xo-facet xo-object2: facet fixes + IPrintable_DString

codegen/facet.hpp.j2

@@ -18,4 +18,8 @@
 #include "{{impl_hpp_subdir}}/{{iface_facet_xfer_hpp_fname}}"
 #include "{{impl_hpp_subdir}}/{{router_facet_hpp_fname}}"
 
+{% for include_fname in user_hpp_includes %}
+#include {{include_fname}}
+{% endfor %}
+
 /* end {{facet_hpp_fname}} */

codegen/genfacet

@@ -93,6 +93,8 @@ def gen_facet(env,
 
     # extra include files (or perhaps other definitions)
     facet_includes = idl['includes']
+    # extra (post) includes for user .hpp e.g. Sequence.hpp
+    user_hpp_includes = idl['user_hpp_includes']
     # arbitrary text after includes, before opening namespaces
     facet_pretext = idl['pretext']
     # detail
@@ -163,6 +165,8 @@ def gen_facet(env,
         'facet_ns2': facet_ns2,
         'facet_name_lc': facet_name_lc,
         'facet_hpp_fname': facet_hpp_fname,
+        #
+        'user_hpp_includes': user_hpp_includes,
         #'name': facet_name,
         'idl_fname': idl_fname,
         #

codegen/router_facet.hpp.j2

@@ -46,6 +46,9 @@ public:
     {% endif %}
     {{router_facet}}() {}
     {{router_facet}}(Object::DataPtr data) : Object{std::move(data)} {}
+    {{router_facet}}(const {{abstract_facet}} * iface, void * data)
+      requires std::is_same_v<typename Object::DataType, xo::facet::DVariantPlaceholder>
+      : Object(iface, data) {}
 
     {% if using_dox %}
     ///@}
@@ -61,7 +64,7 @@ public:
     }
     {% endfor %}
 
-    // non-const methods
+    // non-const methods (still const in router!)
     {% for md in nonconst_methods %}
     {{md.return_type}} {{md.name}}({{md.args | argsnodata}}) {{md | staticqual}} {
         return O::iface()->{{md.name}}({{md.args | argrouting}});