gh-128388: pyrepl on Windows: add meta and ctrl+arrow keybindings #128389

paulie4 · 2025-01-01T05:54:29Z

Fix Lib/_pyrepl/windows_console.py to support more keybindings, like the Ctrl+← and Ctrl+→ word-skipping keybindings and those with meta (i.e. Alt), e.g. to kill-word or backward-kill-word.

Specifics: if Ctrl is pressed, emit "ctrl left" and "ctrl right" instead of just "left" or "right," and if Meta/Alt is pressed, emit the special key code for meta before emitting the other key that was pressed.

NOTE: this is my first PR for https://github.com/python/cpython, so please tell me if I need to do something else, e.g. does this need an entry added somewhere under Misc/NEWS.d?

Issue: pyrepl on Windows: add Ctrl+← and Ctrl+→ word-skipping and other keybindings #128388

cpython-cla-bot · 2025-01-01T05:54:31Z

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bedevere-app · 2025-01-01T05:57:11Z

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

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hugovk · 2025-01-01T06:36:08Z

NOTE: this is my first PR for https://github.com/python/cpython, so please tell me if I need to do something else, e.g. does this need an entry added somewhere under Misc/NEWS.d?

Yes please, and also sign the CLA.

paulie4 · 2025-01-01T07:01:24Z

@hugovk, Misc/NEWS.d is a directory, so I don't know which file(s) in there to edit, especially since it looks like the versions in there have all been released. Do I need to create a new file (or files if it's going to both 3.13.2 and to a 3.14.0a)?

UPDATE: it looks like these are the instructions for which file I should create: https://devguide.python.org/core-developers/committing/#how-to-add-a-news-entry. I think _pyrepr is part of the standard library, right?

I tried signing the CLA, but the SIGN IN WITH GITHUB TO AGREE button doesn't work with the @users.noreply.github.com email address I use for my commits. I submitted a manual CLA, so hopefully that will work. FYI, this is the error I get when I try to use https://cpython-clabot.herokuapp.com/contributor-license-agreement?state=...:

Thank you for authorizing our application, but the CLA must be signed by the users who contributed to the PR. Authors emails are: [email protected].

hugovk · 2025-01-01T07:26:38Z

UPDATE: it looks like these are the instructions for which file I should create: https://devguide.python.org/core-developers/committing/#how-to-add-a-news-entry. I think _pyrepr is part of the standard library, right?

Yes, that's right, the Lib dir is the stdlib.

Misc/NEWS.d/next/Library/2025-01-01-19-24-43.gh-issue-128388.8UdMz_.rst

…8.8UdMz_.rst` Co-authored-by: Hugo van Kemenade <[email protected]>

paulie4 · 2025-01-02T20:21:45Z

@hugovk, thank you for that suggested doc change, which I approved. Is there anything else I need to do, or do we now just need to wait for someone else (e.g. @pablogsal, @lysnikolaou, or @ambv) to review the code changes?

hugovk · 2025-01-03T13:08:23Z

Thanks for the updates. Yes, someone with Windows will need to review, hopefully it shouldn't be too long :)

eendebakpt

I left some comments for improvement of the code, but the PR is good: I tested with Windows 11 and the meta keybindings work now

Lib/_pyrepl/windows_console.py

eendebakpt · 2025-01-03T22:42:04Z

Lib/_pyrepl/windows_console.py

-                    return Event(
-                        evt="key", data=code, raw=rec.Event.KeyEvent.uChar.UnicodeChar
-                    )
+                    if code in ("left", "right") and (ctrlstate := key_event.dwControlKeyState) and ctrlstate & CTRL_OR_ALT_ACTIVE:


This makes Alt+← and Ctrl-Alt+← work just as Ctrl+←. Is that how it should be?

On Unix for me Alt+← gives me capital C (not sure why, does not really make sense to me) and Ctrl-Alt+← triggers my window manager.

In the keymap I also don't see Alt-left with a special meaning:

cpython/Lib/_pyrepl/reader.py

Lines 146 to 161 in f157485

(r"\<up>", "up"),

(r"\<down>", "down"),

(r"\<left>", "left"),

(r"\C-\<left>", "backward-word"),

(r"\<right>", "right"),

(r"\C-\<right>", "forward-word"),

(r"\<delete>", "delete"),

(r"\x1b[3~", "delete"),

(r"\<backspace>", "backspace"),

(r"\M-\<backspace>", "backward-kill-word"),

(r"\<end>", "end-of-line"), # was 'end'

(r"\<home>", "beginning-of-line"), # was 'home'

(r"\<f1>", "help"),

(r"\<f2>", "show-history"),

(r"\<f3>", "paste-mode"),

(r"\EOF", "end"), # the entries in the terminfo database for xterms

Exactly, I didn't see anything existing that was useful for Alt+←, so I figured might as well make it useful. I can remove it if you prefer only Ctrl+← being useful. Also, it would definitely violate separation of concerns if this Lib/_pyrepl/windows_console.py file were to try to read the keymappings in Lib/_pyrepl/reader.py to check if r"\M-\<left>" existed, and I don't expect that to be added anytime soon.

