Steps to reproduce the problem

1. Open the attached HTML file(issueSample.html) in the Chrome browser.
2. When selecting from the character '녕' in the first line to the red character 'ㄱ' (offset irrelevant) in the second line and then typing the Korean character 'ㄱ', the style of the second line is applied to the newly typed 'ㄱ'.
3. Press Ctrl + Z
4. When selecting the same range as in step 2 and then typing any Korean character other than 'ㄱ', or any English letter or number, the style of the first line is applied to the newly typed character.
5. Press Ctrl + Z
6. When selecting from the character 'ㄱ' in the second line to the character 'ㄷ' in the middle of the fourth line, and then typing 'ㄷ', the style of the fourth line is applied to the newly typed 'ㄷ'.
7. Press Ctrl + Z
8. When selecting the same range as in step 6 and then typing any korean character other than 'ㄷ', or any English letter or number, the style of the second line is applied to the newly typed character.

• Actual Result: The styles applied to the newly entered characters in steps 2 and 4 are different, and the styles applied to the newly entered characters in steps 6 and 8 are also different.

• Expected Result: The style applied to the newly entered characters in steps 2 and 4 should be the same, and the style applied to the newly entered characters in steps 6 and 8 should be the same.

Problem Description

In Contenteditable, when selecting text with different styles at the start and end of a range and then typing Korean, the style is not consistently applied.

• Some characters apply the style of the range's starting character, while others apply the style of the range's ending character.

As you can see in the reproduction scenario I wrote, when you enter the same Korean character as the one at the end of the range, the style of the character at the end of the range is applied, which constitutes the issue.

Styles are applied consistently in Safari on macOS.

It appears that when typing characters after selecting a range in Chromium, the characters are generally styled with the format of the range's starting point. So the above problem looks like a bug to me. If it is indeed a bug, I would appreciate it if you could confirm and fix it.

Summary

Inconsistent styles when typing Korean after selecting multi-styled text in Contenteditable.

Custom Questions

Which component does this fall under?

Blink>Editing

Does this work in other browsers?

Yes - This is just a Chrome problem

Additional Data

Category: API
Chrome Channel: Stable
Regression: N/A