crashtesting: fix font-dependent infinite loop in kashida justification

Commit c3c29d31d77ff93aa50634cfd51c62d12dc0f6ec (tdf#140767 Implemented
Syriac justification) indirectly introduced a font-dependent infinite
loop in Writer layout by relaxing some restrictions on kashida candidate
positions. The infinite loop was found in tdf97806-2.odt.

This change fixes an underlying logic bug in Writer, which caused Writer
to attempt to apply kashida justification to non-Arabic/Syriac CTL
scripts. This change also reintroduces some of the previously-lifted
restrictions on kashida candidate positions.

Change-Id: I783bf327f4ef0f1f6a032f0d3dddbcfd60a026fa
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/174503
Tested-by: Jenkins
Reviewed-by: Jonathan Clark <jonathan@libreoffice.org>

2 files changed, 22 insertions, 16 deletions

diff --git a/sw/source/core/text/itradj.cxx b/sw/source/core/text/itradj.cxx
index c072025e7a96..be004457b407 100644
--- a/sw/source/core/text/itradj.cxx
+++ b/sw/source/core/text/itradj.cxx
@@ -167,10 +167,11 @@ static bool lcl_CheckKashidaPositions(SwScriptInfo& rSI, SwTextSizeInfo& rInf, S
         const OUString& rWord = aScanner.GetWord();
 
         // Fetch the set of valid positions from VCL, where possible
-        aValidPositions.clear();
         if (SwScriptInfo::IsKashidaScriptText(rInf.GetText(), TextFrameIndex{ aScanner.GetBegin() },
                                               TextFrameIndex{ aScanner.GetLen() }))
         {
+            aValidPositions.clear();
+
             rItr.SeekAndChgAttrIter(TextFrameIndex{ aScanner.GetBegin() }, rInf.GetRefDev());
 
             vcl::text::ComplexTextLayoutFlags nOldLayout = rInf.GetRefDev()->GetLayoutMode();
@@ -179,13 +180,13 @@ static bool lcl_CheckKashidaPositions(SwScriptInfo& rSI, SwTextSizeInfo& rInf, S
             rInf.GetRefDev()->GetWordKashidaPositions(rWord, &aValidPositions);
 
             rInf.GetRefDev()->SetLayoutMode(nOldLayout);
-        }
 
-        auto stKashidaPos = i18nutil::GetWordKashidaPosition(rWord, aValidPositions);
-        if (stKashidaPos.has_value())
-        {
-            TextFrameIndex nNewKashidaPos{ aScanner.GetBegin() + stKashidaPos->nIndex };
-            aNewKashidaPositions.push_back(nNewKashidaPos);
+            auto stKashidaPos = i18nutil::GetWordKashidaPosition(rWord, aValidPositions);
+            if (stKashidaPos.has_value())
+            {
+                TextFrameIndex nNewKashidaPos{ aScanner.GetBegin() + stKashidaPos->nIndex };
+                aNewKashidaPositions.push_back(nNewKashidaPos);
+            }
         }
     }
 
diff --git a/sw/source/core/text/porlay.cxx b/sw/source/core/text/porlay.cxx
index d433c3bbd3cd..39a260ac0ef8 100644
--- a/sw/source/core/text/porlay.cxx
+++ b/sw/source/core/text/porlay.cxx
@@ -1525,16 +1525,21 @@ void SwScriptInfo::InitScriptInfo(const SwTextNode& rNode,
             // the search has to be performed on a per word base
             while ( aScanner.NextWord() )
             {
-                const OUString& rWord = aScanner.GetWord();
-                auto stKashidaPos = i18nutil::GetWordKashidaPosition(rWord);
-
-                if (stKashidaPos.has_value())
+                if (SwScriptInfo::IsKashidaScriptText(rText, TextFrameIndex{ aScanner.GetBegin() },
+                                                      TextFrameIndex{ aScanner.GetLen() }))
                 {
-                    // Only populate kashida positions for the invalidated tail
-                    TextFrameIndex nNewKashidaPos{aScanner.GetBegin() + stKashidaPos->nIndex};
-                    if(nNewKashidaPos >= nLastKashida) {
-                        m_Kashida.insert(m_Kashida.begin() + nCntKash, nNewKashidaPos);
-                        nCntKash++;
+                    const OUString& rWord = aScanner.GetWord();
+                    auto stKashidaPos = i18nutil::GetWordKashidaPosition(rWord);
+
+                    if (stKashidaPos.has_value())
+                    {
+                        // Only populate kashida positions for the invalidated tail
+                        TextFrameIndex nNewKashidaPos{ aScanner.GetBegin() + stKashidaPos->nIndex };
+                        if (nNewKashidaPos >= nLastKashida)
+                        {
+                            m_Kashida.insert(m_Kashida.begin() + nCntKash, nNewKashidaPos);
+                            nCntKash++;
+                        }
                     }
                 }
             } // end of kashida search