[css-page] marks and bleed

Currently the spec requires crop marks to be on in order to bleed,
and therefore has an initial value of 'bleed: 6pt'. However, there
are cases where bleed is wanted without crop marks.

Since AH and Prince support 'marks' and 'bleed', I suspect there
are many documents that depend on 'marks: crop' turning on bleed.
So we can't just make these two properties independent.

However, since I doubt there are many documents that don't set
crop marks yet also set 'bleed' to a non-zero value, I think we
can work around this by introducing an 'auto' value:

   bleed: auto | <length>
   initial: auto

   auto
     If 'marks' has ''crop'', computes to 6pt. Otherwise compute to zero.

This means that
   @page {
     marks: crop;
   }
or
   @page {
     marks: crop;
     bleed: 6pt;
   }
will still turn on 6pt of bleed along with the crop marks, as currently
specified. But also
   @page {
     bleed: 8pt;
   }
will allow for bleed without crop marks.

Thoughts?

~fantasai

Received on Wednesday, 13 November 2013 08:00:04 UTC