Writer follows the CSS box model when it comes to page borders: there
can be a positive distance between the edge of the page and the border,
and again a positive distance between the border and the body frame.
This ensures that the page border never intersect with the body frame,
which is usually what users expect. Word, however, can work with 2
distances for border and text, both measured from the edge of the page,
leading to a page border, which is inside the body text. This is
described at great detail at
<https://wiki.openoffice.org/wiki/Writer/MSInteroperability/PageBorder#Importing_case_3:>.
Fix the problem by allowing negative border distances: this doesn't
influence the position or the size of the body frame, but it gives us a
way to position the border more towards the center of the page, leading
the matching layout between Writer and Word.
The doc model (to allow negative border distances), UNO API and DOCX
filter is updated in this commit. The ODT filter works without explicit
effort. Other filters are not yet updated in this commit.
Change-Id: I723e1bdb8dc6391129f1686f88826cc089f6fd67
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/135462
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins
1f127a2b9e