libvips/libsrc/iofuncs/object.c

/* abstract base class for all vips objects
 *
 * Edited from nip's base class, 15/10/08
 */

/*

    Copyright (C) 1991-2003 The National Gallery

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

/*

    These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk

 */

/*
#define DEBUG
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>

#include <stdio.h>
#include <string.h>

#include <vips/vips.h>
#include <vips/internal.h>

#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/

/* Our signals. 
 */
enum {
	SIG_CHANGED,	/* VipsObject has changed somehow */
	SIG_LAST
};

static guint vips_object_signals[SIG_LAST] = { 0 };

G_DEFINE_ABSTRACT_TYPE( VipsObject, vips_object, G_TYPE_OBJECT );

void *
vips_object_changed( VipsObject *object )
{
	g_return_val_if_fail( object != NULL, NULL );
	g_return_val_if_fail( VIPS_IS_OBJECT( object ), NULL );

#ifdef DEBUG
	printf( "vips_object_changed: " );
	vips_object_print( object );
#endif /*DEBUG*/

	g_signal_emit( G_OBJECT( object ), 
		vips_object_signals[SIG_CHANGED], 0 );

	return( NULL );
}

int
vips_object_build( VipsObject *object )
{
	VipsObjectClass *object_class = VIPS_OBJECT_GET_CLASS( object );

#ifdef DEBUG
	printf( "vips_object_build: " );
	vips_object_print( object );
#endif /*DEBUG*/

	return( object_class->build( object ) );
}

void
vips_object_print_class( VipsObjectClass *class )
{
	im_buf_t buf;
	char str[1000];

	im_buf_init_static( &buf, str, 1000 );
	class->print_class( class, &buf );
	printf( "%s\n", im_buf_all( &buf ) );
}

void
vips_object_print( VipsObject *object )
{
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
	im_buf_t buf;
	char str[1000];

	vips_object_print_class( class );
	im_buf_init_static( &buf, str, 1000 );
	class->print( object, &buf );
	printf( "\n%s (%p)\n", im_buf_all( &buf ), object );
}

/* Extra stuff we track for properties to do our argument handling.
 */

/* Free a VipsArgumentInstance ... VipsArgumentClass can just be g_free()d.
 */
static void
vips_argument_instance_free( VipsArgumentInstance *argument_instance )
{
	if( argument_instance->destroy_id ) {
		g_signal_handler_disconnect( argument_instance->object,
			argument_instance->destroy_id );
		argument_instance->destroy_id = 0;
	}
	g_free( argument_instance );
}

VipsArgument *
vips__argument_table_lookup( VipsArgumentTable *table, GParamSpec *pspec )
{
	return( g_hash_table_lookup( table, pspec ) );
}

static void
vips_argument_table_replace( VipsArgumentTable *table, VipsArgument *argument )
{
	g_hash_table_replace( table, argument->pspec, argument );
}

static void
vips_argument_table_destroy( VipsArgumentTable *table )
{
	g_hash_table_destroy( table );
}

/* Loop over the vips_arguments to an object.
 */
void *
vips_argument_map( VipsObject *object, 
	VipsArgumentMapFn fn, void *a, void *b )
{
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
	GSList *p;

	for( p = class->argument_table_traverse; p; p = p->next ) {
		VipsArgumentClass *argument_class = 
			(VipsArgumentClass *) p->data;
		VipsArgument *argument = (VipsArgument *) argument_class;
		GParamSpec *pspec = argument->pspec;
		VipsArgumentInstance *argument_instance =
			vips__argument_get_instance( argument_class, object );

		/* We have many props on the arg table ... filter out the ones
		 * for this class.
		 */
		if( g_object_class_find_property( G_OBJECT_CLASS( class ), 
			pspec->name ) == pspec ) {
			void *result;

			if( (result = fn( object, pspec, 
				argument_class, argument_instance, a, b )) )
				return( result );
		}
	}

	return( NULL );
}

static void *
vips_argument_init2( VipsObject *object, GParamSpec *pspec,
	VipsArgumentClass *argument_class, 
	VipsArgumentInstance *argument_instance,
	void *a, void *b )
{
	VipsArgument *argument;

