Question

怎么确定一个html元素的baseline

Answer 1

2. The inline-level boxes are aligned vertically according
to their 'vertical-align'
property.

In case they are aligned 'top' or 'bottom', they must be aligned so as
to minimize the line box height. If such boxes are tall enough, there
are multiple solutions and CSS 2.1 does not define the position
of the line box's baseline (i.e., the position of the strut, see below).
'vertical-align'

…

Applies to: inline-level and 'table-cell' elements

…

baselineAlign the baseline of the box with the baseline of
the parent box. If the box does not have a baseline, align the
bottom margin edge with the parent's baseline.…

The baseline of an 'inline-table' is the baseline of the first row
of the table.
The baseline of an 'inline-block' is the baseline of its last line
box in the normal flow, unless it has either no in-flow line boxes or
if its 'overflow' property has a computed value other than 'visible',
in which case the baseline is the bottom margin edge.