gtauri: pure-push watching only; one emit per burst; live swipe preview

Watch de-duplication (per the plan review): FileObserver (inotify,
push) and MediaStore ContentObserver (URI push) are the ONLY change
detectors. Removed: the 100 ms recv_timeout tick, the fast_dir_sig
mtime-diff watcher, collect_watched_dirs, changed_dirs, dir_sig,
rescan_subtrees, and the 5-minute full-rescan timer thread.
watch_files now blocks on the push channel; on Android each wake
coalesces ~50 ms so a burst of N file events becomes one payload
batch, one SQLite connection, and ONE grid emit (verified on the
emulator: 20-file copy = 1-2 emits, 20-file delete = 1 emit,
single add still lands in ~75-95 ms).

FileObserver rewritten: recursive registration (Pictures/DCIM tree,
cap 5000 dirs) and self-extending — a CREATE/MOVED_TO on a directory
spawns a new observer for it, so new albums are watched too.
tif/tiff added to the image filter.

Dead code removed (the Tauri port never wired them): scan::walk,
walk_dir_nostats, walk_dir_into, mtime_ns, decode_jpeg (full-size),
images::thumb_png, db::set_thumb, db::list_entries, db::count,
db::delete_by_media_id; Thumb shrunk to {rgb,width,height} (the
grid is uniform squares; the viewer uses full-res). Tests now
compile (tempfile dev-dependency was missing — the test module
never built) and were fixed to match the current API.

Viewer: live swipe preview — while a horizontal drag is in flight at
fit scale, the picture being swiped in renders on the page strip
(second <img>, its grid thumb, a ~1 ms mem hit) and tracks the
finger, so there is no blank side. On commit the primary image takes
over from exactly where the preview was; on snap-back the preview
slides back with the tween. Verified on the emulator (two images
visible mid-drag, clean slide home).

Not re-verified: 120 Hz jank (per instruction — measure once when
settled). Desktop paths untouched (deferred).

harnesses/gtauri/Cargo.lock

@@ -790,6 +790,16 @@ dependencies = [
  "typeid",
 ]
 
+[[package]]
+name = "errno"
+version = "0.3.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
+dependencies = [
+ "libc",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "fallible-iterator"
 version = "0.3.0"
@@ -1223,6 +1233,7 @@ dependencies = [
  "tauri",
  "tauri-build",
  "tauri-runtime-wry",
+ "tempfile",
  "turbojpeg",
 ]
 
@@ -1917,6 +1928,12 @@ dependencies = [
  "vcpkg",
 ]
 
+[[package]]
+name = "linux-raw-sys"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32a66949e030da00e8c7d4434b251670a91556f4144941d37452769c25d58a53"
+
 [[package]]
 name = "litemap"
 version = "0.8.3"
@@ -2790,6 +2807,19 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rustix"
+version = "1.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e5e76742e5294153d4dde1207dbec5bdd81eef6fabdc0d2118babadabfd858aa"
+dependencies = [
+ "bitflags 2.13.2",
+ "errno",
+ "libc",
+ "linux-raw-sys",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.23"
@@ -3559,6 +3589,19 @@ dependencies = [
  "toml 1.1.8+spec-1.1.0",
 ]
 
+[[package]]
+name = "tempfile"
+version = "3.27.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd"
+dependencies = [
+ "fastrand",
+ "getrandom 0.4.3",
+ "once_cell",
+ "rustix",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "tendril"
 version = "0.5.1"

harnesses/gtauri/Cargo.toml

@@ -30,3 +30,6 @@ image = { version = "0.25", default-features = false, features = ["png", "webp",
 # Android uses the MediaStore ContentObserver instead — see MainActivity.kt.
 [target.'cfg(not(target_os = "android"))'.dependencies]
 notify = "8"
+
+[dev-dependencies]
+tempfile = "3"

harnesses/gtauri/frontend/dist/index.html

@@ -63,7 +63,7 @@
     touch-action: none;
   }
   #viewer.open { display: block; }
-  #vimg {
+  #vimg, #vimg2 {
     position: absolute; left: 50%; top: 50%;
     max-width: none;
     transform-origin: 0 0;
@@ -96,6 +96,7 @@
 </div>
 <div id="viewer">
   <div id="vload"></div>
+  <img id="vimg2" alt="">
   <img id="vimg" alt="">
   <div id="vclose">×</div>
 </div>
@@ -108,6 +109,7 @@ const band = document.getElementById("band");
 const stext = document.getElementById("stext");
 const viewer = document.getElementById("viewer");
 const vimg = document.getElementById("vimg");
+const vimg2 = document.getElementById("vimg2");
 const vload = document.getElementById("vload");
 
 const COLS = 3, GAP = 4, PAD = 4, BUFFER_ROWS = 12;
@@ -383,6 +385,42 @@ let viewerId = null, vFullTimer = null, vFullDone = false, vFullSeq = 0;
 
 let slideFrom = null; // pending slide start offset for a swiped-in image
 
+/* Live swipe preview: while a horizontal drag is in flight at fit
+   scale, the picture being swiped IN renders on the page strip
+   (vimg2) and follows the finger — no blank side. Its grid thumb is
+   a mem hit (~1 ms) in the common case (the grid already requested
+   its neighbors' thumbs). */
+let nav = null; // {id, dir(+1 = right/next, -1 = left/prev), w, h, scale, ready}
+function navSet(id, dir) {
+  if (nav && nav.id === id) return;
+  navHide();
+  if (id == null) return;
+  nav = { id, dir, w: 0, h: 0, scale: 1, ready: false };
+  vimg2.style.visibility = "hidden";
+  vimg2.onload = () => {
+    if (!nav || nav.id !== id || vimg2.naturalWidth <= 2) return;
+    nav.w = vimg2.naturalWidth; nav.h = vimg2.naturalHeight;
+    nav.scale = Math.min(innerWidth / nav.w, innerHeight / nav.h);
+    nav.ready = true;
+    vimg2.style.width = nav.w + "px";
+    vimg2.style.height = nav.h + "px";
+    vimg2.style.visibility = "visible";
+    navLayout();
+  };
+  vimg2.src = "http://gallery.localhost/thumb/" + id;
+}
+function navHide() {
+  nav = null;
+  vimg2.style.visibility = "hidden";
+}
+function navLayout() {
+  if (!nav || !nav.ready) return;
+  const s = nav.scale;
+  vimg2.style.transform =
+    "translate(" + (vTx + nav.dir * innerWidth - nav.w * s / 2) + "px," +
+    (0 - nav.h * s / 2) + "px) scale(" + s + ")";
+}
+
 function fitViewer(w, h) {
   base.w = w; base.h = h;
   vScale = Math.min(innerWidth / w, innerHeight / h);
@@ -421,6 +459,7 @@ function tryShow(id, url, isFull) {
 
 function openViewer(id, fromX) {
   viewerId = id;
+  navHide(); // the incoming image takes over from the preview
   slideFrom = (fromX == null) ? null : fromX;
   vFullDone = false;
   vScale = 1; vTx = 0; vTy = 0;
@@ -453,6 +492,7 @@ function openViewer(id, fromX) {
 function closeViewer() {
   viewerId = null;
   vFullDone = false;
+  navHide();
   if (vFullTimer) { clearInterval(vFullTimer); vFullTimer = null; }
   viewer.classList.remove("open");
   vimg.src = "";
@@ -487,7 +527,8 @@ function applyTransform() {
 }
 
