tdf#147008 sw_fieldmarkhide: fix invalid NonTextFieldmark positions

Commit ab6176e88f78d0b3aa2490fbc7858304c2d4a437 introduced a crash
in ModelToViewHelper when the positions of a NonTextFieldmark are invalid.

The NonTextFieldmark must always contain 1 CH_TXT_ATR_FORMELEMENT
but after SplitNode() the position is
(rr) p *pFieldMark->m_pPos1
$2 = SwPosition (node 10, offset 1)
(rr) p *pFieldMark->m_pPos2
$3 = SwPosition (node 9, offset 0)

This is because in ContentIdxStoreImpl::SaveBkmks() there is an
asymmetry where the m_pPos2 is recorded to be wrongly corrected to node
9, but if the positions were swapped so that m_pPos1 is the start
position, then it will not be recorded and remain in node 10.

So fix this by changing the NonTextFieldmark to insert its
CH_TXT_ATR_FORMELEMENT differently.

There is some very subtle code in SwTextNode::Update() that is again
asymmetric and (non-obviously) prefers to move m_pPos2 and leave m_pPos1
alone (by moving it to aTmpIdxReg) in case the positions are equal.

But then the fieldmark code increments "rEnd" (which is really the
m_pPos1 i.e. the start after InsertString() returns), and then
decrements m_pPos2.

So avoid the problem by removing these 2 pointless adjustments.

Then it turns a bunch of tests fail because other code assumes that
m_pPos1 is the end of the NonTextFieldmark, so fix
MarkManager::changeFormFieldmarkType(), ModelToViewHelper and
SwHistoryNoTextFieldmark to use GetMarkStart().

Change-Id: I7c82f9a67661121662c95727e0f8f15e06d85a3a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/129289
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>

1 files changed, 3 insertions, 5 deletions

diff --git a/sw/source/core/doc/docbm.cxx b/sw/source/core/doc/docbm.cxx
index 5ed676719622..c15c1dd3fcea 100644
--- a/sw/source/core/doc/docbm.cxx
+++ b/sw/source/core/doc/docbm.cxx
@@ -1419,8 +1419,7 @@ namespace sw::mark
     void MarkManager::deleteFieldmarkAt(const SwPosition& rPos)
     {
         auto const pFieldmark = dynamic_cast<Fieldmark*>(getFieldmarkAt(rPos));
-        if (!pFieldmark)
-            return;
+        assert(pFieldmark); // currently all callers require it to be there
 
         deleteMark(lcl_FindMark(m_vAllMarks, pFieldmark));
     }
@@ -1455,12 +1454,11 @@ namespace sw::mark
 
         // Store attributes needed to create the new fieldmark
         OUString sName = pFieldmark->GetName();
-        SwPaM aPaM(pFieldmark->GetMarkPos());
+        SwPaM const aPaM(pFieldmark->GetMarkStart());
 
         // Remove the old fieldmark and create a new one with the new type
-        if(aPaM.GetPoint()->nContent > 0 && (rNewType == ODF_FORMDROPDOWN || rNewType == ODF_FORMCHECKBOX))
+        if (rNewType == ODF_FORMDROPDOWN || rNewType == ODF_FORMCHECKBOX)
         {
-            --aPaM.GetPoint()->nContent;
             SwPosition aNewPos (aPaM.GetPoint()->nNode, aPaM.GetPoint()->nContent);
             deleteFieldmarkAt(aNewPos);
             return makeNoTextFieldBookmark(aPaM, sName, rNewType);