[gimp] app: allow a NULL src_buffer in gimp_gegl_apply_operation()

[Michael Natterer <mitch src gnome org>]

commit 72a32dd79f9070eac0ca6166dd08f505a85e6a77
Author: Michael Natterer <mitch gimp org>
Date:   Mon Apr 22 10:55:09 2013 +0200

    app: allow a NULL src_buffer in gimp_gegl_apply_operation()
    
    in which case the function just does nothing on the passed operation's
    input and expects it to be already conntected to something. Also allow
    to pass an operation that is already part of another graph.

 app/gegl/gimp-gegl-apply-operation.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)
---
diff --git a/app/gegl/gimp-gegl-apply-operation.c b/app/gegl/gimp-gegl-apply-operation.c
index 3f18b89..09b09f7 100644
--- a/app/gegl/gimp-gegl-apply-operation.c
+++ b/app/gegl/gimp-gegl-apply-operation.c
@@ -43,13 +43,12 @@ gimp_gegl_apply_operation (GeglBuffer          *src_buffer,
                            const GeglRectangle *dest_rect)
 {
   GeglNode      *gegl;
-  GeglNode      *src_node;
   GeglNode      *dest_node;
   GeglRectangle  rect = { 0, };
   gdouble        value;
   gboolean       progress_active = FALSE;
 
-  g_return_if_fail (GEGL_IS_BUFFER (src_buffer));
+  g_return_if_fail (src_buffer == NULL || GEGL_IS_BUFFER (src_buffer));
   g_return_if_fail (progress == NULL || GIMP_IS_PROGRESS (progress));
   g_return_if_fail (GEGL_IS_NODE (operation));
   g_return_if_fail (GEGL_IS_BUFFER (dest_buffer));
@@ -66,18 +65,30 @@ gimp_gegl_apply_operation (GeglBuffer          *src_buffer,
 
   gegl = gegl_node_new ();
 
-  src_node = gegl_node_new_child (gegl,
-                                  "operation", "gegl:buffer-source",
-                                  "buffer",    src_buffer,
-                                  NULL);
+  if (! gegl_node_get_parent (operation))
+    gegl_node_add_child (gegl, operation);
+
+  if (src_buffer)
+    {
+      GeglNode *src_node;
+
+      src_node = gegl_node_new_child (gegl,
+                                      "operation", "gegl:buffer-source",
+                                      "buffer",    src_buffer,
+                                      NULL);
+
+      gegl_node_connect_to (src_node,  "output",
+                            operation, "input");
+    }
+
   dest_node = gegl_node_new_child (gegl,
                                    "operation", "gegl:write-buffer",
                                    "buffer",    dest_buffer,
                                    NULL);
 
-  gegl_node_add_child (gegl, operation);
 
-  gegl_node_link_many (src_node, operation, dest_node, NULL);
+  gegl_node_connect_to (operation, "output",
+                        dest_node, "input");
 
   if (progress)
     {