Bug 15679

Summary: Fixed backgrounds should behave like 'scroll' inside transformed elements
Product: WebKit Reporter: Dave Hyatt <hyatt>
Component: Layout and RenderingAssignee: Vitor Roriz <vitor.roriz>
Status: RESOLVED FIXED    
Severity: Normal CC: karlcow, mattwoodrow, mstange, ntim, simon.fraser, vitor.roriz, webkit-bug-importer
Priority: P2 Keywords: BrowserCompat, InRadar
Version: 523.x (Safari 3)   
Hardware: Mac   
OS: OS X 10.4   
Attachments:
Description Flags
simple example of problem none

Description Dave Hyatt 2007-10-24 13:31:10 PDT
Fixed backgrounds should not be affected by the transform, but should always render as though offset from the viewport.
Comment 1 Ken Martin 2009-03-07 06:01:21 PST
Created attachment 28389 [details]
simple example of problem
Comment 2 Ken Martin 2009-03-07 06:02:16 PST
Seeing this in nightly build, too: 530.1+

Have attached a pretty simple example file. There's WebKit "transform:" rules and everywhere "left:" rules in the CSS to demonstrate the problem. (The "everywhere" section is commented out by default.)
Comment 3 Simon Fraser (smfr) 2011-10-01 08:39:27 PDT
Known issue.
Comment 4 Simon Fraser (smfr) 2013-06-15 13:00:14 PDT
Spec <http://dev.w3.org/csswg/css-transforms/> now says:
"Fixed backgrounds on the root element are affected by any transform specified for that element. For all other elements that are effected by a transform (i.e. have a transform applied to them, or to any of their ancestor elements), a value of ‘fixed’ for the ‘background-attachment’ property is treated as if it had a value of ‘scroll’. The computed value of ‘background-attachment’ is not affected."
Comment 5 Markus Stange 2016-08-05 10:28:51 PDT
(In reply to comment #4)
> Spec <http://dev.w3.org/csswg/css-transforms/> now says:
> "Fixed backgrounds on the root element are affected by any transform
> specified for that element. For all other elements that are effected by a
> transform (i.e. have a transform applied to them, or to any of their
> ancestor elements), a value of ‘fixed’ for the ‘background-attachment’
> property is treated as if it had a value of ‘scroll’. The computed value of
> ‘background-attachment’ is not affected."

We (Mozilla) have shipped this change in Firefox 48. IIRC Edge has also shipped it.
Comment 6 Vitor Roriz 2022-08-17 16:36:55 PDT
Pull request: https://github.com/WebKit/WebKit/pull/3433
Comment 7 Radar WebKit Bug Importer 2022-09-14 10:49:36 PDT
<rdar://problem/99926239>
Comment 8 Matt Woodrow 2022-09-20 18:31:09 PDT
*** Bug 245352 has been marked as a duplicate of this bug. ***
Comment 10 EWS 2022-09-30 17:12:14 PDT
Committed 255055@main (eba490ba3cc4): <https://commits.webkit.org/255055@main>

Reviewed commits have been landed. Closing PR #3433 and removing active labels.
Comment 11 EWS 2022-10-30 09:08:54 PDT
Committed 252432.728@safari-7614-branch (a1d3edc00b16): <https://commits.webkit.org/252432.728@safari-7614-branch>

Reviewed commits have been landed. Closing PR #171 and removing active labels.