Currently, AvaloniaEdit's IME support does not implement the Preedit feature. The TextInputMethodClient.SupportsPreedit property is hardcoded to return false, and SetPreeditText is not implemented. As a result, users cannot see or interact with preedit text from input methods (IME), such as the underline preview when typing Chinese, Japanese, or Korean. This makes it difficult or impossible to input non-alphabetic languages efficiently.

I urgently need AvaloniaEdit to support the IME Preedit feature. This would allow preedit text to be shown and updated in real time, just like in standard text editors (e.g. Notepad, VSCode, etc.).

If necessary, I am happy to provide more details, test builds, or help with the implementation. Thank you!