[balsa] mailbox: LibBalsaMailbox is abstract

[Peter Bloomfield <peterb src gnome org>]

commit 8275dc434d9bdcbd5fd11c26a064ef451c9b94d0
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Fri May 22 13:13:05 2020 -0400

    mailbox: LibBalsaMailbox is abstract
    
    Define it as such, to show that it cannot be instantiated. Similarly
    LibBalsaMailboxLocal and LibBalsaMailboxRemote.

 libbalsa/mailbox.c        | 20 ++++++++++----------
 libbalsa/mailbox_local.c  |  4 ++--
 libbalsa/mailbox_remote.c |  6 +++---
 3 files changed, 15 insertions(+), 15 deletions(-)
---
diff --git a/libbalsa/mailbox.c b/libbalsa/mailbox.c
index 42e34e5bf..603123184 100644
--- a/libbalsa/mailbox.c
+++ b/libbalsa/mailbox.c
@@ -174,16 +174,16 @@ struct _LibBalsaMailboxPrivate {
     ((LibBalsaMailboxIndexEntry *) (((msgno) <= (priv)->mindex->len) ? \
      g_ptr_array_index((priv)->mindex, (msgno) - 1) : NULL))
 
-G_DEFINE_TYPE_WITH_CODE(LibBalsaMailbox,
-                        libbalsa_mailbox,
-                        G_TYPE_OBJECT,
-                        G_IMPLEMENT_INTERFACE(GTK_TYPE_TREE_MODEL,
-                                              mailbox_model_init)
-                        G_IMPLEMENT_INTERFACE(GTK_TYPE_TREE_DRAG_SOURCE,
-                                              mailbox_drag_source_init)
-                        G_IMPLEMENT_INTERFACE(GTK_TYPE_TREE_SORTABLE,
-                                              mailbox_sortable_init)
-                        G_ADD_PRIVATE(LibBalsaMailbox)
+G_DEFINE_ABSTRACT_TYPE_WITH_CODE(LibBalsaMailbox,
+                                 libbalsa_mailbox,
+                                 G_TYPE_OBJECT,
+                                 G_IMPLEMENT_INTERFACE(GTK_TYPE_TREE_MODEL,
+                                                       mailbox_model_init)
+                                 G_IMPLEMENT_INTERFACE(GTK_TYPE_TREE_DRAG_SOURCE,
+                                                       mailbox_drag_source_init)
+                                 G_IMPLEMENT_INTERFACE(GTK_TYPE_TREE_SORTABLE,
+                                                       mailbox_sortable_init)
+                                 G_ADD_PRIVATE(LibBalsaMailbox)
                        )
 
 static void
diff --git a/libbalsa/mailbox_local.c b/libbalsa/mailbox_local.c
index ce4b52e2c..34f342a0e 100644
--- a/libbalsa/mailbox_local.c
+++ b/libbalsa/mailbox_local.c
@@ -130,8 +130,8 @@ static void libbalsa_mailbox_local_check(LibBalsaMailbox *mailbox);
 /* LibBalsaMailboxLocal class method: */
 static void lbm_local_real_remove_files(LibBalsaMailboxLocal * local);
 
-G_DEFINE_TYPE_WITH_PRIVATE(LibBalsaMailboxLocal, libbalsa_mailbox_local,
-                           LIBBALSA_TYPE_MAILBOX)
+G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE(LibBalsaMailboxLocal, libbalsa_mailbox_local,
+                                    LIBBALSA_TYPE_MAILBOX)
 
 static void
 libbalsa_mailbox_local_class_init(LibBalsaMailboxLocalClass * klass)
diff --git a/libbalsa/mailbox_remote.c b/libbalsa/mailbox_remote.c
index 5904b4577..6f40790c0 100644
--- a/libbalsa/mailbox_remote.c
+++ b/libbalsa/mailbox_remote.c
@@ -35,9 +35,9 @@ struct _LibBalsaMailboxRemotePrivate {
     LibBalsaServer *server;
 };
 
-G_DEFINE_TYPE_WITH_PRIVATE(LibBalsaMailboxRemote,
-                           libbalsa_mailbox_remote,
-                           LIBBALSA_TYPE_MAILBOX)
+G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE(LibBalsaMailboxRemote,
+                                    libbalsa_mailbox_remote,
+                                    LIBBALSA_TYPE_MAILBOX)
 
 static void
 libbalsa_mailbox_remote_class_init(LibBalsaMailboxRemoteClass * klass)