Make sanitiseMm100ToTwip simpler and more correct

The result's absolute value is always smaller than n.
Returning an uncorrected value taken from reversing
multiplication and division order when intermediate
value would overflow is better than arbitrary constant.

Also further deduplicate Twips <-> 100th-mm conversion,
and make sure they all are in a single header.

Using conversion implementation that handles negatives
correctly improves accuracy, as seen in unit tests; e.g.
in testPictureEffectPreservation (the original doc had
"dir" equal to "8100000", while we tested that it was
"8076614" after roundtrip).

Change-Id: Icd027af6238a9f45f916f53f8684506cc959e696
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/110433
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/sw/qa/extras/ooxmlexport/ooxmlexport7.cxx b/sw/qa/extras/ooxmlexport/ooxmlexport7.cxx
index 2e8c2c45aa42..e9d8ebd64fd7 100644
--- a/sw/qa/extras/ooxmlexport/ooxmlexport7.cxx
+++ b/sw/qa/extras/ooxmlexport/ooxmlexport7.cxx
@@ -443,7 +443,7 @@ DECLARE_OOXMLEXPORT_EXPORTONLY_TEST(testPictureEffectPreservation, "picture-effe
     // second picture: shadow and reflection effects
     assertXPath(pXmlDoc, "/w:document/w:body/w:p[2]/w:r/mc:AlternateContent/mc:Choice/w:drawing/"
             "wp:anchor/a:graphic/a:graphicData/pic:pic/pic:spPr/a:effectLst/a:outerShdw",
-            "dir", "8076614");
+            "dir", "8100000");
     assertXPath(pXmlDoc, "/w:document/w:body/w:p[2]/w:r/mc:AlternateContent/mc:Choice/w:drawing/"
             "wp:anchor/a:graphic/a:graphicData/pic:pic/pic:spPr/a:effectLst/a:outerShdw/a:srgbClr",
             "val", "000000");