#ifdef DEBUG
	printf( "vips_argument_init_sub: adding instance argument for %s\n",
		pspec->name );
#endif /*DEBUG*/

	/* argument_instance should be NULL since we've not set it yet.
	 */
	g_assert( argument_instance == NULL );

	argument_instance = g_new( VipsArgumentInstance, 1 );
	argument = (VipsArgument *) argument_instance;

	argument->pspec = ((VipsArgument *) argument_class)->pspec;
	argument_instance->object = object;
	argument_instance->assigned = FALSE;
	argument_instance->destroy_id = 0;

	vips_argument_table_replace( object->argument_table, argument );

	return( NULL );
}

/* Create a VipsArgumentInstance for each installed argument property. Ideally
 * we'd do this during _init() but g_object_class_find_property() does not seem
 * to work then :-( so we have to delay it until first access.
 */
static void
vips_argument_init( VipsObject *object )
{
	if( !object->argument_table ) {
		object->argument_table = g_hash_table_new_full( g_direct_hash, 
			g_direct_equal, NULL, 
			(GDestroyNotify) vips_argument_instance_free );

		/* Make a VipsArgumentInstance for each installed argument 
		 * property.
		 */
		vips_argument_map( object, vips_argument_init2, NULL, NULL );
	}
}

/* Convenience ... given the VipsArgumentClass, get the VipsArgumentInstance.
 */
VipsArgumentInstance *
vips__argument_get_instance( VipsArgumentClass *argument_class, 
	VipsObject *object ) 
{
	/* Make sure the instance args are built.
	 */
	vips_argument_init( object );

	return( (VipsArgumentInstance *) 
		vips__argument_table_lookup( object->argument_table,
			((VipsArgument *) argument_class)->pspec ) );
}

static void
vips_object_clear_object( VipsObject *object, GParamSpec *pspec )
{
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
	VipsArgumentClass *argument_class = (VipsArgumentClass *)
		vips__argument_table_lookup( class->argument_table, pspec );
	VipsArgumentInstance *argument_instance =
		vips__argument_get_instance( argument_class, object );
	GObject **member = &G_STRUCT_MEMBER( GObject *, object, 
		argument_class->offset );

	if( *member ) {
		if( argument_class->flags & VIPS_ARGUMENT_INPUT ) {
#ifdef DEBUG_REF
			printf( "vips_object_clear_object: vips object: " );
			vips_object_print( object );
			printf( "  no longer refers to gobject %s (%p)\n", 
				G_OBJECT_TYPE_NAME( *member ), *member );
			printf( "  count down to %d\n", 
				G_OBJECT( *member )->ref_count - 1 );
#endif /*DEBUG_REF*/

			/* We reffed the object.
			 */
			g_object_unref( *member );
		}
		else if( argument_class->flags & VIPS_ARGUMENT_OUTPUT ) {
#ifdef DEBUG_REF
			printf( "vips_object_clear_object: gobject %s (%p)\n",
				G_OBJECT_TYPE_NAME( *member ), *member );
			printf( "  no longer refers to vips object: " ); 
			vips_object_print( object );
			printf( "  count down to %d\n", 
				G_OBJECT( object )->ref_count - 1 );
#endif /*DEBUG_REF*/

