[Webkit-unassigned] [Bug 131946] New: Bounding box is wrong for texts with leading

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=131946

           Summary: Bounding box is wrong for texts with leading
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Text
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: abaldeva at ea.com


Hi,

It seems like bounding box for the text is not correct when the text is using a font with high leading value. This can be reproduced in Safari 6.x/7.x on Mac. I have attached two sample cases. In fontleading1.html, you'll find that the accent on the character goes over the border. In the 2nd, the ascent goes beyond the grey background.

Upon my investigation, the WinCairo port does not suffer from this problem. I noted that the TextMetric returned by windows system API returned 0 for external leading and ascent value appeared as if it already included the external leading into it (so turns out to be normal baseline value). I'd also like to note that the Chrome on PC does not exhibit the bug but Chrome on OS X exhibits the same issue. So it could be an issue of system level API. Normally, the external leading on Windows is not included in ascent calculation however seems like it does in case of this particular font (based on watching values in debugger). 

--Arpit

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