[css-text][text-spacing] Add black square & white square characters to the definition of ideographs?

[xfq]

https://drafts.csswg.org/css-text-4/#ideographs

U+25A0 and U+25A1 can be used to represent a missing ideograph, and should be treated in the same way as Han characters in Chinese contexts. I'm not quite sure how these two characters are usually used in other contexts, though.

Example usage:

[macnmm]

Since these characters exist in both cjk fonts and Latin fonts, they cannot be treated consistently based on code point alone. When they are full width and in a cjk font, they should be treated as ideographic in nature and get mojikumi spacing accordingly as well as be set upright in vertical text. Otherwise they should be treated as Latin characters.

[kidayasuo]

I think these would belong to a class that is neutral, i.e. a class which does not create an extra space with any characters.

[kidayasuo]

@xfq , how common is that usage? When one character is used in multiple ways (and glyphs) it makes things complicated…

[xfq]

This symbol is relatively common in the digitization of ancient Chinese books, especially the white square. It's used to indicate characters that are not legible.

[kidayasuo]

Thank you. Then I agree they should not make a space between other ideographs.

Can they be in a class that does not create space with any characters? If so we can treat them consistently with other symbols in the same way. If not we would need to special case these symbols, but when they are not used as a replacement character the behavior might look odd, i.e. among many similar symbols only these two make space with Latin characters and numbers.

[macnmm]

Thank you. Then I agree they should not make a space between other ideographs.

Can they be in a class that does not create space with any characters? If so we can treat them consistently with other symbols in the same way. If not we would need to special case these symbols, but when they are not used as a replacement character the behavior might look odd, i.e. among many similar symbols only these two make space with Latin characters and numbers.

In my experience, there is always some pairing that requires some space or requires spacing logic beyond "do nothing". Consider full justification expansion, where your "do nothing" class could get no spacing where all other ideographs get 0-100% spacing before the H&J violation state kicks in. Therefore, I think all glyphs/characters need assignment to a class, and that class should be part of the spacing rules table at all times.