Use std::optional to allow optional inclusion of attributes

... instead of converting the O(U)String objects to char*.
Eventually this could allow to drop variants of *Element that take
XFastAttributeListRef.

Change-Id: Ib2748fcd93e655c55a176c00410fdcc7f052930d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/98179
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

9 files changed, 101 insertions, 81 deletions

diff --git a/include/sax/fshelper.hxx b/include/sax/fshelper.hxx
index 235181bf9846..e4b5072345e2 100644
--- a/include/sax/fshelper.hxx
+++ b/include/sax/fshelper.hxx
@@ -25,6 +25,7 @@
 #include <com/sun/star/uno/Sequence.hxx>
 #include <rtl/ustring.hxx>
 #include <sax/saxdllapi.h>
+#include <optional>
 #include <memory>
 #include <utility>
 
@@ -58,16 +59,21 @@ public:
         startElement(elementTokenId, std::forward<Args>(args)...);
     }
     template<typename... Args>
-    void startElement(sal_Int32 elementTokenId, sal_Int32 attribute, const OString& value, Args &&... args)
+    void startElement(sal_Int32 elementTokenId, sal_Int32 attribute,
+                      const std::optional<OString>& value, Args&&... args)
     {
-        pushAttributeValue(attribute, value);
+        if (value)
+            pushAttributeValue(attribute, *value);
         startElement(elementTokenId, std::forward<Args>(args)...);
     }
     template<typename... Args>
-    void startElement(sal_Int32 elementTokenId, sal_Int32 attribute, const OUString& value, Args&&... args)
+    void startElement(sal_Int32 elementTokenId, sal_Int32 attribute,
+                      const std::optional<OUString>& value, Args&&... args)
     {
-        // The temporary created by toUtf8() must stay alive until startElement() ends using it
-        startElement(elementTokenId, attribute, value.toUtf8(), std::forward<Args>(args)...);
+        std::optional<OString> opt;
+        if (value)
+            opt = value->toUtf8();
+        startElement(elementTokenId, attribute, opt, std::forward<Args>(args)...);
     }
     void startElement(sal_Int32 elementTokenId);
 
@@ -87,16 +93,21 @@ public:
         singleElement(elementTokenId, std::forward<Args>(args)...);
     }
     template<typename... Args>
-    void singleElement(sal_Int32 elementTokenId, sal_Int32 attribute, const OString& value, Args &&... args)
+    void singleElement(sal_Int32 elementTokenId, sal_Int32 attribute,
+                       const std::optional<OString>& value, Args&&... args)
     {
-        pushAttributeValue(attribute, value);
+        if (value)
+            pushAttributeValue(attribute, *value);
         singleElement(elementTokenId, std::forward<Args>(args)...);
     }
     template<typename... Args>
-    void singleElement(sal_Int32 elementTokenId, sal_Int32 attribute, const OUString& value, Args&&... args)
+    void singleElement(sal_Int32 elementTokenId, sal_Int32 attribute,
+                       const std::optional<OUString>& value, Args&&... args)
     {
-        // The temporary created by toUtf8() must stay alive until singleElement() ends using it
-        singleElement(elementTokenId, attribute, value.toUtf8(), std::forward<Args>(args)...);
+        std::optional<OString> opt;
+        if (value)
+            opt = value->toUtf8();
+        singleElement(elementTokenId, attribute, opt, std::forward<Args>(args)...);
     }
     void singleElement(sal_Int32 elementTokenId);
 
@@ -150,6 +161,16 @@ private:
 
 typedef std::shared_ptr< FastSerializerHelper > FSHelperPtr;
 
+// Helpers to make intention to pass optional attributes to *Element finctions explicit, instead of
+// using `(condition) ? value.toUtf8().getStr() : nullptr` syntax.
+inline const char* UseIf(const char* s, bool bUse) { return bUse ? s : nullptr; }
+// OString, OUString
+template<class TString>
+std::optional<TString> UseIf(const TString& s, bool bUse)
+{
+    return bUse ? std::optional<TString>(s) : std::optional<TString>();
+}
+
 }
 
