feat: support bottom tab bar placement (#2118)

* feat: support bottom tab bar placement

* fix: preserve mouse cleanup under bottom mode bar

refs #2117

7 files changed, 182 insertions, 11 deletions

diff --git a/src/app/input/mouse.rs b/src/app/input/mouse.rs
index 56b9b676..2c32c95a 100644
--- a/src/app/input/mouse.rs
+++ b/src/app/input/mouse.rs
@@ -483,6 +483,10 @@ impl AppState {
                     }
                 }
 
+                if self.mode_bar_covers_tab_row(mouse.column, mouse.row) {
+                    return None;
+                }
+
                 if self.on_tab_scroll_left_button(mouse.column, mouse.row) {
                     self.scroll_tabs_left();
                     return None;
@@ -913,6 +917,9 @@ impl AppState {
             }
 
             MouseEventKind::ScrollUp | MouseEventKind::ScrollDown
+                if self.mode_bar_covers_tab_row(mouse.column, mouse.row) => {}
+
+            MouseEventKind::ScrollUp | MouseEventKind::ScrollDown
                 if self.on_tab_bar(mouse.column, mouse.row) =>
             {
                 match mouse.kind {
@@ -1063,7 +1070,8 @@ impl AppState {
             }
 
             MouseEventKind::Down(MouseButton::Right)
-                if self.tab_at(mouse.column, mouse.row).is_some() =>
+                if !self.mode_bar_covers_tab_row(mouse.column, mouse.row)
+                    && self.tab_at(mouse.column, mouse.row).is_some() =>
             {
                 if let (Some(ws_idx), Some(tab_idx)) =
                     (self.active, self.tab_at(mouse.column, mouse.row))
@@ -1272,6 +1280,15 @@ impl AppState {
             })
     }
 
+    fn mode_bar_covers_tab_row(&self, col: u16, row: u16) -> bool {
+        self.tab_bar_position == crate::config::TabBarPositionConfig::Bottom
+            && matches!(
+                self.mode,
+                Mode::Navigate | Mode::Prefix | Mode::Copy | Mode::Resize
+            )
+            && self.on_tab_bar(col, row)
+    }
+
     pub(super) fn on_tab_bar(&self, col: u16, row: u16) -> bool {
         let area = self.view.tab_bar_rect;
         area.width > 0
@@ -3393,6 +3410,63 @@ mod tests {
     }
 
