html – 如何在浏览器中确定列宽？

CSS3还没有覆盖,但这部分规范是非规范的,所以浏览器可能并不完全符合(这个行为没有规范的定义).

Column widths are determined as follows:

1. Calculate the minimum content width (MCW) of each cell: the formatted
   content may span any number of lines but may not overflow the cell
   box. If the specified ‘width’ (W) of the cell is greater than MCW,W
   is the minimum cell width. A value of ‘auto’ means that MCW is the
   minimum cell width.
   Also,calculate the “maximum” cell width of each cell: formatting the
   content without breaking lines other than where explicit line breaks
   occur.
2. For each column,determine a maximum and minimum column width from the
   cells that span only that column. The minimum is that required by the
   cell with the largest minimum cell width (or the column ‘width’,
   whichever is larger). The maximum is that required by the cell with
   the largest maximum cell width (or the column ‘width’,whichever is
   larger).
3. For each cell that spans more than one column,increase the minimum
   widths of the columns it spans so that together,they are at least as
   wide as the cell. Do the same for the maximum widths. If possible,
   widen all spanned columns by approximately the same amount.
4. For each column group element with a ‘width’ other than ‘auto’,
   increase the minimum widths of the columns it spans,so that together
   they are at least as wide as the column group’s ‘width’.

This gives a maximum and minimum width for each column.

The caption width minimum (CAPMIN) is determined by calculating for
each caption the minimum caption outer width as the MCW of a
hypothetical table cell that contains the caption formatted as
“display: block”. The greatest of the minimum caption outer widths is
CAPMIN.

Column and caption widths influence the final table width as follows:

1. If the ‘table’ or ‘inline-table’ element’s ‘width’ property has a
   computed value (W) other than ‘auto’,the used width is the greater of
   W,CAPMIN,and the minimum width required by all the columns plus cell
   spacing or borders (MIN). If the used width is greater than MIN,the
   extra width should be distributed over the columns.
2. If the ‘table’ or
   ‘inline-table’ element has ‘width: auto’,the used width is the
   greater of the table’s containing block width,and MIN.
   However,if either CAPMIN or the maximum width required by the columns
   plus cell spacing or borders (MAX) is less than that of the containing
   block,use max(MAX,CAPMIN).

A percentage value for a column width is relative to the table width. If the table has ‘width: auto’,a percentage represents a constraint on the column’s width,which a UA should try to satisfy. (Obviously,this is not always possible: if the column’s width is ‘110%’,the constraint cannot be satisfied.)