[css3-values][css3-page] Viewport-percentage length units in the page context.

Hi,

css3-values defines the vw, vh, vmin and vmax units relative to the 
initial containing block.

In css3-page, this ICB is the content area of the page box which is 
itself based on some of the page’s properties. [1]

Now, what do the new viewport-percentage units means for these 
properties in the page context? It’s easy to construct a circular 
dependency like:

     @page { width: 200vw }

… or dozens of other combinations. We need to break the cycle at some 
point to get a well-defined behavior. I suggest making the 
viewport-percentage units invalid (as they were before css3-values) in 
the page context, either:

* On the problematic properties only [1], or
* On all properties in the page context, for simplicity and consistency

[1] 'size', 'width', 'height', 'margin-*', 'border-*-width', 'padding-*' 
and, through em or ex values, 'font-size'. Am I missing any?


While writing this, I notice another kind of cycle. css3-page defines: 
"The page context inherits from the root element." How about this?

     :root { font-size: 1vw }
     @page { width: 200em }

I can’t find a satisfying way to resolve this one. Any ideas?

Cheers,
-- 
Simon Sapin

Received on Saturday, 13 October 2012 08:56:05 UTC