     #[test]
+    fn bottom_mode_bar_consumes_hidden_tab_mouse_actions() {
+        let mut app = app_for_mouse_test();
+        let mut ws = Workspace::test_new("one");
+        ws.test_add_tab(Some("two"));
+        app.state.workspaces = vec![ws];
+        app.state.active = Some(0);
+        app.state.selected = 0;
+        app.state.mode = Mode::Prefix;
+        app.state.tab_bar_position = crate::config::TabBarPositionConfig::Bottom;
+
+        crate::ui::compute_view(&mut app.state, Rect::new(0, 0, 106, 20));
+        let second_tab = app.state.view.tab_hit_areas[1];
+        let new_tab = app.state.view.new_tab_hit_area;
+
+        app.handle_mouse(mouse(
+            MouseEventKind::Down(MouseButton::Left),
+            second_tab.x,
+            second_tab.y,
+        ));
+        app.handle_mouse(mouse(
+            MouseEventKind::Up(MouseButton::Left),
+            second_tab.x,
+            second_tab.y,
+        ));
+        app.handle_mouse(mouse(
+            MouseEventKind::ScrollDown,
+            second_tab.x,
+            second_tab.y,
+        ));
+        app.handle_mouse(mouse(
+            MouseEventKind::Down(MouseButton::Right),
+            second_tab.x,
+            second_tab.y,
+        ));
+        app.handle_mouse(mouse(
+            MouseEventKind::Down(MouseButton::Left),
+            new_tab.x,
+            new_tab.y,
+        ));
+
+        app.state.drag = Some(DragState {
+            target: DragTarget::SidebarDivider,
+        });
+        app.handle_mouse(mouse(
+            MouseEventKind::Up(MouseButton::Left),
+            second_tab.x,
+            second_tab.y,
+        ));
+
+        assert_eq!(app.state.workspaces[0].active_tab, 0);
+        assert_eq!(app.state.workspaces[0].tabs.len(), 2);
+        assert!(app.state.context_menu.is_none());
+        assert!(app.state.tab_press.is_none());
+        assert!(app.state.drag.is_none());
+    }
+
+    #[test]
     fn right_click_inactive_tab_opens_menu_without_switching_tabs() {
         let mut app = app_for_mouse_test();
         let mut ws = Workspace::test_new("one");
diff --git a/src/app/mod.rs b/src/app/mod.rs
index 2530a05b..f4bc5008 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -642,6 +642,7 @@ impl App {
             pane_gaps: config.ui.pane_gaps,
             show_agent_labels_on_pane_borders: config.ui.show_agent_labels_on_pane_borders,
             hide_tab_bar_when_single_tab: config.ui.hide_tab_bar_when_single_tab,
+            tab_bar_position: config.ui.tab_bar_position,
             pane_history_persistence: config.experimental.pane_history,
             reveal_hidden_cursor_for_cjk_ime: config.experimental.reveal_hidden_cursor_for_cjk_ime,
             cjk_ime_agent_filter_configured: !config.experimental.cjk_ime_agents.is_empty(),
@@ -1450,6 +1451,7 @@ impl App {
                 self.state.show_agent_labels_on_pane_borders =
                     config.ui.show_agent_labels_on_pane_borders;
                 self.state.hide_tab_bar_when_single_tab = config.ui.hide_tab_bar_when_single_tab;
+                self.state.tab_bar_position = config.ui.tab_bar_position;
                 self.state.agent_panel_sort =
                     agent_panel_sort_from_config(config.ui.agent_panel_sort);
                 self.state.sidebar_agents = config.ui.sidebar.agents.clone();
diff --git a/src/app/state.rs b/src/app/state.rs
index a1c5afc1..975144b4 100644
--- a/src/app/state.rs
+++ b/src/app/state.rs
@@ -1,4 +1,6 @@
-use crate::config::{Keybinds, NewTerminalCwdConfig, SoundConfig, ToastConfig, ToastDelivery};
+use crate::config::{
+    Keybinds, NewTerminalCwdConfig, SoundConfig, TabBarPositionConfig, ToastConfig, ToastDelivery,
+};
 use crossterm::event::{KeyCode, KeyModifiers};
 use ratatui::layout::{Direction, Rect};
 use ratatui::style::Color;
@@ -1525,6 +1527,7 @@ pub struct AppState {
     pub pane_gaps: bool,
     pub show_agent_labels_on_pane_borders: bool,
     pub hide_tab_bar_when_single_tab: bool,
+    pub tab_bar_position: TabBarPositionConfig,
     pub pane_history_persistence: bool,
     /// Expose the focused pane's cursor anchor to the outer terminal even when
     /// the pane requested `?25l`. See `[experimental] reveal_hidden_cursor_for_cjk_ime`.
@@ -1899,6 +1902,7 @@ impl AppState {
             pane_gaps: false,
             show_agent_labels_on_pane_borders: false,
             hide_tab_bar_when_single_tab: false,
+            tab_bar_position: TabBarPositionConfig::Top,
             pane_history_persistence: false,
             reveal_hidden_cursor_for_cjk_ime: false,
             cjk_ime_agent_filter_configured: false,
diff --git a/src/config.rs b/src/config.rs
index f07f66ce..f3fc170a 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -21,8 +21,8 @@ pub use self::{
     model::{
         validated_sidebar_bounds, AgentPanelSortConfig, Config, ConfigReloadReport,
         ConfigReloadStatus, HostCursorModeConfig, NewTerminalCwdConfig, ShellModeConfig,
-        SidebarCollapsedModeConfig, ToastClipboardPosition, ToastConfig, ToastDelivery,
-        ToastHerdrPosition, UpdateChannelConfig, MAX_TOAST_DELAY_SECONDS,
+        SidebarCollapsedModeConfig, TabBarPositionConfig, ToastClipboardPosition, ToastConfig,
+        ToastDelivery, ToastHerdrPosition, UpdateChannelConfig, MAX_TOAST_DELAY_SECONDS,
     },
     sidebar::{
         AgentSidebarToken, AgentsSidebarConfig, SidebarConfig, SidebarTokenStyle,
diff --git a/src/config/model.rs b/src/config/model.rs
index 72c81051..b1f0ebc3 100644
--- a/src/config/model.rs
+++ b/src/config/model.rs
@@ -772,6 +772,14 @@ pub struct WorktreesConfig {
     pub directory: String,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Deserialize, Serialize, Default)]
+#[serde(rename_all = "snake_case")]
+pub enum TabBarPositionConfig {
+    #[default]
+    Top,
+    Bottom,
+}
+
 #[derive(Debug, Deserialize)]
 #[serde(default)]
 pub struct UiConfig {
@@ -812,6 +820,8 @@ pub struct UiConfig {
     pub show_agent_labels_on_pane_borders: bool,
     /// Hide the tab row when the workspace has one tab. Default: false.
     pub hide_tab_bar_when_single_tab: bool,
+    /// Desktop tab row placement. Default: top.
+    pub tab_bar_position: TabBarPositionConfig,
     /// Agent sidebar ordering. Saved values are "spaces" or "priority". Default: "spaces".
     pub agent_panel_sort: AgentPanelSortConfig,
     /// Expanded sidebar row composition.
@@ -1014,6 +1024,7 @@ impl Default for UiConfig {
             pane_gaps: true,
             show_agent_labels_on_pane_borders: false,
             hide_tab_bar_when_single_tab: false,
+            tab_bar_position: TabBarPositionConfig::Top,
             agent_panel_sort: AgentPanelSortConfig::Spaces,
             sidebar: SidebarConfig::default(),
             accent: "cyan".into(),
@@ -1245,6 +1256,10 @@ agent_panel_scope = "current"
         assert!(default_config.ui.pane_gaps);
         assert!(!default_config.ui.show_agent_labels_on_pane_borders);
         assert!(!default_config.ui.hide_tab_bar_when_single_tab);
+        assert_eq!(
+            default_config.ui.tab_bar_position,
+            TabBarPositionConfig::Top
+        );
 
