fix(tui): preserve workspace preview across child rails

cmux-tui/crates/cmux-tui/src/app.rs

@@ -9955,6 +9955,7 @@ impl App {
         if !self.tree.select_surface(target.surface) {
             return Ok(());
         }
+        self.commit_workspace_preview();
         self.follow_sidebar_workspace(target.workspace);
         self.pane_focus_history.record(target.pane);
         self.claim_active_terminal_geometry(true);
@@ -9989,6 +9990,7 @@ impl App {
                 if !self.prepare_pty_input_before_mutation() {
                     return Ok(());
                 }
+                self.commit_workspace_preview();
                 self.follow_sidebar_workspace(workspace);
                 self.tree.active_workspace = workspace;
                 if let Some(workspace_view) = self.tree.workspaces.get_mut(workspace) {
@@ -10098,7 +10100,18 @@ impl App {
     }
 
     fn focus_rail(&mut self, kind: RailKind) {
-        if kind != RailKind::Workspace {
+        // A workspace preview is a navigation transaction across the
+        // workspace-dependent rails. Keep it while moving between the
+        // workspace, tabs, and projection rails so those child views follow
+        // the highlighted workspace. A machine rail or pane transition ends
+        // the transaction.
+        let keep_workspace_preview = self.workspace_preview.is_some()
+            && matches!(
+                self.focus,
+                FocusTarget::WorkspaceRail | FocusTarget::TabsRail | FocusTarget::ProjectionRail(_)
+            )
+            && matches!(kind, RailKind::Workspace | RailKind::Tabs | RailKind::Projection(_));
+        if !keep_workspace_preview {
             self.cancel_workspace_preview();
         }
         self.focus = match kind {
@@ -40892,6 +40905,44 @@ mod tests {
         }
     }
 
+    #[test]
+    fn workspace_sidebar_row_click_commits_hover_preview() {
+        let mux = Mux::new("workspace-sidebar-preview-row-click-test", SurfaceOptions::default());
+        let first = mux.new_workspace(Some("Alpha".into()), Some((80, 24))).unwrap();
+        let second = mux.new_workspace(Some("Beta".into()), Some((80, 24))).unwrap();
+        mux.select_workspace(Some(0), None);
+        let mut app = test_app(Session::Local(mux.clone()));
+        app.sidebar_view = SidebarView::Workspaces;
+        app.replace_tree(app.session.tree());
+        app.tree.active_workspace = 0;
+        app.sidebar_workspace_selection = 0;
+        app.workspace_rail_selection = WorkspaceRailSelection::Workspace;
+        app.focus = FocusTarget::WorkspaceRail;
+        app.sync_layout((100, 20));
+
+        let mut terminal = Terminal::new(TestBackend::new(100, 20)).unwrap();
+        terminal.draw(|frame| crate::ui::draw(&mut app, frame)).unwrap();
+        let row = app
+            .hits
+            .iter()
+            .find_map(|(rect, hit)| {
+                matches!(hit, super::Hit::Workspace { index: 1, .. }).then_some(*rect)
+            })
+            .expect("second workspace hit");
+
+        app.handle_hover_with_admission(row.x, row.y, KeyModifiers::NONE, None).unwrap();
+        assert!(app.workspace_preview.is_some());
+        app.handle_left_down(row.x, row.y, KeyModifiers::NONE).unwrap();
+
+        assert_eq!(app.tree.active_workspace, 1);
+        assert_eq!(app.workspace_preview, None);
+        assert_eq!(app.focus, FocusTarget::Pane);
+
+        for surface in [first.id, second.id] {
+            mux.close_surface(surface).unwrap();
+        }
+    }
+
     #[test]
     fn workspace_sidebar_preview_commits_when_pane_is_clicked() {
         let mux = Mux::new("workspace-sidebar-preview-pane-click-test", SurfaceOptions::default());
@@ -41008,6 +41059,118 @@ mod tests {
         }
     }
 
