basic IME support rebase

[KentaTheBugMaker]

General

This PR fix #979,#1544.
iced ime support was broken due to winit 0.27 update .
This PR add event to fit new winit IME event model and introduce new event support for text_input.

how to test

download app from my repo https://github.com/KentaTheBugMaker/iced_text_input_sample/

Phase 1 : Can we input CJK characters?

tested on

• windows MS-IME

Phase 2 : Candidate position is near the TextInput?

You maybe failed to reproduce due to IME version.
candidate positon on X11 require LibX11 1.8.2 or above.

Wayland requirement.

• input_method_v2 popups

tested on

• windows MS-IME

Phase 3 draw underline and cursor

behavior

2022-12-05.23-27-59.mp4

test

not required.
We render underline and cursor correctly if winit correctly report it.

• windows

Note

I don't have a macos device, so if you notice any problems, macos users please fix them.

Some tests were done by other users. but Iced rework enforce me to reimplement completely.
Therefore old tests are not compatible with this version.

feel free to reimplement this.

[AllenDang]

I tracked this pr daily, hope to see it will be merged into main brach some day.

[hecrj]

Work related to IME is slated around the 0.12 release. See the ROADMAP.

I will take a look at this by then!

[rhysd]

Thank you for working on this. This is a mandatory feature for CJK users.

I tried this branch on macOS and I found one small issue. When some character was already input before a cursor, the insert position of IME candidates was a bit wrong.

test.mov

1. Enable Japanese IME
2. Type aiueo and Return
3. Text あいうえお is inserted
4. Type kakikukeko
5. Expected the candidate かきくけこ was positioned at after お, but it was actually positioned before お

After selecting the candidate, the text かきくけこ is inserted at correct position. So only the position of IME candidate is wrong.

[tingfeng-key]

run iced-ime_adavanced_text\examples\todos

[KentaTheBugMaker]

We can't measure width of IME candidate window.
So some overflow may occur but it seems to too large overflow.
We offset candidate window when text content overflow the TextInput widget.

[tingfeng-key]

It's normal, thank you for your efforts

[bajie-git]

The default windows input method can be used normally, but the "Sogou input method" still has problems, and the console will prompt: "libpng warning: iCCP: known incorrect sRGB profile"

[KentaTheBugMaker]

iced now using winit 0.28.6 fork.
therefore you need to test winit ime example.
if same problem ocurred we can't fix this problem.

[Taiyangqihuo]

Awesome work!

[Drodofsky]

Hi, I understand that IME is scheduled for a later release in the roadmap, but it is a crucial feature for me and many others. Please consider moving IME to an earlier release. What is still needed before this feature can be merged? Thank you for the incredible work!

[KentaTheBugMaker]

@hecrj
IME support is a fundamental feature for non-European users.
What's blocking this PR ?
or We need to make some RFC for IME?

[Gezx]

is it support text_editor?

[KentaTheBugMaker]

@Gezx
no when i first wrote there ware no TextEditor widget.
but I have plan to extend to support it.

[bioinformatist]

@KentaTheBugMaker Hey bro, are you still working on this?

[KentaTheBugMaker]

@bioinformatist
Yes . Working on but I'm trying the better way to support it .
currently my implementation is based on winit.
but winit API is too poor to support native like quality.

• focus in and focus out .
• Text highlighting
• Placing candidate window

Iced side also have problem.

if want to support TextEdit widget we need to support below

• setting up input cursor
• underline rendering
• placing candidate window

current design have these difficulties.

• We need to touch too many files (Clipboard like implementation)
• We need some hack to support platform behavior

so I'm re implementing this with better GTK IMContext like API.

           iced-widget
                |
       ___________ _________________________________
      |           |                               |
iced-winit iced-ime(IME backend impl)   iced-core(IME api difinition)

New design .

• we don't touch other widgets.
• we don't touch iced-winit.
• We don't need platform dependent hack (We use platform Native API in backend)
• easier addon to support other IM
  currently I'm working on IBus support.

[Domiryuu]

I want to express my deep thanks for your continued effort on this.

[bioinformatist]

@KentaTheBugMaker Really appreciate!

[KentaTheBugMaker]

progress
ibus testing.
Iced Key to xkb keysym and keycode is not difficult.
most of Iced Key events is tunneling winit ones.
I tested it by very small winit project.
therefore we don't have to touch iced-winit deeply.
but maybe candidate window placing maybe difficult.