Prompt-toolkit

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New features:
- New "placeholder" parameter added to `PromptSession`.

Other changes:
- The "respond to CPR" logic has been moved from the `Input` to `Output`
classes (this does clean up some code).

Fixes:
- Bugfix in shift-selection key bindings.
- Fix height calculation of `FormattedTextControl` when line wrapping is turned
on.
- Fixes for SSH server:
* Missing encoding property.
* Fix failure in "set_line_mode" call.
* Handle `BrokenPipeError`.

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New features:
- The SSH/Telnet adaptors have been refactored and improved in several ways.
See issues 876 and PR 1150 and 1184 on GitHub.
* Handle terminal types for both telnet and SSH sessions.
* Added pipe input abstraction. (base class for `PosixPipeInput` and
`Win32PipeInput`).
* The color depth logic has been refactored and moved to the `Output`
implementations. Added `get_default_color_depth` method to `Output`
objects.
* All line feet are now preceded by a carriage return in the telnet
connection stdout.
- Introduce `REPLACE_SINGLE` input mode for Vi key bindings.
- Improvements to the checkbox implementation:
* Hide the scrollbar for a single checkbox.
* Added a "checked" setter to the checkbox.
- Expose `KeyPressEvent` in key_binding/__init__.py (often used in type
annotations).
- The renderer has been optimized so that no trailing spaces are generated
(this improves copying in some terminals).

Fixes:
- Ignore F21..F24 key bindings by default.
- Fix auto_suggest key bindings when suggestion text is empty.
- Bugfix in SIGWINCH handling.
- Handle bug in HSplit/VSplit when the number of children is zero.
- Bugfix in CPR handling in renderer. Proper cancellation of pending tasks.
- Ensure rprompt aligns with input.
- Use `sys.stdin.encoding` for decoding stdin stream.

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Fixes:
- Bugfix in mouse handling on Windows.

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New features:
- Added many more vt100 ANSI sequences and keys.
- Improved control/shift key support in Windows.
- No Mypy errors in prompt_toolkit anymore.
- Added `set_exception_handler` optional argument to `PromptSession.prompt()`.

Fixes:
- Bugfix in invalidate code. `PromptSession` was invalidating the UI
continuously.
- Add uvloop support (was broken due to an issue in our `call_soon_threadsafe`).
- Forwarded `set_exception_handler` in `Application.run` to the `run_async` call.
- Bugfix in `NestedCompleter` when there is a leading space.

Breaking changes:
- `ShiftControl` has been replaced with `ControlShift` and `s-c` with `c-s` in
key bindings. Aliases for backwards-compatibility have been added.

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New features:
- Improved support for "dumb" terminals.
- Added support for new keys (vt100 ANSI sequences): Alt +
home/end/page-up/page-down/insert.
- Better performance for the "regular languages compiler". Generate fewer and
better regular expressions. This should improve the start-up time for
applications using this feature.
- Better detection of default color depth.
- Improved the progress bar:
* Set "time left" to 0 when done or stopped.
* Added `ProgressBarCounter.stopped`.
- Accept callables for `scroll_offset`, `min_brightness` and `max_brightness`.
- Added `always_prefer_tty` parameters to `create_input()` and `create_output()`.
- Create a new event loop in `Application.run()` if `get_event_loop()` raises
`Runtimeerror`.

Fixes:
- Correct cancellation of flush timers for input. (Fixes resource leak where
too many useless coroutines were created.)
- Improved the Win32 input event loop. This fixes a bug where the
prompt_toolkit application is stopped by something other than user input. (In
that case, the application would hang, waiting for input.) This also fixes a
`RuntimeError` in the progress bar code.
- Fixed `line-number.current` style. (was `current-line-number`.)
- Handle situation where stdout is no longer a tty (fix bug in `get_size`).
- Fix parsing of true color in ANSI strings.
- Ignore `invalidate()` if the application is not running.

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Fixes:
- Bugfix in the UI invalidation. Fixes an issue when the application runs again
on another event loop.
See: https://github.com/ipython/ipython/pull/11973