Wayland (Cosmic 1.5): IME preedit string not rendered inline at cursor — only candidate popup appears

[x3ng]

Environment

• Rio: 0.5.24
• OS: NixOS 26.05
• Compositor: Cosmic 1.5 (native Wayland, not XWayland)
• IME: fcitx5 5.1.x + libpinyin (also tested ibus-libpinyin)
• Session: XDG_SESSION_TYPE=wayland
• Env vars:

GTK_IM_MODULE=fcitx5
QT_IM_MODULE=fcitx5
SDL_IM_MODULE=fcitx5
GLFW_IM_MODULE=ibus

Expected behavior

Preedit string (e.g. nihao — the composing letters before commit) should be rendered inline in the terminal grid at the cursor position, same as the final character slot. Candidate popup should appear separately (already works).

This is how Kitty / Ghostty / WezTerm behave on the same Cosmic session + fcitx5.

Actual behavior

• ✅ Candidate popup appears and follows cursor position
• ❌ No preedit text is drawn in the grid cells at cursor during composition
• ✅ On commit (Space / number selection), final Chinese character is inserted correctly

The cursor visually does not show what is being typed until commit. For CJK inline editing (shell, vim, comments) this makes input effectively blind.

[cattyhouse]

same issue with rio on macOS

[raphamorim]

Fixed by #1849, which landed on main (cd64f8b) and ships in 0.5.28. The composition now renders inline at the cursor as a cursor-colored block on all platforms (the rendering is platform-agnostic; Wayland's preedit events were already arriving, they just drew nothing). Composing shows each cluster at the cursor, conversion segments get an underline caret, and the candidate popup keeps following the caret. If anything still misbehaves on Cosmic + fcitx5 after 0.5.28, please open a fresh issue with the details.

[cattyhouse]

thanks for the fix, could you make a 0.5.28 release?