perf(xref): fix O(n²) AcDs parse and skip host re-tessellation

Opening a drawing that xrefs several 3D-heavy DWGs (e.g. Clinic.dwg with
5 discipline files) took ~137s, effectively all of it inside the DWG
parser's AcDs SAB blob extraction.

Bump the acadrust pin to ceef045, which bounds the AcDs end-marker search
so a missing marker family no longer scans the whole buffer per record.
Total xref resolve for Clinic.dwg drops from ~97s to ~4s.

Also make the post-xref mesh pass incremental: the host solids were
already tessellated by the background loader and the merge assigns fresh
handles to every imported entity, so `populate_missing_meshes_from_document`
keeps the cached host meshes and tessellates only the merged xref solids
instead of clearing and rebuilding the whole document.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Cargo.lock

@@ -71,7 +71,7 @@ checksum = "366ffbaa4442f4684d91e2cd7c5ea7c4ed8add41959a31447066e279e432b618"
 [[package]]
 name = "acadrust"
 version = "0.4.0"
-source = "git+https://github.com/HakanSeven12/acadrust?branch=main#f76e41adb47b09c66b3032d3727468e4303bcaf0"
+source = "git+https://github.com/HakanSeven12/acadrust?branch=main#ceef045ed9fe4658dfb1ad488fe12f65c0311135"
 dependencies = [
  "ahash 0.8.12",
  "anyhow",

src/app/update/file.rs

@@ -394,10 +394,12 @@ pub(super) fn on_open_file(&mut self) -> Task<Message> {
                 // built the mesh caches above, so those caches contain none of
                 // the xref'd geometry. The wire pass rebuilds from the document
                 // each frame (bump_geometry covers it), but 3D-solid meshes are
-                // only tessellated by `populate_meshes_from_document` — re-run it
+                // only tessellated by populate — run the incremental variant so
-                // so xref'd solids (walls, floors, roofs) actually render. (#203)
+                // the already-cached host solids are kept and only the newly
+                // merged xref solids (walls, floors, roofs) are tessellated,
+                // avoiding a full re-tessellation of the whole drawing. (#203)
                 if xref_merged {
-                    self.tabs[i].scene.populate_meshes_from_document();
+                    self.tabs[i].scene.populate_missing_meshes_from_document();
                 }
                 self.tabs[i].scene.selected = rustc_hash::FxHashSet::default();
                 self.tabs[i].scene.preview_wires = vec![];

src/scene/entity.rs

@@ -1209,8 +1209,28 @@ impl Scene {
     /// Called after loading a document or after undo/redo so that every
     /// `Solid3D` entity is represented in the mesh cache.
     pub fn populate_meshes_from_document(&mut self) {
-        self.meshes.clear();
+        self.populate_meshes_impl(false);
-        self.block_meshes.clear();
+    }
+
+    /// Like [`populate_meshes_from_document`] but tessellates only solids
+    /// whose handle is not already cached — the existing meshes are kept.
+    ///
+    /// Used after an XREF merge: the host document's solids were already
+    /// tessellated by the background loader, and the merge assigns brand-new
+    /// handles to every imported xref entity (see `merge_xref_into_block`),
+    /// so cached handles are guaranteed to be host solids. This turns the
+    /// post-xref pass from "re-tessellate host + all xrefs" into "tessellate
+    /// only the newly merged xref solids" — the dominant cost when a drawing
+    /// attaches several large xrefs. (#203)
+    pub fn populate_missing_meshes_from_document(&mut self) {
+        self.populate_meshes_impl(true);
+    }
+
+    fn populate_meshes_impl(&mut self, incremental: bool) {
+        if !incremental {
+            self.meshes.clear();
+            self.block_meshes.clear();
+        }
         // BLOCK-entity handles of the layout (model + paper) blocks. A solid
         // owned by one of these is top-level; anything else lives in a block
         // definition and is instanced per INSERT instead. (#123)
@@ -1234,9 +1254,17 @@ impl Scene {
             .entities()
             .filter_map(|e| match e {
                 EntityType::Solid3D(_) | EntityType::Region(_) | EntityType::Body(_) | EntityType::Surface(_) => {
+                    let handle = e.common().handle;
+                    // Incremental (post-xref) pass: leave already-tessellated
+                    // host solids untouched, only build the newly merged ones.
+                    if incremental
+                        && (self.meshes.contains_key(&handle) || self.block_meshes.contains_key(&handle))
+                    {
+                        return None;
+                    }
                     let color = self.render_style(e).0;
                     let top_level = layout_blocks.contains(&e.common().owner_handle);
-                    Some((e.common().handle, e.clone(), color, top_level))
+                    Some((handle, e.clone(), color, top_level))
                 }
                 _ => None,
             })