diff --git a/ChangeLog b/ChangeLog
index 7f8081a192..1e28df46f3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2008-05-21  Sven Neumann  <sven@gimp.org>
+
+	* app/base/desaturate.[ch]: changed to take a pointer as first
+	argument as all PixelProcessor functions.
+
+	* app/core/gimpdrawable-desaturate.c: changed accordingly.
+
+	* app/tools/gimpdesaturatetool.[ch]: added legacy code path.
+
 2008-05-21  Sven Neumann  <sven@gimp.org>
 
 	* app/base/Makefile.am
diff --git a/app/base/desaturate.c b/app/base/desaturate.c
index df29d9904b..122a8b5991 100644
--- a/app/base/desaturate.c
+++ b/app/base/desaturate.c
@@ -40,14 +40,15 @@ static void  desaturate_region_average    (PixelRegion    *srcPR,
 
 
 void
-desaturate_region (GimpDesaturateMode  mode,
+desaturate_region (GimpDesaturateMode *mode,
                    PixelRegion        *srcPR,
                    PixelRegion        *destPR)
 {
+  g_return_if_fail (mode != NULL);
   g_return_if_fail (srcPR->bytes == destPR->bytes);
   g_return_if_fail (srcPR->bytes == 3 || srcPR->bytes == 4);
 
-  switch (mode)
+  switch (*mode)
     {
     case GIMP_DESATURATE_LIGHTNESS:
       desaturate_region_lightness (srcPR, destPR, srcPR->bytes == 4);
diff --git a/app/base/desaturate.h b/app/base/desaturate.h
index 0efab4bdaa..054c34116c 100644
--- a/app/base/desaturate.h
+++ b/app/base/desaturate.h
@@ -20,7 +20,7 @@
 #define __DESATURATE_H__
 
 
-void  desaturate_region (GimpDesaturateMode  mode,
+void  desaturate_region (GimpDesaturateMode *mode,
                          PixelRegion        *srcPR,
                          PixelRegion        *destPR);
 
diff --git a/app/core/gimpdrawable-desaturate.c b/app/core/gimpdrawable-desaturate.c
index cfc622a2aa..bc33bb1672 100644
--- a/app/core/gimpdrawable-desaturate.c
+++ b/app/core/gimpdrawable-desaturate.c
@@ -88,7 +88,7 @@ gimp_drawable_desaturate (GimpDrawable       *drawable,
                          x, y, width, height, TRUE);
 
       pixel_regions_process_parallel ((PixelProcessorFunc) desaturate_region,
-                                      GINT_TO_POINTER (mode),
+                                      &mode,
                                       2, &srcPR, &destPR);
 
       gimp_drawable_merge_shadow_tiles (drawable, TRUE, _("Desaturate"));
diff --git a/app/tools/gimpdesaturatetool.c b/app/tools/gimpdesaturatetool.c
index 291b5c5cdc..4bed99777b 100644
--- a/app/tools/gimpdesaturatetool.c
+++ b/app/tools/gimpdesaturatetool.c
@@ -27,8 +27,7 @@
 
 #include "tools-types.h"
 
-#include "base/gimplut.h"
-#include "base/lut-funcs.h"
+#include "base/desaturate.h"
 
 #include "gegl/gimpdesaturateconfig.h"
 
@@ -106,6 +105,10 @@ gimp_desaturate_tool_class_init (GimpDesaturateToolClass *klass)
 static void
 gimp_desaturate_tool_init (GimpDesaturateTool *desaturate_tool)
 {
+  GimpImageMapTool *im_tool = GIMP_IMAGE_MAP_TOOL (desaturate_tool);
+
+  im_tool->apply_func = (GimpImageMapApplyFunc) desaturate_region;
+  im_tool->apply_data = &desaturate_tool->mode;
 }
 
 static gboolean
@@ -114,7 +117,7 @@ gimp_desaturate_tool_initialize (GimpTool     *tool,
                                 GError      **error)
 {
   GimpDesaturateTool *desaturate_tool = GIMP_DESATURATE_TOOL (tool);
-  GimpDrawable      *drawable;
+  GimpDrawable       *drawable;
 
   drawable = gimp_image_get_active_drawable (display->image);
 
@@ -145,7 +148,7 @@ gimp_desaturate_tool_get_operation (GimpImageMapTool  *image_map_tool,
                                     GObject          **config)
 {
   GimpDesaturateTool *desaturate_tool = GIMP_DESATURATE_TOOL (image_map_tool);
-  GeglNode          *node;
+  GeglNode           *node;
 
   node = g_object_new (GEGL_TYPE_NODE,
                        "operation", "gimp-desaturate",
@@ -169,6 +172,9 @@ gimp_desaturate_tool_get_operation (GimpImageMapTool  *image_map_tool,
 static void
 gimp_desaturate_tool_map (GimpImageMapTool *image_map_tool)
 {
+  GimpDesaturateTool *desaturate_tool = GIMP_DESATURATE_TOOL (image_map_tool);
+
+  desaturate_tool->mode = desaturate_tool->config->mode;
 }
 
 
@@ -195,9 +201,9 @@ gimp_desaturate_tool_dialog (GimpImageMapTool *image_map_tool)
 }
 
 static void
-gimp_desaturate_tool_config_notify (GObject           *object,
-                                    GParamSpec        *pspec,
-                                   GimpDesaturateTool *desaturate_tool)
+gimp_desaturate_tool_config_notify (GObject            *object,
+                                    GParamSpec         *pspec,
+                                    GimpDesaturateTool *desaturate_tool)
 {
   GimpDesaturateConfig *config = GIMP_DESATURATE_CONFIG (object);
 
diff --git a/app/tools/gimpdesaturatetool.h b/app/tools/gimpdesaturatetool.h
index 7adeab4c7b..94ae3662f7 100644
--- a/app/tools/gimpdesaturatetool.h
+++ b/app/tools/gimpdesaturatetool.h
@@ -39,6 +39,7 @@ struct _GimpDesaturateTool
   GimpImageMapTool       parent_instance;
 
   GimpDesaturateConfig  *config;
+  GimpDesaturateMode     mode;  /*  only for legacy mode  */
 
   /*  dialog  */
   GtkWidget             *button;