docs: record the continuous toolbar application change

Author: tleonhardt

CHANGELOG.md

@@ -1,5 +1,10 @@
 ## 4.3.0 (TBD)
 
+- Bug Fixes
+    - Fixed an intermittent bottom toolbar flicker when running a command. The toolbar's
+      prompt-toolkit application now stays running across both the prompt and command execution
+      instead of stopping and restarting for each one, since prompt-toolkit drops the bottom toolbar
+      from the final frame of every application run.
 - Enhancements
     - `enable_bottom_toolbar=True` now keeps the toolbar visible and refreshing during command
       execution

cmd2/cmd2.py

@@ -2074,9 +2074,10 @@ def get_bottom_toolbar(self) -> AnyFormattedText:
         your application. This could be information like the application name, current state,
         or even a real-time clock.
 
-        During command execution this callback runs in a background UI thread. Protect shared
-        state with a lock when necessary. The built-in pager shares this toolbar. It is suspended
-        while another prompt, external pager, or interactive shell owns the terminal.
+        Inside the command loop this callback runs in a background UI thread, at the prompt as
+        well as during command execution, because a single application renders both. Protect
+        shared state with a lock when necessary. The built-in pager shares this toolbar. It is
+        suspended while another prompt, external pager, or interactive shell owns the terminal.
 
         :return: Content to populate the bottom toolbar.
         """

docs/features/prompt.md

@@ -109,8 +109,9 @@ See the
 example for a demonstration of this technique. Run its `work 5` command to see the clock update
 while the command prints output.
 
-During command execution, `get_bottom_toolbar()` runs in a background UI thread. Keep the callback
-fast and use a lock when reading state that a command or another thread modifies.
+Inside the command loop, `get_bottom_toolbar()` runs in a background UI thread, at the prompt as
+well as during command execution, because a single prompt-toolkit application renders both. Keep the
+callback fast and use a lock when reading state that a command or another thread modifies.
 
 ### Commands That Take Over the Terminal