gh-38066: IDLE: Dedenting with shift+tab

[mlouielu]

• Issue: IDLE: Dedenting with Shift+Tab #38066

[matssson]

This would be really useful, since I use IDLE a lot when I wanna do something fast, and indentation is so important. The other keyboard shortcut doesnt really work on my layout

[StanFromIreland]

Bumping this PR. Very nice feature, implementation seems good, someone should build to double check.

[terryjreedy]

I think I fixed merge conflict okay. But must manually test on multiple OSes before merge.
Will make news entry if decide to merge.

[terryjreedy]

@StanFromIreland
I found ISO keysyms on https://www.tcl-lang.org/man/tcl8.6/TkCmd/keysyms.htm.
Unknown to me and likely new in 8.6. Are these a linux (unix) thing? Would 'tab' really not work?
In any case, 'Key' for the event should still be needed before the keysym.

Suggested change

	smart-dedent=<Shift-ISO_Left_Tab>
	smart-dedent=<Shift-Key-ISO_Left_Tab>

Repeat twice below.

[StanFromIreland]

They are not a tk thing, but an X11 thing.

I tested, and just smart-dedent=<Shift-Key-Tab> does not work.

On my system it is actually not necessary to have Key- (but it is best to have it anyway IMO). Secondly, ISO_Left_Tab implies Shift, although IIRC this is not always the case and causes problems with some apps.

[terryjreedy]

I added comments to issue about what I think ShiftTab should do. I will manually what it does do, on Windows, tomorrow. Stan, can you try it on Linux?

[StanFromIreland]

The current implementation is broken, whenever I try to dedent I get:

Exception in Tkinter callback
Traceback (most recent call last):
  File "cpython/Lib/tkinter/__init__.py", line 2088, in __call__
    return self.func(*args)
           ~~~~~~~~~^^^^^^^
  File "cpython/Lib/idlelib/editor.py", line 1402, in smart_dedent_event
    raw, effective = classifyws(prefix, self.tabwidth)
                     ^^^^^^^^^^
NameError: name 'classifyws' is not defined

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[sharktide]

Bump