Several change:

 - WTableView: Fixed calculation of first in modelRowsAboutToBeRemoved
 - SqlTraits:
   - AuxId = SurrogateId | LiteralJoinId doesn't seem to make sense
   - Added example for custom sql_value_traits (with test)

Author: RockinRoel

src/Wt/Dbo/SqlTraits.h

@@ -56,6 +56,68 @@ class SqlStatement;
  *  - Json::Object
  *  - Json::Array
  *
+ * Example for an enum that is saved as a string rather than an int:
+ * \code
+ * enum class Pet {
+ *   Cat,
+ *   Dog,
+ *   Other
+ * };
+ * 
+ * std::string petToString(Pet p) {
+ *   switch (p) {
+ *   case Pet::Cat:
+ *     return "cat";
+ *   case Pet::Dog:
+ *     return "dog";
+ *   case Pet::Other:
+ *     return "other";
+ *   }
+ *   throw std::invalid_argument("Unknown pet type: " + std::to_string(static_cast<int>(p)));
+ * }
+ * 
+ * Pet petFromString(const std::string &s) {
+ *   if (s == "cat")
+ *     return Pet::Cat;
+ *   else if (s == "dog")
+ *     return Pet::Dog;
+ *   else if (s == "other")
+ *     return Pet::Other;
+ *   else
+ *     throw std::invalid_argument("Unknown pet type: " + s);
+ * }
+ *
+ * namespace Wt {
+ * namespace Dbo {
+ *
+ * template<>
+ * struct sql_value_traits<Pet>
+ * {
+ *   static std::string type(SqlConnection *conn, int size)
+ *   {
+ *     return sql_value_traits<std::string>::type(conn, size);
+ *   }
+
+ *   static void bind(Pet p, SqlStatement *statement, int column, int size)
+ *   {
+ *     statement->bind(column, petToString(p));
+ *   }
+
+ *   static bool read(Pet &p, SqlStatement *statement, int column, int size)
+ *   {
+ *     std::string s;
+ *     bool result = statement->getResult(column, &s, size);
+ *     if (!result)
+ *       return false;
+ *     p = petFromString(s);
+ *     return true;
+ *   }
+ * };
+ *
+ * } // Dbo
+ * } // Wt
+ * \endcode
+ *
  * \sa query_result_traits
  *
  * \ingroup dbo
@@ -115,8 +177,8 @@ enum FieldFlags {
   ForeignKey = 0x20, //!< Field is (part of) a foreign key
   FirstDboField = 0x40,
   LiteralJoinId = 0x80,
-  AuxId = 0x81,
-  AliasedName = 0x100 // there is an AS in the field, so the name is aliased
+  AuxId = 0x100,
+  AliasedName = 0x200 // there is an AS in the field, so the name is aliased
 };
 
 /*! \class FieldInfo Wt/Dbo/SqlTraits.h Wt/Dbo/SqlTraits.h
@@ -170,7 +232,7 @@ class WTDBO_API FieldInfo
    */
   bool isNaturalIdField() const { return (flags_ & NaturalId) != 0; }
 
-  /*! \brief Returns whether the field is a Surroaget Id field.
+  /*! \brief Returns whether the field is a Surrogate Id field.
    */
   bool isSurrogateIdField() const { return flags_ & SurrogateId; }
 

src/Wt/WTableView.C

@@ -1528,7 +1528,7 @@ void WTableView::modelRowsAboutToBeRemoved(const WModelIndex& parent,
 				  start, end + 1);
 
   if (overlapMiddle > 0) {
-    int first = std::min(start, firstRow());
+    int first = std::max(0, start - firstRow());
 
     for (int i = 0; i < renderedColumnsCount(); ++i) {
       ColumnWidget *column = columnContainer(i);

test/dbo/DboTest.C

@@ -72,6 +72,35 @@ struct Coordinate {
   }
 };
 
+enum class Pet {
+  Cat,
+  Dog,
+  Other
+};
+
+std::string petToString(Pet p) {
+  switch (p) {
+  case Pet::Cat:
+    return "cat";
+  case Pet::Dog:
+    return "dog";
+  case Pet::Other:
+    return "other";
+  }
+  throw std::invalid_argument("Unknown pet type: " + std::to_string(static_cast<int>(p)));
+}
+
+Pet petFromString(const std::string &s) {
+  if (s == "cat")
+    return Pet::Cat;
+  else if (s == "dog")
+    return Pet::Dog;
+  else if (s == "other")
+    return Pet::Other;
+  else
+    throw std::invalid_argument("Unknown pet type: " + s);
+}
+
 std::ostream& operator<< (std::ostream& o, const Coordinate& c)
 {
   return o << "(" << c.x << ", " << c.y << ")";
@@ -87,6 +116,30 @@ namespace Wt {
       field(action, coordinate.x, name + "_x", 1000);
       field(action, coordinate.y, name + "_y", 1000);
     }
+
+    template<>
+    struct sql_value_traits<Pet>
+    {
+      static std::string type(SqlConnection *conn, int size)
+      {
+        return sql_value_traits<std::string>::type(conn, size);
+      }
+
+      static void bind(Pet p, SqlStatement *statement, int column, int size)
+      {
+        statement->bind(column, petToString(p));
+      }
+
+      static bool read(Pet &p, SqlStatement *statement, int column, int size)
+      {
+        std::string s;
+        bool result = statement->getResult(column, &s, size);
+        if (!result)
+          return false;
+        p = petFromString(s);
+        return true;
+      }
+    };
   }
 }
 
