Add an optional "visual" bell

Fix #51

kitty/boss.py

@@ -397,7 +397,7 @@ class Boss(Thread):
                     self.tab_manager.render(self.cell_program, self.sprites)
                     for window, rd in render_data.items():
                         if rd is not None:
-                            window.char_grid.render_cells(rd, self.cell_program, self.sprites)
+                            window.render_cells(rd, self.cell_program, self.sprites)
                 active = self.active_window
                 rd = render_data.get(active)
                 if rd is not None:

kitty/config.py

@@ -159,6 +159,7 @@ type_map = {
     'repaint_delay': int,
     'window_border_width': float,
     'wheel_scroll_multiplier': float,
+    'visual_bell_duration': float,
     'click_interval': float,
     'mouse_hide_wait': float,
     'cursor_blink_interval': float,

kitty/kitty.conf

@@ -87,6 +87,10 @@ initial_window_height  400
 # that sufficient for most uses.
 repaint_delay    10
 
+# Visual bell duration. Flash the screen when a bell occurs for the specified number of
+# seconds. Set to zero to disable.
+visual_bell_duration 0.0
+
 # The modifier keys to press when clicking with the mouse on URLs to open the URL
 open_url_modifiers ctrl+shift
 

kitty/window.py

@@ -37,6 +37,7 @@ class Window:
         self._is_visible_in_layout = True
         self.child, self.opts = child, opts
         self.child_fd = child.child_fd
+        self.start_visual_bell_at = None
         self.screen = Screen(self, 24, 80, opts.scrollback_lines)
         self.read_bytes = partial(read_bytes_dump, self.dump_commands) if args.dump_commands else read_bytes
         self.draw_dump_buf = []
@@ -109,6 +110,9 @@ class Window:
     def bell(self):
         with open('/dev/tty', 'wb') as f:
             f.write(b'\007')
+        if self.opts.visual_bell_duration > 0:
+            self.start_visual_bell_at = monotonic()
+            glfw_post_empty_event()
 
     def update_screen(self):
         self.char_grid.update_cell_data()
@@ -264,6 +268,14 @@ class Window:
     def buf_toggled(self, is_main_linebuf):
         self.char_grid.scroll('full', False)
 
+    def render_cells(self, render_data, program, sprites):
+        invert_colors = False
+        if self.start_visual_bell_at is not None:
+            invert_colors = monotonic() - self.start_visual_bell_at <= self.opts.visual_bell_duration
+            if not invert_colors:
+                self.start_visual_bell_at = None
+        self.char_grid.render_cells(render_data, program, sprites, invert_colors)
+
     # actions {{{
 
     def show_scrollback(self):