[glibmm/glibmm-2-62] Glib::Property: Update for compatibility with Gtk::Builder

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 39aa933b4fcf3830cf072caa4307acae8c3f18ae
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Tue Sep 17 09:22:16 2019 +0200

    Glib::Property: Update for compatibility with Gtk::Builder
    
    When an object is created by GtkBuilder, the GObject-derived C object is
    created and its properties set before there is a C++ wrapper to store
    the property values in. Glib::custom_set_property_callback() stores
    property values in a data structure reached via a GQuark in the object.
    PropertyBase::lookup_property() copies those property values to the
    PropertyBase objects when the C++ wrapper is created.

 glib/glibmm/property.cc | 116 +++++++++++++++++++++++++++++++++++-------------
 glib/glibmm/property.h  |  12 ++++-
 2 files changed, 96 insertions(+), 32 deletions(-)
---
diff --git a/glib/glibmm/property.cc b/glib/glibmm/property.cc
index 30de7485..a2624e53 100644
--- a/glib/glibmm/property.cc
+++ b/glib/glibmm/property.cc
@@ -19,6 +19,7 @@
 #include <glibmm/object.h>
 #include <glibmm/class.h>
 #include <cstddef>
+#include <map>
 
 // Temporary hack till GLib gets fixed.
 #undef G_STRLOC
@@ -76,19 +77,34 @@ destroy_notify_obj_iface_props(void* data)
   }
 }
 
-// The type that holds pointers to the custom properties of custom types.
-using custom_properties_type = std::vector<Glib::PropertyBase*>;
+struct custom_properties_type
+{
+  // Pointers to the custom properties of custom types.
+  std::vector<Glib::PropertyBase*> prop_base_vector;
+
+  // Property values, set by custom_set_property_callback() before a
+  // Glib::PropertyBase wrapper has been created. E.g. if the containing
+  // custom GObject has been created by GtkBuilder.
+  std::map<unsigned int, GValue*> prop_value_map;
+};
+
 // The quark used for storing/getting the custom properties of custom types.
 static const GQuark custom_properties_quark =
   g_quark_from_string("gtkmm_CustomObject_custom_properties");
 
-// Delete the vector of pointers to custom properties when an object of
-// a custom type is finalized.
-void
-destroy_notify_obj_custom_props(void* data)
+// Delete the custom properties data when an object of a custom type is finalized.
+void destroy_notify_obj_custom_props(void* data)
 {
-  // Shallow deletion. The vector does not own the objects pointed to.
-  delete static_cast<custom_properties_type*>(data);
+  auto obj_custom_props = static_cast<custom_properties_type*>(data);
+  // prop_base_vector does not own the objects pointed to.
+  // prop_value_map owns the objects pointed to.
+  const auto map_end = obj_custom_props->prop_value_map.end();
+  for (auto it = obj_custom_props->prop_value_map.begin(); it != map_end; ++it)
+  {
+    g_value_unset(it->second);
+    g_free(it->second);
+  }
+  delete obj_custom_props;
 }
 
 custom_properties_type*
@@ -139,19 +155,32 @@ custom_get_property_callback(
   }
   else
   {
+    auto obj_custom_props = get_obj_custom_props(object);
+    const unsigned index = property_id - iface_props_size - 1;
+
     if (Glib::ObjectBase* const wrapper = Glib::ObjectBase::_get_current_wrapper(object))
     {
-      auto obj_custom_props =
-        static_cast<custom_properties_type*>(g_object_get_qdata(object, custom_properties_quark));
-      const unsigned index = property_id - iface_props_size - 1;
-
-      if (obj_custom_props && index < obj_custom_props->size() &&
-          (*obj_custom_props)[index]->object_ == wrapper &&
-          (*obj_custom_props)[index]->param_spec_ == param_spec)
-        g_value_copy((*obj_custom_props)[index]->value_.gobj(), value);
+      if (obj_custom_props && index < obj_custom_props->prop_base_vector.size())
+      {
+        const Glib::PropertyBase* prop_base = (obj_custom_props->prop_base_vector)[index];
+        if (prop_base->object_ == wrapper && prop_base->param_spec_ == param_spec)
+          g_value_copy(prop_base->value_.gobj(), value);
+        else
+          G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, param_spec);
+      }
       else
         G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, param_spec);
     }
+    else
+    {
+      // No C++ wrapper exists. Check if there is a value in obj_custom_props->prop_value_map.
+      auto it = obj_custom_props->prop_value_map.find(index);
+      if (it != obj_custom_props->prop_value_map.end())
+        g_value_copy(it->second, value);
+      else
+        // else return the property's default value.
+        g_value_copy(g_param_spec_get_default_value(param_spec), value);
+    }
   }
 }
 
@@ -164,7 +193,7 @@ custom_set_property_callback(
 
   GType custom_type = G_OBJECT_TYPE(object);
 
-  Class::iface_properties_type* iface_props = static_cast<Class::iface_properties_type*>(
+  auto iface_props = static_cast<Class::iface_properties_type*>(
     g_type_get_qdata(custom_type, Class::iface_properties_quark));
 
   Class::iface_properties_type::size_type iface_props_size = 0;
@@ -176,7 +205,7 @@ custom_set_property_callback(
   {
     // If the object does not have interface property values,
     // copy the class's default values to the object.
-    Class::iface_properties_type* obj_iface_props = static_cast<Class::iface_properties_type*>(
+    auto obj_iface_props = static_cast<Class::iface_properties_type*>(
       g_object_get_qdata(object, Class::iface_properties_quark));
     if (!obj_iface_props)
     {
@@ -197,22 +226,40 @@ custom_set_property_callback(
   }
   else
   {
+    auto obj_custom_props = get_obj_custom_props(object);
+    const unsigned index = property_id - iface_props_size - 1;
+
     if (Glib::ObjectBase* const wrapper = Glib::ObjectBase::_get_current_wrapper(object))
     {
-      auto obj_custom_props =
-        static_cast<custom_properties_type*>(g_object_get_qdata(object, custom_properties_quark));
-      const unsigned index = property_id - iface_props_size - 1;
-
-      if (obj_custom_props && index < obj_custom_props->size() &&
-          (*obj_custom_props)[index]->object_ == wrapper &&
-          (*obj_custom_props)[index]->param_spec_ == param_spec)
+      if (obj_custom_props && index < obj_custom_props->prop_base_vector.size())
       {
-        g_value_copy(value, (*obj_custom_props)[index]->value_.gobj());
-        g_object_notify_by_pspec(object, param_spec);
+        Glib::PropertyBase* prop_base = (obj_custom_props->prop_base_vector)[index];
+        if (prop_base->object_ == wrapper && prop_base->param_spec_ == param_spec)
+        {
+          g_value_copy(value, prop_base->value_.gobj());
+          g_object_notify_by_pspec(object, param_spec);
+        }
+        else
+          G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, param_spec);
       }
       else
         G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, param_spec);
     }
+    else
+    {
+      // No C++ wrapper exists. Store the value in obj_custom_props->prop_value_map.
+      auto it = obj_custom_props->prop_value_map.find(index);
+      if (it != obj_custom_props->prop_value_map.end())
+        g_value_copy(value, it->second);
+      else
+      {
+        GValue* g_value = g_new0(GValue, 1);
+        g_value_init(g_value, G_VALUE_TYPE(value));
+        g_value_copy(value, g_value);
+        obj_custom_props->prop_value_map[index] = g_value;
+      }
+      g_object_notify_by_pspec(object, param_spec);
+    }
   }
 }
 
@@ -244,7 +291,16 @@ PropertyBase::lookup_property(const Glib::ustring& name)
     g_assert(G_PARAM_SPEC_VALUE_TYPE(param_spec_) == G_VALUE_TYPE(value_.gobj()));
     g_param_spec_ref(param_spec_);
 
-    get_obj_custom_props(object_->gobj())->emplace_back(this);
+    auto obj_custom_props = get_obj_custom_props(object_->gobj());
+    const unsigned int pos_in_obj_custom_props = obj_custom_props->prop_base_vector.size();
+    obj_custom_props->prop_base_vector.emplace_back(this);
+
+    // If a value has been set by a call to custom_set_property_callback()
+    // before this Glib::PropertyBase wrapper was creared, copy that value
+    // to value_.
+    auto it = obj_custom_props->prop_value_map.find(pos_in_obj_custom_props);
+    if (it != obj_custom_props->prop_value_map.end())
+      g_value_copy(it->second, value_.gobj());
   }
 
   return (param_spec_ != nullptr);
@@ -270,8 +326,8 @@ PropertyBase::install_property(GParamSpec* param_spec)
 
   auto obj_custom_props = get_obj_custom_props(object_->gobj());
 
-  const unsigned int pos_in_obj_custom_props = obj_custom_props->size();
-  obj_custom_props->emplace_back(this);
+  const unsigned int pos_in_obj_custom_props = obj_custom_props->prop_base_vector.size();
+  obj_custom_props->prop_base_vector.emplace_back(this);
 
   // We need to offset by 1 as zero is an invalid property id.
   const unsigned int property_id = pos_in_obj_custom_props + iface_props_size + 1;
diff --git a/glib/glibmm/property.h b/glib/glibmm/property.h
index 190b10c9..4103b9c5 100644
--- a/glib/glibmm/property.h
+++ b/glib/glibmm/property.h
@@ -129,7 +129,7 @@ private:
  *  * The default value and the minimum and maximum bounds (depending on the type of the property).
  *  * Flags, defining, among other things, whether the property can be read or written.
  *
- * This Property class currently supports the name, nick name, description default value and flags.
+ * This %Property class currently supports the name, nick name, description, default value and flags.
  * The minimum and maximum bounds are set to the full range of the value.
  * Because of internal implementation, flags shouldn't be set to values: Glib::PARAM_STATIC_NAME,
  * Glib::PARAM_STATIC_NICK, Glib::PARAM_STATIC_BLURB, Glib::PARAM_CONSTRUCT and
@@ -146,7 +146,7 @@ private:
  * declare all properties as direct data members of the type.
  *
  * You may register new properties for your class (actually for the underlying GType)
- * simply by adding a Property instance as a class member.
+ * simply by adding a %Property instance as a class member.
  * However, your constructor must call the Glib::ObjectBase constructor with a new GType name,
  * in order to register a new GType.
  *
@@ -175,6 +175,14 @@ private:
  *   Glib::Property<int> property_myint_;
  * };
  * @endcode
+ *
+ * @par %Glib::Property and Gtk::Builder
+ * The new GType is registered, and the properties installed in the GType, when
+ * the first instance of the class is created. When the underlying GObject-derived
+ * instance is created before the wrapping Glib::Object-derived instance, you may
+ * have to first create a dummy instance just to register the GType.
+ * See the description of Gtk::Builder for instructions how to combine %Property
+ * with Gtk::Builder.
  */
 template <class T>
 class Property : public PropertyBase