 #endif // INCLUDED_SAX_FSHELPER_HXX
diff --git a/oox/source/export/drawingml.cxx b/oox/source/export/drawingml.cxx
index 1d52bef4b25c..052ea8f93090 100644
--- a/oox/source/export/drawingml.cxx
+++ b/oox/source/export/drawingml.cxx
@@ -860,8 +860,8 @@ void DrawingML::WriteOutline( const Reference<XPropertySet>& rXPropSet, Referenc
         nEmuLineWidth = oox::drawingml::convertHmmToEmu(nLineWidth);
     mpFS->startElementNS( XML_a, XML_ln,
                           XML_cap, cap,
-                          XML_w, nLineWidth == 0 || (nLineWidth > 1 && nStyleLineWidth != nLineWidth) ?
-                              OString::number(nEmuLineWidth).getStr() : nullptr );
+                          XML_w, sax_fastparser::UseIf(OString::number(nEmuLineWidth),
+                              nLineWidth == 0 || (nLineWidth > 1 && nStyleLineWidth != nLineWidth)) );
 
     if( bColorSet )
     {
@@ -1344,8 +1344,8 @@ void DrawingML::WriteImageBrightnessContrastTransparence(uno::Reference<beans::X
     if (nBright || nContrast)
     {
         mpFS->singleElementNS(XML_a, XML_lum,
-                   XML_bright, nBright ? OString::number(nBright * 1000).getStr() : nullptr,
-                   XML_contrast, nContrast ? OString::number(nContrast * 1000).getStr() : nullptr);
+                   XML_bright, sax_fastparser::UseIf(OString::number(nBright * 1000), nBright != 0),
+                   XML_contrast, sax_fastparser::UseIf(OString::number(nContrast * 1000), nContrast != 0));
     }
 
     if (nTransparence)
@@ -1611,9 +1611,9 @@ void DrawingML::WriteTransformation(const tools::Rectangle& rRect,
 {
 
     mpFS->startElementNS( nXmlNamespace, XML_xfrm,
-                          XML_flipH, bFlipH ? "1" : nullptr,
-                          XML_flipV, bFlipV ? "1" : nullptr,
-                          XML_rot, (nRotation % 21600000) ? OString::number(nRotation).getStr() : nullptr );
+                          XML_flipH, sax_fastparser::UseIf("1", bFlipH),
+                          XML_flipV, sax_fastparser::UseIf("1", bFlipV),
+                          XML_rot, sax_fastparser::UseIf(OString::number(nRotation), nRotation % 21600000 != 0));
 
     sal_Int32 nLeft = rRect.Left();
     sal_Int32 nTop = rRect.Top();
@@ -1890,13 +1890,13 @@ void DrawingML::WriteRunProperties( const Reference< XPropertySet >& rRun, bool
     mpFS->startElementNS( XML_a, nElement,
                           XML_b, bold,
                           XML_i, italic,
-                          XML_lang, usLanguage.isEmpty() ? nullptr : usLanguage.toUtf8().getStr(),
+                          XML_lang, sax_fastparser::UseIf(usLanguage, !usLanguage.isEmpty()),
                           XML_sz, OString::number(nSize),
             // For Condensed character spacing spc value is negative.
-                          XML_spc, nCharKerning ? OString::number(nCharKerning).getStr() : nullptr,
+                          XML_spc, sax_fastparser::UseIf(OString::number(nCharKerning), nCharKerning != 0),
                           XML_strike, strikeout,
                           XML_u, underline,
-                          XML_baseline, nCharEscapement == 0 ? nullptr : OString::number(nCharEscapement*1000).getStr(),
+                          XML_baseline, sax_fastparser::UseIf(OString::number(nCharEscapement*1000), nCharEscapement != 0),
                           XML_cap, cap );
 