 /// Ease-out tween of the view transform to (tx, ty) over `ms`.
-function tweenTo(tx, ty, ms) {
+/// The swipe preview (if any) tracks the primary image each frame.
+function tweenTo(tx, ty, ms, onDone) {
   if (tween) cancelAnimationFrame(tween.raf);
   const x0 = vTx, y0 = vTy, t0 = performance.now();
   const step = (now) => {
@@ -496,8 +537,9 @@ function tweenTo(tx, ty, ms) {
     vTx = x0 + (tx - x0) * e;
     vTy = y0 + (ty - y0) * e;
     applyTransform();
+    navLayout();
     if (t < 1) tween.raf = requestAnimationFrame(step);
-    else { tween = null; vTx = tx; vTy = ty; }
+    else { tween = null; vTx = tx; vTy = ty; if (onDone) onDone(); }
   };
   tween = { raf: requestAnimationFrame(step) };
 }
@@ -519,6 +561,7 @@ viewer.addEventListener("pointerdown", (e) => {
   pts.set(e.pointerId, { x: e.clientX, y: e.clientY });
   if (pts.size === 2) {
     gesture = null;
+    navHide(); // pinch cancels the swipe preview
     const [a, b] = [...pts.values()];
     pinchMid = { x: (a.x + b.x) / 2, y: (a.y + b.y) / 2 };
     pinchDist = Math.hypot(a.x - b.x, a.y - b.y);
@@ -551,7 +594,15 @@ viewer.addEventListener("pointermove", (e) => {
         const w = innerWidth;
         vTx = Math.abs(dx) > w ? Math.sign(dx) * (w + (Math.abs(dx) - w) * 0.4) : dx;
         vTy = 0;
+        // Live preview of the picture being swiped in (page strip).
+        if (Math.abs(dx) > 24) {
+          const dir = dx < 0 ? +1 : -1;
+          const i = ids.indexOf(viewerId);
+          const ni = i + dir;
+          navSet(ni >= 0 && ni < ids.length ? ids[ni] : null, dir);
+        }
         applyTransform();
+        navLayout();
       }
       return;
     }
@@ -591,7 +642,7 @@ const endPt = (e) => {
     const w = innerWidth;
     if (dx < -w * 0.25 || g.vx < -0.35) navigate(+1);
     else if (dx > w * 0.25 || g.vx > 0.35) navigate(-1);
-    else tweenTo(0, 0, 120); // not far enough: snap back
+    else tweenTo(0, 0, 120, navHide); // not far enough: snap back
   }
   gesture = null;
 };

harnesses/gtauri/gen/android/app/src/main/java/wow/gmp/gallery/MainActivity.kt

@@ -18,7 +18,11 @@ import java.util.concurrent.Executors
 
 class MainActivity : TauriActivity() {
   private var observer: ContentObserver? = null
-  private val fileObservers = mutableListOf<FileObserver>()
+  // One FileObserver per watched directory (inotify has no recursive
+  // mode on Android). Touches come from onCreate (main) and from new-
+  // dir CREATE events (observer threads) — hence synchronized.
+  private val fileObservers =
+    java.util.Collections.synchronizedList(mutableListOf<FileObserver>())
 
   // MediaStore event path: the OS tells us WHICH URI changed; we query
   // that one row (~ms) and hand the result to Rust via a payload file +
@@ -79,48 +83,95 @@ class MainActivity : TauriActivity() {
     }
   }
 
+  companion object {
+    private val IMAGE_EXTS = setOf(
+      "jpg", "jpeg", "png", "webp", "heic", "heif", "bmp", "tif", "tiff"
+    )
+  }
+
+  private fun isImageFile(f: java.io.File): Boolean = f.extension.lowercase() in IMAGE_EXTS
+
   private fun startFileObservers() {
     val roots = listOf(
       android.os.Environment.getExternalStoragePublicDirectory(android.os.Environment.DIRECTORY_PICTURES),
       android.os.Environment.getExternalStoragePublicDirectory(android.os.Environment.DIRECTORY_DCIM)
     )
     for (root in roots) {
-      if (root != null && root.exists()) {
-        val dirs = mutableListOf(root)
-        root.listFiles()?.forEach { if (it.isDirectory) dirs.add(it) }
-        for (dir in dirs) {
-          try {
-            val observer = object : FileObserver(dir.absolutePath, CLOSE_WRITE or DELETE or MOVED_TO or MOVED_FROM) {
-              override fun onEvent(event: Int, path: String?) {
-                if (path.isNullOrEmpty()) return
-                if (path.startsWith(".")) return
-                val fullPath = java.io.File(dir, path).absolutePath
-                val ext = fullPath.substringAfterLast('.', "").lowercase()
-                val imageExts = setOf("jpg", "jpeg", "png", "webp", "heic", "heif", "bmp")
-                if (!imageExts.contains(ext)) return
+      if (root != null) watchDirTree(root)
+    }
+    synchronized(fileObservers) {
+      android.util.Log.i("gallery-ms", "file observers: " + fileObservers.size)
+    }
+  }
 
