Re-enable IME support on Linux

[YgorSouza]

Reverts #5188 and adds a different fix to restore IME on Linux without breaking the backspace and arrow keys.

• I have followed the instructions in the PR template

[github-actions]

Preview available at https://egui-pr-preview.github.io/pr/5198-fix-linux-ime
Note that it might take a couple seconds for the update to show up after the preview_build workflow has completed.

[YgorSouza]

@rustbasic @crumblingstatue can you test this?

I've tested with Fedora 40/Gnome 46 with both the regular (Wayland) session and the XOrg session, with the compose key, the Unicode input (Ctrl+Shift+U) and the Chinese (Intelligent Pinyin) input source. Everything seems to work, and the backspace and arrow keys work on both as well.

[crumblingstatue]

I can't test IME, because fcitx (& pals) somehow break my X11 setup (don't ask me how), but I can confirm that backspace and arrow keys work.

[rustbasic]

Dear emilk & Dear YgorSouza

My opinion is,

• Linux: Disable IME to fix backspace/arrow keys #5188
  It seems like it's impossible to input languages ​​other than English that require an IME on Linux.

• Fix: Selectable whether to key handling in IME #5182
  For non-English users using Linux, I think Fix: Selectable whether to key handling in IME #5182 is the right way, because we can control turning it on/off as needed.
  If there are any parts we don't like, we can just edit them.

• Re-enable IME support on Linux #5198
  Re-enable IME support on Linux #5198 It should work fine on Windows, as there are no changes.
  I'm not sure if it will work well on some Linux + Chinese.

[YgorSouza]

I'm not sure if it will work well on some Linux + Chinese

Is there anyone who can test this? I mean, it seems fine to me, but I'm not Chinese so I don't know.

#5182 looks like it would require a major release? It's adding fields to structs, so I guess that's a breaking change. But if we can get the IME to work correctly on all platforms, maybe it won't be needed? And egui-winit already has an allow_ime field, so we could block IME events at this level, if needed, without involving the TextEdit or any other widgets.

egui/crates/egui-winit/src/lib.rs

Lines 844 to 849 in ce744e6

	let allow_ime = ime.is_some();
	if self.allow_ime != allow_ime {
	self.allow_ime = allow_ime;
	crate::profile_scope!("set_ime_allowed");
	window.set_ime_allowed(allow_ime);
	}