Fields in symbols: Ensure visibility is correctly set when reading a file

Also ensure default fields visibility is correctly set when creating a symbol
Change default field visibility to true in SCH_FIELD Ctor

Fixes https://gitlab.com/kicad/code/kicad/-/issues/17767

eeschema/lib_symbol.cpp

@@ -112,6 +112,17 @@ LIB_SYMBOL::LIB_SYMBOL( const wxString& aName, LIB_SYMBOL* aParent, SYMBOL_LIB*
     for( int i = 0; i < MANDATORY_FIELDS; i++ )
         m_drawings[SCH_FIELD_T].push_back( new SCH_FIELD( this, i ) );
 
+    // Ensure reference and value fields are visible when creating a lib symbol
+    // whatever the SCH_FIELD Ctor default value is.
+    GetReferenceField().SetVisible( true );
+    GetValueField().SetVisible( true );
+
+    // Set visibilty to false for these other mandatory fields (at lest for now)
+    // whatever the SCH_FIELD Ctor default value is.
+    GetFootprintField().SetVisible( false );
+    GetDatasheetField().SetVisible( false );
+    GetDescriptionField().SetVisible( false );
+
     SetName( aName );
 
     if( aParent )

eeschema/sch_field.cpp

@@ -71,7 +71,7 @@ SCH_FIELD::SCH_FIELD( const VECTOR2I& aPos, int aFieldId, SCH_ITEM* aParent,
 
     SetTextPos( aPos );
     SetId( aFieldId );  // will also set the layer
-    SetVisible( false );
+    SetVisible( true );
 }
 
 

eeschema/sch_io/kicad_sexpr/sch_io_kicad_sexpr_parser.cpp

@@ -891,6 +891,10 @@ SCH_FIELD* SCH_IO_KICAD_SEXPR_PARSER::parseProperty( std::unique_ptr<LIB_SYMBOL>
     std::unique_ptr<SCH_FIELD> field = std::make_unique<SCH_FIELD>( aSymbol.get(),
                                                                     MANDATORY_FIELDS );
 
+    // By default, fieds are visible.
+    // Invisible fields have the hide style or keyword specified in file
+    field->SetVisible( true );
+
     T token = NextTok();
 
     if( !IsSymbol( token ) )