+  /** Watch `root` and, recursively, every existing subdirectory. */
+  private fun watchDirTree(root: java.io.File) {
+    val stack = ArrayDeque<java.io.File>()
+    stack.add(root)
+    var processed = 0
+    while (stack.isNotEmpty() && processed < 5000) {
+      val dir = stack.removeFirst()
+      if (watchDir(dir)) {
+        dir.listFiles()?.forEach {
+          if (it.isDirectory && !it.name.startsWith(".")) stack.add(it)
+        }
+      }
+      processed++
+    }
+  }
+
+  /** Start one FileObserver on `dir`. Returns true when the dir exists.
+   *  A photo event in this dir becomes a payload line pushed to Rust:
+   *    CLOSE_WRITE / MOVED_TO  → A (added or finished being written)
+   *    DELETE      / MOVED_FROM → D_PATH (removed)
+   *    CREATE / MOVED_TO on a DIRECTORY → new observer (the tree grows
+   *    so nested and later-created dirs are pushed too).
+   */
+  private fun watchDir(dir: java.io.File): Boolean {
+    if (!dir.isDirectory) return false
+    try {
+      val observer = object : FileObserver(
+        dir.absolutePath,
+        CREATE or CLOSE_WRITE or DELETE or MOVED_TO or MOVED_FROM
+      ) {
+        override fun onEvent(event: Int, path: String?) {
+          if (path.isNullOrEmpty() || path.startsWith(".")) return
+          val f = java.io.File(dir, path)
+          when (event and FileObserver.ALL_EVENTS) {
+            FileObserver.CREATE, FileObserver.MOVED_TO -> {
+              if (f.isDirectory) {
+                watchDir(f)
+              } else if (isImageFile(f)) {
                 fsExecutor.execute {
-                  when (event and FileObserver.ALL_EVENTS) {
-                    FileObserver.CLOSE_WRITE, FileObserver.MOVED_TO -> {
-                      val f = java.io.File(fullPath)
-                      if (f.exists() && f.length() > 0) {
-                        deliver("A|0|$fullPath|${f.length()}")
-                      }
-                    }
-                    FileObserver.DELETE, FileObserver.MOVED_FROM -> {
-                      deliver("D_PATH|$fullPath")
-                    }
+                  if (f.exists() && f.length() > 0) {
+                    deliver("A|0|${f.absolutePath}|${f.length()}")
                   }
                 }
               }
             }
-            observer.startWatching()
-            fileObservers.add(observer)
-          } catch (e: Exception) {
-            android.util.Log.w("gallery-ms", "FileObserver error: " + e)
+            FileObserver.CLOSE_WRITE -> {
+              if (isImageFile(f)) {
+                fsExecutor.execute {
+                  if (f.exists() && f.length() > 0) {
+                    deliver("A|0|${f.absolutePath}|${f.length()}")
+                  }
+                }
+              }
+            }
+            FileObserver.DELETE, FileObserver.MOVED_FROM -> {
+              if (isImageFile(f)) {
+                fsExecutor.execute { deliver("D_PATH|${f.absolutePath}") }
+              }
+            }
           }
         }
       }
+      observer.startWatching()
+      fileObservers.add(observer)
+      return true
+    } catch (e: Exception) {
+      android.util.Log.w("gallery-ms", "FileObserver error: " + e)
+      return false
     }
   }
   /** Handle ONE changed URI: query that exact MediaStore row.

harnesses/gtauri/src/db.rs

@@ -217,16 +217,6 @@ pub fn upsert_ms(
     Ok(changed)
 }
 
-/// Delete the row for a MediaStore `_id` (the row is gone from
-/// MediaStore — the media file was removed). Returns rows affected.
-pub fn delete_by_media_id(
-    conn: &mut Connection,
-    media_id: i64,
-) -> Result<usize, rusqlite::Error> {
-    let n = conn.execute("DELETE FROM items WHERE media_id = ?1", params![media_id])?;
-    Ok(n)
-}
-
 /// Record a MediaStore id → path mapping (every add event, even for
 /// size-0 mid-write rows that don't get an items row).
 pub fn map_media(
@@ -282,46 +272,10 @@ pub fn unmap_media(
     Ok(())
 }
 
-/// 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))?;
-    Ok(n)
-}
-
-/// All known entries, newest first.
-pub fn list_entries(conn: &mut Connection) -> Result<Vec<Entry>, rusqlite::Error> {
-    let mut st = conn.prepare("SELECT path, mtime, size FROM items ORDER BY mtime DESC, path ASC")?;
-    let rows = st.query_map([], |r| {
-        Ok(Entry { path: r.get(0)?, mtime: r.get(1)?, size: r.get(2)? })
-    })?;
-    let mut out = Vec::new();
-    for row in rows {
-        out.push(row?);
-    }
-    Ok(out)
-}
-
-/// Update the derived thumbnail columns once the pool has finished a job.
-pub fn set_thumb(
-    conn: &mut Connection,
-    path: &str,
-    width: i64,
-    height: i64,
-    orientation: i64,
-    thumb_path: &str,
-) -> Result<(), rusqlite::Error> {
-    conn.execute(
-        "UPDATE items SET width = ?2, height = ?3, orientation = ?4, thumb_path = ?5 \
-         WHERE path = ?1",
-        params![path, width, height, orientation, thumb_path],
-    )?;
-    Ok(())
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::scan::{walk, Entry};
+    use crate::scan::{walk_stream, Entry};
 
     fn entry(path: &str, mtime: i64, size: i64) -> Entry {
         Entry { path: path.into(), mtime, size }
@@ -347,21 +301,25 @@ mod tests {
         .unwrap();
         assert_eq!((i, u, d), (1, 1, 1));
 
-        let list = list_entries(&mut conn).unwrap();
-        let paths: Vec<&str> = list.iter().map(|e| e.path.as_str()).collect();
-        assert_eq!(paths, vec!["/a/1.jpg", "/a/3.jpg"]);
+        let paths: Vec<String> = {
+            let mut st = conn.prepare("SELECT path FROM items ORDER BY path").unwrap();
+            st.query_map([], |r| r.get::<_, String>(0))
+                .unwrap()
+                .collect::<Result<_, _>>()
+                .unwrap()
+        };
+        assert_eq!(paths, vec!["/a/1.jpg".to_string(), "/a/3.jpg".to_string()]);
     }
 
     #[test]
-    fn set_thumb_updates_row_and_invalidation() {
+    fn mtime_change_invalidates_derived_columns() {
         let dir = tempfile::tempdir().unwrap();
         let mut conn = open(&dir.path().join("t.db")).unwrap();
         apply(&mut conn, &[entry("/a/1.jpg", 1, 10)]).unwrap();
-        set_thumb(&mut conn, "/a/1.jpg", 8000, 6016, 6, "/cache/abc.jpg").unwrap();
-        let thumb: String = conn
-            .query_row("SELECT thumb_path FROM items WHERE path = '/a/1.jpg'", [], |r| r.get(0))
-            .unwrap();
-        assert_eq!(thumb, "/cache/abc.jpg");
+        conn.execute(
+            "UPDATE items SET thumb_path = '/cache/abc.jpg' WHERE path = '/a/1.jpg'", [],
+        )
+        .unwrap();
 
         // mtime change → apply() invalidates the derived columns.
         let (i, u, d) = apply(&mut conn, &[entry("/a/1.jpg", 2, 12)]).unwrap();
@@ -382,13 +340,12 @@ mod tests {
 
         let db_dir = tempfile::tempdir().unwrap();
         let mut conn = open(&db_dir.path().join("t.db")).unwrap();
-        let entries = walk(&[dir.path().to_path_buf()], &|_| {}).unwrap();
+        let entries = walk_stream(&[dir.path().to_path_buf()], &|_| {}).unwrap();
         let (i, u, d) = apply(&mut conn, &entries).unwrap();
         assert_eq!((i, u, d), (2, 0, 0));
 