     // mso doesn't like text color to be placed after typeface
@@ -2409,7 +2409,7 @@ void DrawingML::WriteParagraphNumbering(const Reference< XPropertySet >& rXPropS
                 aBulletChar = SubstituteBullet( aBulletChar, aFontDesc );
             mpFS->singleElementNS( XML_a, XML_buFont,
                                    XML_typeface, aFontDesc.Name,
-                                   XML_charset, (aFontDesc.CharSet == awt::CharSet::SYMBOL) ? "2" : nullptr );
+                                   XML_charset, sax_fastparser::UseIf("2", aFontDesc.CharSet == awt::CharSet::SYMBOL));
         }
 
         OUString aAutoNumType = GetAutoNumType( nNumberingType, bSDot, bPBehind, bPBoth );
@@ -2418,7 +2418,7 @@ void DrawingML::WriteParagraphNumbering(const Reference< XPropertySet >& rXPropS
         {
             mpFS->singleElementNS(XML_a, XML_buAutoNum,
                                   XML_type, aAutoNumType,
-                                  XML_startAt, nStartWith > 1 ? OString::number(nStartWith).getStr() : nullptr);
+                                  XML_startAt, sax_fastparser::UseIf(OString::number(nStartWith), nStartWith > 1));
         }
         else
         {
@@ -2620,18 +2620,18 @@ void DrawingML::WriteParagraphProperties( const Reference< XTextContent >& rPara
 
     if (nParaLeftMargin) // For Paragraph
         mpFS->startElementNS( XML_a, XML_pPr,
-                           XML_lvl, nLevel > 0 ? OString::number(nLevel).getStr() : nullptr,
-                           XML_marL, nParaLeftMargin > 0 ? OString::number(oox::drawingml::convertHmmToEmu(nParaLeftMargin)).getStr() : nullptr,
-                           XML_indent, nParaFirstLineIndent ? OString::number(oox::drawingml::convertHmmToEmu(nParaFirstLineIndent)).getStr() : nullptr,
+                           XML_lvl, sax_fastparser::UseIf(OString::number(nLevel), nLevel > 0),
+                           XML_marL, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nParaLeftMargin)), nParaLeftMargin > 0),
+                           XML_indent, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nParaFirstLineIndent)), nParaFirstLineIndent != 0),
                            XML_algn, GetAlignment( nAlignment ),
-                           XML_rtl, bRtl ? ToPsz10(bRtl) : nullptr );
+                           XML_rtl, sax_fastparser::UseIf(ToPsz10(bRtl), bRtl));
     else
         mpFS->startElementNS( XML_a, XML_pPr,
-                           XML_lvl, nLevel > 0 ? OString::number(nLevel).getStr() : nullptr,
-                           XML_marL, nLeftMargin > 0 ? OString::number(oox::drawingml::convertHmmToEmu(nLeftMargin)).getStr() : nullptr,
-                           XML_indent, nLineIndentation ? OString::number(oox::drawingml::convertHmmToEmu(nLineIndentation)).getStr() : nullptr,
+                           XML_lvl, sax_fastparser::UseIf(OString::number(nLevel), nLevel > 0),
+                           XML_marL, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nLeftMargin)), nLeftMargin > 0),
+                           XML_indent, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nLineIndentation)), nLineIndentation != 0),
                            XML_algn, GetAlignment( nAlignment ),
-                           XML_rtl, bRtl ? ToPsz10(bRtl) : nullptr );
+                           XML_rtl, sax_fastparser::UseIf(ToPsz10(bRtl), bRtl));
 
