feat(statusbar): highlight cycling-list object on row hover

Add a scene hover_highlight handle that renders an entity with the
selection colour without joining the real selection. The cycling list
box sets it on row enter / clears on exit, so hovering a row glows the
matching object in the drawing.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/app/mod.rs

@@ -767,6 +767,8 @@ pub enum Message {
     ToggleSelectionCycling,
     /// Add an object from the selection-cycling list box to the selection.
     CycleSelect(acadrust::Handle),
+    /// Preview (highlight) a cycling-list row's object, or clear with `None`.
+    CycleHover(Option<acadrust::Handle>),
     /// Dismiss the selection-cycling list box without picking.
     CycleCancel,
     /// Toggle the selection-filter type picker open/closed.

src/app/update.rs

@@ -3631,19 +3631,27 @@ impl OpenCADStudio {
             Message::ToggleSelectionCycling => {
                 self.selection_cycling ^= true;
                 self.cycle_candidates = None;
+                self.tabs[self.active_tab].scene.set_hover_highlight(None);
                 Task::none()
             }
             Message::CycleSelect(handle) => {
                 // Add the picked object to the current selection (accumulate).
                 self.cycle_candidates = None;
                 let i = self.active_tab;
+                self.tabs[i].scene.set_hover_highlight(None);
                 self.tabs[i].scene.select_entity(handle, false);
                 self.tabs[i].scene.expand_selection_for_groups(&[handle]);
                 self.refresh_properties();
                 Task::none()
             }
+            Message::CycleHover(handle) => {
+                let i = self.active_tab;
+                self.tabs[i].scene.set_hover_highlight(handle);
+                Task::none()
+            }
             Message::CycleCancel => {
                 self.cycle_candidates = None;
+                self.tabs[self.active_tab].scene.set_hover_highlight(None);
                 Task::none()
             }
             Message::ToggleSelectionFilterPopup => {

src/scene/mod.rs

@@ -553,6 +553,9 @@ pub struct Scene {
     /// `tessellate_block`'s visibility test skips these, so they neither
     /// render nor hit-test until isolation ends.
     pub hidden: HashSet<Handle>,
+    /// Entity drawn with the selection-highlight colour without being part
+    /// of the real selection — used to preview a row in the cycling list box.
+    pub hover_highlight: Option<Handle>,
     /// Whether entity transparency is honoured on screen. When false the
     /// wire shader forces every line opaque (a uniform toggle, no retessellate).
     pub transparency_display: bool,
@@ -704,6 +707,7 @@ impl Scene {
             document: CadDocument::new(),
             selected: HashSet::new(),
             hidden: HashSet::new(),
+            hover_highlight: None,
             transparency_display: true,
             selection_filter: HashSet::new(),
             preview_wires: vec![],
@@ -1334,6 +1338,15 @@ impl Scene {
         !self.hidden.is_empty()
     }
 
+    /// Set (or clear) the previewed entity that renders with the selection
+    /// highlight without joining the real selection. Re-tessellates on change.
+    pub fn set_hover_highlight(&mut self, handle: Option<Handle>) {
+        if self.hover_highlight != handle {
+            self.hover_highlight = handle;
+            self.bump_geometry();
+        }
+    }
+
     /// Hide every drawable entity except the current selection (Isolate).
     pub fn isolate_selected(&mut self) {
         if self.selected.is_empty() {
@@ -2005,7 +2018,19 @@ impl Scene {
         // Tessellate in parallel across all available CPU cores.
         use rayon::prelude::*;
         let doc = &self.document;
-        let sel = &self.selected;
+        // Fold the hover-preview entity into the highlight set so it renders
+        // selected without being part of the real selection.
+        let hl_set;
+        let sel: &HashSet<Handle> = if let Some(h) = self.hover_highlight {
+            hl_set = {
+                let mut s = self.selected.clone();
+                s.insert(h);
+                s
+            };
+            &hl_set
+        } else {
+            &self.selected
+        };
         let avp = self.active_viewport;
         // A paper-space content viewport renders MODEL block entities while
         // the user is sitting in a paper layout — that path expects

src/ui/cycle_popup.rs

@@ -15,7 +15,7 @@ pub fn cycle_popup_overlay(
 ) -> Element<'static, Message> {
     let rows: Vec<Element<'static, Message>> = items
         .into_iter()
-        .map(|(handle, label)| item_row(label, Message::CycleSelect(handle)))
+        .map(|(handle, label)| item_row(handle, label))
         .collect();
 
     let panel = container(column(rows))
@@ -43,10 +43,10 @@ pub fn cycle_popup_overlay(
     mouse_area(positioned).on_press(Message::CycleCancel).into()
 }
 
-fn item_row(label: String, msg: Message) -> Element<'static, Message> {
+fn item_row(handle: acadrust::Handle, label: String) -> Element<'static, Message> {
     let content = text(label).size(11).color(LABEL).align_y(iced::Center);
-    button(content)
-        .on_press(msg)
+    let btn = button(content)
+        .on_press(Message::CycleSelect(handle))
         .style(|_: &Theme, status| button::Style {
             background: Some(Background::Color(match status {
                 button::Status::Hovered => ROW_HOVER,
@@ -55,7 +55,11 @@ fn item_row(label: String, msg: Message) -> Element<'static, Message> {
             ..Default::default()
         })
         .width(Fill)
-        .padding([4, 10])
+        .padding([4, 10]);
+    // Highlight the underlying object while the cursor is over this row.
+    mouse_area(btn)
+        .on_enter(Message::CycleHover(Some(handle)))
+        .on_exit(Message::CycleHover(None))
         .into()
 }