Viewer: clickable breadcrumbs

Every crumb above the page you're on links to where it names: the
section goes to its home (Parties › Tobin Harlow → Parties), and a
reconciliation's trail runs Accounts › its account › it. Same look; a
pointer and "Go to …" on hover. A crumb naming the current page isn't a
link.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX

crates/ledger-gui/src/app.rs

@@ -627,33 +627,46 @@ impl App {
                         }
                         ui.add_space(8.0);
                         ui.with_layout(Layout::left_to_right(Align::Center), |ui| {
-                            let crumb = self
-                                .books
-                                .as_ref()
-                                .map(|b| crate::palette::describe(b, &self.nav.current))
-                                .unwrap_or_default();
-                            let section = self.nav.current.section().title();
-                            // Narrow, the crumb alone says where you are.
-                            if crumb.is_empty() || ui.available_width() >= 260.0 {
-                                ui.add(
-                                    egui::Label::new(
-                                        RichText::new(section)
-                                            .font(theme::regular(13.5))
-                                            .color(p.muted),
-                                    )
-                                    .truncate(),
-                                );
-                            }
-                            if !crumb.is_empty() {
-                                if ui.available_width() >= 260.0 - 80.0 {
+                            let crumbs =
+                                crate::palette::crumbs(self.books.as_deref(), &self.nav.current);
+                            // Narrow, the last crumb alone says where you are.
+                            let skip = if ui.available_width() >= 260.0 {
+                                0
+                            } else {
+                                crumbs.len() - 1
+                            };
+                            let last = crumbs.len() - 1;
+                            let mut go = None;
+                            for (i, (text, to)) in crumbs.iter().enumerate().skip(skip) {
+                                if i > skip && ui.available_width() >= 260.0 - 80.0 {
                                     ui.label(RichText::new(icon::CARET_RIGHT).color(p.faint));
                                 }
-                                ui.add(
-                                    egui::Label::new(
-                                        RichText::new(crumb).font(theme::semibold(13.5)),
-                                    )
-                                    .truncate(),
-                                );
+                                let rich = if i == last && i > 0 {
+                                    RichText::new(text).font(theme::semibold(13.5))
+                                } else {
+                                    RichText::new(text)
+                                        .font(theme::regular(13.5))
+                                        .color(p.muted)
+                                };
+                                let label = egui::Label::new(rich).truncate();
+                                match to {
+                                    Some(to) => {
+                                        let r = ui.add(label.sense(egui::Sense::click()));
+                                        if r.hovered() {
+                                            ui.ctx()
+                                                .set_cursor_icon(egui::CursorIcon::PointingHand);
+                                        }
+                                        if r.on_hover_text(format!("Go to {text}")).clicked() {
+                                            go = Some(to.clone());
+                                        }
+                                    }
+                                    None => {
+                                        ui.add(label);
+                                    }
+                                }
+                            }
+                            if let Some(to) = go {
+                                self.nav.go(to);
                             }
                         });
                     });

crates/ledger-gui/src/palette.rs

@@ -458,6 +458,45 @@ pub fn search(b: &Books, query: &str) -> Vec<Item> {
     out
 }
 
+/// The breadcrumb for a route, outermost first: its section, any page it
+/// sits under (a reconciliation under its account), then the route
+/// itself. Each crumb is its text and where clicking it goes; `None` for
+/// the page you're on, which isn't a link.
+///
+/// ```text
+/// INVARIANTS:
+///   1. The first crumb is the section's title, going to Section::home.
+///   2. The last crumb is the current page: describe(r) when it says
+///      anything, else the section itself (a section's own page).
+///   3. Only the last crumb is None; a crumb whose route is the current
+///      one is never a link.
+/// ```
+pub fn crumbs(b: Option<&Books>, r: &Route) -> Vec<(String, Option<Route>)> {
+    let section = r.section();
+    let here = b.map(|b| describe(b, r)).unwrap_or_default();
+    let mut out = vec![(section.title().to_string(), Some(section.home()))];
+    if let (Some(b), Route::Reconciliation(id)) = (b, r)
+        && let Some(rec) = b.reconciliation(*id)
+    {
+        let account = Route::Account(rec.account_id);
+        out.push((describe(b, &account), Some(account)));
+    }
+    if here.is_empty() {
+        out.truncate(1);
+    } else {
+        out.push((here, None));
+    }
+    for c in &mut out {
+        if c.1.as_ref() == Some(r) {
+            c.1 = None;
+        }
+    }
+    if let Some(last) = out.last_mut() {
+        last.1 = None;
+    }
+    out
+}
+
 /// A short description of a route for the breadcrumb.
 pub fn describe(b: &Books, r: &Route) -> String {
     match r {