TauriActivity() {
     contentResolver.registerContentObserver(
       MediaStore.Images.Media.EXTERNAL_CONTENT_URI, true, obs
     )
+    // Startup fast path: if the app was killed after a photo was taken,
+    // the observer won't fire — push once after the media scanner has
+    // had a moment to index anything recent.
+    mainHandler.postDelayed({ scheduleFsPush() }, 1500)
   }
 
   override fun onDestroy() {
     observer?.let { contentResolver.unregisterContentObserver(it) }
+    fsExecutor.shutdownNow()
     super.onDestroy()
   }
 }
diff --git a/harnesses/gtauri/src/db.rs b/harnesses/gtauri/src/db.rs
index f249cee..f7a3a10 100644
--- a/harnesses/gtauri/src/db.rs
+++ b/harnesses/gtauri/src/db.rs
@@ -193,6 +193,48 @@ pub fn apply(
     Ok((inserted, updated, deleted))
 }
 
+/// Upsert entries: insert new, update changed — NEVER deletes (the full
+/// FS rescan owns deletions). Used by the MediaStore fast path, which
+/// only ever ADDS recently-indexed files.
+pub fn upsert(
+    conn: &mut Connection,
+    entries: &[Entry],
+) -> Result<(usize, usize), rusqlite::Error> {
+    let mut inserted = 0;
+    let mut updated = 0;
+    let tx = conn.transaction()?;
+    {
+        let mut ins = tx.prepare(
+            "INSERT INTO items (path, mtime, size) VALUES (?1, ?2, ?3)",
+        )?;
+        let mut sel = tx.prepare(
+            "SELECT mtime, size FROM items WHERE path = ?1",
+        )?;
+        let mut upd = tx.prepare(
+            "UPDATE items SET mtime = ?2, size = ?3, width = NULL, height = NULL, \
+             orientation = NULL, thumb_path = NULL, date_taken = NULL WHERE path = ?1",
+        )?;
+        for e in entries {
+            let old: Option<(i64, i64)> = sel
+                .query_row(params![e.path], |r| Ok((r.get(0)?, r.get(1)?)))
+                .ok();
+            match old {
+                Some((m, s)) if m == e.mtime && s == e.size => {}
+                Some(_) => {
+                    upd.execute(params![e.path, e.mtime, e.size])?;
+                    updated += 1;
+                }
+                None => {
+                    ins.execute(params![e.path, e.mtime, e.size])?;
+                    inserted += 1;
+                }
+            }
+        }
+    }
+    tx.commit()?;
+    Ok((inserted, updated))
+}
+
 /// Number of rows in the DB.
 pub fn count(conn: &mut Connection) -> Result<i64, rusqlite::Error> {
     let n: i64 = conn.query_row("SELECT COUNT(*) FROM items", [], |r| r.get(0))?;
diff --git a/harnesses/gtauri/src/lib.rs b/harnesses/gtauri/src/lib.rs
index 045b3a9..8a86446 100644
--- a/harnesses/gtauri/src/lib.rs
+++ b/harnesses/gtauri/src/lib.rs
@@ -920,6 +920,84 @@ fn rescan_subtrees(app: &tauri::AppHandle, changed: &[PathBuf]) {
     tr(&format!("watch: incr changed={} fresh={added}", changed.len()));
 }
 
