[IME] Styling is lost after making composition with enabled inline style

[Mgsy]

Originally reported here - https://github.com/ckeditor/ckeditor5-build-classic/issues/69.

Steps to reproduce

1. Put the caret in the editor.
2. Change language to Hiragana.
3. Activate bold.
4. Start composition.

Current result

Styling is lost.

It occurs in all browsers.

[imyyg]

Great God, when will this problem be solved? Or is there any temporary solution? Hope to teach @Mgsy

[Mgsy]

Great God, when will this problem be solved? Or is there any temporary solution? Hope to teach @Mgsy

Actually, it turned out that this is a regression and this case was working in CKEditor 5 v11.2.0. We're going to fix it in this iteration and include it to the next CKEditor 5 release.

This bug has been introduced along with this change - ckeditor/ckeditor5-engine@4f9ac0e.

[Reinmar]

This is a serious issue. @oskarwrobel, is now working on finding a solution. We'll post it here and perhaps release a quick small release of ckeditor5-engine to fix it.

[oskarwrobel]

Selection attributes are refreshed after each operation to be sure that selection is always up to date (https://github.com/ckeditor/ckeditor5-engine/issues/1673). A consequence is that attributes are removed from the selection while the composition is in progress.

What's going on?

1. Executing bold command in the empty editor sets bold attribute as the selection attribute, priority of attribute is normal (not low) because it is a direct change.
2. Typing the first character adds it to the editor with a bold attribute and moves the selection after the character what resets the priority of selection attributes to low (it's no longer a directly set attribute but an attribute set because the previous character is marked as bold).
3. Adding the next character composes it with the previous one, so the previous one is removed, the selection is refreshed and bold is removed from the selection attributes because there is no text with bold around the selection at this stage. Finally, the new, composed character is inserted without any attribute.

[oskarwrobel]

We decided to not refresh the selection after each operation (as it was before). It sounds good to have selection up to date after each operation, but it requires some changes for spell checking and composition to remember attributes before replacing text.

[Reinmar]

Do you think we could release [email protected] with just this change? How unsafe it is?

[Reinmar]

👆 @pjasiun @scofalik @Mgsy @oskarwrobel

[pjasiun]

I believe the fix should be safe. I am not sure how our environment will handle the fact that the single package is released. Since we use "^13.1.0" we should be safe. So theoretically there should be no issues. On the other hand, my intuition tells me that it is a bad idea and something will go wrong, so I would not do it.

[oskarwrobel]

From the engine perspective, this fix should be safe.

[Mgsy]

I played with the editor a bit during testing and haven't experienced any weird behaviour or regression.