[webkit-dev] XML Serialization Issues

[Rob Buis]

Fixed.

More seriously, all bugs mentioned below are fixed/closed, please open
new ones for any regressions/improvements.
Cheers,

Rob.

On 19 June 2013 14:44, Alex Milowski <alex at milowski.com> wrote:
> I was working on using MathJax [1] to turn MathML into SVG and ran into some
> serious serialization issues.  In summary, as MathJax programmatically
> creates SVG renderings of the MathML, when it creates XLink attributes, it
> doesn't seem to define a prefix.  While this works for rendering, it does
> when you try to extract a serialization of the SVG.
>
> That is, MathJax creates SVG 'use' elements like (assuming SVG as the
> default namespace):
>
> <use xlink:href="#MJMATHI-78" xmlns:xlink="http://www.w3.org/1999/xlink"/>
>
> but instead I get:
>
> <use href="#MJMATHI-78" xmlns="http://www.w3.org/1999/xlink"/>
>
> which makes the SVG incorrect as the 'use' element is now in the xlink
> namespace.
>
> You can work around this by manually setting the "prefix" property on each
> xlink:href attribute.
>
> Looking into why this happens, I can see that the serializer seriously
> broken in a number of ways when the DOM is constructed with incomplete (e.g.
> missing namespace declarations) or inconsistent information (e.g. same
> prefix used for different namespaces in the same context).
>
> I found at least 6 bugs outstanding (#16739 [2], #16496 [3], #19121 [4],
> #22958 [5], #83056 [6], #106531 [7]) and filed a new one (#117764 [8]).
> Some of these date back to 2007 (6 years ago!).
>
> These bugs break down to these categories:
>
> 1. Default namespace issues: #16739, #106531, #16496
> 2. Conflicting prefix mappings: #117764, #19121
> 3. Namespace attribute issues: #22958, #83056, #117764
>
> In looking at the code (MarkupAccumulator.cpp), they all suffer from one of
> two problems:
>
> 1. The computed prefix used isn't properly used for the declaration.
>
> 2. The generated namespace mappings aren't properly stored, scoped, or dealt
> with when they are inconsistent.
>
> There is an general assumption in the code that certain prefixes should
> always be used for certain namespaces.  Unfortunately, it does so without
> looking to see whether there is a conflict already in scope.  Also, when the
> namespace is not recognized and there is no prefix, a prefix needs to be
> generated for the serialization.
>
> Having written several robust XML Serializers for other projects, this can
> all be fixed in a straightforward way.  I've looked at the code and know
> what should be done.  The changes are probably modest.
>
> Unfortunately, I can't spend the time to directly write and test the code
> till probably after November.  :(
>
> I am certainly willing to help, explain my strategy, advise, test, etc. if
> there was another willing developer out there who would like to see these
> bugs closed.
>
> [1] http://www.mathjax.org/
> [2] https://bugs.webkit.org/show_bug.cgi?id=16739
> [3] https://bugs.webkit.org/show_bug.cgi?id=16496
> [4] https://bugs.webkit.org/show_bug.cgi?id=19121
> [5] https://bugs.webkit.org/show_bug.cgi?id=22958
> [6] https://bugs.webkit.org/show_bug.cgi?id=83056
> [7] https://bugs.webkit.org/show_bug.cgi?id=106531
> [8] https://bugs.webkit.org/show_bug.cgi?id=117764
>
>
> --
> --Alex Milowski
> "The excellence of grammar as a guide is proportional to the paucity of the
> inflexions, i.e. to the degree of analysis effected by the language
> considered."
>
> Bertrand Russell in a footnote of Principles of Mathematics
>
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