+// ---------------------------------------------------------------------
+// MediaStore fast path (Android): when the OS says the media changed,
+// query MediaStore for images indexed in the last ~2 min. One indexed
+// provider query (~50 ms) vs a ~10 s FUSE re-read of a huge directory —
+// this is what makes a just-taken camera photo appear in ~1 s.
+// ---------------------------------------------------------------------
+/// MediaStore fast path (Android): read the .ms_recent payload dropped
+/// by MainActivity and apply it. The query itself runs on Kotlin's
+/// background executor (no Rust→Java FFI, robust under the native
+/// bridge); only a zero-arg wake crosses JNI.
+#[cfg(target_os = "android")]
+fn apply_mediasotre_payload(app: &tauri::AppHandle) {
+    let path = ms_recent_path();
+    let Ok(text) = std::fs::read_to_string(&path) else { return };
+    let _ = std::fs::remove_file(&path);
+    if text.is_empty() {
+        return;
+    }
+    tr(&format!("mediastore push: {} bytes, {} lines", text.len(), text.lines().count()));
+    mediastore_apply(app, &text);
+}
+
+/// Path of the .ms_recent handoff file (external files dir — MainActivity
+/// writes it with getExternalFilesDir(null)).
+#[cfg(target_os = "android")]
+fn ms_recent_path() -> std::path::PathBuf {
+    external_files_dir().join(".ms_recent")
+}
+
+#[cfg(not(target_os = "android"))]
+fn apply_mediasotre_payload(_app: &tauri::AppHandle) {}
+
+/// MediaStore fast path (Android): apply a "path|addedSec|size" payload
+/// pushed from MainActivity (which does the MediaStore query on a
+/// background thread — no Rust→Java FFI). Upserts the rows, re-emits.
+/// Never deletes (the FS rescan owns deletions). This is what makes a
+/// just-taken camera photo appear in ~1 s instead of waiting for the
+/// ~10 s FUSE re-read of a huge directory.
+#[cfg(target_os = "android")]
+fn mediastore_apply(app: &tauri::AppHandle, text: &str) {
+    let mut entries = Vec::new();
+    for line in text.lines() {
+        let Some(path) = line.split('|').next() else { continue };
+        if path.is_empty() || !scan::is_image_path(path) {
+            continue;
+        }
+        if let Ok(md) = std::fs::metadata(path) {
+            entries.push(scan::Entry {
+                path: path.to_string(),
+                mtime: mtime_ns(&md),
+                size: md.len() as i64,
+            });
+        }
+    }
+    if entries.is_empty() {
+        return;
+    }
+    let mut conn = match db::open(&db::db_path()) {
+        Ok(c) => c,
+        Err(e) => {
+            log::warn!("mediastore db: {e}");
+            return;
+        }
+    };
+    match db::upsert(&mut conn, &entries) {
+        Ok((ins, upd)) => {
+            if ins + upd > 0 {
+                tr(&format!("mediastore fast +{ins} new, {upd} changed"));
+                if let Err(e) = load_meta(&mut conn) {
+                    log::warn!("mediastore meta: {e}");
+                }
+                emit_files(app, false, META.read().unwrap().len());
+            }
+        }
+        Err(e) => log::warn!("mediastore upsert: {e}"),
+    }
+}
+
 /// Watcher wake events.
 #[derive(Debug, Clone, Copy)]
 enum WEvent {
@@ -933,9 +1011,10 @@ enum WEvent {
 static WATCH_TX: LazyLock<Mutex<Option<mpsc::Sender<WEvent>>>> =
     LazyLock::new(|| Mutex::new(None));
 
-/// Android: called by MainActivity's ContentObserver via JNI.
-/// Signature: (JNIEnv*, jobject) for an instance method — both
-/// ignored; the symbol name is what binds.
+/// Android: called by MainActivity's ContentObserver via JNI (and after
+/// each MediaStore fast-path payload drop). Signature: (JNIEnv*,
+/// jobject) for an instance method. One channel send — nothing heavy,
+/// never blocks the main thread.
 #[cfg(target_os = "android")]
 #[no_mangle]
 pub extern "system" fn Java_wow_gmp_gallery_MainActivity_nativeFsChange(
@@ -1035,6 +1114,14 @@ fn watch_files(app: tauri::AppHandle) {
             std::thread::sleep(std::time::Duration::from_millis(600));
             while rx.try_recv().is_ok() {}
         }
+        // MediaStore fast path: MainActivity (which does the MediaStore
+        // query on a background thread) drops a "path|added|size" payload
+        // in .ms_recent and wakes us via nativeFsChange. Apply it now —
+        // a just-taken camera photo lands in ~1 s, without waiting for
+        // the ~10 s FUSE re-read of a huge directory.
+        if matches!(woke, Some(WEvent::Fs) | Some(WEvent::Full)) {
+            apply_mediasotre_payload(&app);
+        }
         let next = dir_sig(&scan::roots());
         let changed = if baseline {
             baseline = false;
@@ -1113,6 +1200,19 @@ pub fn run() {
                 tr(&s);
             });
 
