On Tue, Apr 3, 2012 at 5:29 PM, Robert O'Callahan <rob...@ocallahan.org> wrote: > On Wed, Apr 4, 2012 at 11:14 AM, Ian Hickson <i...@hixie.ch> wrote: >> This layer consists of a stack of elements, which each CSS viewport >> maintains. These stacks are initially empty. When the layer is painted, >> the elements in the stack are rendered in the order that they were added >> to the stack, with the most recently added being rendered closest to the >> user. The 'z-index' property is ignored for this stacking layer. > > Is each element in this stack treated as having its own stacking context? I > assume so, but you'd better say so.
Yes, definitely. > - Define a new pseudo-element ::backdrop which applies to any element in >> such a stack; it addresses a box that exactly covers the viewport >> immediately below the element in the stack, in the same stacking layer, >> whose only applicable properties are the 'background' properties. >> (Alternatively, make it a generic box with properties initially set to >> have position:fixed and positioned to exactly cover the viewport, but >> I don't see much point in letting people fiddle with this box's >> positioning, display type, etc.) > > It's probably more work to make all non-background properties inapplicable > than it would be to simply treat it like ::before/::after generated content. Strongly agreed. For one, it's annoying to restrict things. For two, it's badly-defined what "background" properties are - it's possible for properties that aren't prefixed with "background-" to affect backgrounds (for example, image-resolution). For three, this assumes that we have thought of all possible things that can be applied by non-background properties, including properties not yet dreamed up, and decided that they're all useless. Unless there's a good reason to restrict something, keep it unrestricted. ~TJ