Remove the default font of subtitle grid; use system UI font when config font is empty

[0tkl]

One of the first batch of things that any new Chinese user of Aegisub does after installing the software is to change the font of the subtitle grid. The default typeface, Tahoma, will fallback to SimSun (宋体) / MingLiU (新細明體) under Chinese locales, which looks quite bizarre.

According to Microsoft's documentation, this is a composite font defined in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontLink\SystemLink. The value in it seems to be some ancient settings date back to Windows 2000.

I strongly recommend using different default fonts for each platform. Considering that the current Windows version requirement is Windows 7, using the Segoe UI should result in a good fallback sequence across locales. For example, on Windows 10/11 it could fallback to Microsoft YaHei UI, the default system UI font on zh-cn locale.

In addition, the default font size is too small for Chinese. This PR has increased the default font size from 8pt to 10pt.

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I have no mac to test so I'm not sure if SF Pro is variable, and whether it can be displayed in proper font weight in Aegisub. Looking for feedbacks from mac users.

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As on Linux, I'm quite unsure. KDE users will have Noto installed (I use KDE only), but what about GNOME or XFCE or any other desktop environments? Or, can we use the generic font name "Sans" on wxGTK?

[0tkl]

…I got a better idea. We can just read the system UI font face name from wxNORMAL_FONT when the config font name is blank. Now in Chinese (China) locale, it would be displayed in the precise UI font (Microsoft YaHei UI in the screenshot) rather than the composite Segoe UI font.

If any user wanna switch from custom font to system UI font, they can just remove the font name in the text ctrl. The placeholder text added in this PR will prompt the user that this entry have fallbacked to the system font, plus to what font.

While any typical Europe-language-locale Windows would display the placeholder in “Segoe UI”, I encourge Chinese (Taiwan), Japanese, Korean and Thai users to check if your placeholder is “Microsoft JhengHei UI”, “Yu Gothic UI”, “Malgun Gothic” and “Leelawadee UI”, respectively.

[3gf8jv4dv]

@0tkl

Great idea! I guess I will do some testing on Windows later.

By the way, GHA builds triggered by new commits seem to fail...

[0tkl]

Btw, there's still two “Verdana” left, one is the font of Audio/karaoke, another is hard-coded in:

https://github.com/arch1t3cht/Aegisub/blob/80491bacbfe2b684d1b2be0e031c72e27e39f85b/src/visual_tool_cross.cpp#L83

Both of them are only used to display numbers and punctuations so Verdana should be fine across different locales in Windows/macOS. But I'll probably open another PR, turning the hard-coded font face into a user option, and making Verdana the “platform-specific” default rather than generic default.

[3gf8jv4dv]

I tried compiling a binary myself based on your new commit. I tested it on Windows 10, version 22H2. The results were as you predicted.

Preview

_Chinese (Taiwan)_  _Japanese_  _Korean_  _Thai_ 

[0tkl]

But I'll probably open another PR, turning the hard-coded font face into a user option…

https://github.com/arch1t3cht/Aegisub/pull/145.

…and making Verdana the “platform-specific” default

New PR will come after https://github.com/arch1t3cht/Aegisub/pull/145 is merged.