background-blend-mode vs mix-blend-mode

> > the exact same issue will happen if blending applies to elements (in
> which
> > case stacking contexts are created).
> > For instance, an element with blending that is a child of an element that
> > uses fixed positioning will render differently today in FF and WK.
> >
> > Dropping background-blend-mode will not solve this problem.
>
> Dropping background-blend-mode simplifies it a lot, because you only
> have to consider elements that form stacking contexts when
> addressing it.


All,

I would like to start this thread up again.

I thought that the problem of what constitutes the backdrop of the stacking
context (= mix-blend-mode) or the image (= background-blend-mode) is the
same but Sylvain almost convinced me that that is not the case.
If it's really is too difficult, I would have no issue to change the spec
so background images will blend and composite only with each other.

David,
can you explain why you think that background-blend-mode is harder to
specify (or implement)?

see also: http://dbaron.org/log/20130306-compositing-blending