[Fix #7597] Attribute Table: Reintroduce locale aware sorting

src/gui/attributetable/qgsattributetablefiltermodel.cpp

@@ -57,7 +57,33 @@ bool QgsAttributeTableFilterModel::lessThan( const QModelIndex &left, const QMod
     }
   }
 
-  return QSortFilterProxyModel::lessThan( left, right );
+
+  QVariant leftData = left.data( QgsAttributeTableModel::SortRole );
+  QVariant rightData = right.data( QgsAttributeTableModel::SortRole );
+
+  if ( leftData.isNull() )
+    return true;
+
+  if ( rightData.isNull() )
+    return false;
+
+  switch ( leftData.type() )
+  {
+    case QVariant::Int:
+    case QVariant::UInt:
+    case QVariant::LongLong:
+    case QVariant::ULongLong:
+      return leftData.toLongLong() < rightData.toLongLong();
+
+    case QVariant::Double:
+      return leftData.toDouble() < rightData.toDouble();
+
+    default:
+      return leftData.toString().localeAwareCompare( rightData.toString() ) < 0;
+  }
+
+  // Avoid warning. Will never reach this
+  return false;
 }
 
 void QgsAttributeTableFilterModel::setSelectedOnTop( bool selectedOnTop )

src/gui/attributetable/qgsattributetablemodel.cpp

@@ -495,6 +495,12 @@ QVariant QgsAttributeTableModel::data( const QModelIndex &index, int role ) cons
 
   const QVariant &val = mFeat.attribute( fieldId );
 
+  // For sorting return unprocessed value
+  if ( SortRole == role )
+  {
+    return val;
+  }
+
   if ( val.isNull() )
   {
     // if the value is NULL, show that in table, but don't show "NULL" text in editor
@@ -522,10 +528,6 @@ QVariant QgsAttributeTableModel::data( const QModelIndex &index, int role ) cons
     }
   }
 
-  if ( role == SortRole )
-  {
-    return val;
-  }
 
   return field.displayString( val );
 }