Use code point on OnTextInput

[Cn-mjt44]

In SDL2/3, text input event will only return a complete unicode character. If this part use char in csharp, It can't explane a complete unicode character at one times.

[flibitijibibo]

I might be mixing up types here but what we're intending to do with the current code is convert from UTF8 to wchar_t, which is what char should be in C#. The text buffer in SDL3 got expanded to support whole strings, which is how we handle console text input. Is there a specific test we can try on the various platforms to see the before/after for this change?

[Cn-mjt44]

@flibitijibibo No, I'm sorry, I don't have console. So I can't test for console.
But, even it push whole string to SDL_TEXTINPUT, it can still handel this. Because, the logic is essentially turning the UTF-8 string to UTF-32 string. And then foreach every UTF-32 character push to OnTextInput. The UTF32 character is equle to unicode codepoint. So every character will be validity in unicode.

[Cn-mjt44]

For example, 🤣 is U+1F923. If you try to repecent in c# string(utf-16 string), it take 2 char. If you only takeing one utf-16 character from there, it take no mean for text.

[flibitijibibo]

Interesting - I wonder if this is a serious problem for platforms where sizeof(wchar_t) is 2 rather than 4.

The overall purpose of the patch makes sense to me but I'm surprised it requires so much manual intervention - should we isolate translation to a helper file maybe? Is this something upstream dotnet should care about?

[Cn-mjt44]

@flibitijibibo char.ConvertFromUtf32 and char.ConvertToUtf32 can translate betwen the codepoint and c# string. So you not need to do that.

[flibitijibibo]

Understood - I've marked this as an extension bug for the moment; if it works locally that's great, but I assume this subject has a bunch of weird caveats so I'll let others chime in to make sure we get the next revision of TextInputEXT correct, since it's hard to modify extensions unless we're really sure the change is both necessary and absolutely correct.

Expect some reviews over time, either way: Thanks for checking this out!

[Cn-mjt44]