[Webkit-unassigned] [Bug 130326] New: Improve preferred width computation of stretchy operators

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=130326

           Summary: Improve preferred width computation of stretchy
                    operators
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: MathML
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: fred.wang at free.fr
                CC: mrobinson at webkit.org
        Depends on: 121416,130322


This issue has been known for a long time, I'm opening a bug for the record.

In general for delimiters (parenthesis, brackets...) the width of size variants and glyph assembly is the same as the base character, so the stretchy operator width does not depend on the stretch height and we can compute the preferred width without knowing the height. Also, for large operators in displaystyle (e.g. sums), we already know which glyph will be picked when we compute the preferred width, so that's not a problem either.

However, there are some cases where the glyph width strongly depends on the stretch height that will be used at the end. For example "FRACTION SLASH" in the STIX Math or the large operators when they have the "stretchy" property. Fortunately, these operators are not stretchy by default so the situation does not really happen in practice. However, it would be good to find a solution that does not reintroduce the security issue of bug 121416, perhaps following what Gecko does.

See also bug 122837 comment 2, for a related issue which seems specific to STIX fonts. I'll have to check if there are similar issues in MATH fonts.

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