[libdazzle] properties-group: be more flexible in use

[Christian Hergert <chergert src gnome org>]

commit 346fc2c530e252f7a81b35e18bb363c5e6b45af1
Author: Christian Hergert <chergert redhat com>
Date:   Fri Jul 7 18:01:15 2017 -0700

    properties-group: be more flexible in use
    
    We can allow the creation of actions without a real object
    instance. We can also be more flexible about changing the object
    at runtime.
    
    Both of these can be useful when needing to setup initial
    state before the objects are ready.

 src/actions/dzl-properties-group.c |  169 +++++++++++++++++++++++++++++-------
 src/actions/dzl-properties-group.h |    1 +
 2 files changed, 138 insertions(+), 32 deletions(-)
---
diff --git a/src/actions/dzl-properties-group.c b/src/actions/dzl-properties-group.c
index fb0718f..1ccd9b6 100644
--- a/src/actions/dzl-properties-group.c
+++ b/src/actions/dzl-properties-group.c
@@ -51,6 +51,11 @@ struct _DzlPropertiesGroup
   GObject parent_instance;
 
   /*
+   * All subsequent set_object() calls must be this type.
+   */
+  GType prerequisite;
+
+  /*
    * Weak ref to the object we are monitoring for property changes.
    * We hold both a GWeakRef and a g_object_weak_ref() on the object
    * so that we can get notified of destruction *AND* know when we
@@ -83,6 +88,7 @@ typedef struct
 enum {
   PROP_0,
   PROP_OBJECT,
+  PROP_OBJECT_TYPE,
   N_PROPS
 };
 
@@ -493,22 +499,13 @@ get_state_type_for_type (GType type)
 }
 
 static void
-dzl_properties_group_weak_notify (gpointer  data,
-                                  GObject  *where_object_was)
+dzl_properties_group_notify_all_disabled (DzlPropertiesGroup *self)
 {
-  DzlPropertiesGroup *self = data;
-
   g_assert (DZL_IS_PROPERTIES_GROUP (self));
 
-  /*
-   * Mark all of the actions as disabled due to losing our reference
-   * on the source object.
-   */
-
   for (guint i = 0; i < self->mappings->len; i++)
     {
       const Mapping *mapping = &g_array_index (self->mappings, Mapping, i);
-
       g_action_group_action_enabled_changed (G_ACTION_GROUP (self),
                                              mapping->action_name,
                                              FALSE);
@@ -516,15 +513,50 @@ dzl_properties_group_weak_notify (gpointer  data,
 }
 
 static void
+dzl_properties_group_weak_notify (gpointer  data,
+                                  GObject  *where_object_was)
+{
+  DzlPropertiesGroup *self = data;
+
+  g_assert (DZL_IS_PROPERTIES_GROUP (self));
+
+  dzl_properties_group_notify_all_disabled (self);
+}
+
+static void
 dzl_properties_group_set_object (DzlPropertiesGroup *self,
                                  GObject            *object)
 {
+  g_autoptr(GObject) old_object = NULL;
+
   g_assert (DZL_IS_PROPERTIES_GROUP (self));
   g_assert (!object || G_IS_OBJECT (object));
 
+  old_object = g_weak_ref_get (&self->object_ref);
+
+  /* Nothing to do if we aren't changing anything */
+  if (object == old_object)
+    return;
+
+  if (self->prerequisite == G_TYPE_INVALID && object != NULL)
+    self->prerequisite = G_OBJECT_TYPE (object);
+
+  /* Disconnect previous life-cycle tracking */
+  if (old_object != NULL)
+    {
+      g_signal_handlers_disconnect_by_func (old_object,
+                                            G_CALLBACK (dzl_properties_group_notify),
+                                            self);
+      g_object_weak_unref (old_object,
+                           dzl_properties_group_weak_notify,
+                           self);
+      g_weak_ref_set (&self->object_ref, NULL);
+    }
+
+  /* Mark all actions as disabled if we lost our object */
   if (object == NULL)
     {
-      g_critical ("DzlPropertiesGroup: object must be non-NULL.");
+      dzl_properties_group_notify_all_disabled (self);
       return;
     }
 
