Quick manual checks on linux and macOS would be nice: load a non-trivial file such as editor.py and scroll up and down. Scrolling in a sidebar should not be affected by this PR. Open a module browser and expand enough to scroll both over the items and in the blank space. @StanFromIreland I forget whether you have mac or only linux.

EDIT: I have done the above on Windows and the unittest is system independent, as it patches the x11 indicator (which Serhiy wrote and tested on x11.)

@StanFromIreland I forget whether you have mac or only linux.

Only Linux, maybe ask a Mac expert to test it on a Mac.

@ronaldoussoren @ned-deily Could one of you quickly test that scrolling still works on macOS in editor and module browser?

Failures are mysteries to me.
test_idle worker non-zero exit code�[0m (Exit code -5 (SIGTRAP)) macOS
?? no detail
test_idle worker non-zero exit code�[0m (Exit code -11 (SIGSEGV)) macOS intel and macOS free threading
File "/Users/runner/work/cpython/cpython/Lib/tkinter/init.py", line 1579 in update
File "/Users/runner/work/cpython/cpython/Lib/test/support/init.py", line 306 in _is_gui_available
File "/Users/runner/work/cpython/cpython/Lib/test/support/init.py", line 346 in requires
File "/Users/runner/work/cpython/cpython/Lib/idlelib/idle_test/test_configdialog.py", line 7 in
?? How does patch affect tkinter.init when running test_configdialog??

UBSan has repeated failures like this:
Traceback (most recent call last):
File "/home/runner/work/cpython/cpython/Lib/unittest/loader.py", line 433, in _find_test_path
module = self._get_module_from_name(name)
File "/home/runner/work/cpython/cpython/Lib/unittest/loader.py", line 374, in _get_module_from_name
import(name)
~~~~~~~~~~^^^^^^
File "/home/runner/work/cpython/cpython/Lib/idlelib/idle_test/test_browser.py", line 3, in
from idlelib import browser
File "/home/runner/work/cpython/cpython/Lib/idlelib/browser.py", line 16, in
from idlelib import pyshell
File "/home/runner/work/cpython/cpython/Lib/idlelib/pyshell.py", line 39, in
from idlelib.editor import EditorWindow
File "/home/runner/work/cpython/cpython/Lib/idlelib/editor.py", line 29, in
from idlelib.util import py_extensions
File "/home/runner/work/cpython/cpython/Lib/idlelib/util.py", line 73, in
root = tkinter.Tk() # Use this as process root?
File "/home/runner/work/cpython/cpython/Lib/tkinter/init.py", line 2687, in init
self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
_tkinter.TclError: no display name and no $DISPLAY environment variable
Failed to import test module: idlelib.idle_test.test_debugobj

with different idle_test.test_x for each failure
Hypothesis has failures like this also.
?? Why does this particular (and new) Tk() call fail?? and just on some tests.

Re-running some

I pushed an alternative, #156974, with the same goals.

The import-time tkinter.Tk() in util has three consequences:

• pyshell imports fix_win_hidpi from util and calls it, but the import now creates a root first, so SetProcessDpiAwareness fails with E_ACCESSDENIED — swallowed by the function's except — and the Windows HiDPI fix silently stops working. turtledemo does the same thing.
• run.py imports util, so the user process would create and destroy a Tk root on every Run. That process should not need tkinter at all — it already has to unload the submodules idlelib drags in (scrub_tkinter_submodules, IDLE: user code 'import tkinter; tkinter.font' should fail #69693) — and a root is a connection to the window server, not merely an import.
• import idlelib.util raises TclError without a display, so test_browser, test_iomenu, test_editor … would error instead of skipping. test_idle runs headless today: 307 tests, 83 skips.

Two smaller things:

• wheel_event should take the direction from the event rather than the platform: a <Button-4> event arriving while x11_buttons is false reads delta == 0 and scrolls down. num is 4 or 5 for a button and '??' for a wheel.
• Assigning util.x11_buttons in the test exercises the flag, not the code path, and requires('gui') at module level gives up the tests that need no display.

Nits: <Mousewheel missing its >, "generally=", "test delagation", the leftover coverage %, the walrus in (widget2 := _Widget()), the unrelated blank line removed after class TreeNode:, no NEWS entry.

In #156974, x11_buttons(widget) is a function and bind_wheel(widget, func) hides the choice from the call sites; util imports tkinter only inside the function that needs it, so importing util pulls in no tkinter at all. Happy to close mine if you would rather fix this one.

Before me, run.py was written to avoid disturbing tk, so it calls tkinter.Tcl().update () inside of handle_tk_events, called within the main loop when there is no request. I believe this is there to advance user tkinter code without a Tk().mainloop(). In any case, creating a Tk upon util import is bad. Serhiy's alternative has other advantages, including passing CI. So closing this.