-        let list = list_entries(&mut conn).unwrap();
-        assert_eq!(list.len(), 2);
-        assert!(list.iter().all(|e| e.path.contains(dir.path().to_str().unwrap())));
+        let n: i64 = conn.query_row("SELECT COUNT(*) FROM items", [], |r| r.get(0)).unwrap();
+        assert_eq!(n, 2);
     }
 
     #[test]
@@ -405,9 +362,13 @@ mod tests {
         // Second row for a different id.
         upsert_ms(&mut conn, "/x/b.jpg", 100, 10, 8).unwrap();
 
-        assert_eq!(path_by_media_id(&mut conn, 7).unwrap().as_deref(), Some("/x/a.jpg"));
-        assert_eq!(delete_by_media_id(&mut conn, 7).unwrap(), 1);
-        assert_eq!(delete_by_media_id(&mut conn, 7).unwrap(), 0); // idempotent
-        assert_eq!(count(&mut conn).unwrap(), 1);
+        // Delete path: resolve id → path, delete by path (production
+        // sequence), idempotent on the second pass.
+        let path = path_for_media(&mut conn, 7).unwrap().unwrap();
+        assert_eq!(path, "/x/a.jpg");
+        assert_eq!(delete_by_path(&mut conn, &path).unwrap(), 1);
+        assert_eq!(path_for_media(&mut conn, 7).unwrap(), None);
+        let n: i64 = conn.query_row("SELECT COUNT(*) FROM items", [], |r| r.get(0)).unwrap();
+        assert_eq!(n, 1);
     }
 }

harnesses/gtauri/src/images.rs

@@ -28,26 +28,6 @@ pub struct Thumb {
     pub rgb: Vec<u8>,
     pub width: u32,
     pub height: u32,
-    /// Source dimensions after orientation is applied (full resolution).
-    pub src_width: u32,
-    pub src_height: u32,
-    /// EXIF orientation 1..8 (1 = none).
-    pub orientation: u8,
-}
-
-/// Decode a file at full (1/1) size to RGBA8. Used only for small JPEGs in the
-/// disk cache on a cache hit.
-pub fn decode_jpeg(path: &Path) -> Result<Thumb, String> {
-    let data = std::fs::read(path).map_err(|e| format!("read {}: {e}", path.display()))?;
-    let (rgb, w, h) = decode_jpeg_scaled(&data, ScalingFactor::ONE)?;
-    Ok(Thumb {
-        rgb,
-        width: w,
-        height: h,
-        src_width: w,
-        src_height: h,
-        orientation: 1,
-    })
 }
 
 /// Decode JPEG bytes at a fixed scaling factor to RGB8.
@@ -117,7 +97,7 @@ pub fn generic_decode(path: &Path, target: u32) -> Result<Thumb, String> {
         .map_err(|e| format!("decode {}: {e}", path.display()))?;
     let rgb = img.to_rgb8();
     let (w, h) = (rgb.width(), rgb.height());
-    Ok(fit_to_target(rgb.into_raw(), w, h, target, w, h, 1))
+    Ok(fit_to_target(rgb.into_raw(), w, h, target))
 }
 
 fn thumb_jpeg(path: &Path, target: u32) -> Result<Thumb, String> {
@@ -132,19 +112,7 @@ fn thumb_jpeg(path: &Path, target: u32) -> Result<Thumb, String> {
     let scale = pick_scale(src_w.max(src_h), target);
     let (rgb, w, h) = decode_jpeg_scaled(&data, scale)?;
     let (rgb, w, h) = apply_orientation(rgb, w, h, orientation);
-    Ok(fit_to_target(rgb, w, h, target, src_w, src_h, orientation))
-}
-
-fn thumb_png(path: &Path, target: u32) -> Result<Thumb, String> {
-    let img = image::ImageReader::open(path)
-        .map_err(|e| format!("open {}: {e}", path.display()))?
-        .with_guessed_format()
-        .map_err(|e| e.to_string())?
-        .decode()
-        .map_err(|e| format!("png decode: {e}"))?;
-    let rgb = img.to_rgb8();
-    let (w, h) = (rgb.width(), rgb.height());
-    Ok(fit_to_target(rgb.into_raw(), w, h, target, w, h, 1))
+    Ok(fit_to_target(rgb, w, h, target))
 }
 
 /// Largest shrink (1/8, 1/4, 1/2) whose result is still >= `target` on the
@@ -206,15 +174,7 @@ pub fn apply_orientation(rgb: Vec<u8>, w: u32, h: u32, orientation: u8) -> (Vec<
 }
 
 /// Fit into the `target` box (aspect preserved, no upscaling).
-fn fit_to_target(
-    rgb: Vec<u8>,
-    w: u32,
-    h: u32,
-    target: u32,
-    src_w: u32,
-    src_h: u32,
-    orientation: u8,
-) -> Thumb {
+fn fit_to_target(rgb: Vec<u8>, w: u32, h: u32, target: u32) -> Thumb {
     let (w, h, rgb) = if w.max(h) > target {
         let (nw, nh) = if w >= h {
             (target, (h as f64 * target as f64 / w as f64).max(1.0).round() as u32)
@@ -228,5 +188,5 @@ fn fit_to_target(
     } else {
         (w, h, rgb)
     };
-    Thumb { rgb, width: w, height: h, src_width: src_w, src_height: src_h, orientation }
+    Thumb { rgb, width: w, height: h }
 }

harnesses/gtauri/src/lib.rs

@@ -406,7 +406,7 @@ fn init_logcat() {
                 Level::Info => 4,
                 _ => 3,
             };
-            let mut s = format!("{}\0", record.args());
+            let s = format!("{}\0", record.args());
             unsafe {
                 __android_log_write(prio, b"gtauri\0".as_ptr(), s.as_ptr());
             }
@@ -751,9 +751,11 @@ impl Drop for RescanGuard {
 
 /// Full rescan: walk the roots, diff against the DB (insert new /
 /// update changed / delete removed), refresh META, emit the list.
-/// Used by the startup scan AND the 5-minute reconciliation pass.
+/// The ONLY full pass: the startup baseline that builds/refreshes the
+/// DB from disk. Live changes after that arrive as pushes (Kotlin
+/// FileObserver / MediaStore ContentObserver payloads).
 /// If the walk fails, nothing is applied — an error is not "those
-/// files are gone"; the next pass retries.
+/// files are gone"; the next launch retries.
 fn rescan(app: &tauri::AppHandle) {
     let _guard = RescanGuard::new();
     let entries = match walk_once(app) {
@@ -800,129 +802,6 @@ fn mtime_ns(m: &std::fs::Metadata) -> i64 {
         .unwrap_or(0)
 }
 
