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Re: [CSS21] Proposal for a replacement for section 17.2.1 (table anonymous objects)

From: Giovanni Campagna <scampa.giovanni@gmail.com>
Date: Sun, 31 May 2009 16:30:27 +0200
Message-ID: <65307430905310730n2f17c038re6a0c60a6f26b1a3@mail.gmail.com>
To: Boris Zbarsky <bzbarsky@mit.edu>
Cc: Brad Kemper <brad.kemper@gmail.com>, www-style list <www-style@w3.org>
2009/5/31 Boris Zbarsky <bzbarsky@mit.edu>:
> Giovanni Campagna wrote:
>>>
>>> If desired, we could probably make display compute to none in cases like
>>> this instead of having the rule about throwing out the box.  It probably
>>> doesn't matter much either way; all that's affected is what the DOM style
>>> APIs return for the relevant nodes; the rendering is the same either way.
>>
>> As a general rule, finding the computed value of a property does not
>> require laying out the page, so this point should change only the used
>> value. This is the reason we have specified, computed, used and actual
>> values, differently from CSS2.0.
>
> There is no need for layout here.  All the rule would say is that computed
> display is none if the computed display of the node's parent is
> 'table-column' and that it's none if the specified value is not
> 'table-column' and the parent's display is 'table-column-group'.  This is no
> worse than the behavior of "display: inherit" in that all it needs is the
> computed display of the parent and the specified display of the child to
> decide on the computed display value of the child.

Reading again the algorithm, I see that a box can be discarded if one
of the following are true:
- it is a child of table-column
- it is a child of table-column-group, and it is not a table-column
- it only contains one _discardable_ (whitespace) box (and it has a
table-*-group, table, inline-table, table-row display)
- it is out-of-flow and its _related inline box_ (a concept I
personally dislike) is discarded
This means that rule 1) is superflous, since the _related inline box_
of a out-of-flow box is never _discardable_, so out-of-flow boxes can
be discarded only if children of table-column / table-column-group,
which makes the solution with the computed value fine (assuming that
elements with display:none generate no boxes for them or their
children / descendants).

A final solution which removes the _discard_ concept is just to say that
- The computed value for display is none if the parent's display is
"table-column", or if the parent's is "table-column-group" and the
specified is not "table-column"
- The "white-space" property does not apply to table,
table-header-group, table-row-group, table-row display types, and it
is always processed as "normal" (collapsing and discarding all
whitespace not explicitly wrapped in container elements)

> -Boris
>

Giovanni
Received on Sunday, 31 May 2009 14:31:05 GMT

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