Comment 1 for bug 487695

When the user has selected the page size "A4",
all other page size entries in the PPD are
meaningless.

When the user has selected the page size "A4"
plus "duplex printing", the ImageableArea is still
those for "A4".

When the the ImageableArea for "A4" does not work
for "duplex printing", there must be matching
UIConstraints in the PPD to exclude both mutually.

Have a look at
https://bugs.launchpad.net/evince/+bug/428588/comments/22
and
https://bugs.launchpad.net/hplip/+bug/237342

On the one hand:
Whenever some kind of settings cannot work together,
appropriate UIConstraints must be specified in the PPD
so that the user's printing interface can show impossible
settings before a wrong or unexpected printout happens.

But on the other hand:
The defaults in a PPD must be so that all UIConstraints
are fulfilled so that by default printing "just works".