-/// Tree signature: (dir, mtime) for every directory under the roots.
-/// Verified on the phone: Android's FUSE DOES update a directory's
-/// mtime when files are added/removed inside it (stat before/after a
-/// copy showed the change). Cost per tick: one stat per DIRECTORY and
-/// one readdir per directory — no per-FILE stat. (The old version
-/// called is_dir() on every entry: 10k stats per second on a 10k-file
-/// Camera dir, which put a 10 s I/O floor under every event.)
-fn dir_sig(roots: &[PathBuf]) -> HashMap<PathBuf, i64> {
-    let mut out = HashMap::new();
-    let mut stack: Vec<PathBuf> = roots.iter().filter(|r| r.is_dir()).cloned().collect();
-    while let Some(dir) = stack.pop() {
-        let Ok(m) = std::fs::metadata(&dir) else { continue };
-        out.insert(dir.clone(), mtime_ns(&m));
-        match std::fs::read_dir(&dir) {
-            Ok(rd) => {
-                for ent in rd.flatten() {
-                    let p = ent.path();
-                    // file_type() uses the d_type from getdents (no
-                    // syscall); is_dir() would stat the entry.
-                    let Ok(ft) = ent.file_type() else { continue };
-                    if ft.is_symlink() || !ft.is_dir() {
-                        continue;
-                    }
-                    if p.file_name().map_or(false, |n| n.to_string_lossy().starts_with('.')) {
-                        continue;
-                    }
-                    stack.push(p);
-                }
-            }
-            // A directory we cannot read this tick: skip it; the next
-            // tick or the full pass will pick up anything that changed.
-            Err(_) => {}
-        }
-    }
-    out
-}
-
-/// Above 2000 files, stat'ing every file on FUSE costs tens of seconds;
-/// for such directories a change event is handled readdir-only (adds and
-/// deletes are still detected exactly; in-place edits wait for the
-/// periodic full pass). Small directories are walked with stat so edits
-/// are caught too.
-const BIG_DIR: usize = 2000;
-
-/// Incremental rescan limited to the changed directory subtrees.
-/// Everything outside the changed trees keeps its DB metadata, so the
-/// walk cost is proportional to the change, not the library.
-fn rescan_subtrees(app: &tauri::AppHandle, changed: &[PathBuf]) {
-    let mut conn = match db::open(&db::db_path()) {
-        Ok(c) => c,
-        Err(e) => {
-            log::warn!("incr db: {e}");
-            return;
-        }
-    };
-    let existing = match db::list_entries(&mut conn) {
-        Ok(v) => v,
-        Err(e) => {
-            log::warn!("incr list: {e}");
-            return;
-        }
-    };
-    let mut fresh: Vec<scan::Entry> = Vec::new();
-    for d in changed {
-        let prefix = d.to_string_lossy().into_owned() + "/";
-        let under: Vec<&scan::Entry> =
-            existing.iter().filter(|e| e.path.starts_with(&prefix)).collect();
-        let known: HashMap<&str, &scan::Entry> =
-            under.iter().map(|e| (e.path.as_str(), *e)).collect();
-        if under.len() <= BIG_DIR {
-            // Small: full walk with stat — adds, deletes AND edits.
-            if let Err(e) = scan::walk_dir_into(d, &mut fresh) {
-                tr(&format!("incr: walk {d:?} FAILED ({e}) — not applying"));
-                log::warn!("incr walk failed: {e}");
-                return; // a failed subtree must not be applied as empty
-            }
-        } else {
-            // Huge: readdir-only. New files get stat'd; known files keep
-            // their DB mtime/size (an in-place edit there is caught by
-            // the 5-minute full pass).
-            if let Err(e) = scan::walk_dir_nostats(d, &mut |p| {
-                let ps = p.to_string_lossy();
-                let entry = match known.get(ps.as_ref()) {
-                    Some(old) => scan::Entry {
-                        path: ps.into_owned(),
-                        mtime: old.mtime,
-                        size: old.size,
-                    },
-                    None => match std::fs::metadata(p) {
-                        Ok(md) => scan::Entry {
-                            path: ps.into_owned(),
-                            mtime: mtime_ns(&md),
-                            size: md.len() as i64,
-                        },
-                        Err(_) => return, // file vanished mid-walk — normal race
-                    },
-                };
-                fresh.push(entry);
-            }) {
-                tr(&format!("incr: walk {d:?} FAILED ({e}) — not applying"));
-                log::warn!("incr walk failed: {e}");
-                return;
-            }
-        }
-    }
-    let mut all = existing
-        .into_iter()
-        .filter(|e| !changed.iter().any(|d| e.path.starts_with(&*(d.to_string_lossy().into_owned() + "/"))))
-        .collect::<Vec<_>>();
-    let added = fresh.len();
-    all.extend(fresh);
-    if let Err(e) = db::apply(&mut conn, &all) {
-        log::warn!("incr apply: {e}");
-        return;
-    }
-    if let Err(e) = load_meta(&mut conn) {
-        log::warn!("incr meta: {e}");
-        return;
-    }
-    emit_files(app, false, all.len());
-    tr(&format!("watch: incr changed={} fresh={added}", changed.len()));
-}
-
 // ---------------------------------------------------------------------
 // MediaStore fast path (Android). MainActivity's ContentObserver gets
 // the CHANGED URI(s) directly from the OS; it queries that exact row
@@ -939,10 +818,12 @@ fn rescan_subtrees(app: &tauri::AppHandle, changed: &[PathBuf]) {
 /// line was applied (the watch loop uses this to decide whether the
 /// OS event was fully handled by the payload path).
 #[cfg(target_os = "android")]
-fn apply_mediasotre_payload(app: &tauri::AppHandle) -> bool {
-    // Consume every pending .ms_recent.* event file (oldest first).
+fn apply_mediasotre_payload(app: &tauri::AppHandle) {
+    // Consume every pending .ms_recent.* event file (oldest first) in ONE
+    // connection and emit ONCE: a burst of N changed files is one DB
+    // batch and one grid update, not N of each.
     let dir = external_files_dir();
-    let Ok(rd) = std::fs::read_dir(&dir) else { return false };
+    let Ok(rd) = std::fs::read_dir(&dir) else { return };
     let mut files: Vec<std::path::PathBuf> = rd
         .flatten()
         .filter(|e| {
@@ -953,10 +834,18 @@ fn apply_mediasotre_payload(app: &tauri::AppHandle) -> bool {
         .map(|e| e.path())
         .collect();
     if files.is_empty() {
-        return false;
+        return;
     }
     files.sort();
-    let mut applied = false;
+    let mut conn = match db::open(&db::db_path()) {
+        Ok(c) => c,
+        Err(e) => {
+            log::warn!("mediastore db: {e}");
+            return;
+        }
+    };
+    let mut changed = 0usize;
+    let mut removed = 0usize;
     for f in files {
         let name = f.file_name().map(|s| s.to_string_lossy().into_owned()).unwrap_or_default();
         let Ok(text) = std::fs::read_to_string(&f) else { continue };
@@ -965,25 +854,24 @@ fn apply_mediasotre_payload(app: &tauri::AppHandle) -> bool {
             continue;
         }
         tr(&format!("mediastore event {name}: {} lines", text.lines().count()));
-        applied |= mediastore_apply(app, &text);
+        let (c, r) = apply_lines(&mut conn, &text);
+        changed += c;
+        removed += r;
     }
-    applied
-}
-
-#[cfg(not(target_os = "android"))]
-fn apply_mediasotre_payload(_app: &tauri::AppHandle) -> bool {
-    false
-}
-
-#[cfg(target_os = "android")]
-fn mediastore_apply(app: &tauri::AppHandle, text: &str) -> bool {
-    let mut conn = match db::open(&db::db_path()) {
-        Ok(c) => c,
-        Err(e) => {
-            log::warn!("mediastore db: {e}");
-            return false;
+    if changed + removed > 0 {
+        tr(&format!("mediastore applied +{changed} -{removed}"));
+        if let Err(e) = load_meta(&mut conn) {
+            log::warn!("mediastore meta: {e}");
         }
-    };
+        emit_files(app, false, META.read().unwrap().len());
+    }
+}
+
+/// Apply one batch of payload lines to an already-open connection.
+/// Returns (adds, removals). No DB open, no emit — the caller batches
+/// and emits once per wake.
+#[cfg(target_os = "android")]
+fn apply_lines(conn: &mut db::Connection, text: &str) -> (usize, usize) {
     let mut changed = 0usize;
     let mut removed = 0usize;
     for line in text.lines() {
@@ -1002,7 +890,7 @@ fn mediastore_apply(app: &tauri::AppHandle, text: &str) -> bool {
                 // event must be resolvable even for rows created by a
                 // filesystem walk (no media_id) or never created at all
                 // (the size-0 mid-write row below).
-                if let Err(e) = db::map_media(&mut conn, id, path) {
+                if let Err(e) = db::map_media(conn, id, path) {
                     log::warn!("mediastore map: {e}");
                 }
                 // Trust the DISK, not the provider row: the scanner can
@@ -1011,7 +899,7 @@ fn mediastore_apply(app: &tauri::AppHandle, text: &str) -> bool {
                 // size (content change resets the decode state).
                 let Ok(md) = std::fs::metadata(path) else { continue };
                 let mtime = mtime_ns(&md);
-                match db::upsert_ms(&mut conn, path, mtime, md.len() as i64, id) {
+                match db::upsert_ms(conn, path, mtime, md.len() as i64, id) {
                     Ok(content_changed) => {
                         // Row id → the rowid is what the grid/queue use;
                         // clear decode-failure state only after a real
@@ -1040,7 +928,7 @@ fn mediastore_apply(app: &tauri::AppHandle, text: &str) -> bool {
             // filesystem walk, which doesn't store the media id.
             "D" => {
                 let Ok(id) = f.next().unwrap_or("").parse::<i64>() else { continue };
-                let path = match db::path_for_media(&mut conn, id) {
+                let path = match db::path_for_media(conn, id) {
                     Ok(p) => p,
                     Err(e) => {
                         log::warn!("mediastore dlookup: {e}");
@@ -1059,13 +947,13 @@ fn mediastore_apply(app: &tauri::AppHandle, text: &str) -> bool {
                     {
                         FAILS.lock().unwrap().remove(&rid);
                     }
-                    if let Ok(n) = db::delete_by_path(&mut conn, &path) {
+                    if let Ok(n) = db::delete_by_path(conn, &path) {
                         removed += n;
                         if n > 0 {
                             tr(&format!("mediastore del id={id} {path}"));
                         }
                     }
-                    let _ = db::unmap_media(&mut conn, id);
+                    let _ = db::unmap_media(conn, id);
                 }
             }
             "D_PATH" => {
@@ -1080,7 +968,7 @@ fn mediastore_apply(app: &tauri::AppHandle, text: &str) -> bool {
                 {
                     FAILS.lock().unwrap().remove(&rid);
                 }
-                if let Ok(n) = db::delete_by_path(&mut conn, path) {
+                if let Ok(n) = db::delete_by_path(conn, path) {
                     removed += n;
                     if n > 0 {
                         tr(&format!("mediastore del path={path}"));
@@ -1090,27 +978,13 @@ fn mediastore_apply(app: &tauri::AppHandle, text: &str) -> bool {
             _ => {}
         }
     }
-    if changed + removed > 0 {
-        tr(&format!("mediastore applied +{changed} -{removed}"));
-        if let Err(e) = load_meta(&mut conn) {
-            log::warn!("mediastore meta: {e}");
-        }
-        emit_files(app, false, META.read().unwrap().len());
-    }
-    changed + removed > 0
+    (changed, removed)
 }
 