 
     if( bHasLinespacing )
@@ -2836,15 +2836,15 @@ void DrawingML::WriteText( const Reference< XInterface >& rXIface, const OUStrin
         }
         mpFS->startElementNS( (nXmlNamespace ? nXmlNamespace : XML_a), XML_bodyPr,
                                XML_wrap, pWrap,
-                               XML_fromWordArt, bFromWordArt ? "1" : nullptr,
-                               XML_lIns, (nLeft != DEFLRINS) ? OString::number(oox::drawingml::convertHmmToEmu(nLeft)).getStr() : nullptr,
-                               XML_rIns, (nRight != DEFLRINS) ? OString::number(oox::drawingml::convertHmmToEmu(nRight)).getStr() : nullptr,
-                               XML_tIns, (nTop != DEFTBINS) ? OString::number(oox::drawingml::convertHmmToEmu(nTop)).getStr() : nullptr,
-                               XML_bIns, (nBottom != DEFTBINS) ? OString::number(oox::drawingml::convertHmmToEmu(nBottom)).getStr() : nullptr,
+                               XML_fromWordArt, sax_fastparser::UseIf("1", bFromWordArt),
+                               XML_lIns, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nLeft)), nLeft != DEFLRINS),
+                               XML_rIns, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nRight)), nRight != DEFLRINS),
+                               XML_tIns, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nTop)), nTop != DEFTBINS),
+                               XML_bIns, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nBottom)), nBottom != DEFTBINS),
                                XML_anchor, sVerticalAlignment,
-                               XML_anchorCtr, bHorizontalCenter ? "1" : nullptr,
+                               XML_anchorCtr, sax_fastparser::UseIf("1", bHorizontalCenter),
                                XML_vert, sWritingMode,
-                               XML_rot, ((nTextPreRotateAngle + nTextRotateAngle) != 0) ? oox::drawingml::calcRotationValue( (nTextPreRotateAngle + nTextRotateAngle) * 100 ).getStr() : nullptr );
+                               XML_rot, sax_fastparser::UseIf(oox::drawingml::calcRotationValue((nTextPreRotateAngle + nTextRotateAngle) * 100), (nTextPreRotateAngle + nTextRotateAngle) != 0));
         if (bIsFontworkShape)
         {
             if (aAdjustmentSeq.hasElements())
@@ -2933,7 +2933,7 @@ void DrawingML::WriteText( const Reference< XInterface >& rXIface, const OUStrin
                 }
 
                 mpFS->singleElementNS(XML_a, XML_normAutofit, XML_fontScale,
-                    ( nFontScale < MAX_SCALE_VAL && nFontScale > 0 ) ? OString::number(nFontScale).getStr() : nullptr);
+                    sax_fastparser::UseIf(OString::number(nFontScale), nFontScale < MAX_SCALE_VAL && nFontScale > 0));
             }
             else
             {
diff --git a/oox/source/export/shapes.cxx b/oox/source/export/shapes.cxx
index 8cab446a3488..5729c9d27a66 100644
--- a/oox/source/export/shapes.cxx
+++ b/oox/source/export/shapes.cxx
@@ -802,7 +802,7 @@ ShapeExport& ShapeExport::WriteCustomShape( const Reference< XShape >& xShape )
         pFS->startElementNS( mnXmlNamespace, XML_cNvPr,
                 XML_id, OString::number(GetNewShapeID(xShape)),
                 XML_name, GetShapeName(xShape),
-                XML_hidden, isVisible ? nullptr : "1" );
+                XML_hidden, sax_fastparser::UseIf("1", !isVisible));
 
         if( GETA( URL ) )
         {
@@ -1194,7 +1194,7 @@ void ShapeExport::WriteGraphicObjectShapePart( const Reference< XShape >& xShape
     pFS->startElementNS( mnXmlNamespace, XML_cNvPr,
                           XML_id,     OString::number(GetNewShapeID(xShape)),
                           XML_name,   GetShapeName(xShape),
-                          XML_descr,  bHaveDesc ? sDescr.toUtf8().getStr() : nullptr );
+                          XML_descr,  sax_fastparser::UseIf(sDescr, bHaveDesc));
 
     // OOXTODO: //cNvPr children: XML_extLst, XML_hlinkHover
     if (bHasMediaURL)
@@ -1780,8 +1780,8 @@ void ShapeExport::WriteTableCellProperties(const Reference< XPropertySet>& xCell
     aRightMargin >>= nRightMargin;
 
     mpFS->startElementNS(XML_a, XML_tcPr,
-    XML_marL, nLeftMargin > 0 ? OString::number(oox::drawingml::convertHmmToEmu(nLeftMargin)).getStr() : nullptr,
-    XML_marR, nRightMargin > 0 ? OString::number(oox::drawingml::convertHmmToEmu(nRightMargin)).getStr() : nullptr);
+    XML_marL, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nLeftMargin)), nLeftMargin > 0),
+    XML_marR, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nRightMargin)), nRightMargin > 0));
 