I would prefer all implementations (unix, windows, etc.) to have the same implementation. Please revert the changes to ALT. There might be good use for the ALT modifier, but that would be for another PR.

That brings up a good question, why don't we add (r"\M-\<left>", "backward-word") and (r"\M-\<right>", "forward-word") to the default_keymap, so that way all implementations will have something useful for Alt+←?

Also, I just tested that, and it made me realize that the Lib\_pyrepl\windows_console.py code also needs to # queue the key, return the meta command in the special key == "\x00" section (see 46b22d1 for the fix and removal of treating Alt+← as Ctrl+←).

I guess adding (r"\M-\<left>", "backward-word") and (r"\M-\<right>", "forward-word") to the default_keymap can be part of a separate GH Issue+PR...

Are you ok with the changes I made so we can resolve this conversation?

Misc/NEWS.d/next/Library/2025-01-01-19-24-43.gh-issue-128388.8UdMz_.rst

Co-authored-by: Pieter Eendebak <[email protected]>

Lib/_pyrepl/windows_console.py

eendebakpt · 2025-01-04T21:50:34Z

Lib/_pyrepl/windows_console.py

+                        self.event_queue.insert(0, Event(evt="key", data=key, raw=key))
+                        return Event(evt="key", data="\033")  # keymap.py uses this for meta


I don't know the answer. But why pass the ctrl modifier as a key f'ctrl {key}`, and the alt modifier using a special event?

Yeah, it took me a while to figure out what was going on in Lib\_pyrepl\keymap.py, cause the code is not very readable, but that's what it expects. If we wanted Ctrl and Alt to be treated in a similar way, we'd probably have to make some major edits to Lib\_pyrepl\keymap.py and Lib\_pyrepl\unix_eventqueue.py.

Co-authored-by: Pieter Eendebak <[email protected]>

vstinner · 2025-01-07T10:49:37Z

Lib/_pyrepl/windows_console.py

@@ -102,6 +102,10 @@ def __init__(self, err: int | None, descr: str | None = None) -> None:
 MOVE_DOWN = "\x1b[{}B"
 CLEAR = "\x1b[H\x1b[J"

+# State of control keys: https://learn.microsoft.com/en-us/windows/console/key-event-record-str
+ALT_ACTIVE = 0x01 | 0x02


I'm not sure about including the right ALT in ALT_ACTIVE. On Linux, ALT+Backspace removes a whole word, whereas AltGr+Backspace removes a single character.

Lib/_pyrepl/keymap.py doesn't distinguish between right and left (it just has C- and M-), so I'm not sure that was a conscious decision that was made for the Linux code. Maybe that's actually a bug in the _pyrepl/unix_* code?

Lib/_pyrepl/keymap.py doesn't distinguish between right and left

Python 3.14 on Linux behaves differently for left Alt and right AltGr:

Left Alt + backspace: remove a word

Right AltGr + backspace: remove a single character

On my Linux, the English keyboard layout has Right Alt which generally works like Left Alt (in a terminal).
The French or Czech layout has AltGr instead, which is apparently not Meta enough, so AltGr+Backspace works like Backspace (in both pyrepl and bash).

I tried on some Windows consoles:

LAlt+Backspace RAlt+Backspace AltGr+Backspace

cmd Delete single character Nothing Nothing

powershell Nothing Nothing Nothing

Doesn't look useful, so it's probably best to have Linux-like behaviour here.

I don't understand what you are saying. Are you saying because the existing functionality isn't useful, we should continue to make the right Alt key not be useful in _pyrepl?

Either way, if this is about AltGr, I think we have to really understand how it works in Windows... I don't have an AltGr key, so I can't test it, but https://en.wikipedia.org/wiki/AltGr_key says, "Windows interprets Ctrl+Alt as AltGr," and since the _KEY_EVENT_RECORD doc doesn't show a dwControlKeyState value for AltGr, doesn't that mean that RIGHT_ALT_PRESSED is not the same thing as AltGr and that the Lib/_pyrepl/windows_console.py code would actually have to look for a combination of Ctrl (left/right) and Alt (left/right) (or maybe just lefts?) being pressed to know if AltGr is being pressed, or am I misunderstanding how the _KEY_EVENT_RECORD works?

