IDLE: On macOS, cntl-space/backslash display as ^S/^B

[terryjreedy]

BPO	44398
Nosy	@terryjreedy, @ronaldoussoren, @taleinat, @ned-deily

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/terryjreedy'
closed_at = None
created_at = <Date 2021-06-11.19:36:14.961>
labels = ['OS-mac', 'expert-IDLE', 'type-bug', '3.11']
title = 'IDLE: On macOS, cntl-space/backslash display as ^S/^B'
updated_at = <Date 2021-06-11.20:25:10.727>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2021-06-11.20:25:10.727>
actor = 'terry.reedy'
assignee = 'terry.reedy'
closed = False
closed_date = None
closer = None
components = ['IDLE', 'macOS']
creation = <Date 2021-06-11.19:36:14.961>
creator = 'terry.reedy'
dependencies = []
files = []
hgrepos = []
issue_num = 44398
keywords = []
message_count = 2.0
messages = ['395656', '395660']
nosy_count = 4.0
nosy_names = ['terry.reedy', 'ronaldoussoren', 'taleinat', 'ned.deily']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue44398'
versions = ['Python 3.11']

Linked PRs

• GH-88564: Make sure IDLE keybindings are correctly shown on macOS #99564
• GH-88564: IDLE - fix 2 Edit menu hotkey displays #99743

[terryjreedy]

(Related to the more general macOS hotkey bpo-18444.)
'Edit => Show completions' invokes pseudoevent <<force-open-completions>>. In all built-in keysets, the latter is bound to Control-space. This includes on macOS, as can be seen on the Settings Keys tab.

On Windows, and I presume *nix, this is displayed on the menu as 'Cntl+space'. On macOS, the menu hotkeys are displayed differently than on other systems (how?). 'Cntl+' is condensed to '^', which is fine and which would be okay elsewhere. However, 'space' is condensed to 'S', which is a bug. Can this be fixed? If not, we could add ^S as an alternate hotkey on macOS.

'^S' causes 'Edit' to flash, indicating, I believe, that it is recognized as an Edit menu hotkey. But nothing happens as IDLE/tk does not recognize it on macOS. (On Windows, it means 'save'.)

^space, currently works to show completions with 3.10.0b2. The same will be true after the PR for bpo-40128 is merged and backported.

The situation is the same for Edit => Show calltip, <<force-open-calltip>>, and control-backslash, except that 'backslash' is visible as '\'. If the hotkey were displayed on Windows as 'Cntl+\', perhaps the result on macOS would be the correct '^\'.

[terryjreedy]

^B would work as an alternate binding for <<force-open-calltip>> as it is not used otherwise, but I prefer not to have to do this.

These are the only named keys other than the 'F#'s.

[ronaldoussoren]

The "^S" problem seem to be behaviour of Tk on macOS, and one with a workaround (see at the end of this message).

The following program creates a menubar that also shows "Ctrl-Space" als a shortcut, and that works fine (that is, shows "^Space" as the shortcut for "Item" in the File menu. When you change "Ctrl+Space" to "Ctrl+space" (note the lower-case S) the behaviour matches that of IDLE: Show "^S" als the shortcut.

from tkinter import *

class Window(Frame):
    def __init__(self, master=None):
        Frame.__init__(self, master)
        self.master = master

        menu = Menu(self.master)
        self.master.config(menu=menu)

        fileMenu = Menu(menu)
        fileMenu.add_command(label="Item", command=self.sayHello, underline=1, accelerator="Ctrl+Space")
        fileMenu.add_command(label="Exit", command=self.exitProgram, accelerator="Ctrl+X")
        menu.add_cascade(label="File", menu=fileMenu)

        self.bind_all("<Control-space>", self.sayHello)

        editMenu = Menu(menu)
        editMenu.add_command(label="Undo")
        editMenu.add_command(label="Redo")
        menu.add_cascade(label="Edit", menu=editMenu)

    def exitProgram(self,*args):
        exit()

    def sayHello(self, *args):
        print("hello", args)
        
root = Tk()
app = Window(root)
root.wm_title("Tkinter window")
root.mainloop()