@@ -541,6 +573,17 @@ dzl_properties_group_set_object (DzlPropertiesGroup *self,
   g_object_weak_ref (G_OBJECT (object),
                      dzl_properties_group_weak_notify,
                      self);
+
+  /* Emit state changes for all properties */
+  for (guint i = 0; i < self->mappings->len; i++)
+    {
+      const Mapping *mapping = &g_array_index (self->mappings, Mapping, i);
+      g_autoptr(GVariant) state = get_action_state (object, mapping);
+
+      g_action_group_action_state_changed (G_ACTION_GROUP (self),
+                                           mapping->action_name,
+                                           state);
+    }
 }
 
 static void
@@ -550,10 +593,17 @@ dzl_properties_group_finalize (GObject *object)
   g_autoptr(GObject) weak_obj = NULL;
 
   weak_obj = g_weak_ref_get (&self->object_ref);
+
   if (weak_obj != NULL)
-    g_object_weak_unref (weak_obj,
-                         dzl_properties_group_weak_notify,
-                         self);
+    {
+      /*
+       * No need to disconnect signal handler as we are in finalize and
+       * g_signal_connect_object() tracks this for us.
+       */
+      g_object_weak_unref (weak_obj,
+                           dzl_properties_group_weak_notify,
+                           self);
+    }
 
   g_weak_ref_clear (&self->object_ref);
 
@@ -576,6 +626,10 @@ dzl_properties_group_get_property (GObject    *object,
       g_value_take_object (value, g_weak_ref_get (&self->object_ref));
       break;
 
+    case PROP_OBJECT_TYPE:
+      g_value_set_gtype (value, self->prerequisite);
+      break;
+
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
     }
@@ -595,6 +649,12 @@ dzl_properties_group_set_property (GObject      *object,
       dzl_properties_group_set_object (self, g_value_get_object (value));
       break;
 
+    case PROP_OBJECT_TYPE:
+      if (g_value_get_gtype (value) != G_TYPE_INVALID &&
+          g_value_get_gtype (value) != G_TYPE_OBJECT)
+        self->prerequisite = g_value_get_gtype (value);
+      break;
+
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
     }
@@ -614,7 +674,14 @@ dzl_properties_group_class_init (DzlPropertiesGroupClass *klass)
                          "Object",
                          "The source object for the properties",
                          G_TYPE_OBJECT,
-                         (G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_STATIC_STRINGS));
+                         (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
+
+  properties [PROP_OBJECT_TYPE] =
+    g_param_spec_gtype ("object-type",
+                        "Object Type",
+                        "A type the object must conform to.",
+                        G_TYPE_OBJECT,
+                        (G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY | G_PARAM_STATIC_STRINGS));
 
   g_object_class_install_properties (object_class, N_PROPS, properties);
 }
@@ -648,8 +715,11 @@ dzl_properties_group_init (DzlPropertiesGroup *self)
 DzlPropertiesGroup *
 dzl_properties_group_new (GObject *object)
 {
+  g_return_val_if_fail (G_IS_OBJECT (object), NULL);
+
   return g_object_new (DZL_TYPE_PROPERTIES_GROUP,
                        "object", object,
+                       "object-type", G_OBJECT_TYPE (object),
                        NULL);
 }
 
@@ -673,8 +743,7 @@ dzl_properties_group_add_property_full (DzlPropertiesGroup *self,
                                         const gchar        *property_name,
                                         DzlPropertiesFlags  flags)
 {
-  g_autoptr(GObject) object = NULL;
-  GObjectClass *object_class;
+  GObjectClass *object_class = NULL;
   GParamSpec *pspec;
   Mapping mapping = { 0 };
 
@@ -682,22 +751,27 @@ dzl_properties_group_add_property_full (DzlPropertiesGroup *self,
   g_return_if_fail (name != NULL);
   g_return_if_fail (property_name != NULL);
 
-  object = g_weak_ref_get (&self->object_ref);
-
-  if (object == NULL)
+  if (self->prerequisite == G_TYPE_INVALID)
     {
-      g_warning ("Cannot add property, object was already disposed.");
+      g_warning ("Cannot add properties before object has been set.");
       return;
     }
 
