[webkit-dev] mfenced - more MathML questions

David Hyatt hyatt at apple.com
Wed Sep 9 09:08:04 PDT 2009

It's hard for me to understand what this problem is without more  
information.  Are these objects inlines or blocks or what?


On Sep 8, 2009, at 6:30 PM, Alex Milowski wrote:

> I've been doing some comprehensive testing and find that my technique
> for handling fencing isn't working properly when use in nest  
> constructs or
> other situations.
> Specifically, the two major problems are:
>   * the fences do not scale well for large objects
>   * nested fencing does not seem to be handled properly
> The first problem is probably something where I'll need to special  
> cast
> certain common fencing constructors (e.g. square or curly brackets)  
> and
> draw them directly.  For example, a matrix bracketed by square  
> brackets
> will probably only look proper when I draw the brackes directly.
> The problem of nested fences is much more tricky.  I thought I had a  
> handle on
> this with the only odd thing being the need to adjust the fence size  
> after
> a layout pass.  You can see this code in the patch [1] and  
> specifically
> by looking and RenderFenced.cpp in [2].
> I've been able to make it behave a bit better by calling setHeight()  
> with the
> fence height online #205.  It still has trouble laying out the the  
> open and
> close fences and often overlaps the line boxes.
> The real problem seems to relate to nested mfenced constructs.  A  
> single
> mfenced works but an construct like:
> { < x > }
> does not work properly when the 'x' construct has an extended  
> vertical height
> (e.g. a rational function or other large fraction).  Then the nested  
> mfenced
> seems to get mixed up.  Again, it is like it is trying to constrain  
> the fencing
> into a certain box width or height, the line boxes do not fit, and  
> then overlap
> happens.
> Is it possible that just setting the height doesn't help because it  
> is a writing
> direction layout/width problem?
> [1] https://bugs.webkit.org/show_bug.cgi?id=28982
> [2] https://bugs.webkit.org/attachment.cgi?id=39223&action=prettypatch
> -- 
> --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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