         let toml = r#"
 [ui]
@@ -1252,12 +1267,14 @@ pane_borders = false
 pane_gaps = true
 show_agent_labels_on_pane_borders = true
 hide_tab_bar_when_single_tab = true
+tab_bar_position = "bottom"
 "#;
         let config: Config = toml::from_str(toml).unwrap();
         assert!(!config.ui.pane_borders);
         assert!(config.ui.pane_gaps);
         assert!(config.ui.show_agent_labels_on_pane_borders);
         assert!(config.ui.hide_tab_bar_when_single_tab);
+        assert_eq!(config.ui.tab_bar_position, TabBarPositionConfig::Bottom);
     }
 
     #[test]
diff --git a/src/main.rs b/src/main.rs
index 098693f1..8fc51d6b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -315,6 +315,9 @@ const DEFAULT_CONFIG: &str = r##"# herdr configuration
 # New tabs can still be created with the configured keybinding.
 # hide_tab_bar_when_single_tab = false
 
+# Desktop tab row placement: "top" or "bottom".
+# tab_bar_position = "top"
+
 # Agent panel ordering: "spaces" (grouped by space) or "priority" (attention queue).
 # "workspaces" is accepted as an alias for "spaces".
 # agent_panel_sort = "spaces"
diff --git a/src/ui.rs b/src/ui.rs
index bf67d9fd..60143fe4 100644
--- a/src/ui.rs
+++ b/src/ui.rs
@@ -195,9 +195,18 @@ fn desktop_tab_bar_and_terminal_area(
 ) -> (Rect, Rect) {
     let hide_single_tab_bar = app.hide_tab_bar_when_single_tab && ws.tabs.len() == 1;
     if !hide_single_tab_bar && main_area.height > 1 {
-        let [tab_bar_rect, terminal_area] =
-            Layout::vertical([Constraint::Length(1), Constraint::Min(1)]).areas(main_area);
-        (tab_bar_rect, terminal_area)
+        match app.tab_bar_position {
+            crate::config::TabBarPositionConfig::Top => {
+                let [tab_bar_rect, terminal_area] =
+                    Layout::vertical([Constraint::Length(1), Constraint::Min(1)]).areas(main_area);
+                (tab_bar_rect, terminal_area)
+            }
+            crate::config::TabBarPositionConfig::Bottom => {
+                let [terminal_area, tab_bar_rect] =
+                    Layout::vertical([Constraint::Min(1), Constraint::Length(1)]).areas(main_area);
+                (tab_bar_rect, terminal_area)
+            }
+        }
     } else {
         (Rect::default(), main_area)
     }
@@ -410,6 +419,15 @@ pub fn render_with_runtime_registry(
     render_notifications(app, frame, terminal_area);
     render_popup_pane(app, terminal_runtimes, frame, terminal_area);
 
