[Webkit-unassigned] [Bug 103757] New: background-position sometimes doesn't work properly with background-attachment: fixed

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=103757

           Summary: background-position sometimes doesn't work properly
                    with background-attachment: fixed
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Macintosh Intel
               URL: http://wystawy.bn.org.pl/norblin/fullscreen/#object_ty
                    pe=catalogue#object_id=2
        OS/Version: Mac OS X 10.8
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: CSS
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: m.goleb+bugzilla at gmail.com


1) Look at http://wystawy.bn.org.pl/norblin/fullscreen/#object_type=catalogue#object_id=2 in Firefox and look at styles applied to the only element with a class "sd_visible_rect". You'll see sth like:
background-attachment: fixed
background-position: 1460px 682px;
Background position is set relatively to the top-left window corner.

2) The same site breaks on Safari & Chrome on OS X (on Windows in Chrome it sometimes work and sometimes not, it's hard to say what's the reason). Actually the above site renders correctly but only because I'm applying a special background-position specifically for Webkit browsers, relative to the parent, not the window corner:
background-position: 5px 5px;

I wanted to reproduce it on a less complicated example but when I just download the site and open a static HTML file, it seems to render correctly. The issue probably exists only when set by JavaScript and only in certain conditions. Unfortunately, this behaviour seems to change periodically so this one rectangle has a broken background in WebKit browsers a lot.

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