More MANDATORY_FIELDS work.

Also fixes a crasher when Cancelling a FIELDS_GRID
dialog with one of the grid editors currently open.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/19762

eeschema/dialogs/dialog_label_properties.h

@@ -40,6 +40,8 @@ public:
     DIALOG_LABEL_PROPERTIES( SCH_EDIT_FRAME* parent, SCH_LABEL_BASE* aLabel );
     ~DIALOG_LABEL_PROPERTIES();
 
+    FIELDS_GRID_TABLE* GetFieldsGridTable() { return m_fields; }
+
 private:
     /**
      * wxEVT_COMMAND_ENTER event handler for single-line control.

eeschema/fields_grid_table.cpp

@@ -1046,6 +1046,13 @@ bool FIELDS_GRID_TABLE::BoolFromString( const wxString& aValue ) const
 }
 
 
+void FIELDS_GRID_TABLE::DetachFields()
+{
+    for( SCH_FIELD& field : *this )
+        field.SetParent( nullptr );
+}
+
+
 void FIELDS_GRID_TRICKS::showPopupMenu( wxMenu& menu, wxGridEvent& aEvent )
 {
     if( m_grid->GetGridCursorRow() == FOOTPRINT_FIELD && m_grid->GetGridCursorCol() == FDC_VALUE

eeschema/fields_grid_table.h

@@ -119,6 +119,8 @@ public:
     wxString StringFromBool( bool aValue ) const;
     bool BoolFromString( const wxString& aValue ) const;
 
+    void DetachFields();
+
 protected:
     void initGrid( WX_GRID* aGrid );
 

eeschema/sch_field.cpp

@@ -1507,18 +1507,28 @@ VECTOR2I SCH_FIELD::GetParentPosition() const
 
 bool SCH_FIELD::IsMandatory() const
 {
-    if( m_parent && m_parent->Type() == SCH_SHEET_T )
+    if( !m_parent )
+        return false;
+
+    switch( m_parent->Type() )
     {
+    case SCH_SHEET_T:
         return m_id == SHEETNAME
             || m_id == SHEETFILENAME;
-    }
-    else
-    {
+
+    case SCH_SYMBOL_T:
+    case LIB_SYMBOL_T:
         return m_id == REFERENCE_FIELD
             || m_id == VALUE_FIELD
             || m_id == FOOTPRINT_FIELD
             || m_id == DATASHEET_FIELD
             || m_id == DESCRIPTION_FIELD;
+
+    case SCH_GLOBAL_LABEL_T:
+        return m_id == INTERSHEET_REFS;
+
+    default:
+        return false;
     }
 }
 

eeschema/sch_io/kicad_sexpr/sch_io_kicad_sexpr.cpp

@@ -1326,6 +1326,11 @@ void SCH_IO_KICAD_SEXPR::saveText( SCH_TEXT* aText )
     aText->EDA_TEXT::Format( m_out, 0 );
     KICAD_FORMAT::FormatUuid( m_out, aText->m_Uuid );
 
+    if( label && label->Type() == SCH_GLOBAL_LABEL_T )
+        m_nextFreeFieldId = GLOBALLABEL_MANDATORY_FIELD_COUNT;
+    else
+        m_nextFreeFieldId = 0;
+
     if( label )
     {
         for( SCH_FIELD& field : label->GetFields() )

eeschema/sch_label.cpp

@@ -1799,7 +1799,7 @@ SCH_GLOBALLABEL::SCH_GLOBALLABEL( const VECTOR2I& pos, const wxString& text ) :
 
     SetVertJustify( GR_TEXT_V_ALIGN_CENTER );
 
-    m_fields.emplace_back( SCH_FIELD( pos, 0, this, wxT( "Sheet References" ) ) );
+    m_fields.emplace_back( SCH_FIELD( pos, INTERSHEET_REFS, this, wxT( "Sheet References" ) ) );
     m_fields[0].SetText( wxT( "${INTERSHEET_REFS}" ) );
     m_fields[0].SetVisible( false );
     m_fields[0].SetLayer( LAYER_INTERSHEET_REFS );

eeschema/sch_label.h

@@ -130,6 +130,17 @@ enum FLAG_SHAPE : unsigned int
 };
 
 
+enum  GLOBALLABEL_FIELD_T
+{
+    INTERSHEET_REFS = 0,
+
+    /// The first 2 are mandatory, and must be instantiated in SCH_SHEET
+    GLOBALLABEL_MANDATORY_FIELD_COUNT
+};
+
+#define GLOBALLABEL_MANDATORY_FIELDS { INTERSHEET_REFS }
+
+
 class SCH_LABEL_BASE : public SCH_TEXT
 {
 public:

eeschema/tools/sch_drawing_tools.cpp

@@ -1692,6 +1692,7 @@ SCH_TEXT* SCH_DRAWING_TOOLS::createNewText( const VECTOR2I& aPosition, int aType
         // QuasiModal required for syntax help and Scintilla auto-complete
         if( dlg.ShowQuasiModal() != wxID_OK )
         {
+            dlg.GetFieldsGridTable()->DetachFields();
             delete labelItem;
             return nullptr;
         }
@@ -1735,6 +1736,7 @@ SCH_TEXT* SCH_DRAWING_TOOLS::createNewText( const VECTOR2I& aPosition, int aType
     return textItem;
 }
 
+
 SCH_SHEET_PIN* SCH_DRAWING_TOOLS::createNewSheetPin( SCH_SHEET* aSheet, const VECTOR2I& aPosition )
 {
     SCHEMATIC_SETTINGS& settings = aSheet->Schematic()->Settings();
@@ -1751,6 +1753,7 @@ SCH_SHEET_PIN* SCH_DRAWING_TOOLS::createNewSheetPin( SCH_SHEET* aSheet, const VE
     return pin;
 }
 
+
 SCH_SHEET_PIN* SCH_DRAWING_TOOLS::createNewSheetPinFromLabel( SCH_SHEET*      aSheet,
                                                               const VECTOR2I& aPosition,
                                                               SCH_HIERLABEL*  aLabel )