Port mozc_renderer to GTK 4

[Arfrever]

mozc_renderer currently still uses GTK+ 2.

GTK 4.0 was released on 2020-12-16:

What’s old

GTK 4 is now stable, and we consider it ready for consumption. That does not mean GTK 3 is dead – we will continue to support and update it for the foreseeable future (the latest release, 3.24.24, quietly went out a few days ago). It does mean, however, that GTK 2 has reached the end of its life. We will do one final 2.x release in the coming days, and we encourage everybody to port their GTK 2 applications to GTK 3 or 4.

(That library can be called GTK+ for versions 1.*, 2.* and 3.*, but it was renamed to GTK (without +) for versions 4.*.)

mozc_renderer should be ported ideally to GTK 4, or intermediately to GTK+ 3.

[hiroyuki-komatsu]

Hi Arfrever,

We understand the announce that GTK 2 has reached the end of its life.
We consider how to deal with it including to port it to GTK 4 and other options.

Thanks,

[Arfrever]

Commit 3b3068e started introducing Qt-based renderer.
Currently support in src/renderer/renderer.gyp is missing.

[hiroyuki-komatsu]

a191e82 added colors and the usage information window.

It's still experimental.

[hiroyuki-komatsu]

We have changed this Qt based candidate window to the default renderer for Bazel build.

• Gtk based candidate window is also able to be built with Bazel.
  • bazel build renderer:gtk_mozc_renderer --config oss_linux -c opt
• We don't have a plan to support it for GYP build. GYP build is under maintenance mode

We close this issue. If there are bugs on the Qt-based candidate window, please create new issues.
Thank you,