Avoid rendering tab bar more than once per tick

kitty/boss.py

@@ -451,7 +451,12 @@ class Boss:
             w = tm.active_window
             if w is not None:
                 w.focus_changed(focused)
-            tm.update_tab_bar()
+            tm.mark_tab_bar_dirty()
+
+    def update_tab_bar_data(self, os_window_id):
+        tm = self.os_window_map.get(os_window_id)
+        if tm is not None:
+            tm.update_tab_bar_data()
 
     def on_drop(self, os_window_id, paths):
         tm = self.os_window_map.get(os_window_id)

kitty/child-monitor.c

@@ -572,6 +572,10 @@ prepare_to_render_os_window(OSWindow *os_window, double now, unsigned int *activ
     bool needs_render = os_window->needs_render;
     os_window->needs_render = false;
     if (TD.screen && os_window->num_tabs > 1) {
+        if (!os_window->tab_bar_data_updated) {
+            call_boss(update_tab_bar_data, "K", os_window->id);
+            os_window->tab_bar_data_updated = true;
+        }
         if (send_cell_data_to_gpu(TD.vao_idx, 0, TD.xstart, TD.ystart, TD.dx, TD.dy, TD.screen, os_window)) needs_render = true;
     }
     if (OPT(mouse_hide_wait) > 0 && now - os_window->last_mouse_activity_at > OPT(mouse_hide_wait)) hide_mouse(os_window);

kitty/state.c

@@ -490,6 +490,14 @@ PYWRAP1(set_titlebar_color) {
     Py_RETURN_FALSE;
 }
 
+PYWRAP1(mark_tab_bar_dirty) {
+    id_type os_window_id = PyLong_AsUnsignedLongLong(args);
+    WITH_OS_WINDOW(os_window_id)
+        os_window->tab_bar_data_updated = false;
+    END_WITH_OS_WINDOW
+    Py_RETURN_NONE;
+}
+
 static inline bool
 fix_window_idx(Tab *tab, id_type window_id, unsigned int *window_idx) {
     for (id_type fix = 0; fix < tab->num_windows; fix++) {
@@ -615,6 +623,7 @@ static PyMethodDef module_methods[] = {
     MW(viewport_for_window, METH_VARARGS),
     MW(mark_os_window_for_close, METH_VARARGS),
     MW(set_titlebar_color, METH_VARARGS),
+    MW(mark_tab_bar_dirty, METH_O),
     MW(update_window_visibility, METH_VARARGS),
     MW(set_boss, METH_O),
     MW(set_display_state, METH_VARARGS),

kitty/state.h

@@ -105,6 +105,7 @@ typedef struct {
     unsigned int active_tab, num_tabs, capacity, last_active_tab, last_num_tabs, last_active_window_id;
     bool focused_at_last_render, needs_render;
     ScreenRenderData tab_bar_render_data;
+    bool tab_bar_data_updated;
     bool is_focused;
     double cursor_blink_zero_time, last_mouse_activity_at;
     double mouse_x, mouse_y;

kitty/tabs.py

@@ -11,9 +11,9 @@ from .child import Child
 from .config import build_ansi_color_table
 from .constants import WindowGeometry, appname, get_boss, is_macos, is_wayland
 from .fast_data_types import (
-    DECAWM, Screen, add_tab, glfw_post_empty_event, remove_tab, remove_window,
+    DECAWM, Screen, add_tab, glfw_post_empty_event, mark_tab_bar_dirty,
-    set_active_tab, set_tab_bar_render_data, swap_tabs, viewport_for_window,
+    remove_tab, remove_window, set_active_tab, set_tab_bar_render_data,
-    x11_window_id
+    swap_tabs, viewport_for_window, x11_window_id
 )
 from .layout import Rect, all_layouts
 from .session import resolved_shell
@@ -89,7 +89,7 @@ class Tab:  # {{{
             tm = self.tab_manager_ref()
             if tm is not None:
                 self.relayout_borders()
-                tm.update_tab_bar()
+                tm.mark_tab_bar_dirty()
 
     @property
     def active_window(self):
@@ -103,19 +103,19 @@ class Tab:  # {{{
         self.name = title or ''
         tm = self.tab_manager_ref()
         if tm is not None:
-            tm.update_tab_bar()
+            tm.mark_tab_bar_dirty()
 
     def title_changed(self, window):
         if window is self.active_window:
             tm = self.tab_manager_ref()
             if tm is not None:
-                tm.update_tab_bar()
+                tm.mark_tab_bar_dirty()
 
     def on_bell(self, window):
         tm = self.tab_manager_ref()
         if tm is not None:
             self.relayout_borders()
-            tm.update_tab_bar()
+            tm.mark_tab_bar_dirty()
 
     def visible_windows(self):
         for w in self.windows:
@@ -412,7 +412,6 @@ class TabManager:  # {{{
         for t in startup_session.tabs:
             self._add_tab(Tab(self, session_tab=t))
         self._set_active_tab(max(0, min(startup_session.active_tab_idx, len(self.tabs) - 1)))
-        self.update_tab_bar()
 
     @property
     def active_tab_idx(self):
@@ -464,21 +463,24 @@ class TabManager:  # {{{
         self.resize(only_tabs=True)
         glfw_post_empty_event()
 
-    def update_tab_bar(self):
+    def mark_tab_bar_dirty(self):
         if len(self.tabs) > 1:
-            self.tab_bar.update(self.tab_bar_data)
+            mark_tab_bar_dirty(self.os_window_id)
+
+    def update_tab_bar_data(self):
+        self.tab_bar.update(self.tab_bar_data)
 
     def resize(self, only_tabs=False):
         if not only_tabs:
             self.tab_bar.layout()
-            self.update_tab_bar()
+            self.mark_tab_bar_dirty()
         for tab in self.tabs:
             tab.relayout()
 
     def set_active_tab_idx(self, idx):
         self._set_active_tab(idx)
         self.active_tab.relayout_borders()
-        self.update_tab_bar()
+        self.mark_tab_bar_dirty()
 
     def set_active_tab(self, tab):
         try:
@@ -531,19 +533,19 @@ class TabManager:  # {{{
             self.tabs[idx], self.tabs[nidx] = self.tabs[nidx], self.tabs[idx]
             swap_tabs(self.os_window_id, idx, nidx)
             self._set_active_tab(nidx)
-            self.update_tab_bar()
+            self.mark_tab_bar_dirty()
 
     def new_tab(self, special_window=None, cwd_from=None):
         idx = len(self.tabs)
         self._add_tab(Tab(self, special_window=special_window, cwd_from=cwd_from))
         self._set_active_tab(idx)
-        self.update_tab_bar()
+        self.mark_tab_bar_dirty()
         return self.tabs[idx]
 
     def remove(self, tab):
         self._remove_tab(tab)
         self._set_active_tab(max(0, min(self.active_tab_idx, len(self.tabs) - 1)))
-        self.update_tab_bar()
+        self.mark_tab_bar_dirty()
         tab.destroy()
 
     @property