Horizontal-in-vertical (tate-chu-yoko) lacks support, especially for the digits value

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This issue is applicable to Chinese, Japanese, Korean, and Mongolian.

The CSS text-combine-upright property works with the all value in all major browsers. However, the CSS digits value is not supported by recent version of major browser engines.

For more details, see this GitHub issue, which is being used to track this gap. Please add any discussion there, and not to this issue.

[xfq]

The first comment in this issue contains text that will automatically appear in one or more gap-analysis documents as a subsection with the same title as this issue. Any edits made to that comment will be immediately available in the Editor's draft of the document. Proposals for changes or discussion of the content can be made by adding comments below this point.