Fix #823: Support virtual coordinate in mozc_renderer to fix its window position on HiDPI displays

[ftake]

Description

Qt6 applications use virtual coordinates. Since IBus use the device pixel coordinate system to represent a position of a pre-edit area, mozc_renderer converts it to the virtual coordinate.

Issue IDs

823

Steps to test new behaviors (if any)

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

• OS: Linux
• Steps:
  1. Enable display scaling on a desktop environment (e.g. 125%)
  2. Start a GTK application (e.g. gedit)
  3. Type some keys with ibus-mozc enabled and the candidate window is now shown under the cursor.

Additional context

See #823

[hiroyuki-komatsu]

Hi ftake, We have been running the internal process to accept your PR.

Thank you for your contribution.

[ftake]

Thank you for your review comments and I'm sorry to be late. I revised the code.

[hiroyuki-komatsu]

We have merged your PR. Thank you for your contribution!