Re: the *precise* definition of 1em


 > So if the only criterion being used is that 1em should give you the same
 > size as the parent, 

This is indeed the intention.

 > the approximating will cause problems when using mutliple
 > fonts, and we shouldn't approximate.

But since not all font sizes are available you must approximate in
order to display anyting. Since the specification does not say which
of the approximated values child elements should use, you are free to
pick your favorite (perhaps use the one that encloses the child
element). Also, in this case I'd say it's reasonable to inherit the
non-approximated value. When an element only uses one font size, I
think the spec is right in saying that the approximated value should
be inherited.

 >    I don't quite understand what you mean here. The UA may have to
 >    approximate even if '11pt' is specified. If '1em' is specified, it is
 >    relative (1em=100%) to the font size of the parent element (HTML).
 > What I mean is that if some element which is a child of our
 > font-family: numbers, someotherfont is declared with font-size: 1em,
 > we want that child to look the same as if 1em had not been specified.

Right. Declaring 'font-size: 1em' is exactly the same as using the
inherited value (provided that there are no other competing
declarations: since cascading is "stronger" than inheritance, setting
font size to '1em' is a way of "strengthening" the inherited value).



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