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Bug 24232 - The containing block of fixpos elements in the top layer shouldn't be the ICB
Summary: The containing block of fixpos elements in the top layer shouldn't be the ICB
Alias: None
Product: WebAppsWG
Classification: Unclassified
Component: Fullscreen (show other bugs)
Version: unspecified
Hardware: All All
: P2 normal
Target Milestone: ---
Assignee: Anne
QA Contact: public-webapps-bugzilla
Depends on:
Reported: 2014-01-08 05:59 UTC by Matt Falkenhagen
Modified: 2014-01-10 16:36 UTC (History)
7 users (show)

See Also:


Description Matt Falkenhagen 2014-01-08 05:59:33 UTC
The spec says the containing block of an element in the top layer is the initial containing block. However, this would mean elements with fixed positioning don't behave as such: they would be positioned relative to the document's origin rather than the viewport's. Instead, the containing block of fixpos elements should be the viewport, as normal.
Comment 1 Anne 2014-01-08 09:10:49 UTC
Ian and Robert came up with this if I remember correctly. I'd like them to comment here first.
Comment 2 Anne 2014-01-08 09:11:43 UTC
To be clear, comment 0 is about which should eventually move into CSS.
Comment 3 Robert O'Callahan (Mozilla) 2014-01-09 04:03:59 UTC
I don't think it was me. However, viewport sounds right.
Comment 4 Anne 2014-01-09 13:30:40 UTC
So, instead of "Its containing block is the initial containing block." we should have "If its position property computes to fixed, its containing block is the viewport, and the initial containing block otherwise."
Comment 5 Matt Falkenhagen 2014-01-10 04:26:44 UTC
comment 4 looks good to me.