@@ -172,11 +225,22 @@ public:
   std::chrono::duration<int, std::milli> timeduration;
   bool checked;
   int i;
+  Pet pet;
   ::int64_t i64;
   long long ll;
   float f;
   double d;
 
+  A()
+    : checked(false),
+      i(0),
+      pet(Pet::Other),
+      i64(0),
+      ll(0),
+      f(0),
+      d(0)
+  { }
+
   bool operator== (const A& other) const {
     if (binary.size() != other.binary.size()){
           DEBUG(std::cerr << "ERROR: binary.size = " << binary.size()
@@ -261,6 +325,9 @@ public:
     if (i != other.i) {
       DEBUG(std::cerr << "ERROR: i = " << i << " | " << other.i << std::endl);
     }
+    if (pet != other.pet) {
+      DEBUG(std::cerr << "ERROR: pet = " << petToString(pet) << " | " << petToString(other.pet) << std::endl);
+    }
     if (i64 != other.i64) {
       DEBUG(std::cerr << "ERROR: i64 = " <<i64  << " | "
             << other.i64 << std::endl);
@@ -299,6 +366,7 @@ public:
     std::cout << "date = " << date.toString() << " ; " << other.date.toString() << std::endl;
     std::cout << "datetime = " << datetime.toString() << " ; " << other.datetime.toString() << std::endl;
     std::cout << "i = " << i << " ; " << other.i << std::endl;
+    std::cout << "pet = " << petToString(pet) << " ; " << petToString(other.pet) << std::endl;
     std::cout << "i64 = " << i64 << " ; " << other.i64 << std::endl;
     std::cout << "ll = " << ll << " ; " << other.ll << std::endl;
     std::cout << "f = " << f << " ; " << other.f << std::endl;
@@ -323,6 +391,7 @@ public:
       && timepoint == other.timepoint
       && timeduration == other.timeduration
       && i == other.i
+      && pet == other.pet
       && i64 == other.i64
       && ll == other.ll
       && checked == other.checked
@@ -355,6 +424,7 @@ public:
     dbo::field(a, timepoint, "timepoint");
     dbo::field(a, timeduration, "timeduration");
     dbo::field(a, i, "i");
+    dbo::field(a, pet, "pet");
     dbo::field(a, i64, "i64");
     dbo::field(a, ll, "ll");
     dbo::field(a, checked, "checked");
@@ -558,6 +628,7 @@ BOOST_AUTO_TEST_CASE( dbo_test1 )
   a1.timeduration = std::chrono::hours(1) + std::chrono::seconds(10);
   a1.checked = true;
   a1.i = 42;
+  a1.pet = Pet::Cat;
   a1.i64 = 9223372036854775805LL;
   a1.ll = 6066005651767221LL;
   a1.f = (float)42.42;
@@ -651,6 +722,7 @@ BOOST_AUTO_TEST_CASE( dbo_test2 )
   a1.string = "There";
   a1.checked = false;
   a1.i = 42;
+  a1.pet = Pet::Dog;
   a1.i64 = 9223372036854775804LL;
   a1.ll = 6066005651767221LL;
   a1.f = (float)42.42;
@@ -826,6 +898,7 @@ BOOST_AUTO_TEST_CASE( dbo_test4 )
     a1.modify()->wstring = "Hello";
     a1.modify()->string = "There";
     a1.modify()->i = 42;
+    a1.modify()->pet = Pet::Cat;
     a1.modify()->i64 = 9223372036854775803LL;
     a1.modify()->ll = 6066005651767220LL;
     a1.modify()->f = (float)42.42;
@@ -1658,6 +1731,7 @@ BOOST_AUTO_TEST_CASE( dbo_test14 )
   a1.string = "There";
   a1.checked = false;
   a1.i = 42;
+  a1.pet = Pet::Other;
   a1.i64 = 9223372036854775804LL;
   a1.ll = 6066005651767221LL;
   a1.f = (float)42.42;