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Re: Testing THEAD support on user agents (Test file, Linux results)

From: Ian B. Jacobs <ij@w3.org>
Date: Fri, 14 Jun 2002 12:24:19 -0400
Message-ID: <3D0A18B3.4070301@w3.org>
To: Masayasu Ishikawa <mimasa@w3.org>
CC: w3c-wai-ua@w3.org

Masayasu Ishikawa wrote:
> Sorry to interrupt, but ...
> "Ian B. Jacobs" <ij@w3.org> wrote:
>>At today's teleconference [1], we talked about support
>>for THEAD in HTML user agents. The context: Do user agents
>>support the rendering where THEAD rows are fixed on the screen
>>while other data cells are scrolled by.
>>To test this, I have published a test table [2] that uses
>>THEAD for the first row (the one starting "Rows").
> I think your expectation is wrong.  "11.2.3 Row groups: the THEAD,
> TFOOT, and TBODY elements" of HTML 4 says as follows [3]:
>     Table rows may be grouped into a table head, table foot, and one
>     or more table body sections, using the THEAD, TFOOT and TBODY
>     elements, respectively. This division enables user agents to
>     support scrolling of table bodies independently of the table head
>     and foot.
> Note that this division *enables* user agents to support scrolling.
> It doesn't mean TBODY must always be scrollable when THEAD is present.
> HTML markup specifies table head - body - foot structure, and that's
> it.  If you want specific presentation, use style sheets.  Your test
> file doesn't attach any style sheets, so it seems quite natural to
> me that user agents don't make tables scrollable.

When we discussed this at the teleconference yesterday, I
pointed out that this behavior was not required by user agents.
It would be possible, even without style sheets, for a user agent
to offer a configuration to exhibit such behavior. I have not
found this option in any browser I've tested. Nor did I find
scrolling as the default behavior (which was my expectation).

>>I also tried using 'position:fixed' on the THEAD element
>>for user agents that support CSS fixed positioning. However,
>>since fixed positioning pulls an element out of the flow,
>>the result (at least on Opera) is that the THEAD row is
>>not formatted the same as the other (TBODY) rows. So while
>>the THEAD row remains fixed on the screen, the cells in
>>the other rows don't line up with it, so this approach is
>>not helpful.
> What you want is to make TBODY scrollable, isn't it?  Then don't
> try to do something for THEAD.    Something like
>   TBODY { height: 10em; overflow: auto; }
> would enable user agents to make TBODY scrollable when the height
> of the table body is more than 10em, for example.  It should at least
> work with Gecko-based user agents.

Will do. Thank you for the input Masayasu!

The results for Masayasu's technique (now part of the test file):

  Mozilla (Gecko engine): Yes (both THEAD, TFOOT since set on TBODY).
                          This implies (though not tested) that
                          Galeon and Netscape 7 should work as well.
  Konqueror 2.2.2: No.
  Amaya: No.
  Opera 6.0: No.

  _ Ian

>>[1] http://lists.w3.org/Archives/Public/w3c-wai-ua/2002AprJun/0192
>>[2] http://www.w3.org/WAI/UA/2002/06/thead-test
> [3] http://www.w3.org/TR/html4/struct/tables.html#h-11.2.3
> Regards,

Ian Jacobs (ij@w3.org)   http://www.w3.org/People/Jacobs
Tel:                     +1 718 260-9447
Received on Friday, 14 June 2002 12:27:05 UTC

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