[gegl] buffer-source: Correctly store result of g_signal_connect

[Jon Nordby <jonnor src gnome org>]

commit d9a636391c5004c2d54d11c2f9274c4f22bf14c8
Author: Jon Nordby <jononor gmail com>
Date:   Sun May 6 04:48:07 2012 +0200

    buffer-source: Correctly store result of g_signal_connect
    
    Also add assertions to validate the invariant we rely on.

 operations/common/buffer-source.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/operations/common/buffer-source.c b/operations/common/buffer-source.c
index 03f5822..4d414c1 100644
--- a/operations/common/buffer-source.c
+++ b/operations/common/buffer-source.c
@@ -89,11 +89,13 @@ my_set_property (GObject  *gobject,
   {
     case PROP_buffer:
       if (o->buffer) {
+        // Invariant: valid buffer should always have valid signal handler
+        g_assert(p->buffer_changed_handler > 0);
         g_signal_handler_disconnect (o->buffer, p->buffer_changed_handler);
       }
       buffer = G_OBJECT (g_value_get_object (value));
       if (buffer) {
-        g_signal_connect (buffer, "changed", G_CALLBACK(buffer_changed), operation);
+        p->buffer_changed_handler = g_signal_connect (buffer, "changed", G_CALLBACK(buffer_changed), operation);
       }
       break;
     default:
@@ -140,6 +142,8 @@ dispose (GObject *object)
 
   if (o->buffer)
     {
+      // Invariant: valid buffer should always have valid signal handler
+      g_assert(p->buffer_changed_handler > 0);
       g_signal_handler_disconnect (o->buffer, p->buffer_changed_handler);
       g_object_unref (o->buffer);
       o->buffer = NULL;