     // Write background fill for table cell.
     // TODO
diff --git a/sc/source/filter/excel/xecontent.cxx b/sc/source/filter/excel/xecontent.cxx
index 9e596fdcf35d..88e2018b16ab 100644
--- a/sc/source/filter/excel/xecontent.cxx
+++ b/sc/source/filter/excel/xecontent.cxx
@@ -525,14 +525,13 @@ void XclExpHyperlink::SaveXml( XclExpXmlStream& rStrm )
     OUString sId = !msTarget.isEmpty() ? rStrm.addRelation( rStrm.GetCurrentStream()->getOutputStream(),
             oox::getRelationship(Relationship::HYPERLINK),
             msTarget, true ) : OUString();
+    std::optional<OString> sTextMark;
+    if (mxTextMark)
+        sTextMark = XclXmlUtils::ToOString(*mxTextMark);
     rStrm.GetCurrentStream()->singleElement( XML_hyperlink,
             XML_ref,                XclXmlUtils::ToOString(rStrm.GetRoot().GetDoc(), maScPos),
-            FSNS( XML_r, XML_id ),  !sId.isEmpty()
-                                       ? sId.toUtf8().getStr()
-                                       : nullptr,
-            XML_location,           mxTextMark
-                                        ? XclXmlUtils::ToOString( *mxTextMark ).getStr()
-                                        : nullptr,
+            FSNS( XML_r, XML_id ),  sax_fastparser::UseIf(sId, !sId.isEmpty()),
+            XML_location,           sTextMark,
             // OOXTODO: XML_tooltip,    from record HLinkTooltip 800h wzTooltip
             XML_display,            m_Repr );
 }
@@ -1549,8 +1548,8 @@ void XclExpIconSet::SaveXml( XclExpXmlStream& rStrm )
     const char* pIconSetName = ScIconSetFormat::getIconSetName(mrFormat.GetIconSetData()->eIconSetType);
     rWorksheet->startElement( XML_iconSet,
             XML_iconSet, pIconSetName,
-            XML_showValue, mrFormat.GetIconSetData()->mbShowValue ? nullptr : "0",
-            XML_reverse, mrFormat.GetIconSetData()->mbReverse ? "1" : nullptr );
+            XML_showValue, sax_fastparser::UseIf("0", !mrFormat.GetIconSetData()->mbShowValue),
+            XML_reverse, sax_fastparser::UseIf("1", mrFormat.GetIconSetData()->mbReverse));
 
     maCfvoList.SaveXml( rStrm );
 
diff --git a/sc/source/filter/excel/xeescher.cxx b/sc/source/filter/excel/xeescher.cxx
index 8afbe2e3752b..0e78fbf251da 100644
--- a/sc/source/filter/excel/xeescher.cxx
+++ b/sc/source/filter/excel/xeescher.cxx
@@ -1192,10 +1192,10 @@ void XclExpTbxControlObj::SaveXml( XclExpXmlStream& rStrm )
                 // Insets are used just as internal margins for text boxes within shapes.
                 // If this attribute is omitted, then a value of 45720 or 0.05 inches is implied.
                 pDrawing->startElementNS(XML_a, XML_bodyPr,
-                    XML_lIns, (nLeft != DEFLRINS) ? OString::number(oox::drawingml::convertHmmToEmu(nLeft)).getStr() : nullptr,
-                    XML_rIns, (nRight != DEFLRINS) ? OString::number(oox::drawingml::convertHmmToEmu(nRight)).getStr() : nullptr,
-                    XML_tIns, (nTop != DEFTBINS) ? OString::number(oox::drawingml::convertHmmToEmu(nTop)).getStr() : nullptr,
-                    XML_bIns, (nBottom != DEFTBINS) ? OString::number(oox::drawingml::convertHmmToEmu(nBottom)).getStr() : nullptr,
+                    XML_lIns, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nLeft)), nLeft != DEFLRINS),
+                    XML_rIns, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nRight)), nRight != DEFLRINS),
+                    XML_tIns, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nTop)), nTop != DEFTBINS),
+                    XML_bIns, sax_fastparser::UseIf(OString::number(oox::drawingml::convertHmmToEmu(nBottom)), nBottom != DEFTBINS),
                     XML_anchor, "ctr");
 
