diff --git a/ChangeLog b/ChangeLog
index 7d403090..980152d5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -13,6 +13,7 @@
 - yafr-smooth reworked along the lines of bicubic
 - cleanups after yafr hacking
 - added affinei_all
+- don't set im_error() on failed callback
 
 11/9/08 started 7.16.3
 - oop typo in manpage for im_project()
diff --git a/TODO b/TODO
index db11a52e..75ad9f5d 100644
--- a/TODO
+++ b/TODO
@@ -1,5 +1,6 @@
-- make a new package for "resample"? im_shrink & friends could go in there too
+- started adding 
 
+#define IM_TYPE_GOBJECT "gobject"       /* A GObject of a specified class */
   or maybe "transform"? flip/rot90/embed etc. as well?
 
 - make a "deprecated" package too
@@ -9,11 +10,41 @@
 - try walking the class hierarchy below VipsInterpolate and see if we can see
   all the interpolators
 
-  classes need some extra fields
+  want bicubic args to be
 
-  	nickname, eg. "bicubic"
-	caption, eg. "catmull-rom bicubic interpolation"
+  	IM_GOBJECT( "VipsInterpolate", "interpolate" );
 
+  ie. pass a gobject which is a sub-type of VipsInterpolate in an arg called
+  "interpolate"
+
+  then we need to create an object of that class, get the param list, set from
+  any args, call object_init, and pass
+
+  on return, unref the object
+
+  so 
+  
+  	im_affinei_all in.v out.v "yafrsmooth(2.4)" 0.9 0 0 0.9 0 0
+
+  creates a yafrsmooth, sets the param,
+
+
+  in nip2, 
+
+  	inter = g_object_new "VipsInterpolateBicubic" [$sharpness => 2.4];
+
+  also need something to return a list of GTypes below a name etc., find class
+  description:w
+
+
+  need k
+
+
+
+- make a new package for "resample"? im_shrink & friends could go in there too
+
+- how to expose things like yafrsmooth's "sharpening" parameter to
+  nip2/C++/Python?
   can we write a find-by-nickname function? eg.
 
   	GType vips_get_type (const char *base, const char *nickname)
@@ -54,9 +85,6 @@
 
 - im_render should use a hash for tile lookup ... or+shift x/y together
 
-- eval callbacks shouldn't set an errormsg? or maybe it should for debugging
-  and stuff
-
 - bilinear should be a true subclass of interpolate ... and put the tables
   into the base class
 
diff --git a/include/vips/dispatch.h b/include/vips/dispatch.h
index 751823f7..edddc9af 100644
--- a/include/vips/dispatch.h
+++ b/include/vips/dispatch.h
@@ -55,6 +55,7 @@ extern "C" {
 #define IM_TYPE_IMAGE "image"           /* IMAGE descriptor */
 #define IM_TYPE_DISPLAY "display"	/* Display descriptor */
 #define IM_TYPE_GVALUE "gvalue"		/* GValue wrapper */
+#define IM_TYPE_GOBJECT "gobject"	/* A GObject of a specified class */
 typedef char *im_arg_type;              /* Type of argument id */
 
 /* Internal representation of an argument to an image processing function.
diff --git a/include/vips/object.h b/include/vips/object.h
index f25dbc1e..e21de826 100644
--- a/include/vips/object.h
+++ b/include/vips/object.h
@@ -65,6 +65,15 @@ typedef struct _VipsObjectClass {
 	/* Try to print something about the object, handy for debugging.
 	 */
 	void (*print)( VipsObject *, im_buf_t * );
+
+	/* Class nickname, eg. "VipsInterpolateBicubic" has "bicubic" as a
+	 * nickname. Not internationalised. 
+	 */
+	const char *nickname;
+
+	/* Class description. Used for help messages, so internationalised.
+	 */
+	const char *description;
 } VipsObjectClass;
 
 void *vips_object_changed( VipsObject *vips_object );
diff --git a/include/vips/util.h b/include/vips/util.h
index 3b1b9caa..2002b577 100644
--- a/include/vips/util.h
+++ b/include/vips/util.h
@@ -300,6 +300,12 @@ void *im_map_equal( void *a, void *b );
 
 void *im_hash_table_map( GHashTable *hash, VSListMap2Fn fn, void *a, void *b );
 
+typedef void *(*VTypeMapFn)( GType, void * );
+typedef void *(*VTypeMap2Fn)( GType, void *, void * );
+void *im_type_map( GType base, VTypeMap2Fn fn, void *a, void *b );
+void *im_type_map_concrete_all( GType base, VTypeMapFn fn, void *a );
+GType im_type_find( const char *basename, const char *nickname );
+
 char *im_strncpy( char *dest, const char *src, int n );
 char *im_strrstr( const char *haystack, const char *needle );
 char *im_strdup( IMAGE *im, const char *str );
diff --git a/libsrc/iofuncs/callback.c b/libsrc/iofuncs/callback.c
index d01420b5..365118fa 100644
--- a/libsrc/iofuncs/callback.c
+++ b/libsrc/iofuncs/callback.c
@@ -9,6 +9,8 @@
  *	- now always calls all callbacks, even if some fail
  * 2/7/08
  *	- added invalidate callbacks
+ * 26/11/08
+ * 	- don't set im_error() on callback failed, that's the user's job
  */
 
