Fix preedit decoration in ibus-mozc under Wayland

[ftake]

Description

Wayland protocols do not support specifying arbitrary RGB colors for preedit styling. This commit switchs preedidt decoration to IBus semantic preedit hints (available since 1.5.33) so that decoration works correctly under Wayland.

Issue IDs

#1484

Steps to test new behaviors (if any)

A clear and concise description about how to verify new behaviors (if any).

• OS: Linux, Plasma Wayland
• Steps:
  1. Open Kate
  2. Type Watashinonamaeha
  3. Type Space
  4. Check the first segment is highlighted

Additional context

• This fix requires newer IBus (1.5.33). If necessary, we can keep some codes for backward compatibility.
• This change affects X11 session. The highlight color will be changed from #D1EAFF to IBus's default.

[yukawa]

This fix requires newer IBus (1.5.33). If necessary, we can keep some codes for backward compatibility.

Our CI relies on Ubuntu 24.04, where IBus 1.5.29 seems to be used. Does your change break our CI? If yes, I think the answer is clear and we need to keep the backward compatibility.

mozc/.github/workflows/linux.yaml

Lines 16 to 19 in a2303d2

	build:
	# https://github.com/actions/runner-images/blob/main/images/ubuntu/Ubuntu2404-Readme.md
	runs-on: ubuntu-24.04
	timeout-minutes: 60

[ftake]

Does your change break our CI?

Yes...
Is there any plan to update the CI environment to Ubuntu 26.04?

[yukawa]

Is there any plan to update the CI environment to Ubuntu 26.04?

Yes, we are going to update to Ubuntu 26.04 when it becomes available. See the following tasks when we updated our CI Ubuntu version in the past.

• Upgrade reference build environment for Linux/Android to Ubuntu 24.04 #924
• Upgrade the linux GitHub action to Ubuntu 22.04 #763

That said chances are high that GitHub will not release new Ubuntu version soon. As for Ubuntu 26.04, it was September 25 when it became GA.

• https://github.blog/changelog/2024-09-25-actions-new-images-and-ubuntu-latest-changes/

I think keeping backward compatibility is a realistic path forward.