[Bug] 中文输入法的选项不能显示

[Corditegere]

Description

不能显示中文输入法的选项

When typing Chinese in the editor on Windows 11, the Chinese IME candidate selection box fails to render/display near the cursor. However, if I type the Pinyin and press the space bar, the Chinese characters can still be input normally into the edit area. This only affects the candidate box display, not the actual Chinese input function, and it severely impacts the Chinese typing experience.

Environment

• OS: Windows11
• Ferrite version: 0.2.7
• Rust version: unknown
• Installation method: MSI installer

Steps to Reproduce

1. Open the Ferrite editor and click the edit area to activate the input cursor.
2. Switch the system input method to any Chinese IME (Pinyin).
3. Type any Chinese Pinyin (e.g., "nihao", "zhongwen") in the edit area.
4. Check if the Chinese IME candidate selection box pops up near the cursor.

Expected Behavior

After typing Chinese Pinyin, the IME candidate box should render and float normally below/next to the input cursor, allowing selection of the corresponding Chinese characters.

Actual Behavior

The Chinese IME candidate selection box is completely invisible when typing Pinyin; no floating panel appears at all. Pressing the space bar can convert the Pinyin to the correct Chinese characters and input them into the editor (the input function itself works).

• Switching between fullscreen/windowed mode (F11) does not fix the issue.
• Restarting the Ferrite editor does not resolve the problem.
• Disabling hardware acceleration in Ferrite settings also has no effect.

Screenshots

A key detail: When I press the Windows screenshot shortcut (Win+Shift+S) to open the screenshot overlay, the Chinese IME candidate box temporarily appears normally in the screenshot interface. But once I exit the screenshot mode and return to Ferrite's edit interface, the candidate box disappears again immediately. This confirms the issue is caused by the rendering layer conflict between Ferrite and the Windows IME, not the input method itself.
我怀疑整个窗口是置顶了，导致其他的窗口都被遮挡了。

Log Output

If applicable, paste any relevant error messages or log output:

No relevant error logs found in the Ferrite log directory.

Additional Context

• English input works perfectly with no any issues.
• The problem occurs with all Chinese IMEs (system-built Microsoft Pinyin + third-party Sogou/WeChat Input), not just a single one.
• Other Rust/TAURI-based Markdown editors (e.g., Notable, Typora) on the same Windows 11 system work normally with Chinese IME (candidate box displays correctly).
• No other system software/extensions are interfering with the input method (IME works normally in all other Windows apps).

Regression

• This worked in a previous version
• If yes, which version?

[OlaProeis]

Hi @Corditegere!

Thank you for this excellent and detailed bug report, the observation about the candidate box appearing during the Win+Shift+S screenshot overlay was particularly insightful and helped us narrow down the root cause.

Investigation Findings

Your suspicion was correct, this is a rendering layer/z-order issue, not an IME input problem. We've identified two contributing factors:

1. Missing Coordinate Transform (Confirmed Bug)

Our custom editor (FerriteEditor) sets the IME cursor area using local widget coordinates, but egui's built-in TextEdit applies a layer_transform_to_global() transform to convert to screen coordinates first. Without this transform, the OS receives incorrect coordinates for positioning the candidate window.

Our code:

o.ime = Some(IMEOutput { rect, cursor_rect }); // local coords

What egui's TextEdit does:

let to_global = ui.ctx().layer_transform_to_global(ui.layer_id());
o.ime = Some(IMEOutput {
    rect: to_global * rect,           // screen coords
    cursor_rect: to_global * primary_cursor_rect,
});

2. Custom Window Decorations Z-Order (Suspected)

Ferrite uses with_decorations(false) for its custom title bar, which changes the Win32 window styles. This may cause the IME candidate popup to be placed behind the application window in the z-order — explaining why the candidate box becomes visible when the screenshot overlay temporarily changes the compositing order.

Relationship to #15

This is related to our existing tracked issue #15 (IME candidate box positioning). Your report provides a more severe manifestation (completely invisible vs. offset) and the screenshot overlay observation was the key clue that confirmed the z-order hypothesis.

Fix Plan

1. Apply to_global transform to rect and cursor_rect when setting IMEOutput in our custom editor
2. Investigate Win32 z-order workarounds for the candidate popup with custom-decorated windows
3. Test with multiple IMEs (Microsoft Pinyin, Sogou, WeChat Input) on Windows 10/11

Timeline

This fix is scheduled for v0.2.8. Since the coordinate transform fix is straightforward, we expect that alone may resolve the issue for most configurations. The z-order investigation may require additional work if the transform fix isn't sufficient.

Thank you again for the detailed reproduction steps and the screenshot overlay observation — that was the breakthrough insight. We'll update this issue when the fix is ready for testing.

[Corditegere]

Hi, @OlaProeis！

After reopening Ferrite and switching to light mode, the IME candidate box suddenly became visible. However, it’s showing up in a weird position. It should appear right below the Pinyin I’m typing, but instead it’s showing up at the very bottom of the screen.

[OlaProeis]

Thanks for the follow-up and screenshot @Corditegere , this is very helpful!

The candidate box appearing at the bottom of the screen instead of near your cursor confirms exactly what we suspected: we're passing local widget coordinates to the OS instead of screen coordinates. Windows is faithfully positioning the candidate box where we tell it to, it's just that the coordinates we're giving it are wrong.

The fix is straightforward — a one-line coordinate transform in our editor code. We'll have this resolved in v0.2.8.