ui: the selection filter follows what the selection holds (#341, #371)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/ui-egui/src/lib.rs

@@ -1264,6 +1264,11 @@ impl ModelApp {
         if self.pick.selection.apply(items, mode) {
             self.pick.generation = self.pick.generation.wrapping_add(1);
         }
+        // The filter label follows what the selection holds (a seed picked in the browser selects
+        // its edge whatever the filter was, #341).
+        if let Some(f) = self.pick.selection.filter() {
+            self.pick.filter = f;
+        }
         let mut text = format!("Selected: {}", self.pick.selection.summary());
         if self.pick.selection.capped() {
             text.push_str(&format!(" (at most {} items)", selection::MAX_SELECTION));

crates/ui-egui/src/selection.rs

@@ -72,6 +72,21 @@ impl Filter {
         }
     }
 
+    /// The filter that picks `item`.
+    pub fn of(item: &Item) -> Filter {
+        match item {
+            Item::Geometry(g) => match g.entity {
+                Entity::Body => Filter::Bodies,
+                Entity::Face(_) => Filter::Faces,
+                Entity::Edge(_) => Filter::Edges,
+                Entity::Vertex(_) => Filter::Vertices,
+            },
+            Item::Node(_) => Filter::Nodes,
+            Item::Element(_) => Filter::Elements,
+            Item::Face(_) => Filter::ElementFaces,
+        }
+    }
+
     /// Geometry (named) rather than mesh (labelled) entities.
     pub fn geometry(self) -> bool {
         matches!(self, Filter::Faces | Filter::Edges | Filter::Vertices | Filter::Bodies)
@@ -142,6 +157,13 @@ impl Selection {
         &self.items
     }
 
+    /// The one filter that picks every selected item (`None` when empty or mixed).
+    pub fn filter(&self) -> Option<Filter> {
+        let mut kinds = self.items.iter().map(Filter::of);
+        let first = kinds.next()?;
+        kinds.all(|k| k == first).then_some(first)
+    }
+
     pub fn len(&self) -> usize {
         self.items.len()
     }
@@ -974,6 +996,20 @@ mod tests {
 
     use super::*;
 
+    /// The filter a selection holds: one kind names it, a mix or nothing names none (#341).
+    #[test]
+    fn a_selection_names_the_filter_of_what_it_holds() {
+        let edge = Item::Geometry(GeometryRef::new("Bar", Entity::Edge("top".into())).unwrap());
+        let mut sel = Selection::default();
+        assert_eq!(sel.filter(), None);
+        sel.apply([edge], Mode::Replace);
+        assert_eq!(sel.filter(), Some(Filter::Edges));
+        sel.apply([Item::Node(3)], Mode::Add);
+        assert_eq!(sel.filter(), None);
+        sel.apply([Item::Node(4)], Mode::Replace);
+        assert_eq!(sel.filter(), Some(Filter::Nodes));
+    }
+
     /// `nx × ny × nz` unit hex8 cells, the faces at x = nx tagged as face `end` of body `Bar`, the
     /// solids as the body, the edge along x = nx, z = nz as edge `top` and the corner node at
     /// (nx, 0, 0) as vertex `v`.