Merge PR #322: perf — responsive large copy/paste + point picking

External contributor sLuCHa (sLuCHaa). Gates O(k²) snap intersection
passes, O(1) handle lookups in preview, bbox paste anchor/ghost,
count-only properties panel for huge selections, incremental paste mesh.

src/app/command_driver.rs

@@ -2085,7 +2085,12 @@ impl OpenCADStudio {
             })
             .collect();
         self.merge_clipboard_ext_objects(i, &by_index);
-        self.tabs[i].scene.populate_meshes_from_document();
+        // Incremental: `add_entity` already tessellated every pasted top-level
+        // solid, and existing document solids are still cached — so only newly
+        // introduced block-definition solids need building. The full rebuild
+        // would clear and re-tessellate the entire document (every solid in the
+        // drawing) on each paste, which is what made a large paste stall.
+        self.tabs[i].scene.populate_missing_meshes_from_document();
         by_index
     }
 

src/app/commands/blocks.rs

@@ -70,8 +70,9 @@ impl OpenCADStudio {
                         .iter()
                         .filter_map(|&h| self.tabs[i].scene.document.get_entity(h).cloned())
                         .collect();
-                    self.clipboard_centroid = super::super::helpers::entities_centroid(
-                        &self.tabs[i].scene.wire_models_for(&handles),
+                    self.clipboard_centroid = super::super::helpers::entities_centroid_by_bbox(
+                        &self.tabs[i].scene.document,
+                        &handles,
                     );
                     self.clipboard = entities;
                     self.clipboard_deps = super::super::ClipboardDeps::capture(
@@ -158,8 +159,9 @@ impl OpenCADStudio {
                         .iter()
                         .filter_map(|&h| self.tabs[i].scene.document.get_entity(h).cloned())
                         .collect();
-                    self.clipboard_centroid = super::super::helpers::entities_centroid(
-                        &self.tabs[i].scene.wire_models_for(&handles),
+                    self.clipboard_centroid = super::super::helpers::entities_centroid_by_bbox(
+                        &self.tabs[i].scene.document,
+                        &handles,
                     );
                     let count = entities.len();
                     self.clipboard = entities;

src/app/helpers.rs

@@ -1,4 +1,3 @@
-use crate::scene::WireModel;
 use crate::ui::overlay::GridPlane;
 use acadrust::tables::Ucs;
 
@@ -253,28 +252,27 @@ pub(super) fn polar_constrain_near(
 
 // ── Clipboard / selection helpers ──────────────────────────────────────────
 
-/// Compute the centroid of a set of wire models (average of all points).
-pub(super) fn entities_centroid(wires: &[WireModel]) -> glam::DVec3 {
-    // Reconstruct each vertex's absolute f64 from the double-single high/low
-    // pair and accumulate in f64: summing the f32 `points` alone at UTM scale
-    // (~5.7e6) both quantizes each term ~0.5 m and loses low bits across the
-    // running total, drifting the paste base / block base metres off.
+/// Cheap copy/paste anchor: the mean of each entity's bounding-box centre.
+/// Replaces averaging every tessellated wire vertex, which cost O(total
+/// geometry) and stalled a whole-drawing copy. The anchor only sets which point
+/// of the selection sits under the cursor, so a per-entity bbox centre is an
+/// equally valid, far cheaper origin.
+pub(super) fn entities_centroid_by_bbox(
+    doc: &acadrust::CadDocument,
+    handles: &[acadrust::Handle],
+) -> glam::DVec3 {
     let mut sum = glam::DVec3::ZERO;
     let mut count = 0usize;
-    for w in wires {
-        for (i, p) in w.points.iter().enumerate() {
-            // Wire models carry NaN points as separators between disjoint
-            // segments; summing them poisons the whole centroid into NaN,
-            // which then makes every paste base point NaN. (#129)
-            if !p[0].is_finite() || !p[1].is_finite() || !p[2].is_finite() {
-                continue;
-            }
-            let l = w.points_low.get(i).copied().unwrap_or([0.0; 3]);
-            sum += glam::DVec3::new(
-                p[0] as f64 + l[0] as f64,
-                p[1] as f64 + l[1] as f64,
-                p[2] as f64 + l[2] as f64,
-            );
+    for &h in handles {
+        let Some(e) = doc.get_entity(h) else { continue };
+        let bb = e.as_entity().bounding_box();
+        let c = glam::DVec3::new(
+            (bb.min.x + bb.max.x) * 0.5,
+            (bb.min.y + bb.max.y) * 0.5,
+            (bb.min.z + bb.max.z) * 0.5,
+        );
+        if c.x.is_finite() && c.y.is_finite() && c.z.is_finite() {
+            sum += c;
             count += 1;
         }
     }

src/app/properties.rs

@@ -5,6 +5,11 @@ use crate::scene::view::dispatch;
 use crate::ui;
 use acadrust::{EntityType, Handle};
 
+/// Above this many selected objects the Properties panel skips per-entity
+/// property aggregation (which is O(n) per row, plus an O(n²) group filter) and
+/// shows a count-only summary instead. Bulk edits still go through the ribbon.
+const MAX_PROP_AGGREGATE: usize = 2_000;
+
 impl OpenCADStudio {
     /// Rebuild the PropertiesPanel from the current entity selection.
     /// Preserves UI state (open pickers, edit buffer) across refreshes.
@@ -432,6 +437,23 @@ impl OpenCADStudio {
                         ..Default::default()
                     }
                 }
+                // Property aggregation is O(n) per row plus an O(n²) group filter
+                // (`group.handles.contains` scans per entity), stalling the rebuild
+                // for seconds at tens of thousands of objects. Above the cap show a
+                // count-only panel; bulk edits still go through the ribbon.
+                n if n > MAX_PROP_AGGREGATE => ui::PropertiesPanel {
+                    title: format!("{} objects selected", n),
+                    layer_combo: iced::widget::combo_box::State::new(layer_names.clone()),
+                    linetype_combo: iced::widget::combo_box::State::new(linetype_items.clone()),
+                    lineweight_combo: iced::widget::combo_box::State::new(
+                        ui::properties::lw_options(),
+                    ),
+                    hatch_pattern_combo: iced::widget::combo_box::State::new(
+                        crate::scene::model::hatch_patterns::names(),
+                    ),
+                    linetype_items,
+                    ..Default::default()
+                },
                 _ => {
                     let groups = build_selection_groups(&selected);
                     let active_group = selected_group