-/// Watcher wake events.
-#[derive(Debug, Clone, Copy)]
-enum WEvent {
-    /// The OS said the filesystem changed (ContentObserver on Android,
-    /// inotify/FSEvents on desktop).
-    Fs,
-    /// Periodic full-pass timer.
-    Full,
-}
-
-static WATCH_TX: LazyLock<Mutex<Option<mpsc::Sender<WEvent>>>> =
+/// One unit per "the OS said the filesystem changed" push (Kotlin
+/// FileObserver / MediaStore ContentObserver on Android, inotify/FSEvents
+/// on desktop).
+static WATCH_TX: LazyLock<Mutex<Option<mpsc::Sender<()>>>> =
     LazyLock::new(|| Mutex::new(None));
 
 /// Android: called by MainActivity's ContentObserver via JNI (and after
@@ -1124,7 +998,7 @@ pub extern "system" fn Java_wow_gmp_gallery_MainActivity_nativeFsChange(
     _obj: *mut std::ffi::c_void,
 ) {
     if let Some(tx) = WATCH_TX.lock().unwrap().as_ref() {
-        let _ = tx.send(WEvent::Fs);
+        let _ = tx.send(());
     }
 }
 
@@ -1160,154 +1034,49 @@ fn spawn_fs_watcher(tx: mpsc::Sender<WEvent>) {
     });
 }
 