			/* The object reffed us. Stop listening link to the
			 * object's "destroy" signal. We can come here from
			 * object being destroyed, in which case the handler
			 * will already have been disconnected for us. 
			 */
			if( g_signal_handler_is_connected( object,
				argument_instance->destroy_id ) )
				g_signal_handler_disconnect( object,
					argument_instance->destroy_id );
			argument_instance->destroy_id = 0;
			*member = NULL;

			g_object_unref( object );
		}

		*member = NULL;
	}
}

/* Free any args which are holding resources.
 */
static void *
vips_object_dispose_argument( VipsObject *object, GParamSpec *pspec, 
	VipsArgumentClass *argument_class, 
	VipsArgumentInstance *argument_instance,
	void *a, void *b )
{
#ifdef DEBUG
	printf( "vips_object_dispose_argument: %s.%s\n", 
		object->name, pspec->name );
#endif /*DEBUG*/

	g_assert( ((VipsArgument *) argument_class)->pspec == pspec );
	g_assert( ((VipsArgument *) argument_instance)->pspec == pspec );

	if( G_IS_PARAM_SPEC_STRING( pspec ) ) {
		char **member = &G_STRUCT_MEMBER( char *, object, 
			argument_class->offset );

		IM_FREE( *member ); 
	}
	else if( G_IS_PARAM_SPEC_OBJECT( pspec ) ) 
		vips_object_clear_object( object, pspec );
	else if( G_IS_PARAM_SPEC_BOXED( pspec ) ) {
		gpointer *member = &G_STRUCT_MEMBER( gpointer, object, 
			argument_class->offset );

		if( *member ) {
			g_boxed_free( G_PARAM_SPEC_VALUE_TYPE( pspec ), 
				*member );
			*member = NULL;
		}
	}

	return( NULL );
}

static void
vips_object_dispose( GObject *gobject )
{
	VipsObject *object = VIPS_OBJECT( gobject );

#ifdef DEBUG
	printf( "vips_object_dispose: " );
	vips_object_print( object );
#endif /*DEBUG*/

	/* Clear all our arguments: they may be holding refs we should drop.
	 */
	vips_argument_map( object, vips_object_dispose_argument, NULL, NULL );

	G_OBJECT_CLASS( vips_object_parent_class )->dispose( gobject );
}

static void
vips_object_finalize( GObject *gobject )
{
	VipsObject *object = VIPS_OBJECT( gobject );

#ifdef DEBUG
	printf( "vips_object_finalize: " );
	vips_object_print( object );
#endif /*DEBUG*/

	IM_FREEF( vips_argument_table_destroy, object->argument_table );
	IM_FREE( object->name );

	G_OBJECT_CLASS( vips_object_parent_class )->finalize( gobject );
}

static void
vips_object_arg_destroy( GObject *argument, 
	VipsArgumentInstance *argument_instance )
{
	VipsObject *object = argument_instance->object;
	GParamSpec *pspec = ((VipsArgument *) argument_instance)->pspec;

	/* Argument had reffed us ... now it's being destroyed, so we unref.
	 */
	vips_object_clear_object( object, pspec );
} 

static void
vips_object_set_object( VipsObject *object, GParamSpec *pspec, 
	GObject *argument )
{
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( object );
	VipsArgumentClass *argument_class = (VipsArgumentClass *)
		vips__argument_table_lookup( class->argument_table, pspec );
	VipsArgumentInstance *argument_instance =
		vips__argument_get_instance( argument_class, object );
	GObject **member = &G_STRUCT_MEMBER( GObject *, object, 
		argument_class->offset );

	g_assert( !*member );

	*member = argument;

	if( *member ) {
		if( argument_class->flags & VIPS_ARGUMENT_INPUT ) {
#ifdef DEBUG_REF
			printf( "vips_object_set_object: vips object: " );
			vips_object_print( object );
			printf( "  refers to gobject %s (%p)\n", 
				G_OBJECT_TYPE_NAME( *member ), *member );
			printf( "  count up to %d\n", 
				G_OBJECT( *member )->ref_count );
#endif /*DEBUG_REF*/

			/* Ref the argument.
			 */
			g_object_ref( *member );
		}
		else if( argument_class->flags & VIPS_ARGUMENT_OUTPUT ) {
#ifdef DEBUG_REF
			printf( "vips_object_set_object: gobject %s (%p)\n",
				G_OBJECT_TYPE_NAME( *member ), *member );
			printf( "  refers to vips object: " ); 
			vips_object_print( object );
			printf( "  count up to %d\n", 
				G_OBJECT (object)->ref_count );
#endif /*DEBUG_REF*/

