tdf#99984 render inferred mrow as group {}

In case an element has no content, but has got an SmXMLRowContext,
an empty group {} is inserted. The result is, that empty table
cells are rendered without error, so that files, which use a
mtable element to arrange things, no longer break on import.

Change-Id: Iae158226e6478f2f9f397b8485044860ee8767c2
Reviewed-on: https://gerrit.libreoffice.org/25273
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: jan iversen <jani@documentfoundation.org>

2 files changed, 16 insertions, 5 deletions

diff --git a/starmath/qa/extras/mmlimport-test.cxx b/starmath/qa/extras/mmlimport-test.cxx
index f9f1405b5740..846ea87681a6 100644
--- a/starmath/qa/extras/mmlimport-test.cxx
+++ b/starmath/qa/extras/mmlimport-test.cxx
@@ -108,7 +108,7 @@ void Test::testMaction()
 void Test::testtdf99556()
 {
     loadURL(m_directories.getURLFromSrc("starmath/qa/extras/data/tdf99556-1.mml"));
-    OUString sExpected("sqrt");
+    OUString sExpected("sqrt { {} }");
     CPPUNIT_ASSERT_EQUAL_MESSAGE("loaded text", sExpected, mxDocShell->GetText());
 }
 
diff --git a/starmath/source/mathmlimport.cxx b/starmath/source/mathmlimport.cxx
index 971d349c5600..5be05264945a 100644
--- a/starmath/source/mathmlimport.cxx
+++ b/starmath/source/mathmlimport.cxx
@@ -2249,14 +2249,25 @@ void SmXMLRowContext_Impl::EndElement()
             return;
         }
     }
-    else //Multiple newlines result in empty row elements
+    else
     {
-        aRelationArray.resize(1);
+        // The elements msqrt, mstyle, merror, menclose, mpadded, mphantom, mtd, and math
+        // treat their content as a single inferred mrow in case their content is empty.
+        // Here an empty group {} is used to catch those cases and transform them without error
+        // to StarMath.
+        aRelationArray.resize(2);
         SmToken aToken;
-        aToken.cMathChar = '\0';
+        aToken.cMathChar = MS_LBRACE;
         aToken.nLevel = 5;
-        aToken.eType = TNEWLINE;
+        aToken.eType = TLGROUP;
+        aToken.aText = "{";
         aRelationArray[0] = new SmLineNode(aToken);
+
+        aToken.cMathChar = MS_RBRACE;
+        aToken.nLevel = 0;
+        aToken.eType = TRGROUP;
+        aToken.aText = "}";
+        aRelationArray[1] = new SmLineNode(aToken);
     }
 
     SmToken aDummy;