[Webkit-unassigned] [Bug 31862] New: Lines in svg shift up 1 pixel

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=31862

           Summary: Lines in svg shift up 1 pixel
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Macintosh
        OS/Version: Mac OS X 10.5
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: SVG
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: shubay at gmail.com


Created an attachment (id=43831)
 --> (https://bugs.webkit.org/attachment.cgi?id=43831)
A minimal test case for this bug.

Steps to reproduce:

1. Open the attached xml file, which draws a line at y=0.
2. Observe that the line does not appear.
3. Change the zoom level (cmd +/-) and observe that the line appears.

Expected results: The line should always be visible.

Actual results: The line is only visible in some zoom levels.

Discussion: It seems that this problem is specific to core-graphics (rendering
on mac), and does not reproduce on chrome windows or linux which use skia for
rendering. I encountered this problem when I was trying to draw a line between
2 rectangles, the line appears 1 pixel higher in Safari mac than it does in
other browsers. It seems the all the horizontal lines in the SVG appear 1 pixel
higher. It seems that adding 0.5 to the y position causes the line to be
displayed correctly.

Other browsers tested:
- webkit nightly/Safari 4.0.3 Mac - fail.
- Chrome Windows/Linux - OK.
- Chrome Mac - fail.
- Firefox 3.5 on Windows - OK.
- Firefox 3.0 - fail.

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