@HB_OT_LAYOUT_BASELINE_TAG_ROMAN: The baseline used by alphabetic scripts such as Latin, Cyrillic and Greek. In vertical writing mode, the alphabetic baseline for characters rotated 90 degrees clockwise. (This would not apply to alphabetic characters that remain upright in vertical writing mode, since these characters are not rotated.) @HB_OT_LAYOUT_BASELINE_TAG_HANGING: The hanging baseline. In horizontal direction, this is the horizontal line from which syllables seem, to hang in Tibetan and other similar scripts. In vertical writing mode, for Tibetan (or some other similar script) characters rotated 90 degrees clockwise. @HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_BOTTOM_OR_LEFT: Ideographic character face bottom or left edge, if the direction is horizontal or vertical, respectively. @HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT: Ideographic character face top or right edge, if the direction is horizontal or vertical, respectively. @HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT: Ideographic em-box bottom or left edge, if the direction is horizontal or vertical, respectively. @HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT: Ideographic em-box top or right edge baseline, if the direction is horizontal or vertical, respectively. @HB_OT_LAYOUT_BASELINE_TAG_MATH: The baseline about which mathematical characters are centered. In vertical writing mode when mathematical characters rotated 90 degrees clockwise, are centered.
Baseline tags from https://docs.microsoft.com/en-us/typography/opentype/spec/baselinetags
2.6.0