			/* The argument reffs us.
			 */
			g_object_ref( object );
			argument_instance->destroy_id =
				g_signal_connect( *member, "destroy",
					G_CALLBACK( vips_object_arg_destroy ),
					argument_instance );
		}
	}
}

/* Also used by subclasses, so not static.
 */
void
vips_object_set_property( GObject *gobject, 
	guint property_id, const GValue *value, GParamSpec *pspec )
{
	VipsObject *object = VIPS_OBJECT( gobject );
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( gobject );
	VipsArgumentClass *argument_class = (VipsArgumentClass *)
		vips__argument_table_lookup( class->argument_table, pspec );
	VipsArgumentInstance *argument_instance =
		vips__argument_get_instance( argument_class, object );

	if( !argument_class ) {
		G_OBJECT_WARN_INVALID_PROPERTY_ID( gobject, 
			property_id, pspec );
		return;
	}

#ifdef DEBUG
{
	char *str_value;

	str_value = g_strdup_value_contents( value );
	printf( "vips_object_set_property: %s.%s = %s\n", 
		object->name, pspec->name, str_value );
	g_free( str_value );
}
#endif /*DEBUG*/

	g_assert( ((VipsArgument *) argument_class)->pspec == pspec );
	g_assert( ((VipsArgument *) argument_instance)->pspec == pspec );

	/* If this is a construct-only argument, we can only set before we've
	 * built.
	 */
	if( argument_class->flags & VIPS_ARGUMENT_CONSTRUCT && 
		object->constructed ) {
		g_warning( "%s: can't assign '%s' after construct", G_STRLOC,
			((VipsArgument *) argument_class)->pspec->name);
		return;
	}

	/* If this is a set-once argument, check we've not set it before.
	 */
	if( argument_class->flags & VIPS_ARGUMENT_SET_ONCE &&
		argument_instance->assigned ) {
		g_warning( "%s: can only assign '%s' once", G_STRLOC,
			((VipsArgument *)argument_class)->pspec->name );
		return;
	}

	if( G_IS_PARAM_SPEC_STRING( pspec ) ) {
		char **member = &G_STRUCT_MEMBER( char *, object, 
			argument_class->offset );

		IM_SETSTR( *member, g_value_get_string( value ) );
	}
	else if( G_IS_PARAM_SPEC_OBJECT( pspec ) ) {
		/* Remove any old object.
		 */
		vips_object_clear_object( object, pspec );

		/* Install the new object.
		 */
		vips_object_set_object( object, pspec, 
			g_value_get_object( value ) );
	}
	else if( G_IS_PARAM_SPEC_INT( pspec ) ) {
		int *member = &G_STRUCT_MEMBER( int, object, 
			argument_class->offset );

		*member = g_value_get_int( value );
	}
	else if( G_IS_PARAM_SPEC_BOOLEAN( pspec ) ) {
		gboolean *member = &G_STRUCT_MEMBER( gboolean, object, 
			argument_class->offset );

		*member = g_value_get_boolean( value );
	}
	else if( G_IS_PARAM_SPEC_ENUM( pspec ) ) {
		int *member = &G_STRUCT_MEMBER( int, object, 
			argument_class->offset );

		*member = g_value_get_enum( value );
	}
	else if( G_IS_PARAM_SPEC_POINTER( pspec ) ) {
		gpointer *member = &G_STRUCT_MEMBER( gpointer, object, 
			argument_class->offset );

		*member = g_value_get_pointer( value );
	}
	else if( G_IS_PARAM_SPEC_DOUBLE( pspec ) ) {
		double *member = &G_STRUCT_MEMBER( double, object, 
			argument_class->offset );

		*member = g_value_get_double( value );
	}
	else if( G_IS_PARAM_SPEC_BOXED( pspec ) ) {
		gpointer *member = &G_STRUCT_MEMBER( gpointer, object, 
			argument_class->offset );

		if( *member ) {
			g_boxed_free( G_PARAM_SPEC_VALUE_TYPE( pspec ), 
				*member );
			*member = NULL;
		}