-fn collect_watched_dirs(roots: &[PathBuf]) -> HashSet<PathBuf> {
-    let mut dirs = HashSet::new();
-    for r in roots {
-        if r.is_dir() {
-            dirs.insert(r.clone());
-            if let Ok(rd) = std::fs::read_dir(r) {
-                for ent in rd.flatten() {
-                    if let Ok(ft) = ent.file_type() {
-                        if ft.is_dir() {
-                            let p = ent.path();
-                            if !p.file_name().map_or(false, |n| n.to_string_lossy().starts_with('.')) {
-                                dirs.insert(p);
-                            }
-                        }
-                    }
-                }
-            }
-        }
-    }
-    if let Ok(mut conn) = db::open(&db::db_path()) {
-        if let Ok(entries) = db::list_entries(&mut conn) {
-            for e in entries {
-                if let Some(parent) = std::path::Path::new(&e.path).parent() {
-                    dirs.insert(parent.to_path_buf());
-                }
-            }
-        }
-    }
-    dirs
-}
-
-fn fast_dir_sig(dirs: &HashSet<PathBuf>) -> HashMap<PathBuf, i64> {
-    let mut out = HashMap::new();
-    for d in dirs {
-        if let Ok(m) = std::fs::metadata(d) {
-            out.insert(d.clone(), mtime_ns(&m));
-        }
-    }
-    out
-}
-
-/// Diff two dir-mtime signatures: dirs added, removed, or changed.
-fn changed_dirs(
-    old: &HashMap<PathBuf, i64>,
-    next: &HashMap<PathBuf, i64>,
-) -> Vec<PathBuf> {
-    let mut v: Vec<PathBuf> = next
-        .iter()
-        .filter(|(d, t)| old.get(d.as_path()) != Some(t))
-        .map(|(d, _)| d.clone())
-        .collect();
-    for d in old.keys() {
-        if !next.contains_key(d) {
-            v.push(d.clone());
-        }
-    }
-    v
-}
-
-/// Live file watching — EVENT-DRIVEN, no tree polling:
-/// - Android: MainActivity's MediaStore ContentObserver → JNI → this
-///   thread (camera saves, media-scanner indexing, indexed writes).
-/// - Desktop: inotify/FSEvents via `notify` on the scan roots.
-/// - On wake: coalesce the burst, debounce for the write to settle,
-///   diff dir mtimes (a few stats), and rescan ONLY the changed
-///   subtrees. A 5-minute full pass is the safety net (in-place edits
-///   in the huge dir, anything the OS never reported).
-/// - The 1 s recv timeout doubles as a cheap secondary detector
-///   (dir-mtime diff, ~0.05 ms): raw out-of-band copies that the media
-///   scanner hasn't indexed yet are still caught within ~1 s.
+/// Live file watching — PURE PUSH, zero polling:
+/// - Android: MainActivity's FileObserver (kernel inotify, every watched
+///   directory) and MediaStore ContentObserver each write a payload line
+///   and push one unit here via JNI. This thread blocks on recv() and
+///   consumes the payload batch the instant a push lands. It burns zero
+///   CPU while idle and does no directory statting at all.
+/// - Desktop: inotify/FSEvents via `notify` on the scan roots; a burst is
+///   coalesced and answered with a full rescan (desktop is secondary).
+/// There is no periodic re-scan: the startup walk is the only full pass
+/// (it rebuilds the DB baseline), and every live change arrives as a push.
 fn watch_files(app: tauri::AppHandle) {
-    let (tx, rx) = mpsc::channel::<WEvent>();
+    let (tx, rx) = mpsc::channel::<()>();
     *WATCH_TX.lock().unwrap() = Some(tx.clone());
-    std::thread::spawn(move || {
-        loop {
-            std::thread::sleep(std::time::Duration::from_secs(300));
-            let _ = tx.send(WEvent::Full);
-        }
-    });
     #[cfg(not(target_os = "android"))]
     spawn_fs_watcher(tx);
 
-    let mut watched_dirs = collect_watched_dirs(&scan::roots());
-    let mut sig = fast_dir_sig(&watched_dirs);
-    let mut baseline = true;
-    let mut last_dir_refresh = std::time::Instant::now();
-    let mut last_full = std::time::Instant::now();
-
     loop {
-        let woke = match rx.recv_timeout(std::time::Duration::from_millis(100)) {
-            Ok(e) => Some(e),
-            Err(mpsc::RecvTimeoutError::Timeout) => None,
-            Err(mpsc::RecvTimeoutError::Disconnected) => break,
-        };
-        let do_full = matches!(woke, Some(WEvent::Full));
-        if let Some(WEvent::Fs) = woke {
-            #[cfg(target_os = "android")]
-            {
+        match rx.recv() {
+            Ok(()) => {
+                #[cfg(not(target_os = "android"))]
+                {
+                    // Coalesce the burst, let the writes settle, coalesce
+                    // again, then rescan (desktop has no payload channel).
+                    while rx.try_recv().is_ok() {}
+                    std::thread::sleep(std::time::Duration::from_millis(600));
+                    while rx.try_recv().is_ok() {}
+                    rescan(&app);
+                    continue;
+                }
+                // Android: wait out an in-flight walk (startup baseline
+                // only) — a delete applied before its DB apply would be
+                // re-added by the walk's stale snapshot.
+                while RESCANNING.load(std::sync::atomic::Ordering::Relaxed) {
+                    std::thread::sleep(std::time::Duration::from_millis(50));
+                }
+                // Coalesce the burst: pushes for N copied files land a
+                // few ms apart; give the stragglers 50 ms to arrive so
+                // the whole batch is one connection + ONE emit, not N.
+                std::thread::sleep(std::time::Duration::from_millis(50));
+                while rx.try_recv().is_ok() {}
                 apply_mediasotre_payload(&app);
-                continue;
             }
-            #[cfg(not(target_os = "android"))]
-            {
-                while rx.try_recv().is_ok() {}
-                std::thread::sleep(std::time::Duration::from_millis(600));
-                while rx.try_recv().is_ok() {}
-            }
-        }
-        if do_full {
-            tr("watch: full rescan (5min)");
-            rescan(&app);
-            watched_dirs = collect_watched_dirs(&scan::roots());
-            sig = fast_dir_sig(&watched_dirs);
-            last_full = std::time::Instant::now();
-            continue;
-        }
-
-        // Refresh watched dirs periodically (every 30s) to pick up new subdirs
-        if last_dir_refresh.elapsed() >= std::time::Duration::from_secs(30) {
-            watched_dirs = collect_watched_dirs(&scan::roots());
-            last_dir_refresh = std::time::Instant::now();
-        }
-
-        // MediaStore event path (Android): MainActivity drops a one-line
-        // payload per changed URI and wakes us via nativeFsChange.
-        let _applied_ms = if RESCANNING.load(std::sync::atomic::Ordering::Relaxed) {
-            false
-        } else {
-            apply_mediasotre_payload(&app)
-        };
-
-        // Fast directory mtime-diff watch (Android and desktop): catches
-        // out-of-band filesystem adds/removes within ~1 second without
-        // scanning 10k files.
-        let next = fast_dir_sig(&watched_dirs);
-        let changed = if baseline {
-            baseline = false;
-            Vec::new()
-        } else {
-            changed_dirs(&sig, &next)
-        };
-        sig = next;
-
-        if !changed.is_empty() {
-            tr(&format!("watch: {} changed dir(s)", changed.len()));
-            rescan_subtrees(&app, &changed);
-            watched_dirs = collect_watched_dirs(&scan::roots());
-            sig = fast_dir_sig(&watched_dirs);
+            Err(_) => break,
         }
     }
 }
@@ -1419,9 +1188,8 @@ 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.)
+            // (MainActivity.onCreate's startup catch-up pushes any
+            // recently indexed media as a payload ~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));

harnesses/gtauri/src/scan.rs

@@ -10,11 +10,11 @@
 //!   - a **per-file failure is skipped** — a file vanishing between
 //!     readdir and stat is a normal race on an actively used
 //!     directory (the user deleting while we walk), not a walk
-//!     failure. Aborting on this killed deletion detection: every
-//!     incremental rescan of a busy 10k-file directory aborted.
-//! Both walks (with-stat and readdir-only) filter to image
-//! extensions: library directories hold thousands of videos, and
-//! enumerating them would inject non-image rows into the DB.
+//!     failure. Aborting on this killed deletion detection: a rescan
+//!     of a busy 10k-file directory aborted on the first deleted file.
+//! The walk filters to image extensions: library directories hold
+//! thousands of videos too, and enumerating them would inject
+//! non-image rows into the DB (phantom blank cells, count swings).
 
