[webkit-dev] RenderObject is-a boolean methods

Alex Milowski alex at milowski.org
Mon Jan 4 15:21:13 PST 2010

On Mon, Jan 4, 2010 at 1:02 PM, Eric Seidel <eric at webkit.org> wrote:
> My understanding is that RenderObject::isRenderMathMLBlock() is the
> right approach, yes.  Although if MathML base renderer (like
> RenderBoxModelObject or RenderSVGModelObject), then an
> isMathMLModelObject() would be even better.  Then you only add one
> method to RenderObject and the rest can go on your base renderer.

The base for all my objects is currently RenderBlock as I use the line
layout for its interior.  Most of the time they are set to display as

If the line layout was more of a generic algorithm, I could reuse it
without having to inherit from RenderBlock.  I suspect there are times
where I may not want RenderBlock as a parent.  In other cases, I
use other render objects directly (e.g. RenderTable for mtable).

In MathML, even simple elements like "mo" (math operator) can
have complex content.  For example, a stretchable operator like
a left bracket is made from stacking left-to-right glyphs vertically.  I
currently use a sequence of blocks stacked vertically to handle
this and it seems to work quite nicely.

While I have some reservations about inheriting from RenderBlock, for
now this seems like the right thing to do.  My only other option
would be somehow "duplicate" the line layout--which is something
I have no justification for right now.

--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

Bertrand Russell in a footnote of Principles of Mathematics

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