From 904803510db025d040914890a96bc8b8c5d94df8 Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Tue, 21 Oct 2014 09:27:34 +0100
Subject: [PATCH] box/unbox hooks in C API

should help us pass C++ objects as args
---
 cplusplus/VImage.cc              |  9 +++++++--
 libvips/include/vips/operation.h | 14 ++++++++++++++
 libvips/iofuncs/operation.c      | 15 ++++++++++++++-
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/cplusplus/VImage.cc b/cplusplus/VImage.cc
index 187f5baf..3875ed52 100644
--- a/cplusplus/VImage.cc
+++ b/cplusplus/VImage.cc
@@ -70,6 +70,11 @@ void thread_shutdown()
 	vips_thread_shutdown(); 
 }
 
+
+
+
+
+
 // see vips_image_new_from_file()
 VImage::VImage( const char *name, ... ) 
 	__attribute__((sentinel)) throw( VError )
@@ -140,7 +145,7 @@ void VImage::write( const char *name, ... )
 
 	va_start( ap, name );
 	result = vips_call_split_option_string( operation_name, option_string,
-		ap, image, filename );
+		ap, this.im, filename );
 	va_end( ap );
 
 	if( result )
@@ -165,7 +170,7 @@ void *VImage::write( const char *suffix, size_t *size, ... )
 
 	va_start( ap, size );
 	result = vips_call_split_option_string( operation_name, option_string,
-		ap, in, &blob );
+		ap, this.im, &blob );
 	va_end( ap );
 
 	if( result )
diff --git a/libvips/include/vips/operation.h b/libvips/include/vips/operation.h
index d35ae1c9..53dd63b5 100644
--- a/libvips/include/vips/operation.h
+++ b/libvips/include/vips/operation.h
@@ -74,6 +74,20 @@ typedef struct _VipsOperation {
 	 */
 	int pixels;
 
+	/* Get and set functions, used by eg. the C++ interface to box and
+	 * unbox VImage.
+	 */
+
+	/* The value has been read from the VipsOperation and written to the arg
+	 * pointer. @arg is eg. gboolean* for a bool value.
+	 */
+	void (*collect_get)( GParamSpec *pspec, void *arg ); 
+
+	/* The value has been read from argv into a GValue. Do any
+	 * boxing/unboxing before the GValue is used to set the property.
+	 */
+	void (*collect_set)( GParamSpec *pspec, GValue *value );
+
 } VipsOperation;
 
 typedef struct _VipsOperationClass {
diff --git a/libvips/iofuncs/operation.c b/libvips/iofuncs/operation.c
index a540c7df..5f8aca87 100644
--- a/libvips/iofuncs/operation.c
+++ b/libvips/iofuncs/operation.c
@@ -603,6 +603,9 @@ vips_operation_set_valist_required( VipsOperation *operation, va_list ap )
 			}
 #endif /*VIPS_DEBUG */
 
+			if( operation->collect_set )
+				operation->collect_set( pspec, &value ); 
+
 			g_object_set_property( G_OBJECT( operation ),
 				g_param_spec_get_name( pspec ), &value );
 
@@ -645,7 +648,7 @@ vips_operation_get_valist_required( VipsOperation *operation, va_list ap )
 
 			/* It'd be nice to be able to test for arg being a
 			 * valid gobject pointer, since passing in a valid
-			 * pointer, and having us destroy it, is a common
+			 * pointer (and having us destroy it) is a common
 			 * error and a cause of hard-to-find leaks.
 			 *
 			 * Unfortunately, G_IS_OBJECT() can't be given an
@@ -667,6 +670,11 @@ vips_operation_get_valist_required( VipsOperation *operation, va_list ap )
 				g_object_unref( object ); 
 			}
 
+			/* Do any boxing/unboxing.
+			 */
+			if( operation->collect_get )
+				operation->collect_get( pspec, arg );
+
 			VIPS_ARGUMENT_COLLECT_END
 		}
 	} VIPS_ARGUMENT_FOR_ALL_END
@@ -725,6 +733,11 @@ vips_operation_get_valist_optional( VipsOperation *operation, va_list ap )
 				object = *((GObject **) arg);
 				g_object_unref( object ); 
 			}
+
+			/* Do any boxing/unboxing.
+			 */
+			if( operation->collect_get )
+				operation->collect_get( pspec, arg );
 		}
 
 		VIPS_ARGUMENT_COLLECT_END