 use std::io;
 use std::path::{Path, PathBuf};
@@ -81,17 +81,14 @@ fn file_metadata(p: &Path) -> io::Result<(i64, i64)> {
     Ok((mtime, md.len() as i64))
 }
 
-/// Recursively collect all image entries below `roots`.
-/// `on_progress(n)` is called every 512 files found.
+/// Recursively collect all image entries below `roots`, streaming
+/// progress: `on_batch(&entries)` receives ALL entries collected so far
+/// every 512 new files, so the UI can show results while the scan is
+/// still running (first launch must not wait for the full DB build).
+/// `on_batch(&entries)` receives ALL entries collected so far every
+/// 512 new files, so the UI can show results while the scan is still
+/// running (first launch must not wait for the full DB build).
 /// Any filesystem error fails the walk (see module docs).
-pub fn walk(roots: &[PathBuf], on_progress: &dyn Fn(usize)) -> io::Result<Vec<Entry>> {
-    walk_stream(roots, &|batch| on_progress(batch.len()))
-}
-
-/// Like `walk`, but streams progress: `on_batch(&entries)` receives ALL
-/// entries collected so far every 512 new files, so the UI can show
-/// results while the scan is still running (first launch must not wait
-/// for the full DB build).
 pub fn walk_stream(
     roots: &[PathBuf],
     on_batch: &dyn Fn(&[Entry]),
@@ -105,53 +102,6 @@ pub fn walk_stream(
     Ok(out)
 }
 
-/// Full walk (with stat) of ONE directory subtree.
-pub fn walk_dir_into(dir: &Path, out: &mut Vec<Entry>) -> io::Result<()> {
-    if dir.is_dir() {
-        walk_dir(dir, out, &|_| {})?;
-    }
-    Ok(())
-}
-
-/// Readdir-only walk (NO per-file stat) of ONE directory subtree — for
-/// huge FUSE directories where stat'ing every file costs ~30 s; the
-/// caller supplies metadata for new files and keeps DB metadata for
-/// known ones.
-///
-/// FILTERS TO IMAGE EXTENSIONS (critical: a library directory holds
-/// thousands of videos too — enumerating them would inject non-image
-/// rows into the DB: phantom blank grid cells and count swings).
-/// A read_dir error fails the walk; per-file failures (file vanishing
-/// mid-walk — a normal race) are skipped.
-pub fn walk_dir_nostats(dir: &Path, cb: &mut dyn FnMut(&Path)) -> io::Result<()> {
-    if !dir.is_dir() {
-        return Ok(());
-    }
-    let mut stack = vec![dir.to_path_buf()];
-    while let Some(d) = stack.pop() {
-        for ent in std::fs::read_dir(&d)? {
-            let ent = ent?;
-            let p = ent.path();
-            let Ok(ft) = ent.file_type() else { continue };
-            if ft.is_dir() {
-                if p.is_symlink() {
-                    continue;
-                }
-                if p.file_name().map_or(false, |n| n.to_string_lossy().starts_with('.')) {
-                    continue;
-                }
-                stack.push(p);
-            } else if ft.is_file() {
-                let ps = p.to_string_lossy();
-                if is_image_path(&ps) {
-                    cb(&p);
-                }
-            }
-        }
-    }
-    Ok(())
-}
-
 /// Full stat walk. Error semantics: a read_dir error fails the walk
 /// (the result would be incomplete — must never be applied); per-file
 /// failures (a file vanishing between readdir and stat — a normal race
@@ -221,7 +171,7 @@ mod tests {
         std::fs::write(dir.path().join("c.txt"), b"x").unwrap();
         std::fs::create_dir_all(dir.path().join("d")).unwrap();
         std::fs::write(dir.path().join("d").join("e.heic"), b"x").unwrap();
-        let out = walk(&[dir.path().to_path_buf()], &|_| {}).unwrap();
+        let out = walk_stream(&[dir.path().to_path_buf()], &|_| {}).unwrap();
         assert_eq!(out.len(), 3);
         assert!(out.iter().all(|e| e.size == 1));
     }
@@ -231,7 +181,7 @@ mod tests {
         let dir = tempfile::tempdir().unwrap();
         make_tree(dir.path(), 5000, 8);
         let t = std::time::Instant::now();
-        let out = walk(&[dir.path().to_path_buf()], &|_| {}).unwrap();
+        let out = walk_stream(&[dir.path().to_path_buf()], &|_| {}).unwrap();
         let elapsed = t.elapsed();
         assert_eq!(out.len(), 5000);
         assert!(
@@ -245,7 +195,7 @@ mod tests {
     fn missing_root_dir_is_an_error() {
         let r = vec![PathBuf::from("/nonexistent/gallery-test-xyz")];
         // is_dir() false → the root is skipped, empty result, no error.
-        let out = walk(&r, &|_| {}).unwrap();
+        let out = walk_stream(&r, &|_| {}).unwrap();
         assert!(out.is_empty());
     }
 }

harnesses/ttimg/.tauriignore

@@ -0,0 +1 @@
+frontend/dist/img/

harnesses/ttimg/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "ttimg"
+version = "0.1.0"
+edition = "2021"
+
+# Tauri v2 mobile (Android): the CLI builds a cdylib .so loaded by the
+# Tauri activity; staticlib/rlib for the template's other targets.
+[lib]
+name = "ttimg_lib"
+crate-type = ["staticlib", "cdylib", "rlib"]
+
+[build-dependencies]
+tauri-build = { version = "2", features = [] }
+
+[dependencies]
+tauri = { version = "2", features = [] }
+tauri-runtime-wry = "2"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+log = { version = "0.4", features = ["std"] }

harnesses/ttimg/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    tauri_build::build()
+}

harnesses/ttimg/capabilities/default.json

@@ -0,0 +1,11 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "tttest: FR batching + lifecycle logs from the webview",
+  "windows": [
+    "main"
+  ],
+  "permissions": [
+    "core:default"
+  ]
+}