[libpeas] Add new API peas_engine_get_default()

[Steve Frécinaux <sfre src gnome org>]

commit b5790681ee0a6239be515c56923cb7e80cfb2486
Author: Steve Frécinaux <code istique net>
Date:   Thu Aug 26 10:58:21 2010 +0200

    Add new API peas_engine_get_default()
    
    https://bugzilla.gnome.org/show_bug.cgi?id=628194

 libpeas/peas-engine.c |   26 ++++++++++++++++++++++++++
 libpeas/peas-engine.h |    1 +
 2 files changed, 27 insertions(+), 0 deletions(-)
---
diff --git a/libpeas/peas-engine.c b/libpeas/peas-engine.c
index ef13770..e88e690 100644
--- a/libpeas/peas-engine.c
+++ b/libpeas/peas-engine.c
@@ -57,6 +57,8 @@
  **/
 G_DEFINE_TYPE (PeasEngine, peas_engine, G_TYPE_OBJECT);
 
+static PeasEngine *default_engine = NULL;
+
 /* Signals */
 enum {
   LOAD_PLUGIN,
@@ -291,6 +293,12 @@ add_loader (PeasEngine       *engine,
 static void
 peas_engine_init (PeasEngine *engine)
 {
+  /* Set the default engine pointer, for peas_engine_get_default().
+   * We only allow one single instance of a PeasEngine subclass. */
+  g_assert (default_engine == NULL);
+  default_engine = engine;
+  g_object_add_weak_pointer (engine, &default_engine);
+
   if (!g_module_supported ())
     {
       g_warning ("libpeas is not able to initialize the plugins engine.");
@@ -1105,3 +1113,21 @@ peas_engine_new (void)
   return PEAS_ENGINE (g_object_new (PEAS_TYPE_ENGINE,
                                     NULL));
 }
+
+/**
+ * peas_engine_get_default:
+ *
+ * Return the existing instance of #PeasEngine or a subclass of it.
+ * If no #PeasEngine subclass has been instantiated yet, the first call
+ * of this function will return a new instance of #PeasEngine.
+ *
+ * Returns: the existing instance of #PeasEngine.
+ */
+PeasEngine *
+peas_engine_get_default (void)
+{
+  if (default_engine == NULL)
+    return peas_engine_new ();
+
+  return default_engine;
+}
diff --git a/libpeas/peas-engine.h b/libpeas/peas-engine.h
index 1194b69..0e7bd86 100644
--- a/libpeas/peas-engine.h
+++ b/libpeas/peas-engine.h
@@ -69,6 +69,7 @@ struct _PeasEngineClass {
 
 GType             peas_engine_get_type            (void) G_GNUC_CONST;
 PeasEngine       *peas_engine_new                 (void);
+PeasEngine       *peas_engine_get_default         (void);
 
 void              peas_engine_add_search_path     (PeasEngine      *engine,
                                                    const gchar     *plugin_dir,