Allow showing the name of the current layout and the number of windows in tab titles

Fixes #2634

docs/changelog.rst

@@ -8,6 +8,9 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 0.17.4 [future]
 --------------------
 
+- Allow showing the name of the current layout and the number of windows
+  in tab titles (:iss:`2634`)
+
 - macOS: Fix a regression in the previous release that caused ligatures to be
   not be centered horizontally (:iss:`2591`)
 

kitty/config_data.py

@@ -870,6 +870,11 @@ def active_tab_title_template(x: str) -> Optional[str]:
 the title. If you wish to include the tab-index as well,
 use something like: :code:`{index}: {title}`. Useful
 if you have shortcuts mapped for :code:`goto_tab N`.
+In addition you can use :code:`{layout_name}` for the current
+layout name and :code:`{num_windows}` for the number of windows
+in the tab. Note that formatting is done by Python's string formatting
+machinery, so you can use, for instance, :code:`{layout_name[:2].upper()}` to
+show only the first two letters of the layout name, upper-cased.
 '''))
 o('active_tab_title_template', 'none', option_type=active_tab_title_template, long_text=_('''
 Template to use for active tabs, if not specified falls back

kitty/tab_bar.py

@@ -21,6 +21,8 @@ class TabBarData(NamedTuple):
     title: str
     is_active: bool
     needs_attention: bool
+    num_windows: int
+    layout_name: str
 
 
 class DrawData(NamedTuple):
@@ -56,7 +58,7 @@ def draw_title(draw_data: DrawData, screen: Screen, tab: TabBarData, index: int)
     if tab.is_active and draw_data.active_title_template is not None:
         template = draw_data.active_title_template
     try:
-        title = template.format(title=tab.title, index=index)
+        title = template.format(title=tab.title, index=index, layout_name=tab.layout_name, num_windows=tab.num_windows)
     except Exception as e:
         if template not in template_failures:
             template_failures.add(template)

kitty/tabs.py

@@ -138,6 +138,7 @@ def _set_current_layout(self, layout_name: str) -> None:
         self._last_used_layout = self._current_layout_name
         self.current_layout = self.create_layout_object(layout_name)
         self._current_layout_name = layout_name
+        self.mark_tab_bar_dirty()
 
     def startup(self, session_tab: 'SessionTab') -> None:
         for cmd in session_tab.windows:
@@ -183,10 +184,13 @@ def active_window_idx(self, val: int) -> None:
                 old_active_window.focus_changed(False)
             if new_active_window is not None:
                 new_active_window.focus_changed(True)
-            tm = self.tab_manager_ref()
-            if tm is not None:
-                self.relayout_borders()
-                tm.mark_tab_bar_dirty()
+            self.relayout_borders()
+            self.mark_tab_bar_dirty()
+
+    def mark_tab_bar_dirty(self) -> None:
+        tm = self.tab_manager_ref()
+        if tm is not None:
+            tm.mark_tab_bar_dirty()
 
     @property
     def active_window(self) -> Optional[Window]:
@@ -330,6 +334,7 @@ def launch_child(
     def _add_window(self, window: Window, location: Optional[str] = None) -> None:
         self.active_window_idx = self.current_layout.add_window(self.windows, window, self.active_window_idx, location)
         self.relayout_borders()
+        self.mark_tab_bar_dirty()
 
     def new_window(
         self,
@@ -431,6 +436,7 @@ def remove_window(self, window: Window, destroy: bool = True) -> None:
         else:
             self.active_window_idx = active_window_idx
         self.relayout_borders()
+        self.mark_tab_bar_dirty()
         active_window = self.active_window
         if active_window:
             self.title_changed(active_window)
@@ -804,7 +810,10 @@ def tab_bar_data(self) -> List[TabBarData]:
                 if w.needs_attention:
                     needs_attention = True
                     break
-            ans.append(TabBarData(title, t is at, needs_attention))
+            ans.append(TabBarData(
+                title, t is at, needs_attention,
+                len(t), t.current_layout.name or ''
+            ))
         return ans
 
     def activate_tab_at(self, x: int) -> None: