tdf#129452 writerfilter: use column, not cell when comparing rows

A natural mistake - especially when there are no existing
functions - is to assume that cell number defines column
number, and so it is valid to compare between rows.

This patch provides the functions, and switches this bug's
earlier patch to properly use columns instead of cells.

This commit depends on two prior patches in bug 129452:
  Change-Id: Ie305477f0e3468a4a923095d76f520d97fe99ffe
  Change-Id: Ibfdac336bbb1f7303c7e585a85c94be37ad6f916

I hope that this implementation covers all the bases.
This code is dreadful to understand,
as witnessed by comments from those much smarter than I.

P.S. I also cancelled a vertical merge if the cell
is not there (in a gridAfter situation).
If a row is shorter than the previous ones,
then a vertically merged cell should not be considered
to be able to span that gap. If the cells below are still
merged, it would be considered a new merged cell.

Change-Id: I63158ac73b1bf86d9f75dd3c1299d1b1a3f08064
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/97434
Tested-by: Justin Luth <justin_luth@sil.org>
Tested-by: László Németh <nemeth@numbertext.org>
Reviewed-by: Justin Luth <justin_luth@sil.org>
Reviewed-by: László Németh <nemeth@numbertext.org>

0 files changed, 0 insertions, 0 deletions