                 {
diff --git a/sc/source/filter/excel/xeextlst.cxx b/sc/source/filter/excel/xeextlst.cxx
index db770b0dc6cd..35d2fac152d7 100644
--- a/sc/source/filter/excel/xeextlst.cxx
+++ b/sc/source/filter/excel/xeextlst.cxx
@@ -340,7 +340,7 @@ void XclExpExtIconSet::SaveXml(XclExpXmlStream& rStrm)
 
     rWorksheet->startElementNS(XML_x14, XML_iconSet,
             XML_iconSet, mpIconSetName,
-            XML_custom, mbCustom ? ToPsz10(mbCustom) : nullptr,
+            XML_custom, sax_fastparser::UseIf(ToPsz10(mbCustom), mbCustom),
             XML_reverse, ToPsz10(mbReverse),
             XML_showValue, ToPsz10(mbShowValue));
 
@@ -398,7 +398,7 @@ void XclExpExtCfRule::SaveXml( XclExpXmlStream& rStrm )
     sax_fastparser::FSHelperPtr& rWorksheet = rStrm.GetCurrentStream();
     rWorksheet->startElementNS( XML_x14, XML_cfRule,
                                 XML_type, pType,
-                                XML_priority, mnPriority == -1 ? nullptr : OString::number(mnPriority + 1).getStr(),
+                                XML_priority, sax_fastparser::UseIf(OString::number(mnPriority + 1), mnPriority != -1),
                                 XML_operator, mOperator,
                                 XML_id, maId );
 
diff --git a/sc/source/filter/excel/xestyle.cxx b/sc/source/filter/excel/xestyle.cxx
index e91b64b5687c..76d9c2fb572f 100644
--- a/sc/source/filter/excel/xestyle.cxx
+++ b/sc/source/filter/excel/xestyle.cxx
@@ -1600,7 +1600,7 @@ void XclExpCellAlign::SaveXml( XclExpXmlStream& rStrm ) const
             // OOXTODO: XML_relativeIndent,     mnIndent?
             // OOXTODO: XML_justifyLastLine,
             XML_shrinkToFit,        ToPsz( mbShrink ),
-            XML_readingOrder, mnTextDir == EXC_XF_TEXTDIR_CONTEXT ? nullptr : OString::number(mnTextDir).getStr() );
+            XML_readingOrder, sax_fastparser::UseIf(OString::number(mnTextDir), mnTextDir != EXC_XF_TEXTDIR_CONTEXT) );
 }
 
 namespace {
@@ -2200,7 +2200,7 @@ void XclExpXF::SaveXml( XclExpXmlStream& rStrm )
             XML_fontId,             OString::number(mnXclFont),
             XML_fillId,             OString::number(mnFillId),
             XML_borderId,           OString::number(mnBorderId),
-            XML_xfId,               IsStyleXF() ? nullptr : OString::number( nXfId ).getStr(),
+            XML_xfId,               sax_fastparser::UseIf(OString::number(nXfId), !IsStyleXF()),
             // OOXTODO: XML_quotePrefix,
             // OOXTODO: XML_pivotButton,
             // OOXTODO: XML_applyNumberFormat,  ;
diff --git a/sd/source/filter/eppt/pptx-animations.cxx b/sd/source/filter/eppt/pptx-animations.cxx
index ec0f723c4974..90720501d07a 100644
--- a/sd/source/filter/eppt/pptx-animations.cxx
+++ b/sd/source/filter/eppt/pptx-animations.cxx
@@ -215,7 +215,7 @@ void WriteAnimateValues(const FSHelperPtr& pFS, const Reference<XAnimate>& rXAni
         if (aValues[i].hasValue())
         {
             pFS->startElementNS(XML_p, XML_tav, XML_fmla,
-                                sFormula.isEmpty() ? nullptr : sFormula.toUtf8().getStr(), XML_tm,
+                                sax_fastparser::UseIf(sFormula, !sFormula.isEmpty()), XML_tm,
                                 OString::number(static_cast<sal_Int32>(aKeyTimes[i] * 100000.0)));
             pFS->startElementNS(XML_p, XML_val);
             ValuePair aPair;
@@ -901,10 +901,9 @@ void PPTXAnimationExport::WriteAnimationNodeAnimate(sal_Int32 nXmlNodeType)
         }
 
