[Webkit-unassigned] [Bug 39549] New: 1px background shift but content unmoved

Sat May 22 17:13:25 PDT 2010

https://bugs.webkit.org/show_bug.cgi?id=39549

           Summary: 1px background shift but content unmoved
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: Windows 7
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P3
         Component: New Bugs
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jeremiahzg at gmail.com

Created an attachment (id=56799)
 --> (https://bugs.webkit.org/attachment.cgi?id=56799)
Bug reduction and screenshots.

At certain browser sizes, a page's background-image (when background-position is 0% 50%) will be shifted a single pixel to the right, but the page's content (<body> elements) does not move. This creates a noticeable difference between the background-image and the body elements when using faux columns.

Rendering area dimensions that I've noticed this bug occurring at:
1326x361 (without vscroll bar) - Bug does not occur
1326x361 (with vscroll bar) - Bug occurs
1329x361 (without vscroll bar) - Bug occurs
1329x361 (with vscroll bar) - Bug does not occur

Due to the presence of the vscroll bar effecting whether or not this bug occurs, I believe it is related to the value of 50% of the rendering area's width. Because 50% of an odd number cannot be even, a half-pixel is created and the value is rounded up, causing the background-image to be shifted to the right by one pixel.

Reduced bug and screenshots of rendering areas with the above dimensions attached. Use 'add more content' to cause a vertical scroll bar.

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