https://drafts.csswg.org/css-line-grid/#line-grid

The spec describes snapping the text line baseline to the line grid, with what appears to be two possible settings (roman baseline and "center" baseline). When aligning CJK text lines to a grid, and especially aligning different text flows to a common grid point, it is necessary to offer snapping points other than the Roman baseline: [Ideographic] embox top or bottom are used as well when the text flows being aligned are of differing text sizes.

Hope to discuss this with @dbaron et al in regard to his https://github.com/dbaron/css-line-spacing/blob/master/explainer.md piece in an upcoming CSSWG meeting. @fantasai @jensimmons @astearns