         mpFS->startElementNS(XML_p, nXmlNodeType, XML_calcmode, pCalcMode, XML_valueType,
-                             pValueType, XML_from,
-                             sFrom.isEmpty() ? nullptr : sFrom.toUtf8().getStr(), XML_to,
-                             sTo.isEmpty() ? nullptr : sTo.toUtf8().getStr(), XML_by,
-                             sBy.isEmpty() ? nullptr : sBy.toUtf8().getStr());
+                             pValueType, XML_from, sax_fastparser::UseIf(sFrom, !sFrom.isEmpty()),
+                             XML_to, sax_fastparser::UseIf(sTo, !sTo.isEmpty()), XML_by,
+                             sax_fastparser::UseIf(sBy, !sBy.isEmpty()));
         bTo = sTo.isEmpty() && sFrom.isEmpty() && sBy.isEmpty();
     }
 
@@ -982,7 +981,7 @@ void PPTXAnimationExport::WriteAnimationNodeAnimateInside(bool bSimple, bool bWr
 void PPTXAnimationExport::WriteAnimationNodeCommonPropsStart()
 {
     const Reference<XAnimationNode>& rXNode = getCurrentNode();
-    const char* pDuration = nullptr;
+    std::optional<OString> sDuration;
     const char* pRestart = nullptr;
     const char* pNodeType = nullptr;
     const char* pPresetClass = nullptr;
@@ -999,7 +998,7 @@ void PPTXAnimationExport::WriteAnimationNodeCommonPropsStart()
         if (aAny >>= eTiming)
         {
             if (eTiming == Timing_INDEFINITE)
-                pDuration = "indefinite";
+                sDuration = "indefinite";
         }
         else
             aAny >>= fDuration;
@@ -1013,17 +1012,20 @@ void PPTXAnimationExport::WriteAnimationNodeCommonPropsStart()
         pNodeType = convertEffectNodeType(nType);
         if (nType == EffectNodeType::TIMING_ROOT)
         {
-            if (!pDuration)
-                pDuration = "indefinite";
+            if (!sDuration)
+                sDuration = "indefinite";
             if (!pRestart)
                 pRestart = "never";
         }
         else if (nType == EffectNodeType::MAIN_SEQUENCE)
         {
-            pDuration = "indefinite";
+            sDuration = "indefinite";
         }
     }
 
+    if (fDuration != 0)
+        sDuration = OString::number(static_cast<sal_Int32>(fDuration * 1000.0));
+
     sal_uInt32 nPresetClass = mpContext->getEffectPresetClass();
     if (nPresetClass != DFF_ANIM_PRESS_CLASS_USER_DEFINED)
         pPresetClass = convertEffectPresetClass(nPresetClass);
@@ -1057,13 +1059,11 @@ void PPTXAnimationExport::WriteAnimationNodeCommonPropsStart()
     bool bAutoReverse = rXNode->getAutoReverse();
 
