[Feature Request] Support IME Preedit (SupportsPreedit/SetPreeditText)

[Soar360]

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!

[realybin]

The original code (AvalonEdit) implement ime is based on win32,
I browsed the source code (AvaloniaEdit) and I find that AvaloniaEdit not fully implement the ime specific region.
And he implementation part led some problems (#489)
And the InputMethodClient takes control the textview so the child control will also be effect(e.g. searchtool)

So we might need a solution of managing IME. At present, most works at a glitch state.

textview layer and it's child (avalonedit)

[love-linger]

@Gillibald I see that you self-assigned ths issue.

My native language is Chinese, and I rely heavily on this feature. Is there any problem with PR #532? Or will the official team have a better implementation plan?

Looking forward to your reply.

[Timskt]

I hope this issue can be resolved, as this feature is extremely useful for the Chinese-speaking community