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Reported by Morten Stenshorne The 'overflow' property needs to apply to flexboxes, but it doesn't do so "automatically" due to the "Applies To" line in CSS21 stating that 'overflow' applies to block containers. (See also Bug 15381 which aims to have 'overflow' apply to table boxes in addition.) It would be nice if the spec could be tweaked so that 'overflow' would "automatically" apply to new types of formatting context, without needing to explicitly spec that in each and every new spec which needs it. Conversation begins: Bug description: http://lists.w3.org/Archives/Public/www-style/2012May/0438.html
Proposal: http://lists.w3.org/Archives/Public/www-style/2012May/0494.html This proposal is precisely the combination of accepting Proposal A for Bug 17121 (found in Comment 2: https://www.w3.org/Bugs/Public/show_bug.cgi?id=17121#c2) together with one further change: In 11.1.1 (Overflow), replace: | Applies to: block containers with: | Applies to: block containers and boxes that establish a formatting context Note that this proposal incorporates a fix to Bug 15381.
(Hence the proposal in comment 1 has a dependency on Bug 15381)
This issue has parallels with Bug 15686
Note that in http://lists.w3.org/Archives/Public/www-style/2012May/0438.html Morten points out the following: BTW: When it comes to "the other non-block container thing", namely tables, it looks like we have all agreed to honor overflow:hidden, while overflow:scroll and overflow:auto are treated as overflow:visible... So we should first decide whether tables are a special case or whether the described behaviour will be typical of formatting contexts.
The WG resolved to accept Proposal A for Bug 17121 (found in Comment number 2 therein) and to accept, in principle and in approach, the proposal for this bug found in Comment 1.[1,2] The dependency on Bug 15381 remains, however; and so the exact wording of the proposal in Comment 1 is subject to change. [1] http://lists.w3.org/Archives/Public/www-style/2012Jun/0475.html [2] http://lists.w3.org/Archives/Public/www-style/2012Jun/0656.html
Regarding the proposal for this bug found in Comment 1, Øyvind Stenhaug made the comment that "Applies to" is supposed to list the *elements* to which the property applies, not boxes. (Whether that's actually what we want is an orthogonal question unlikely to be addressed for CSS21.) No-one expressed any objection to hand-waving that issue away by blaming it on the spec-wide element vs box sloppiness. See http://lists.w3.org/Archives/Public/www-style/2012May/0793.html In fact, though, this bug has a dependency on http://lists.w3.org/Archives/Public/www-style/2012Jul/0338.html (not yet accepted as a Bug) which proposes to define "block container element" in CSS21. If that happens, the proposal for this bug can be rewritten in terms of elements not boxes: | Applies to: block container elements and elements that establish a | formatting context Where as proposal in Comment 1 is expressed in terms of boxes and aims to "capture" table boxes via the second clause, the proposal above captures them via either clause, since a table element would be both a block container element (since its principal table wrapper box is a block container) and an element which establishes (not just one but) two formatting contexts. The 'overflow' property itself has its effect on the table box not the table wrapper box, as per the property distribution rules in 17.4. It doesn't seem worth making a change to the second clause without the change to the first clause though, since that just muddies the waters further by mixing elements and boxes in the same phrase. Hence the dependency on defining "block container element".
The proposal in Comment 1 has been added to the errata document: http://www.w3.org/Style/css2-updates/REC-CSS2-20110607-errata.html#s.11.1.1
In response to Comment 5: The 'overflow' property has its effect on the table box not the table wrapper box of an (inline-)table element. (See Bug 17505 Comment no.9.) The requirements of Bug 15381 are thus clear, and a fix to that bug is incorporated into the proposal for this current bug in Comment 1 above, which has been added to the errata document. A fix to Bug 15381 will also be incorporated into any competing proposal for this current bug, such as that in Comment 6. Hence Bug 15381 has been marked as resolved.