A printer has two challenges that don't affect a browser (much...):
1. The @page rule allows an author to create a document with multiple page
styles, and different pages can have different widths available for
content.
2. There is no scrollbar on a printer, so we are highly motivated to
compress a table to make it fit on the width of a page.
Thus, it is conceivable that a printer might find itself with a table with
wide content on one page, but which flows onto a narrower page. An
advanced algorithm might take advantage of this and change the column
widhts to better fit on the new page. If the new page is narrower than the
first, reducing column width is probably bettter than falling off the edge
of the page.
Does this create problems for the user? I don't think it necessarily does.
I think it is OK for XHTML-Print to allow this; although certainly we
don't want to require it.
E.
------------------------------------------
Elliott Bradshaw
Director, Software Engineering
Oak Technology Imaging Group
781 638-7534
"SILBERNAGEL,SCO
TT To: "'xp@pwg.org'" <xp@pwg.org>
(HP-Vancouver,ex cc:
1)" Subject: XP> Table column width algorithms
<scott_silbernag
el@hp.com>
Sent by:
owner-xp@pwg.org
11/15/2002 01:53
PM
Hello,
The following are comments to the latest update slides from the New Orleans
PWG meeting.
Taken from Slide #22:
XHTML-Print: 3.8 Basic Tables Module
· Column width may vary from page to page when width is
determined by td content.
Allowing column width to vary page to page would be inconsistent with the
way table column widths are normally computed and rendered (in browsers and
according to CSS2). Table columns are normally computed (and fixed for the
entire table) solely on either: the first tr element and its child td/th
elements (table-layout: fixed) -or- all tr and td/th elements in the table
along with the contents of those td/th elements (table-layout: auto).
When using the auto column width algorithm, column widths will be large
enough to handle the widest td/th in the table and varying the column
widths
page by page would never be necessary. Unfortunately, a minimally
conforming printer cannot be forced to use this algorithm since it is not
always possible to store the entire table in memory.
This leaves us with the fixed algorithm for computing column widths. With
the fixed method, column widths are only computed by looking at the first
tr
element and the widths of the first rows cells. The CSS2 specification
clearly states that the cells beyond the first table row do not affect
column widths (section 17.5.2):
<quote>
In this manner, the user agent can begin to lay out the table once the
entire first row has been received. Cells in subsequent rows do not affect
column widths. Any cell that has content that overflows uses the 'overflow'
property to determine whether to clip the overflow content.
</quote>
So, in my opinion, allowing varying column widths in a single table would
conflict with statements made in the CSS2 spec as well the "standard"
rendering of web pages by popular web browsers (IE, Opera,
Mozilla/Netscape).
Other questions/concerns:
If we did allow table columns to vary page-by-page, how would this behavior
affect table cells that span multiple pages? Would they suddenly get wider
or narrower when crossing a page boundary or would we only vary column
widths between rows? If we only varied between rows, the table would look
pretty strange (cell borders between columns would not line up...).
Scott Silbernagel
Hewlett-Packard
This archive was generated by hypermail 2b29 : Fri Nov 15 2002 - 14:04:30 EST