Double clicking on empty tab bar area now opens a new tab

Fixes #3201

docs/changelog.rst

@@ -17,6 +17,8 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
   run. The system-wide PATH is used first, then system specific default paths,
   and finally the PATH inside the shell.
 
+- Double clicking on empty tab bar area now opens a new tab (:iss:`3201`)
+
 
 0.19.3 [2020-12-19]
 -------------------

kitty/boss.py

@@ -520,10 +520,10 @@ class Boss:
             run_update_check(self.opts.update_check_interval * 60 * 60)
             self.update_check_started = True
 
-    def activate_tab_at(self, os_window_id: int, x: int) -> int:
+    def activate_tab_at(self, os_window_id: int, x: int, is_double: bool = False) -> int:
         tm = self.os_window_map.get(os_window_id)
         if tm is not None:
-            tm.activate_tab_at(x)
+            tm.activate_tab_at(x, is_double)
 
     def on_window_resize(self, os_window_id: int, w: int, h: int, dpi_changed: bool) -> None:
         if dpi_changed:

kitty/mouse.c

@@ -516,8 +516,12 @@ HANDLER(handle_event) {
 
 static inline void
 handle_tab_bar_mouse(int button, int UNUSED modifiers) {
+    static monotonic_t last_click_at = 0;
     if (button != GLFW_MOUSE_BUTTON_LEFT || !global_state.callback_os_window->mouse_button_pressed[button]) return;
-    call_boss(activate_tab_at, "Kd", global_state.callback_os_window->id, global_state.callback_os_window->mouse_x);
+    monotonic_t now = monotonic();
+    bool is_double = now - last_click_at <= OPT(click_interval);
+    last_click_at = is_double ? 0 : now;
+    call_boss(activate_tab_at, "KdO", global_state.callback_os_window->id, global_state.callback_os_window->mouse_x, is_double ? Py_True : Py_False);
 }
 
 static inline bool

kitty/tabs.py

@@ -753,9 +753,12 @@ class TabManager:  # {{{
             ))
         return ans
 
-    def activate_tab_at(self, x: int) -> None:
+    def activate_tab_at(self, x: int, is_double: bool = False) -> None:
         i = self.tab_bar.tab_at(x)
-        if i is not None:
+        if i is None:
+            if is_double:
+                self.new_tab()
+        else:
             self.set_active_tab_idx(i)
 
     @property