[xep-support] Re: Full page background image on each page

At 2012-05-23 09:58 +1000, Justin Lipton wrote:
>We need to have a background image that is effectively a full page
>watermark that needs to appear on each page.
>The document also has headers so we can't use background-image as
>this swill only apply to the current region (will not extend to the header).
>One solution that almost works is to use an absolutely positioned
>block-container with the image in the region after - this ensures
>that the image will appear on each page and covers all regions. The
>issue with this approach is that we cannot seem to get the image to
>appear under the region-body content even with the z-index on the
>block-container set to -1.

As I understand it, the regions do not participate in the
z-index. Objects in a given region participate in each region's
z-index. But different formatters will put different regions in a
region-z-index-order (my terminology, not the spec).

>Any ideas on how to handle this type of scenario without having to
>carve up the background image?

I can't.

And while it seems that none of the formatters I've worked with
report the error, as I understand it, the specification says that the
"black" of one region cannot occupy the same pixel as the "black" of
another region. Thus, every pixel that isn't background can be
painted by only one of the regions. Therefore, there is no need to
dictate the z-index of the regions since the spec says there must not
be a conflict for any pixel.

So even if you could rely on region z-index, overlapping regions
doesn't help because parts of your watermark and your "foreground"
content would occupy the same pixels.

Long ago I employed the trick you tried with my XSL-FO stylesheets
for OASIS Universal Business Language (UBL) documents. The before
region contains repeated header, footer and table borders, while the
body region contains the paginated table content (without
borders). To the reader, it looks like a bordered table, without any
clue that the borders of the "background" region are surrounding text
of the "foreground" region. There are samples in this package:

     http://www.CraneSoftwrights.com/resources/ublss/#ubl2-ss

... and those stylesheets work on a number of commercial formatters,
including RenderX.

So I think you are out of luck. Carving up the background has its
challenges if the formatter (RenderX) or the renderer (Acrobat) is
rounding boundary arithmetic. There may be gaps.

Good luck. I hope this has helped understand some of the situation.

. . . . . . . . . . Ken

p.s. forgive me for not finding the time to look up chapter and verse
of the specification citations above ... I could try to do so if it
is important.

--
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