		/* Copy the boxed into our pointer (will use eg.
		 * vips__object_vector_dup ()).
		 */
		*member = g_value_dup_boxed( value );
	}
	else {
		g_warning( "%s: '%s' has unimplemented type", G_STRLOC,
			((VipsArgument *) argument_class)->pspec->name );
	}

	/* Note that it's now been set. 
	 */
	argument_instance->assigned = TRUE;
}

/* Also used by subclasses, so not static.
 */
void
vips_object_get_property( GObject *gobject, 
	guint property_id, GValue *value, GParamSpec *pspec )
{
	VipsObject *object = VIPS_OBJECT( gobject );
	VipsObjectClass *class = VIPS_OBJECT_GET_CLASS( gobject );
	VipsArgumentClass *argument_class = (VipsArgumentClass *)
		vips__argument_table_lookup( class->argument_table, pspec );

	if( !argument_class ) {
		G_OBJECT_WARN_INVALID_PROPERTY_ID( gobject, 
			property_id, pspec );
		return;
	}

	g_assert( ((VipsArgument *) argument_class)->pspec == pspec );

	if( G_IS_PARAM_SPEC_STRING( pspec ) ) {
		char *member = G_STRUCT_MEMBER( char *, object, 
			argument_class->offset );

		g_value_set_string( value, member );
	}
	else if( G_IS_PARAM_SPEC_OBJECT( pspec ) ) {
		GObject **member = &G_STRUCT_MEMBER( GObject *, object, 
			argument_class->offset );

		g_value_set_object( value, *member );
	}
	else if( G_IS_PARAM_SPEC_INT( pspec ) ) {
		int *member = &G_STRUCT_MEMBER( int, object, 
			argument_class->offset );

		g_value_set_int( value, *member );
	}
	else if( G_IS_PARAM_SPEC_BOOLEAN( pspec ) ) {
		gboolean *member = &G_STRUCT_MEMBER( gboolean, object, 
			argument_class->offset );

		g_value_set_boolean( value, *member );
	}
	else if( G_IS_PARAM_SPEC_ENUM( pspec ) ) {
		int *member = &G_STRUCT_MEMBER( int, object, 
			argument_class->offset );

		g_value_set_enum( value, *member );
	}
	else if( G_IS_PARAM_SPEC_POINTER( pspec ) ) {
		gpointer *member = &G_STRUCT_MEMBER( gpointer, object, 
			argument_class->offset );

		g_value_set_pointer( value, *member );
	}
	else if( G_IS_PARAM_SPEC_BOXED( pspec ) ) {
		gpointer *member = &G_STRUCT_MEMBER( gpointer, object, 
			argument_class->offset );

		/* Copy the boxed into our pointer (will use eg.
		 * vips__object_vector_dup ()).
		 */
		g_value_set_boxed( value, *member );
	}
	else {
		g_warning( "%s: unimplemented property type", G_STRLOC );
	}
}

static void *
vips_object_check_required( VipsObject *object, GParamSpec *pspec, 
	VipsArgumentClass *argument_class, 
	VipsArgumentInstance *argument_instance,
	void *a, void *b )
{
	int *result = (int *) a;

	if( (argument_class->flags & VIPS_ARGUMENT_REQUIRED) &&
		(argument_class->flags & VIPS_ARGUMENT_CONSTRUCT) &&
		!argument_instance->assigned ) {
		im_error( "check_required", 
			_( "required construct param %s to %s %s not set" ),
			pspec->name,
			G_OBJECT_TYPE_NAME( object ),
			object->name );
		*result = -1;
	}

	return( NULL );
}

static int
vips_object_real_build( VipsObject *object )
{
	int result;

	g_assert( !object->constructed );

	/* Check all required arguments have been supplied, don't stop on 1st
	 * error.
	 */
	result = 0;
	(void) vips_argument_map( object,
		vips_object_check_required, &result, NULL );