-  object_class = G_OBJECT_GET_CLASS (object);
+  object_class = g_type_class_ref (self->prerequisite);
+
+  if (object_class == NULL || !G_IS_OBJECT_CLASS (object_class))
+    {
+      g_warning ("Implausable result for prerequisite, not a GObjectClass");
+      goto failure;
+    }
+
   pspec = g_object_class_find_property (object_class, property_name);
 
   if (pspec == NULL)
     {
       g_warning ("No such property \"%s\" on type %s",
-                 property_name, G_OBJECT_TYPE_NAME (object));
-      return;
+                 property_name, G_OBJECT_CLASS_NAME (object_class));
+      goto failure;
     }
 
   mapping.action_name = g_intern_string (name);
@@ -709,11 +783,14 @@ dzl_properties_group_add_property_full (DzlPropertiesGroup *self,
 
   /* we already warned, ignore this */
   if (mapping.state_type == NULL)
-    return;
+    goto failure;
 
   g_array_append_val (self->mappings, mapping);
 
   g_action_group_action_added (G_ACTION_GROUP (self), mapping.action_name);
+
+failure:
+  g_clear_pointer (&object_class, g_type_class_unref);
 }
 
 /**
@@ -784,22 +861,26 @@ dzl_properties_group_remove (DzlPropertiesGroup *self,
 void
 dzl_properties_group_add_all_properties (DzlPropertiesGroup *self)
 {
-  g_autoptr(GObject) object = NULL;
   g_autofree GParamSpec **pspec = NULL;
-  GObjectClass *object_class;
+  GObjectClass *object_class = NULL;
   guint n_pspec = 0;
 
   g_return_if_fail (DZL_IS_PROPERTIES_GROUP (self));
 
-  object = g_weak_ref_get (&self->object_ref);
-
-  if (object == NULL)
+  if (self->prerequisite == G_TYPE_INVALID)
     {
-      g_warning ("Cannot add properties, object has already been disposed");
+      g_warning ("Cannot add properties, no object has been set");
       return;
     }
 
-  object_class = G_OBJECT_GET_CLASS (object);
+  object_class = g_type_class_ref (self->prerequisite);
+
+  if (object_class == NULL || !G_IS_OBJECT_CLASS (object_class))
+    {
+      g_warning ("Implausable result, not a GObjectClass");
+      goto failure;
+    }
+
   pspec = g_object_class_list_properties (object_class, &n_pspec);
 
   for (guint i = 0; i < n_pspec; i++)
@@ -818,4 +899,28 @@ dzl_properties_group_add_all_properties (DzlPropertiesGroup *self)
           break;
         }
     }
+
+failure:
+  g_clear_pointer (&object_class, g_type_class_unref);
+}
+
+/**
+ * dzl_properties_group_new_for_type:
+ * @object_type: A #GObjectClass based type
+ *
+ * This creates a new #DzlPropertiesGroup for which the initial object is
+ * %NULL.
+ *
+ * Set @object_type to a type of a class which is a #GObject-based type.
+ *
+ * Returns: (transfer none): A #DzlPropertiesGroup.
+ */
+DzlPropertiesGroup *
+dzl_properties_group_new_for_type (GType object_type)
+{
+  g_return_val_if_fail (g_type_is_a (object_type, G_TYPE_OBJECT), NULL);
+
+  return g_object_new (DZL_TYPE_PROPERTIES_GROUP,
+                       "object-type", object_type,
+                       NULL);
 }
diff --git a/src/actions/dzl-properties-group.h b/src/actions/dzl-properties-group.h
index f30d748..7722a6c 100644
--- a/src/actions/dzl-properties-group.h
+++ b/src/actions/dzl-properties-group.h
@@ -33,6 +33,7 @@ typedef enum
 } DzlPropertiesFlags;
 
 DzlPropertiesGroup *dzl_properties_group_new                (GObject            *object);
+DzlPropertiesGroup *dzl_properties_group_new_for_type       (GType               object_type);
 void                dzl_properties_group_add_property       (DzlPropertiesGroup *self,
                                                              const gchar        *name,
                                                              const gchar        *property_name);