Add WindowBase::setImePreEditPosition

[Edgaru089]

Description

This PR adds a method to WindowBase, setImePreEditPosition(const Vector2i& pos), that hints to the OS/IME framework where to put the preedit window.

Tasks

• Tested on Linux (Fcitx5)
• Tested on Linux (IBus)
• Tested on Windows
• Tested on macOS (Not implemented)

I'm completely illiterate when it comes to macOS/Objective-C (or any other Apple stuff), and I need help on that part.

How to test this PR?

Install an IME if you don't have one, and run this example.

This is relatively straightforward on Windows 10: install a language of Chinese Simplified/Traditional or Japanese in the Settings app, and press Win+Space to switch to that input.

#include <SFML/Graphics.hpp>

int main() {
    sf::RenderWindow window(sf::VideoMode({ 400, 400 }), "IME position");
    window.setFramerateLimit(60);

    while (window.isOpen()) {
        for (sf::Event event; window.pollEvent(event);) {
            if (event.type == sf::Event::Closed)
                window.close();
            else if (event.type == sf::Event::MouseButtonPressed) {
                auto pos = sf::Mouse::getPosition(window);
                window.setImePreEditPosition({pos.x, pos.y});  // Try negating these values and see what happens    
            }
        }

        window.clear();
        window.display();
    }
}

Click around in the opened window, and try typing with the IME engaged.

[Edgaru089]

This patch also works with IBus on a fresh Ubuntu VM.

[Bromeon]

Small note: we generally use PascalCase for abbreviations (Utf, UdpSocket, Http, AlResource).

This would mean IMEPreeditPosition should be ImePreeditPosition.

(Strictly speaking, WindowImplDRM is also not consistent, but that's out of scope for this PR).

[codecov]

Codecov Report

Merging #2469 (5e9c13c) into master (9105148) will decrease coverage by 0.05%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2469      +/-   ##
==========================================
- Coverage   38.54%   38.49%   -0.05%     
==========================================
  Files         229      229              
  Lines       19806    19834      +28     
  Branches     4733     4737       +4     
==========================================
+ Hits         7635     7636       +1     
- Misses      11147    11243      +96     
+ Partials     1024      955      -69     

Files Changed	Coverage Δ
include/SFML/Window/WindowBase.hpp	0.00% <ø> (ø)
src/SFML/Window/Unix/WindowImplX11.cpp	32.62% <0.00%> (-0.14%)	⬇️
src/SFML/Window/Win32/WindowImplWin32.cpp	25.21% <0.00%> (-0.34%)	⬇️
src/SFML/Window/Win32/WindowImplWin32.hpp	83.33% <ø> (ø)
src/SFML/Window/WindowBase.cpp	62.32% <0.00%> (-1.49%)	⬇️
src/SFML/Window/WindowImpl.hpp	50.00% <ø> (ø)
src/SFML/Window/iOS/WindowImplUIKit.mm	0.00% <0.00%> (ø)
src/SFML/Window/macOS/WindowImplCocoa.mm	23.90% <0.00%> (-0.20%)	⬇️

... and 6 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9105148...5e9c13c. Read the comment docs.

[Edgaru089]

Issues fixed and rebased to latest master.

[eXpl0it3r]

Is preedit really the most commonly referred to name for that window?
I like the "Composition" term that the Windows API uses "nicer", mostly wonder though what term IME users generally use.

If we stick with preedit, I suggest to use PreEdit instead: setImePreeditPosition vs setImePreEditPosition

PR needs to be rebased

[Edgaru089]

Rebased to latest master.

I won't prefer the word 'Composition'. Please correct me if I'm wrong, but in my understanding the word more describes the use of the Compose key to combine accent marks with Latin alphabet in some European languages. IMEs are something quite different.

People around me call that window something like 'input method window' or '(input method) selection pending box'. I'm from China mainland btw.