	/* ... more checks go here.
	 */
	object->constructed = TRUE;

	return( result );
}

static void
vips_object_real_changed( VipsObject *object )
{
#ifdef DEBUG
	printf( "vips_object_real_changed: " );
	vips_object_print( object );
#endif /*DEBUG*/
}

static void
vips_object_real_print_class( VipsObjectClass *class, im_buf_t *buf )
{
	im_buf_appendf( buf, "%s", G_OBJECT_CLASS_NAME( class ) );
	if( class->nickname )
		im_buf_appendf( buf, " (%s)", class->nickname );
	if( class->description )
		im_buf_appendf( buf, ", %s", class->description );
}

static void
vips_object_real_print( VipsObject *object, im_buf_t *buf )
{
	if( object->name )
		im_buf_appendf( buf, "\"%s\"", object->name );
}

static void
transform_string_double( const GValue *src_value, GValue *dest_value )
{
	g_value_set_double( dest_value, 
		g_ascii_strtod( g_value_get_string( src_value ), NULL ) );
}

static void
vips_object_class_init( VipsObjectClass *class )
{
	GObjectClass *gobject_class = G_OBJECT_CLASS( class );

	gobject_class->dispose = vips_object_dispose;
	gobject_class->finalize = vips_object_finalize;
	gobject_class->set_property = vips_object_set_property;
	gobject_class->get_property = vips_object_get_property;

	class->build = vips_object_real_build;
	class->changed = vips_object_real_changed;
	class->print_class = vips_object_real_print_class;
	class->print = vips_object_real_print;
	class->nickname = "object";
	class->description = _( "VIPS base class" );

	/* Table of VipsArgumentClass ... we can just g_free() them.
	 */
	class->argument_table = g_hash_table_new_full( 
		g_direct_hash, g_direct_equal, NULL, (GDestroyNotify) g_free );
	class->argument_table_traverse = NULL;

	vips_object_signals[SIG_CHANGED] = g_signal_new( "changed",
		G_OBJECT_CLASS_TYPE( gobject_class ),
		G_SIGNAL_RUN_FIRST,
		G_STRUCT_OFFSET( VipsObjectClass, changed ),
		NULL, NULL,
		g_cclosure_marshal_VOID__VOID,
		G_TYPE_NONE, 0 );

	/* For setting double arguments from the command-line.
	 */
	g_value_register_transform_func( G_TYPE_STRING, G_TYPE_DOUBLE,
		transform_string_double );
}

static void
vips_object_init( VipsObject *object )
{
#ifdef DEBUG
	printf( "vips_object_init: " );
	vips_object_print( object );
#endif /*DEBUG*/
}

void
vips_object_set_name( VipsObject *object, const char *name )
{
	IM_SETSTR( object->name, name );
	vips_object_changed( object );
}

/* Add a vipsargument ... automate some stuff with this.
 */
void
vips_object_class_install_argument( VipsObjectClass *object_class, 
	GParamSpec *pspec, VipsArgumentFlags flags, guint offset )
{
	VipsArgumentClass *argument_class = g_new( VipsArgumentClass, 1 );

#ifdef DEBUG
	printf( "vips_object_class_install_argument: %s\n", pspec->name );
#endif /*DEBUG*/

	/* Must be a new one.
	 */
	g_assert( !vips__argument_table_lookup( object_class->argument_table,
		pspec ) );

	/* Mustn't have INPUT and OUTPUT both set.
	 */
	g_assert( !(
		(flags & VIPS_ARGUMENT_INPUT) && 
		(flags & VIPS_ARGUMENT_OUTPUT)) );

	((VipsArgument *) argument_class)->pspec = pspec;
	argument_class->object_class = object_class;
	argument_class->flags = flags;
	argument_class->offset = offset;

	vips_argument_table_replace( object_class->argument_table,
		(VipsArgument *) argument_class );
	object_class->argument_table_traverse = g_slist_append( 
		object_class->argument_table_traverse, argument_class );
}