 /*
@@ -135,8 +137,9 @@ call_callback( VCallback *cbs, int *result )
 	int res;
 
 	if( (res = cbs->fn( cbs->a, cbs->b )) ) {
-		im_error( "im__trigger_callbacks", _( "user callback "
-			"failed for %s" ), cbs->im->filename );
+		/* We don't set im_error() here, that's the callback's
+		 * responsibility.
+		 */
 		*result = res;
 
 #ifdef DEBUG_IO
diff --git a/libsrc/iofuncs/object.c b/libsrc/iofuncs/object.c
index 560efd83..2cd0277e 100644
--- a/libsrc/iofuncs/object.c
+++ b/libsrc/iofuncs/object.c
@@ -148,6 +148,8 @@ vips_object_class_init( VipsObjectClass *class )
 
 	class->changed = vips_object_real_changed;
 	class->print = vips_object_real_print;
+	class->nickname = "object";
+	class->description = _( "VIPS base class" );
 
 	vips_object_signals[SIG_CHANGED] = g_signal_new( "changed",
 		G_OBJECT_CLASS_TYPE( gobject_class ),
diff --git a/libsrc/iofuncs/util.c b/libsrc/iofuncs/util.c
index d8e31fc2..87a8a1a4 100644
--- a/libsrc/iofuncs/util.c
+++ b/libsrc/iofuncs/util.c
@@ -242,6 +242,101 @@ im_hash_table_map( GHashTable *hash, VSListMap2Fn fn, void *a, void *b )
 	return( pair.result );
 }
 
+/* Map over all a type's children.
+ */
+void *
+im_type_map( GType base, VTypeMap2Fn fn, void *a, void *b )
+{
+	GType *child;
+	guint n_children;
+	int i;
+	void *result;
+
+	child = g_type_children( base, &n_children );
+	result = NULL;
+	for( i = 0; i < n_children && !result; i++ )
+		result = fn( child[i], a, b );
+	g_free( child );
+
+	return( result );
+}
+
+/* Loop over all the concrete subtypes of a base type.
+ */
+void *
+im_type_map_concrete_all( GType base, VTypeMapFn fn, void *a )
+{
+	void *result;
+
+	result = NULL;
+	if( !G_TYPE_IS_ABSTRACT( base ) )
+		result = fn( base, a );
+	if( !result )
+		result = im_type_map( base, 
+			(VTypeMap2Fn) im_type_map_concrete_all, fn, a );
+
+	return( result );
+}
+
+static GType
+test_name( GType type, const char *nickname )
+{
+	GTypeClass *class;
+	VipsObjectClass *vips_class;
+
+	/* Does this class exist? Try to create if not.
+	 */
+	if( !(class = g_type_class_peek( type )) ) 
+		/* We don't unref, so the class is never finalized. This will
+		 * make the peek work next time around and save us from
+		 * constantly building and destroying classes.
+		 */
+		if( !(class = g_type_class_ref( type )) ) 
+			return( 0 );
+
+	if( !VIPS_IS_OBJECT_CLASS( class ) )
+		return( 0 );
+	vips_class = VIPS_OBJECT_CLASS( class );
+	if( strcasecmp( vips_class->nickname, nickname ) != 0 )
+		return( 0 );
+
+	return( type );
+}
+
+/* Find a GType ... search below base, return the first match on a nickname or
+ * a name.
+ */
+GType
+im_type_find( const char *basename, const char *nickname )
+{
+	GType base;
+	GType type;
+
+	if( !(base = g_type_from_name( basename )) ) {
+		im_error( "im_type_find", 
+			_( "base type \"%s\" not found" ), basename ); 
+		return( 0 );
+	}
+
+	/* Users can pass the real name instead of a nickname, provided the
+	 * real name names a subclass of base.
+	 */
+	if( (type = g_type_from_name( nickname )) ) 
+		if( g_type_is_a( type, base ) )
+			return( type );
+
+	/* Nope, need to search.
+	 */
+	if( (type = (GType) im_type_map_concrete_all( base, 
+		(VTypeMapFn) test_name, (void *) nickname )) ) 
+		return( type );
+
+	im_error( "im_type_find", 
+		_( "type \"%s\" not found" ), nickname ); 
+
+	return( 0 );
+}
+
 /* Like strncpy(), but always NULL-terminate, and don't pad with NULLs.
  */
 char *
diff --git a/libsrc/mosaicing/bicubic.cpp b/libsrc/mosaicing/bicubic.cpp
index b72276be..b16fdb49 100644
--- a/libsrc/mosaicing/bicubic.cpp
+++ b/libsrc/mosaicing/bicubic.cpp
@@ -380,12 +380,16 @@ vips_interpolate_bicubic_interpolate( VipsInterpolate *interpolate,
 static void
 vips_interpolate_bicubic_class_init( VipsInterpolateBicubicClass *iclass )
 {
+	VipsObjectClass *object_class = VIPS_OBJECT_CLASS( iclass );
 	VipsInterpolateClass *interpolate_class = 
 		VIPS_INTERPOLATE_CLASS( iclass );
 
 	vips_interpolate_bicubic_parent_class = 
 		VIPS_INTERPOLATE_CLASS( g_type_class_peek_parent( iclass ) );
 
+	object_class->nickname = "bicubic";
+	object_class->description = _( "Bicubic interpolation (Catmull-Rom)" );
+
 	interpolate_class->interpolate = vips_interpolate_bicubic_interpolate;
 	interpolate_class->window_size = 4;