Ensure Tab.destroy is only called once

kitty/boss.py

@@ -67,7 +67,6 @@ class Boss(Thread):
         Thread.__init__(self, name='ChildMonitor')
         self.cursor_blinking = True
         self.glfw_window_title = None
-        self.current_tab_bar_height = 0
         self.action_queue = Queue()
         self.pending_resize = True
         self.resize_gl_viewport = False
@@ -116,6 +115,10 @@ class Boss(Thread):
                     self.glfw_window.set_should_close(True)
                     glfw_post_empty_event()
 
+    @property
+    def current_tab_bar_height(self):
+        return self.tab_manager.tab_bar_height
+
     def __iter__(self):
         return iter(self.tab_manager)
 

kitty/tabs.py

@@ -5,7 +5,7 @@
 from collections import deque
 
 from .child import Child
-from .constants import get_boss, appname, shell_path
+from .constants import get_boss, appname, shell_path, cell_size
 from .fast_data_types import glfw_post_empty_event
 from .layout import all_layouts
 from .borders import Borders
@@ -118,9 +118,10 @@ class Tab:
         return window in self.windows
 
     def destroy(self):
-        for w in self.windows:
-            w.destroy()
-        del self.windows
+        if hasattr(self, 'windows'):
+            for w in self.windows:
+                w.destroy()
+            del self.windows
 
     def render(self):
         self.borders.render(get_boss().borders_program)
@@ -142,6 +143,10 @@ class TabManager:
     def active_tab(self):
         return self.tabs[0] if self.tabs else None
 
+    @property
+    def tab_bar_height(self):
+        return 0 if len(self.tabs) < 1 else cell_size.height
+
     def remove(self, tab):
         ' Must be called in the GUI thread '
         self.tabs.remove(tab)