As a quick hack I applied the following patch locally (fairly recent checkout of main):

diff --git a/Lib/idlelib/editor.py b/Lib/idlelib/editor.py
index 08d6aa2efd..4e54f4321d 100644
--- a/Lib/idlelib/editor.py
+++ b/Lib/idlelib/editor.py
@@ -903,6 +903,8 @@ def ApplyKeybindings(self):
                                 event = menuEventDict[menubarItem][itemName]
                         if event:
                             accel = get_accelerator(keydefs, event)
+                            print(f"accelerator update for {event} to {accel!r}")
+                            if accel == "Ctrl+space": accel = "Ctrl+Space"
                             menu.entryconfig(index, accelerator=accel)
 
     def set_notabs_indentwidth(self):
@@ -1193,11 +1195,15 @@ def fill_menus(self, menudefs=None, keydefs=None):
                     def command(text=text, eventname=eventname):
                         text.event_generate(eventname)
                     if checkbutton:
+                        print(f"create CB for {label} with {accelerator!r}")
+                        if accelerator == "Ctrl+space": accelerator = "Ctrl+Space"
                         var = self.get_var_obj(eventname, BooleanVar)
                         menu.add_checkbutton(label=label, underline=underline,
                             command=command, accelerator=accelerator,
                             variable=var)
                     else:
+                        print(f"create command for {label} with {accelerator!r}")
+                        if accelerator == "Ctrl+space": accelerator = "Ctrl+Space"
                         menu.add_command(label=label, underline=underline,
                                          command=command,
                                          accelerator=accelerator)

With this patch I get the correct behaviour from IDLE, but this is obviously not the correct fix. I don't know what the correct fix is though, changing config-keys.def to use "" instead of "" causes an exception.

Adding s = re.sub('space', 'Space', s) to the end of get_accelerator in editor.py seem to work. Is that the correct way to fix this? (If it is I can create a PR).

The "Ctrl+Backslash" issue is likely a similar issue, but I haven't found the correct representation for that yet.

[ronaldoussoren]

In the same test program I mentioned earlier I can use "Control+\" as the accelerator and "<Control-\>" as the key name (in bind-all) to get a working binding for ^, with the correct text in the menu. I haven't tried to add a workaround for this to IDLE's code yet.

[ronaldoussoren]

I've added a PR that fixes this issue. The PR renames the "Ctrl+space" and "Ctrl+backslash" accelerators on macOS only.

I don't have access to Windows or Linux and can therefore not test if it would be safe to the renaming unconditionally.

[terryjreedy]

Thank you. This gives me something to test.

[ronaldoussoren]

@terryjreedy, sorry to bother you but when do you have time to test my PR? I'd prefer to merge this soonish to avoid letting the PR languish.

[terryjreedy]

Tk keysym names are lowercase for printable ascii chars ('space', 'slash', and apparently printable other characters) and uppercase for non-printable keys ('Return', 'Up'). IDLE's 'Get New Keys' dialog checks validity of keystrings (with tk, I believe) and rejects 'Space' as invalid. I would prefer not to display the wrong name.

Alternate proposals:

1. Add 'backslash': r'\\', to keynames, above the function, to display the symbol, as done for other names. I am fine with this for all systems if it works.
2. What happens if 'Control-' is not replaced with 'Ctrl-' on Mac? Does the munging still happen? Or what if we directly replace 'Control-' with '^' on Mac. Does '^space' get munged, or left alone? I will try both of these tomorrow if you don't do so first.

[terryjreedy]

I closed #90655 as a duplicate. OP noted that the problem seems to involve conflicts with macOS standard bindings, as evidenced by part of problem going away when disabled. I noted that this is a subset of problems discussed in #62644

[ronaldoussoren]

Tk keysym names are lowercase for printable ascii chars ('space', 'slash', and apparently printable other characters) and uppercase for non-printable keys ('Return', 'Up'). IDLE's 'Get New Keys' dialog checks validity of keystrings (with tk, I believe) and rejects 'Space' as invalid. I would prefer not to display the wrong name.

Alternate proposals:

1. Add 'backslash': r'\\', to keynames, above the function, to display the symbol, as done for other names. I am fine with this for all systems if it works.

I have no idea how to implement this. The only reason I found that capitalising "space" works is that I made a typo when creating a small reproducer without IDLE.

2. What happens if 'Control-' is not replaced with 'Ctrl-' on Mac? Does the munging still happen? Or what if we directly replace 'Control-' with '^' on Mac. Does '^space' get munged, or left alone? I will try both of these tomorrow if you don't do so first.

"Control+Space" as value for "accelerator" also works, but "Control-space" does not. The latter shows "^S" in the menu, just like "Ctrl+space")

[ronaldoussoren]

1. Add 'backslash': r'\\', to keynames, above the function, to display the symbol, as done for other names. I am fine with this for all systems if it works.

I have no idea how to implement this. The only reason I found that capitalising "space" works is that I made a typo when creating a small reproducer without IDLE.

Never mind, I found your PR. As mentioned there: changing the keynames list causes a crash on my system.

My, now closed, PR does work and is IMHO a fairly minimal change.

It might also be worthwhile to file an issue with the Tcl/Tk project about this, but only when we can demonstrate that the behaviour of CocoaTk is buggy compared to other platforms.