[Windows] Use modern fonts for CJK

[petercpg]

Describe the bug
On zh-TW Windows, the VPN App uses a thin serif font to render UI message, which is difficult to read and weird from English texts.

VPN version:
2.23.1 (2.202406271914)

Affected Platforms:

• Windows 11 23H2 (OS Build 22631.4169) Traditional Chinese

Prerequisites:
N/A

Steps to reproduce:

1. Get a Windows 11 instance, set to zh-TW UI
2. Install VPN, launch it
3. Observe UI font

Expected result:

1. For UI message in Traditional Chinese, should use OS default fonts (Microsft Jhenghei / 微軟正黑體) for better legibility

Actual result:

1. Some thin serif font (PMingLiu?) was used, making UI message hard to read (Probably a font fallback issue?)
2. Switching VPN App to other CJK locales such as zh-CN, ja-JP did not change to its default font (Microsoft YaHei or Yu Gothic UI) either.

Additional notes:

[petercpg]

mozillavpn-2024-9-23.log

[albionx]

Thanks for the report Peter. I'm having trouble replicating with a newer version of the App. Here's a comparison of your screenshot (right) vs the client as I see it on Windows (left), using Traditional Chinese.

As you can see, the way I see it is much more crisp than on your screenshot. I wonder if this is a resolution problem. Would you mind updating to the latest stable client and letting us know if you still see the same issue?

[petercpg]

Hi @albionx, I'm now on latest nightly 2.25.0 (2.202410310643) and it still looks like the Chinese characters are still rendered with the old PMingLiu font, while Latin Alphabets are not.

I did a little bit more compare and it seems the font used to render your Mozilla VPN UI are Yu Gothic UI, the default for Japanese Windows, based on this Article.

The resolution set for my PC is 1920x1080, and 125% dpi. Let me know if there are more logs or settings that would be helpful on reproducing this issue.

[mcleinman]

What are the default fonts on your system for various languages? We're not selecting specific fonts in these languages, and believe we are falling back to the system defaults.

(Packaging our own fonts for CJK would add 150MB to the client size, and we've decided that a large increase of the binary size is not worth the improvement we'd get from bundling them.)

[petercpg]

For zh-TW Windows 11, it is supposed to be Microsoft JhengHei UI and I'm not changing it. For other languages I already pointed out the default locale-font list.

What I'm saying is, based on @albionx's screenshot, it is not using default font for zh-TW - but most likely a Japanese one.

I don't think packing CJK fonts into app is a good idea either, but just wanted to make sure we have the default font used correctly :)