gdk: Implement GInitable on GdkDisplayManager

Add GInitable interface with a default implementation that always
succeeds. This allows backends to override the GInitable implementation
and add their own checks to determine if the backend can be loaded.  If
a backend cannot be loaded, GDK can attempt to load the next available
backend.

Since backends may need to read any relevant options (such as the
display flag) to determine if they can be created successfully, this
patch also removes calls that attempt to create the display manager
before the options have been parsed.

https://bugzilla.gnome.org/show_bug.cgi?id=694465

1 files changed, 34 insertions, 19 deletions

diff --git a/gdk/gdkdisplaymanager.c b/gdk/gdkdisplaymanager.c
index 0a0ee85744..f4706112e8 100644
--- a/gdk/gdkdisplaymanager.c
+++ b/gdk/gdkdisplaymanager.c
@@ -125,7 +125,24 @@ static void gdk_display_manager_get_property (GObject                *object,
 
 static guint signals[LAST_SIGNAL] = { 0 };
 
-G_DEFINE_TYPE (GdkDisplayManager, gdk_display_manager, G_TYPE_OBJECT)
+static void g_initable_iface_init (GInitableIface *iface);
+
+G_DEFINE_TYPE_WITH_CODE (GdkDisplayManager, gdk_display_manager, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (G_TYPE_INITABLE, g_initable_iface_init))
+
+static gboolean
+gdk_display_manager_initable_init (GInitable     *initable,
+                                   GCancellable  *cancellable,
+                                   GError       **error)
+{
+  return TRUE;
+}
+
+static void
+g_initable_iface_init (GInitableIface *iface)
+{
+  iface->init = gdk_display_manager_initable_init;
+}
 
 static void
 gdk_display_manager_class_init (GdkDisplayManagerClass *klass)
@@ -236,33 +253,31 @@ gdk_display_manager_get (void)
       backend = g_getenv ("GDK_BACKEND");
 #ifdef GDK_WINDOWING_QUARTZ
       if (backend == NULL || strcmp (backend, "quartz") == 0)
-        manager = g_object_new (gdk_quartz_display_manager_get_type (), NULL);
-      else
+        manager = g_initable_new (gdk_quartz_display_manager_get_type (), NULL, NULL, NULL);
 #endif
 #ifdef GDK_WINDOWING_WIN32
-      if (backend == NULL || strcmp (backend, "win32") == 0)
-        manager = g_object_new (gdk_win32_display_manager_get_type (), NULL);
-      else
+      if (!manager && (backend == NULL || strcmp (backend, "win32") == 0))
+        manager = g_initable_new (gdk_win32_display_manager_get_type (), NULL, NULL, NULL);
 #endif
 #ifdef GDK_WINDOWING_X11
-      if (backend == NULL || strcmp (backend, "x11") == 0)
-        manager = g_object_new (gdk_x11_display_manager_get_type (), NULL);
-      else
+      if (!manager && (backend == NULL || strcmp (backend, "x11") == 0))
+        manager = g_initable_new (gdk_x11_display_manager_get_type (), NULL, NULL, NULL);
 #endif
 #ifdef GDK_WINDOWING_WAYLAND
-      if (backend == NULL || strcmp (backend, "wayland") == 0)
-        manager = g_object_new (gdk_wayland_display_manager_get_type (), NULL);
-      else
+      if (!manager && (backend == NULL || strcmp (backend, "wayland") == 0))
+        manager = g_initable_new (gdk_wayland_display_manager_get_type (), NULL, NULL, NULL);
 #endif
 #ifdef GDK_WINDOWING_BROADWAY
-      if (backend == NULL || strcmp (backend, "broadway") == 0)
-        manager = g_object_new (gdk_broadway_display_manager_get_type (), NULL);
-      else
+      if (!manager && (backend == NULL || strcmp (backend, "broadway") == 0))
+        manager = g_initable_new (gdk_broadway_display_manager_get_type (), NULL, NULL, NULL);
 #endif
-      if (backend != NULL)
-        g_error ("Unsupported GDK backend: %s", backend);
-      else
-        g_error ("No GDK backend found");
+      if (!manager)
+        {
+          if (backend != NULL)
+            g_error ("Unsupported GDK backend: %s", backend);
+          else
+            g_error ("No GDK backend found");
+        }
     }
 
   return manager;