[webkit-dev] HTML5 Parsing & MathML

[Alex Milowski]

I'm curious as to what the current HTML5 parser does when MathML
and SVG are mixed.  In a recent review of MathML 3 I made the comment
that this kind of markup, in XHTML, works just fine:

 <math xmlns="ttp://www.w3.org/1998/Math/MathML">
      <mfrac>
          <svg .. >happy smilely..</svg>
          <mrow>
               <svg .. >happy smilely..</svg>
               <mo>+</mo>
               <svg .. >unhappy smilely..</svg>
          </mrow>
      </mfrac>
   </math>

Yet, it does not seem to be blessed by MathML3 as valid or allowed.  I'm
still debating that restriction with others.  Note that the svg elements would
need to have the SVG namespace declared and used somehow.

In HTML5, the namespace declarations and use for MathML or
SVG wouldn't be required (or really allowed).

<div>
<math>
      <mfrac>
          <svg .. >happy smilely..</svg>
          <mrow>
               <svg .. >happy smilely..</svg>
               <mo>+</mo>
               <svg .. >unhappy smilely..</svg>
          </mrow>
      </mfrac>
   </math>
</div>

So, my question is:  What does webkit do?

>From reading the section on "in foreign content' [1], it would seem that it
should assign the 'svg' elements to the MathML namespace when they
are embedded as above.  That means cutting and pasting the same
content fragment gives two very different interpretations--which is more
of a problem for the HTML5 spec than webkit.

I've looked at HTMLTreeBuilder.cpp and it looks like it will assign
all child elements to the MathML namespace.  That's not 100%
correct as the 'annotation-xml' has a special case for SVG
annotations.

>From a browser perspective, when you are using the XHTML syntax,
you can compose elements from different namespaces--embedding
them as above--and it does work.  In fact, the above kind of embedding
of SVG as direct actors in rendering a fraction works right now in
WebKit.  That is, of course, an unsanctioned behavior.

[1] http://dev.w3.org/html5/spec/Overview.html#parsing-main-inforeign

-- 
--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