     mpFS->startElementNS(
-        XML_p, XML_cTn, XML_id, OString::number(GetNextAnimationNodeId(rXNode)), XML_dur,
-        fDuration != 0 ? OString::number(static_cast<sal_Int32>(fDuration * 1000.0)).getStr()
-                       : pDuration,
-        XML_autoRev, bAutoReverse ? "1" : nullptr, XML_restart, pRestart, XML_nodeType, pNodeType,
-        XML_fill, pFill, XML_presetClass, pPresetClass, XML_presetID,
-        bPresetId ? OString::number(nPresetId).getStr() : nullptr, XML_presetSubtype,
-        bPresetSubType ? OString::number(nPresetSubType).getStr() : nullptr);
+        XML_p, XML_cTn, XML_id, OString::number(GetNextAnimationNodeId(rXNode)), XML_dur, sDuration,
+        XML_autoRev, sax_fastparser::UseIf("1", bAutoReverse), XML_restart, pRestart, XML_nodeType,
+        pNodeType, XML_fill, pFill, XML_presetClass, pPresetClass, XML_presetID,
+        sax_fastparser::UseIf(OString::number(nPresetId), bPresetId), XML_presetSubtype,
+        sax_fastparser::UseIf(OString::number(nPresetSubType), bPresetSubType));
 
     WriteAnimationCondList(mpContext->getCondition(true), XML_stCondLst);
     WriteAnimationCondList(mpContext->getCondition(false), XML_endCondLst);
@@ -1192,8 +1192,8 @@ void PPTXAnimationExport::WriteAnimationNodeAudio()
 
     mpFS->startElementNS(XML_p, XML_tgtEl);
     mpFS->singleElementNS(XML_p, XML_sndTgt, FSNS(XML_r, XML_embed),
-                          sRelId.isEmpty() ? nullptr : sRelId.toUtf8().getStr(), XML_name,
-                          sUrl.isEmpty() ? nullptr : sName.toUtf8().getStr());
+                          sax_fastparser::UseIf(sRelId, !sRelId.isEmpty()), XML_name,
+                          sax_fastparser::UseIf(sName, !sUrl.isEmpty()));
     mpFS->endElementNS(XML_p, XML_tgtEl);
 
     mpFS->endElementNS(XML_p, XML_cMediaNode);
diff --git a/sd/source/filter/eppt/pptx-epptooxml.cxx b/sd/source/filter/eppt/pptx-epptooxml.cxx
index e1cb766858c5..9de1eb5b3f60 100644
--- a/sd/source/filter/eppt/pptx-epptooxml.cxx
+++ b/sd/source/filter/eppt/pptx-epptooxml.cxx
@@ -119,9 +119,9 @@ void WriteSndAc(const FSHelperPtr& pFS, const OUString& sSoundRelId, const OUStr
 {
         pFS->startElementNS(XML_p, XML_sndAc);
         pFS->startElementNS(XML_p, XML_stSnd);
-        pFS->singleElementNS(XML_p, XML_snd,
-            FSNS(XML_r, XML_embed), sSoundRelId.isEmpty() ? nullptr : sSoundRelId.toUtf8().getStr(),
-            XML_name, sSoundName.isEmpty() ? nullptr : sSoundName.toUtf8().getStr());
+        pFS->singleElementNS(XML_p, XML_snd, FSNS(XML_r, XML_embed),
+                             sax_fastparser::UseIf(sSoundRelId, !sSoundRelId.isEmpty()), XML_name,
+                             sax_fastparser::UseIf(sSoundName, !sSoundName.isEmpty()));
         pFS->endElement(FSNS(XML_p, XML_stSnd));
         pFS->endElement(FSNS(XML_p, XML_sndAc));
 }
@@ -900,7 +900,7 @@ void PowerPointExport::WriteTransition(const FSHelperPtr& pFS)
 
     pFS->startElementNS(XML_p, XML_transition,
         XML_spd, speed,
-        XML_advTm, isAdvanceTimingSet ? OString::number(advanceTiming * 1000).getStr() : nullptr);
+        XML_advTm, sax_fastparser::UseIf(OString::number(advanceTiming * 1000), isAdvanceTimingSet));
 
     if (nTransition)
     {