sw_redlinehide: SwRedlineItr::Seek_() needs to do something

... in Hide mode, such as locate the next Delete that GetNextRedln looks
for.

Change-Id: Ie0ab35c99f34bd3a071798fd54efd12f1f82a118

sw/source/core/text/redlnitr.cxx

@@ -301,7 +301,6 @@ SwRedlineItr::~SwRedlineItr() COVERITY_NOEXCEPT_FALSE
 // The return value of SwRedlineItr::Seek tells you if the current font
 // has been manipulated by leaving (-1) or accessing (+1) of a section
 short SwRedlineItr::Seek_(SwFont& rFnt, sal_uLong const nNode, sal_Int32 const nNew, sal_Int32 const nOld)
-    //TODO use nNode to compare
 {
     short nRet = 0;
     if( ExtOn() )
@@ -386,6 +385,36 @@ short SwRedlineItr::Seek_(SwFont& rFnt, sal_uLong const nNode, sal_Int32 const n
             m_nEnd = COMPLETE_STRING;
         }
     }
+    else if (m_eMode == Mode::Hide)
+    {   // ... just iterate to update m_nAct for GetNextRedln();
+        // there is no need to care about formatting in this mode
+        if (m_nAct == SwRedlineTable::npos || nOld == COMPLETE_STRING)
+        {   // reset, or move backward
+            m_nAct = m_nFirst;
+        }
+        for ( ; m_nAct < m_rDoc.getIDocumentRedlineAccess().GetRedlineTable().size(); ++m_nAct)
+        {   // only Start matters in this mode
+            // Seeks until it finds a RL that starts at or behind the seek pos.
+            // - then update m_nStart/m_nEnd to the intersection of it with the
+            // current node (if any).
+            // The only way to skip to a different node is if there is a Delete
+            // RL, so if there is no intersection we'll never skip again.
+            // Note: here, assume that delete can't nest inside delete!
+            SwRangeRedline const*const pRedline(
+                m_rDoc.getIDocumentRedlineAccess().GetRedlineTable()[m_nAct]);
+            SwPosition const*const pStart(pRedline->Start());
+            if (pRedline->GetType() == nsRedlineType_t::REDLINE_DELETE
+                && (nNode < pStart->nNode.GetIndex()
+                    || (nNode == pStart->nNode.GetIndex()
+                        && nNew <= pStart->nContent.GetIndex())))
+            {
+                pRedline->CalcStartEnd(nNode, m_nStart, m_nEnd);
+                break;
+            }
+            m_nStart = COMPLETE_STRING;
+            m_nEnd = COMPLETE_STRING;
+        }
+    }
     return nRet + EnterExtend(rFnt, nNode, nNew);
 }