[CSS21] Errata: does 'overflow' affect the table box or the wrapper box?

Recall that the spec used to say that the 'overflow' property has its 
effect on the table box of a table or inline-table element, but now 
effectively says that it doesn't apply to table elements at all.[1]

Clearly 'overflow' should apply to either the table box or the table 
wrapper box, and the WG discussed this and resolved to follow the 
implementation majority.[2]

The test 
http://test.csswg.org/shepherd/testcase/overflow-applies-to-013/ is 
theoretically relevant to this issue, since the table box has a 
positive-width border and hence it is possible to detect whether 
'overflow' is being applied to the table box (and thus clipping the 
overflowing content at the table box's padding area) or to the parent 
wrapper box.  Gecko, Webkit, Presto and Trident all pass this test. 
However, it turns out that the test doesn't reveal the vagaries of 
Webkit and Presto's behaviour and so is not suitable for drawing 
conclusions on this issue.

Instead, I've created a test case at [3] (based on one provided by 
√ėyvind) that demonstrates the following result:

Gecko and Trident (IE9) apply 'overflow' to the table box; whereas 
Webkit and Presto (Op12) seem to apply it to the table wrapper box but
define the clipping area in a curious manner: it has the size of the 
table box's padding area in the horizontal dimension, and then it has 
the size of the table wrapper box's padding area in the vertical 
dimension (in the case of Webkit) or the size of the table wrapper box's 
padding area minus the sum of the table box's vertical border widths in 
the vertical dimension (in the case of Presto).

Given the interoperability of the horizontal overflow at least, I 
propose defining 'overflow' to apply to the table box, just as it used 
to be defined.

[1] https://www.w3.org/Bugs/Public/show_bug.cgi?id=15381
[2] http://lists.w3.org/Archives/Public/www-style/2012Jun/0656.html
[3] https://www.w3.org/Bugs/Public/show_bug.cgi?id=17505#c7

Anton Prowse

Received on Sunday, 15 July 2012 12:04:48 UTC