+            // JS ready handshake: the WebView's page loads ~2-3 s after
+            // process start, while the first gallery-files emit can land
+            // 10 ms in (small/fast DB) and be lost. On handshake, re-emit
+            // the current state so the grid always gets its initial list.
+            let _ = app.listen("gtauri-js-ready", move |event| {
+                let _ = event;
+                let h = APP_HANDLE.lock().unwrap().clone();
+                if let Some(h) = h {
+                    tr("js ready — re-emitting state");
+                    emit_files(&h, false, META.read().unwrap().len());
+                }
+            });
+
             // Scroll anchor from JS (throttled to ~7 Hz): `a` = index of the
             // first visible grid cell. REPLACES the prefetch window with
             // [a, a+60) — the visible band plus ~13 rows ahead. Stale
@@ -1162,6 +1262,9 @@ pub fn run() {
             // Warm the first two screens before Chromium's lazy loader gets
             // to them (it requests ~30 at once; we'd rather be ahead).
             set_prefetch_window(0, 36);
+            // (The startup MediaStore fast path is triggered by
+            // MainActivity.onCreate — it pushes via
+            // nativeMediaStoreResults ~1.5 s in.)
             spawn_scan(handle.clone());
             // New photos appear in the grid ~2 s after being written.
             std::thread::spawn(move || watch_files(handle));
diff --git a/harnesses/gtauri/src/scan.rs b/harnesses/gtauri/src/scan.rs
index 2341b5e..b7a5eee 100644
--- a/harnesses/gtauri/src/scan.rs
+++ b/harnesses/gtauri/src/scan.rs
@@ -20,6 +20,19 @@ pub const IMAGE_EXTS: &[&str] = &[
     "jpg", "jpeg", "png", "webp", "heic", "heif", "bmp", "tif", "tiff",
 ];
 
+/// True if the path looks like an image we index (hidden files and
+/// non-image extensions excluded).
+pub fn is_image_path(p: &str) -> bool {
+    let pb = std::path::Path::new(p);
+    let name = pb.file_name().and_then(|n| n.to_str()).unwrap_or("");
+    if name.starts_with('.') {
+        return false;
+    }
+    pb.extension()
+        .and_then(|e| e.to_str())
+        .is_some_and(|e| IMAGE_EXTS.contains(&e.to_ascii_lowercase().as_str()))
+}
+
 /// Scan roots. `GALLERY_SCAN_DIRS` (colon-separated) overrides — test hook.
 pub fn roots() -> Vec<PathBuf> {
     if let Ok(d) = std::env::var("GALLERY_SCAN_DIRS") {
@@ -163,6 +176,17 @@ fn walk_dir(
         Some(e) => e,
         None => return,
     };
+    // GROUND-TRUTH INSTRUMENTATION: raw getdents count for this directory,
+    // before any filtering. If raw < reality, the VFS served a short
+    // listing to this process; if raw == reality but the walk total is
+    // low, a filter below dropped entries (our bug).
+    if dir.parent().is_some() {
+        crate::tr(&format!(
+            "rawdir {:?}: {} entries",
+            dir.file_name().map(|s| s.to_string_lossy().into_owned()).unwrap_or_default(),
+            entries.len()
+        ));
+    }
     // STALE-LISTING CROSS-CHECK (see walk_stream docs): if the DB holds
     // many more files for this directory than the enumeration produced,
     // re-read the directory a few times and keep the best listing.
@@ -197,9 +221,13 @@ fn walk_dir(
             }
         }
     }
+    let mut n_ftfail = 0u32;
+    let mut n_statfail = 0u32;
+    let mut n_pushed = 0u32;
+    let raw_n = entries.len();
     for ent in entries {
         let p = ent.path();
-        let Ok(ft) = ent.file_type() else { continue };
+        let Ok(ft) = ent.file_type() else { n_ftfail += 1; continue };
         if ft.is_dir() {
             // Skip hidden dirs (.thumbnails, .trash, …) — metadata, not photos.
             if p.file_name().and_then(|n| n.to_str()).is_some_and(|n| n.starts_with('.')) {
@@ -225,7 +253,10 @@ fn walk_dir(
         if !IMAGE_EXTS.contains(&ext.to_ascii_lowercase().as_str()) {
             continue;
         }
-        let Ok(md) = std::fs::metadata(&p) else { continue };
+        let Ok(md) = std::fs::metadata(&p) else {
+            n_statfail += 1;
+            continue;
+        };
         let mtime = md
             .modified()
             .ok()
@@ -237,10 +268,21 @@ fn walk_dir(
             mtime,
             size: md.len() as i64,
         });
+        n_pushed += 1;
         if out.len() % 512 == 0 {
             on_batch(out);
         }
     }
+    if n_ftfail > 0 || n_statfail > 0 {
+        crate::tr(&format!(
+            "walkdir {:?}: raw {} pushed {} ftfail {} statfail {}",
+            dir.file_name().map(|s| s.to_string_lossy().into_owned()).unwrap_or_default(),
+            raw_n,
+            n_pushed,
+            n_ftfail,
+            n_statfail
+        ));
+    }
 }
 
 #[cfg(test)]