+    #[test]
+    fn workspace_preview_survives_workspace_dependent_rail_navigation() {
+        let mux = Mux::new("workspace-sidebar-preview-child-rail-test", SurfaceOptions::default());
+        let first = mux.new_workspace(Some("Alpha".into()), Some((80, 24))).unwrap();
+        let second = mux.new_workspace(Some("Beta".into()), Some((80, 24))).unwrap();
+        let tree = Session::Local(mux.clone()).tree();
+        let first_workspace = tree.workspaces[0].id;
+        let second_workspace = tree.workspaces[1].id;
+        let mut app = test_app(Session::Local(mux.clone()));
+        app.sidebar_view = SidebarView::Workspaces;
+        app.config.sidebar.columns_explicit = true;
+        app.config.sidebar.columns = vec![
+            crate::config::SidebarColumn {
+                kind: SidebarColumnKind::Workspaces,
+                width: 24,
+                max_width: 0,
+            },
+            crate::config::SidebarColumn { kind: SidebarColumnKind::Tabs, width: 24, max_width: 0 },
+        ];
+        app.config.sidebar.views = app
+            .config
+            .sidebar
+            .columns
+            .iter()
+            .map(|column| SidebarViewSpec::legacy(column.kind, column.width, column.max_width))
+            .collect();
+        app.config.sidebar.views_explicit = true;
+        app.replace_tree(app.session.tree());
+        app.tree.active_workspace = 0;
+        app.sidebar_workspace_selection = 1;
+        app.workspace_rail_selection = WorkspaceRailSelection::Workspace;
+        app.workspace_preview =
+            Some(WorkspacePreview { origin: first_workspace, target: second_workspace });
+        app.tree.active_workspace = 1;
+        app.focus = FocusTarget::WorkspaceRail;
+        app.sync_layout((100, 20));
+
+        app.handle_key(KeyEvent::new(KeyCode::Right, KeyModifiers::NONE)).unwrap();
+
+        assert_eq!(app.focus, FocusTarget::TabsRail);
+        assert_eq!(
+            app.workspace_preview,
+            Some(WorkspacePreview { origin: first_workspace, target: second_workspace })
+        );
+        assert_eq!(app.sidebar_workspace_selection, 1);
+        assert!(app.sidebar_tab_targets().iter().all(|target| target.workspace == 1));
+        assert!(app.sidebar_tab_targets().iter().any(|target| target.surface == second.id));
+
+        app.handle_key(KeyEvent::new(KeyCode::Right, KeyModifiers::NONE)).unwrap();
+
+        assert_eq!(app.focus, FocusTarget::Pane);
+        assert_eq!(app.workspace_preview, None);
+        assert_eq!(app.tree.active_workspace, 0);
+
+        for surface in [first.id, second.id] {
+            mux.close_surface(surface).unwrap();
+        }
+    }
+
+    #[test]
+    fn workspace_preview_commits_when_tabs_rail_target_is_activated() {
+        let mux =
+            Mux::new("workspace-sidebar-preview-tabs-activate-test", SurfaceOptions::default());
+        let first = mux.new_workspace(Some("Alpha".into()), Some((80, 24))).unwrap();
+        let second = mux.new_workspace(Some("Beta".into()), Some((80, 24))).unwrap();
+        let tree = Session::Local(mux.clone()).tree();
+        let first_workspace = tree.workspaces[0].id;
+        let second_workspace = tree.workspaces[1].id;
+        let mut app = test_app(Session::Local(mux.clone()));
+        app.sidebar_view = SidebarView::Workspaces;
+        app.config.sidebar.columns_explicit = true;
+        app.config.sidebar.columns = vec![
+            crate::config::SidebarColumn {
+                kind: SidebarColumnKind::Workspaces,
+                width: 24,
+                max_width: 0,
+            },
+            crate::config::SidebarColumn { kind: SidebarColumnKind::Tabs, width: 24, max_width: 0 },
+        ];
+        app.config.sidebar.views = app
+            .config
+            .sidebar
+            .columns
+            .iter()
+            .map(|column| SidebarViewSpec::legacy(column.kind, column.width, column.max_width))
+            .collect();
+        app.config.sidebar.views_explicit = true;
+        app.replace_tree(app.session.tree());
+        app.tree.active_workspace = 0;
+        app.sidebar_workspace_selection = 1;
+        app.workspace_rail_selection = WorkspaceRailSelection::Workspace;
+        app.workspace_preview =
+            Some(WorkspacePreview { origin: first_workspace, target: second_workspace });
+        app.tree.active_workspace = 1;
+        app.focus = FocusTarget::WorkspaceRail;
+        app.sync_layout((100, 20));
+
+        app.handle_key(KeyEvent::new(KeyCode::Right, KeyModifiers::NONE)).unwrap();
+        assert_eq!(app.focus, FocusTarget::TabsRail);
+        assert!(app.workspace_preview.is_some());
+
+        app.handle_key(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE)).unwrap();
+
+        assert_eq!(app.focus, FocusTarget::Pane);
+        assert_eq!(app.workspace_preview, None);
+        assert_eq!(app.tree.active_workspace, 1);
+
+        for surface in [first.id, second.id] {
+            mux.close_surface(surface).unwrap();
+        }
+    }
+
     #[test]
     fn workspace_preview_reconciliation_aligns_selection_when_a_workspace_disappears() {
         let mux = Mux::new("workspace-sidebar-preview-reconcile-test", SurfaceOptions::default());