+    let mode_bar_area = if app.view.layout == ViewLayout::Desktop
+        && app.tab_bar_position == crate::config::TabBarPositionConfig::Bottom
+        && tab_bar_area.height > 0
+    {
+        tab_bar_area
+    } else {
+        terminal_area
+    };
+
     match app.mode {
         Mode::Onboarding => render_onboarding_overlay(app, frame, frame.area()),
         Mode::ReleaseNotes => render_release_notes_overlay(app, frame, frame.area()),
@@ -417,10 +435,10 @@ pub fn render_with_runtime_registry(
         Mode::Navigate if app.view.layout == ViewLayout::Mobile => {
             render_mobile_panel(app, terminal_runtimes, frame, frame.area())
         }
-        Mode::Navigate => render_navigate_overlay(app, frame, terminal_area),
-        Mode::Prefix => render_prefix_overlay(app, frame, terminal_area),
-        Mode::Copy => render_copy_mode_overlay(app, frame, terminal_area),
-        Mode::Resize => render_resize_overlay(app, frame, terminal_area),
+        Mode::Navigate => render_navigate_overlay(app, frame, mode_bar_area),
+        Mode::Prefix => render_prefix_overlay(app, frame, mode_bar_area),
+        Mode::Copy => render_copy_mode_overlay(app, frame, mode_bar_area),
+        Mode::Resize => render_resize_overlay(app, frame, mode_bar_area),
         Mode::ConfirmClose => {
             render_confirm_close_overlay(app, terminal_runtimes, frame, terminal_area)
         }
@@ -794,6 +812,35 @@ mod tests {
     }
 
     #[test]
+    fn desktop_tab_bar_position_controls_geometry_and_mode_bar_placement() {
+        let mut app = crate::app::state::AppState::test_new();
+        app.workspaces = vec![Workspace::test_new("one")];
+        app.active = Some(0);
+        app.selected = 0;
+        app.mode = Mode::Prefix;
+
+        compute_view(&mut app, Rect::new(0, 0, 80, 20));
+        assert_eq!(app.view.tab_bar_rect, Rect::new(26, 0, 54, 1));
+        assert_eq!(app.view.terminal_area, Rect::new(26, 1, 54, 19));
+
+        app.tab_bar_position = crate::config::TabBarPositionConfig::Bottom;
+        compute_view(&mut app, Rect::new(0, 0, 80, 20));
+        assert_eq!(app.view.terminal_area, Rect::new(26, 0, 54, 19));
+        assert_eq!(app.view.tab_bar_rect, Rect::new(26, 19, 54, 1));
+        assert!(app.view.tab_hit_areas.iter().all(|rect| rect.y == 19));
+        assert_eq!(app.view.new_tab_hit_area.y, 19);
+
+        let mut terminal = Terminal::new(TestBackend::new(80, 20)).unwrap();
+        terminal.draw(|frame| render(&app, frame)).unwrap();
+        let mode_row = buffer_row_text(
+            terminal.backend().buffer(),
+            app.view.tab_bar_rect,
+            app.view.tab_bar_rect.y,
+        );
+        assert!(mode_row.contains("PREFIX"), "{mode_row}");
+    }
+
+    #[test]
     fn hide_tab_bar_when_single_tab_toggles_geometry_with_tab_count() {
         let mut app = crate::app::state::AppState::test_new();
         app.hide_tab_bar_when_single_tab = true;
@@ -827,6 +874,30 @@ mod tests {
         assert_eq!(app.view.new_tab_hit_area, Rect::default());
     }
 
+    #[test]
+    fn bottom_tab_bar_still_hides_when_single_tab() {
+        let mut app = crate::app::state::AppState::test_new();
+        app.hide_tab_bar_when_single_tab = true;
+        app.tab_bar_position = crate::config::TabBarPositionConfig::Bottom;
+        app.workspaces = vec![Workspace::test_new("one")];
+        app.active = Some(0);
+        app.selected = 0;
+        app.mode = Mode::Prefix;
+
+        compute_view(&mut app, Rect::new(0, 0, 80, 20));
+        assert_eq!(app.view.tab_bar_rect, Rect::default());
+        assert_eq!(app.view.terminal_area, Rect::new(26, 0, 54, 20));
+
+        let mut terminal = Terminal::new(TestBackend::new(80, 20)).unwrap();
+        terminal.draw(|frame| render(&app, frame)).unwrap();
+        let mode_row = buffer_row_text(
+            terminal.backend().buffer(),
+            app.view.terminal_area,
+            app.view.terminal_area.y + app.view.terminal_area.height - 1,
+        );
+        assert!(mode_row.contains("PREFIX"), "{mode_row}");
+    }
+
     #[tokio::test]
     async fn hide_tab_bar_when_single_tab_resizes_background_tabs_per_workspace() {
         let mut app = crate::app::state::AppState::test_new();