[css3-exclusions] Shapes depend on which box?

Hey all,

The current draft of the spec says that the coordinate system and resolved
percentages for declared shapes uses the border box of the element. I am
thinking it might make more sense to use the content box of the element.
As it stands, specifying a 100% width and height rectangle to shape-inside
can change how its inline content is laid out (depending on the border and
padding). If we change the coordinate system and percentages to use the
content box, then a 100% width and height rectangle for shape-inside
changes nothing, and modifications to percentages are relative to what
you'd get without defining a shape-inside.

As for shape-outside, the current definition says that a 100% width and
height rectangle for shape-outside on a float would shrink the float area
from the margin box to the border box. Making the change would further
shrink the float area to the content box, which isn't any less confusing
than before. I'm assuming a single, consistent definition of how lengths
and percentages work with shapes is preferable to having separate
definitions for shape-inside and shape-outside (particularly when you're
using the same shape for both).

And on a related note, the shape-outside:auto value says that the shape is
computed based on the border box of the element. I'm assuming this should
be amended to say that it's computed based on the border box for
exclusions, or computed based on the margin box for floats.

Thanks,

Alan