/* Set a named arg from a string.
 */
static int
vips_object_set_arg( VipsObject *object, const char *name, const char *value )
{
	GValue gvalue = { 0, };

	g_value_init( &gvalue, G_TYPE_STRING );
	g_value_set_string( &gvalue, value );
	g_object_set_property( G_OBJECT( object ), name, &gvalue );
	g_value_unset( &gvalue );

	return( 0 );
}

static void *
vips_object_set_required_test( VipsObject *object,
	GParamSpec *pspec,
	VipsArgumentClass *argument_class, 
	VipsArgumentInstance *argument_instance,
	void *a, void *b )
{
	if( (argument_class->flags & VIPS_ARGUMENT_REQUIRED) &&
		(argument_class->flags & VIPS_ARGUMENT_CONSTRUCT) &&
		!argument_instance->assigned )
		return( pspec );

	return( NULL );
}

/* Set the first unassigned required arg to the string.
 */
static int
vips_object_set_required( VipsObject *object, const char *value )
{
	GParamSpec *pspec;

	if( !(pspec = vips_argument_map( object, 
		vips_object_set_required_test, NULL, NULL )) ) {
		im_error( "vips_object_set_required", 
			_( "no unset required arguments for %s" ), value );
		return( -1 );
	}

	if( vips_object_set_arg( object, pspec->name, value ) )
		return( -1 );

	return( 0 );
}

/* Set object args from a string. We've seen the '(', we need to check for the
 * closing ')' and make sure there's no extra stuff.
 */
static int
vips_object_set_args( VipsObject *object, const char *p )
{
	VipsToken token;
	char string[PATH_MAX];
	char string2[PATH_MAX];

	do {
		if( !(p = vips__token_need( p, VIPS_TOKEN_STRING, 
			string, PATH_MAX )) ) 
			return( -1 );

		/* We have to look for a '=', ')' or a ',' to see if string is 
		 * a param name or a value.
		 */
		if( !(p = vips__token_must( p, &token, string2, PATH_MAX )) ) 
			return( -1 );
		if( token == VIPS_TOKEN_EQUALS ) {
			if( !(p = vips__token_need( p, VIPS_TOKEN_STRING, 
				string2, PATH_MAX )) ) 
				return( -1 );
			if( vips_object_set_arg( object, string, string2 ) )
				return( -1 );
			if( !(p = vips__token_must( p, &token, 
				string2, PATH_MAX )) ) 
				return( -1 );
		}
		else {
			if( vips_object_set_required( object, string ) )
				return( -1 );
		}

		/* Now must be a , or a ).
		 */
		if( token != VIPS_TOKEN_RIGHT && token != VIPS_TOKEN_COMMA ) {
			im_error( "set_args", "%s", 
				_( "not , or ) after parameter" ) );
			return( -1 );
		}
	} while( token != VIPS_TOKEN_RIGHT );

	if( (p = vips__token_get( p, &token, string, PATH_MAX )) ) {
		im_error( "set_args", "%s",
			_( "extra tokens after ')'" ) );
		return( -1 );
	}

	return( 0 );
}

VipsObject *
vips_object_new_from_string( const char *basename, const char *p )
{
	VipsToken token;
	char string[PATH_MAX];
	GType type;
	VipsObject *object;

	if( !(p = vips__token_need( p, VIPS_TOKEN_STRING, string, PATH_MAX )) ||
		!(type = vips_type_find( basename, string )) ) 
		return( NULL );

	object = VIPS_OBJECT( g_object_new( type, NULL ) );

	if( (p = vips__token_get( p, &token, string, PATH_MAX )) ) {
		if( token == VIPS_TOKEN_LEFT &&
			vips_object_set_args( object, p ) ) {
			im_error( "object_new", "%s",
				_( "bad object arguents" ) );
			g_object_unref( object );
			return( NULL );
		}
	}

	if( vips_object_build( object ) ) {
		g_object_unref( object );
		return( NULL );
	}

	return( object );
}