IME Support

[lunabunn]

egui master recently got support for IMEs (Input Method Editors; emilk/egui#248). These new events should be handled by egui_sdl2_gl.

[ArjunNair]

Cool. Will look into it!

[ArjunNair]

I seem to have it working fine on Mac (see branch https://github.com/ArjunNair/egui_sdl2_gl/tree/ime_support).

However, I can't seem to get this to work on Windows. Looks like this could be a SDL 2 issue (Rust-SDL2/rust-sdl2#1042). Even with the "bundled" feature that tries to patch the 1042 fix mentioned above, I couldn't get Chinese characters or the candidate window to show up correctly in the input box.

Neovide (https://github.com/Kethku/neovide) seemed to have similar issues and as far as I can tell they switched to winit for the windowing events to get around this? Not entirely sure.

Unfortunately, I've run into a brick wall for the moment as far as windows IME support goes. Any pointers or help would be appreicated!