Connect: read the whole app from app.sab instead of component by component

Saves the app on the device, reads app.sab and fills the Sox cache with the tree,
config and links in one go: 8 s instead of 116 s for 230 components on a P-ION,
0.9 s instead of 16 s for 194 on an Orion. Sox keeps the cache current from
there as before. On any failure, or when app.sab does not match the running
tree, it falls back to lazy loading. A sheet's first open reads only runtime
values; a tree expand with nothing to load no longer rebuilds the DOM.

bench_sab_seed.py times both ways against a device.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

device_session.py

@@ -31,6 +31,18 @@ def _slot_precision(type_name, slot_name):
     return 2
 
 
+def _as_sox_value(slot, val):
+    """An app.sab config value as a Sox config read leaves it in the cache."""
+    if "s" in slot.flags:
+        return val
+    if slot.type in ("sys::Buf", "buf"):
+        # Sox reads every Buf as a Str: its bytes but the last, as text.
+        return val[:-1].decode("utf-8", errors="replace") if val else ""
+    if slot.type == "bool":
+        return val is not False      # Sox reads a bool as u1 != 0, so null is true
+    return val
+
+
 class DeviceSession:
     """High-level session manager for a live Sedona device connection."""
 
@@ -38,6 +50,10 @@ class DeviceSession:
         self.sox_client = None
         self._event_queue = queue.Queue()
         self._current_subs = set()   # comp_ids we subscribed for the open wiresheet
+        # Components whose config and links came from app.sab and have not been read
+        # since: their first sheet open skips reading those again.
+        self._seeded = set()
+        self.seed_info = ""          # how the cache was filled, for the status bar
 
     # ── Connect / Disconnect ────────────────────────────────────
 
@@ -53,11 +69,18 @@ class DeviceSession:
 
         self._load_slot_registry(parts)
 
-        root_comp = self.sox_client.load(0)
+        self.sox_client.load(0)
+        try:
+            count = self.seed_from_sab()
+            self.seed_info = f"app read from app.sab: {count} components"
+        except Exception as e:
+            self.seed_info = f"app.sab not used: {e}"
+
+        root_comp = self.sox_client.cache_get(0)
         if root_comp and root_comp.children:
             children = self.load_children(root_comp.id)
             if children:
-                self.sox_client.update(children, CONFIG | RUNTIME)
+                self.sox_client.update(children, self._values_to_read(children))
         return root_comp
 
     def disconnect(self, unsubscribe=True):
@@ -161,6 +184,74 @@ class DeviceSession:
                 if c is not None and c.kit_id == kit_id and c.type_id == type_id_val:
                     c.type_name = full_name
 
+    # ── Seeding from app.sab ────────────────────────────────────
+
+    def seed_from_sab(self):
+        """Fills the cache with the whole app — tree, config and links — from app.sab.
+
+        Reading component by component costs a round trip each, and a device answers one
+        request per pass of its loop: 230 components took 116 s on a P-ION, where saving
+        the app and reading app.sab took 8 s. The app is saved first, so app.sab holds
+        what is running. From here on Sox keeps the cache current, as it does for a
+        lazily loaded one; runtime values are still read when a sheet opens.
+
+        Nothing goes into the cache unless the whole file decodes and its tree matches the
+        device's, so on any failure the caller falls back to lazy loading. Returns the
+        number of components.
+        """
+        import app_backup
+        import sab_app
+        from sox import Link
+
+        client = self.sox_client
+        root = client.cache_get(0) or client.load(0)
+        app_backup.save_app(client)
+        app = sab_app.SabApp(client.get_file(app_backup.APP_SAB))
+
+        # app.sab numbers kits by the app's schema and Sox by kits.scode's; the two can
+        # differ, so types are matched by name, and a kit only when its checksum agrees.
+        device_kits = {p.name: f"{p.checksum & 0xFFFFFFFF:08x}" for p in client.schema_parts}
+        for name, checksum in app.kit_parts:
+            if device_kits.get(name) != checksum:
+                raise ValueError(f"kit {name} in app.sab is not the device's")
+        type_key = {qname: key for key, qname in client.type_name_map.items()}
+
+        if [k["id"] for k in app.app["kids"]] != root.children:
+            raise ValueError("app.sab does not match the running app")
+
+        comps = {}
+        for c in app.comps.values():
+            key = type_key.get(c["type"])
+            if key is None:
+                raise ValueError(f"no manifest for {c['type']}")
+            comp = SoxComponent(c["id"], key[0], key[1], c["type"])
+            comp.name = c["name"]
+            comp.parent = c["parentId"]
+            comp.children = [k["id"] for k in c["kids"]]
+            comp.permissions = root.permissions
+            for slot, val in c["props"]:
+                comp.values[slot.name] = _as_sox_value(slot, val)
+            comps[comp.id] = comp
+        comps[0].subscription = root.subscription
+
+        # Sox reads a component's links both ways, into it and out of it.
+        for from_c, from_slot, to_c, to_slot in app.links:
+            link = Link(from_c["id"], from_slot, to_c["id"], to_slot)
+            comps[from_c["id"]].links.append(link)
+            if to_c["id"] != from_c["id"]:
+                comps[to_c["id"]].links.append(link)
+
+        for comp in comps.values():
+            client.cache_add(comp)
+        self._seeded = set(comps)
+        return len(comps)
+
+    def _values_to_read(self, comps):
+        """What to read for `comps` on a sheet open: config too, unless app.sab gave it."""
+        if all(c.id in self._seeded for c in comps):
+            return RUNTIME
+        return CONFIG | RUNTIME
+
     # ── Lazy Loading ────────────────────────────────────────────
 
     def load_children(self, comp_id):
@@ -253,9 +344,9 @@ class DeviceSession:
 
         all_link_remote_ids = set()
         for child in children:
-            links = self.sox_client.read_links(child.id)
-            child.links = links
-            for lnk in links:
+            if child.id not in self._seeded:
+                child.links = self.sox_client.read_links(child.id)
+            for lnk in child.links:
                 all_link_remote_ids.add(lnk.from_comp_id)
                 all_link_remote_ids.add(lnk.to_comp_id)
 
@@ -267,7 +358,14 @@ class DeviceSession:
         if remote_ids:
             self.sox_client.load_ids(remote_ids, checked=False)
 
-        self.sox_client.update(children, CONFIG | RUNTIME)
+        seeded = [c for c in children if c.id in self._seeded]
+        others = [c for c in children if c.id not in self._seeded]
+        if seeded:
+            self.sox_client.update(seeded, RUNTIME)
+        if others:
+            self.sox_client.update(others, CONFIG | RUNTIME)
+        # Subscribed from here on, so Sox keeps them current; a later open reads again.
+        self._seeded -= child_ids
 
         folder_comp = self.sox_client.cache_get(folder_comp_id)
         to_subscribe = [folder_comp] + children if folder_comp else children