bpo-42318: Fix support of non-BMP characters in Tkinter on macOS

[serhiy-storchaka]

https://bugs.python.org/issue42318

[ronaldoussoren]

The PR looks good to me.

I've tested the PR with the copy of Tk 8.6.10 that I reported the issue for, and with this patch the problem is gone. I also get correct syntax colouring in edit windows.

[ronaldoussoren]

I had to reread this loop a couple of times before I understood how the contents of "u" is updated. My C is getting a bit rusty ;-)

The code looks fine though.

[miss-islington]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 3.8, 3.9.
🐍🍒⛏🤖

[miss-islington]

Sorry, @serhiy-storchaka, I could not cleanly backport this to 3.9 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker a26215db11cfcf7b5f55cab9e91396761a0e0bcf 3.9

[miss-islington]

Sorry @serhiy-storchaka, I had trouble checking out the 3.8 backport branch.
Please backport using cherry_picker on command line.
cherry_picker a26215db11cfcf7b5f55cab9e91396761a0e0bcf 3.8

[bedevere-bot]

GH-23784 is a backport of this pull request to the 3.9 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot s390x RHEL8 LTO + PGO 3.9 has failed when building commit 28bf6ab.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/436/builds/422) and take a look at the build logs.
4. Check if the failure is related to this commit (28bf6ab) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/436/builds/422

Summary of the results of the build (if available):

== Tests result: ENV CHANGED ==

409 tests OK.

10 slowest tests:

• test_concurrent_futures: 2 min 40 sec
• test_multiprocessing_spawn: 1 min 10 sec
• test_multiprocessing_forkserver: 1 min
• test_multiprocessing_fork: 56.5 sec
• test_asyncio: 48.3 sec
• test_signal: 47.1 sec
• test_io: 34.7 sec
• test_imaplib: 33.5 sec
• test_pydoc: 31.1 sec
• test_subprocess: 29.6 sec

1 test altered the execution environment:
test_asyncio

15 tests skipped:
test_devpoll test_gdb test_ioctl test_kqueue test_msilib test_nis
test_ossaudiodev test_startfile test_tix test_tk test_ttk_guionly
test_winconsoleio test_winreg test_winsound test_zipfile64

Total duration: 4 min 47 sec

Click to see traceback logs

Traceback (most recent call last):
  File "/home/dje/cpython-buildarea/3.9.edelsohn-rhel8-z.lto-pgo/build/Lib/asyncio/sslproto.py", line 321, in __del__
    self.close()
  File "/home/dje/cpython-buildarea/3.9.edelsohn-rhel8-z.lto-pgo/build/Lib/asyncio/sslproto.py", line 316, in close
    self._ssl_protocol._start_shutdown()
  File "/home/dje/cpython-buildarea/3.9.edelsohn-rhel8-z.lto-pgo/build/Lib/asyncio/sslproto.py", line 590, in _start_shutdown
    self._abort()
  File "/home/dje/cpython-buildarea/3.9.edelsohn-rhel8-z.lto-pgo/build/Lib/asyncio/sslproto.py", line 731, in _abort
    self._transport.abort()
  File "/home/dje/cpython-buildarea/3.9.edelsohn-rhel8-z.lto-pgo/build/Lib/asyncio/selector_events.py", line 680, in abort
    self._force_close(None)
  File "/home/dje/cpython-buildarea/3.9.edelsohn-rhel8-z.lto-pgo/build/Lib/asyncio/selector_events.py", line 731, in _force_close
    self._loop.call_soon(self._call_connection_lost, exc)
  File "/home/dje/cpython-buildarea/3.9.edelsohn-rhel8-z.lto-pgo/build/Lib/asyncio/base_events.py", line 746, in call_soon
    self._check_closed()
  File "/home/dje/cpython-buildarea/3.9.edelsohn-rhel8-z.lto-pgo/build/Lib/asyncio/base_events.py", line 510, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed