Re: [csswg-drafts] [css-fonts] `system-ui` behavior is undesired for some users (#3658)

> I see. However, this fact still does not resolve the problem that a Chinese/Japanese font is assigned to Japanese/Chinese text in a Chinese/Japanese OS expect for pan-CJK fonts like Noto Sans CJK or Source Han Sans. I doubt that the current specifications have an UA assign Microsoft YaHei UI or PinFang SC to a Chinese text where lang=zh even in a Japanese OS.

Demo site: https://onecompiler.com/html/43x3qu8n5
A quick check with my friend found that MacOS and iOS do support language-specific tagging in `system-ui`, albeit only tested in English OS. This is a true OS-level text shaping support as SC, TC and JP uses different fonts (PingFang SC, PingFang TC [different 示] and Hiragino Kaku), so I suspect it'll work on Chinese/Japanese OS too. Screenshot of Safari on Mac, Chrome on Mac and Safari on iPad:

<img width="1920" height="1080" alt="Image" src="https://github.com/user-attachments/assets/6ebc58ce-dc1b-45e1-8c6f-0de9c27e5453" />
<img width="1920" height="1080" alt="Image" src="https://github.com/user-attachments/assets/cd3dbdd0-9c65-483c-b4d1-25c52f7ca661" />
<img width="1011" height="703" alt="Image" src="https://github.com/user-attachments/assets/ce4266bb-f4c6-4c1d-9687-12236f111edb" />

Android "support" it too like you mentioned, but it's using one singular Noto Sans CJK for pan-CJK support and not on system-level, and thus do break down if I use another font. Shown is my POCO phone that uses MiSans by default on first row _(no pan-CJK support, but P/S: demonstrate that `system-ui` does correctly use what my system is using)_, Noto CJK on second and third row.

<img width="1521" height="703" alt="Image" src="https://github.com/user-attachments/assets/0c4d94f5-d1e7-49d7-a3ec-5fa9dac55f25" />


-- 
GitHub Notification of comment by NightFurySL2001
Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/3658#issuecomment-3306983266 using your GitHub account


-- 
Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config

Received on Thursday, 18 September 2025 11:37:30 UTC