use boost::optional in EditFieldInfo

it is inefficient to allocate a tiny object like Color separately on the
heap

Change-Id: I2f03538f987ff032857f3316ed2d8c2c8d731549
Reviewed-on: https://gerrit.libreoffice.org/67968
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

include/editeng/outliner.hxx

@@ -49,6 +49,7 @@
 #include <editeng/paragraphdata.hxx>
 #include <o3tl/typed_flags_set.hxx>
 
+#include <boost/optional.hpp>
 #include <functional>
 #include <memory>
 #include <vector>
@@ -497,8 +498,8 @@ private:
     Outliner*           pOutliner;
     const SvxFieldItem& rFldItem;
 
-    std::unique_ptr<Color> pTxtColor;
-    std::unique_ptr<Color> pFldColor;
+    boost::optional<Color> mxTxtColor;
+    boost::optional<Color> mxFldColor;
 
     OUString            aRepresentation;
 
@@ -522,15 +523,11 @@ public:
 
     const SvxFieldItem& GetField() const { return rFldItem; }
 
-    Color*          GetTextColor() const { return pTxtColor.get(); }
-    void            SetTextColor( const Color& rColor )
-                        { pTxtColor.reset( new Color( rColor ) ); }
+    boost::optional<Color> const & GetTextColor() const { return mxTxtColor; }
+    void            SetTextColor( boost::optional<Color> xCol ) { mxTxtColor = xCol; }
 
-    Color*          GetFieldColor() const { return pFldColor.get(); }
-    void            SetFieldColor( const Color& rColor )
-                        { pFldColor.reset( new Color( rColor ) ); }
-    void            ClearFieldColor()
-                        { pFldColor.reset(); }
+    boost::optional<Color> const & GetFieldColor() const { return mxFldColor; }
+    void            SetFieldColor( boost::optional<Color> xCol ) { mxFldColor = xCol; }
 
     sal_Int32       GetPara() const { return nPara; }
     sal_Int32       GetPos() const { return nPos; }

sd/source/ui/app/sdmod2.cxx

@@ -343,7 +343,7 @@ IMPL_LINK(SdModule, CalcFieldValueHdl, EditFieldInfo*, pInfo, void)
     }
     else if ( dynamic_cast< const SdrMeasureField* >(pField))
     {
-        pInfo->ClearFieldColor();
+        pInfo->SetFieldColor(boost::optional<Color>()); // clear the field color
     }
     else if ((pCustomPropertyField = dynamic_cast<const editeng::CustomPropertyField*>(pField)) != nullptr)
     {

sw/source/core/doc/docdraw.cxx

@@ -541,8 +541,8 @@ IMPL_LINK(SwDoc, CalcFieldValueHdl, EditFieldInfo*, pInfo, void)
     }
     else if (dynamic_cast<const SdrMeasureField*>( pField))
     {
-        // Measure field
-        pInfo->ClearFieldColor();
+        // Clear measure field
+        pInfo->SetFieldColor(boost::optional<Color>());
     }
     else if ( auto pTimeField = dynamic_cast<const SvxExtTimeField*>( pField) )
     {