gh-154511: IDLE - Update mousewheel event handling

[terryjreedy]

• Issue: IDLE - Update mousewheel event handling #154511

[terryjreedy]

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]

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

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

[serhiy-storchaka]

Bug: x11_buttons is always false.

_windowingsystem is a property, and it's accessed here on the class, not an instance.

[terryjreedy]

Fixed by creating root. After pulling pyshell.main into a new start/main module, I will consider possibility of making util.root the master root. The windowing system could also be saved and imported by macos. Separate issue/pr.

[terryjreedy]

Anyway, wheel should now work on linux and 8.6.

[terryjreedy]

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

[terryjreedy]

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

[serhiy-storchaka]

Simply do not make it a global variable. If you want to share a code, make it a function that takes a widget as argument.

[terryjreedy]

Which? x11_buttons is just False/True. Creating root at top level is a standard idiom for non-class tkinter code. Is tcl/tk broken on macOS? I'm not sure I understand the second sentence. Are you suggesting something like below?
(I now realize that root counts as a widget, and that widget._win... is root.win... .

def x11b(widget):
    return widget._windowingsystem == 'x11' and tkinter.TkVersion <= 8.6
x11_buttons = x11b(root)

A function makes no sense to me since the windowing system does not depend on the widget, so it seems sensible to cache it (which, I just read, tkinter does).