I didn't know that other keyboards have a right ALT key different than AltGr. In this case, I'm fine with ALT_ACTIVE = 0x01 | 0x02.

I don't understand what you are saying.

Sorry for being unclear!
I meant that the behaviour of Windows terminals I tried (cmd & powershell) is not useful, so Python should not emulate that.

I don't have an AltGr key, so I can't test it

It's a feature of the keyboard layout, not the physical keyboard. To test it you can add, for example, French "AZERTY" in system settings.

vstinner

LGTM. It works as expected: CTRL+Left skips a whole word and ALT+Backspace deletes a word.

vstinner · 2025-01-08T18:34:18Z

Lib/_pyrepl/windows_console.py

@@ -102,6 +102,10 @@ def __init__(self, err: int | None, descr: str | None = None) -> None:
 MOVE_DOWN = "\x1b[{}B"
 CLEAR = "\x1b[H\x1b[J"

+# State of control keys: https://learn.microsoft.com/en-us/windows/console/key-event-record-str
+ALT_ACTIVE = 0x01 | 0x02


I didn't know that other keyboards have a right ALT key different than AltGr. In this case, I'm fine with ALT_ACTIVE = 0x01 | 0x02.

paulie4 requested review from pablogsal, lysnikolaou and ambv as code owners January 1, 2025 05:54

bedevere-app bot mentioned this pull request Jan 1, 2025

pyrepl on Windows: add Ctrl+← and Ctrl+→ word-skipping and other keybindings #128388

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pyrepl on Windows: add meta and ctrl+arrow keybindings

283e7c3

paulie4 force-pushed the fix-issue-128388 branch from 6606f63 to 283e7c3 Compare January 1, 2025 05:57

hugovk added OS-windows topic-repl Related to the interactive shell labels Jan 1, 2025

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2025-01-01-19-24-43.gh-issue-128388.8UdMz_.rst: fix typo

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Misc/NEWS.d/next/Library/2025-01-01-19-24-43.gh-issue-128388.8UdMz_.rst Outdated Show resolved Hide resolved

lint fix `Misc/NEWS.d/next/Library/2025-01-01-19-24-43.gh-issue-12838…

abe1f62

…8.8UdMz_.rst` Co-authored-by: Hugo van Kemenade <[email protected]>

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paulie4 and others added 4 commits January 3, 2025 20:39

Lib/_pyrepl/windows_console.py: temp var ctrlstate is not needed

3d07c34

Co-authored-by: Pieter Eendebak <[email protected]>

Lib/_pyrepl/windows_console.py: clearer comment

16f2a13

Co-authored-by: Pieter Eendebak <[email protected]>

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e3f6438

Lib\_pyrepl\windows_console.py: fix Alt+← handling

46b22d1

eendebakpt reviewed Jan 4, 2025

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Lib/_pyrepl/windows_console.py: standardize Ctrl+special key

55e4fbf

Co-authored-by: Pieter Eendebak <[email protected]>

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vstinner approved these changes Jan 8, 2025

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Merge branch 'main' into fix-issue-128388

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encukou merged commit 688f3a0 into python:main Jan 10, 2025
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gh-128388: pyrepl on Windows: add meta and ctrl+arrow keybindings #128389

gh-128388: pyrepl on Windows: add meta and ctrl+arrow keybindings #128389

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	(r"\<up>", "up"),
	(r"\<down>", "down"),
	(r"\<left>", "left"),
	(r"\C-\<left>", "backward-word"),
	(r"\<right>", "right"),
	(r"\C-\<right>", "forward-word"),
	(r"\<delete>", "delete"),
	(r"\x1b[3~", "delete"),
	(r"\<backspace>", "backspace"),
	(r"\M-\<backspace>", "backward-kill-word"),
	(r"\<end>", "end-of-line"), # was 'end'
	(r"\<home>", "beginning-of-line"), # was 'home'
	(r"\<f1>", "help"),
	(r"\<f2>", "show-history"),
	(r"\<f3>", "paste-mode"),
	(r"\EOF", "end"), # the entries in the terminfo database for xterms

		self.event_queue.insert(0, Event(evt="key", data=key, raw=key))
		return Event(evt="key", data="\033") # keymap.py uses this for meta

	LAlt+Backspace	RAlt+Backspace	AltGr+Backspace
cmd	Delete single character	Nothing	Nothing
powershell	Nothing	Nothing	Nothing

gh-128388: pyrepl on Windows: add meta and ctrl+arrow keybindings #128389

gh-128388: pyrepl on Windows: add meta and ctrl+arrow keybindings #128389

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