[IME][Safari] IME composition broken in empty paragraph in Safari

[farthinker]

The original issue was described in #1333.

I've tried to fix it in https://github.com/ckeditor/ckeditor5-typing, but failed. Some IME cannot bear any DOM selection update.

So I thought maybe we should prevent DOM selection change while composing in the render process(like return false in _domSelectionNeedsUpdate). I'll submit a PR later.

[mlewand]

Related PR: ckeditor/ckeditor5-engine#1783

[scofalik]

Unfortunately, we have to revert the PR that fixed this issue: ckeditor/ckeditor5-engine#1783.

After some deeper tests, it appeared that this fix is causing serious problems with track changes on Android (GBoard keyboard).

As of now, the only way to reproduce the error is to use track changes plugin, which requires some additional set up: https://ckeditor.com/docs/ckeditor5/latest/features/collaboration/track-changes/track-changes.html. Basically, it is enough to turn on track changes and start typing at the beginning of a block (paragraph). The editor crashes after writing a few characters and a space. It is easier to crash if the paragraph has some bolded text in it.

We will let you know if we have any further information about this issue.

[scofalik]

I've pushed branch ckeditor5-typing#i/4533 which includes a manual test showcasing the problem. The test simulates what happens in track changes mode, it modifies a marker when some content is inserted in the editor. It should be used with the code prepared in this PR to reproduce the below error.

Testing scenario:

1. Run tests using yarn manual --files=typing.
2. Open http://localhost:8125/ckeditor5-typing/tests/manual/4533/1.html on Chrome@Android with Gboard keyboard and all autocorrection/suggestion options on.
3. Put the caret at the beginning of the paragraph.
4. Type A then type B.

As you can see, on typing A the caret is incorrectly moved before the letter and then on typing B the editor crashes.

This does not happen without the fix proposed in @farthinker's PR:

Or when using a desktop browser.

[Reinmar]

TODO: Verify whether #1333 is related to this issue.

[CKEditorBot]

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[CKEditorBot]

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