[gnome-photos/wip/rishi/serialize] utils: Borrow serialization code from GEGL

[Debarshi Ray <debarshir src gnome org>]

commit 94f31e2a963fc7196861bf3288b91542986c47e5
Author: Debarshi Ray <debarshir gnome org>
Date:   Tue Jan 5 18:13:26 2016 +0100

    utils: Borrow serialization code from GEGL
    
    This is a pre-LGPLv3+ (ie. LGPLv2+) implementation of what is today
    known as gegl_node_to_xml. Copying LGPLv2+ code into a GPLv2+ code base
    (ie. this one) means that the result is still GPLv2+. On the other
    hand, copying LGPLv3+ code would have made the resulting combination
    GPLv3+.
    
    We are going to use this to write our own serialization method that
    only serializes till a certain node in the graph, instead of going all
    the way to the source like gegl_node_to_xml does.
    
    http://www.gnu.org/licenses/gpl-faq.en.html#AllCompatibility

 src/photos-utils.c |  183 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 src/photos-utils.h |    4 +-
 2 files changed, 185 insertions(+), 2 deletions(-)
---
diff --git a/src/photos-utils.c b/src/photos-utils.c
index 7d46d4d..0677215 100644
--- a/src/photos-utils.c
+++ b/src/photos-utils.c
@@ -1,6 +1,7 @@
 /*
  * Photos - access, organize and share your photos on GNOME
- * Copyright © 2012, 2013, 2014, 2015 Red Hat, Inc.
+ * Copyright © 2006 Øyvind Kolås
+ * Copyright © 2012, 2013, 2014, 2015, 2016 Red Hat, Inc.
  * Copyright © 2009 Yorba Foundation
  *
  * This program is free software; you can redistribute it and/or
@@ -61,6 +62,16 @@
 #include "photos-utils.h"
 
 
+typedef struct _PhotosUtilsSerializeState PhotosUtilsSerializeState;
+
+struct _PhotosUtilsSerializeState
+{
+  GHashTable *clones;
+  GString *buf;
+  const gchar *path_root;
+  gint clone_count;
+};
+
 static const gdouble EPSILON = 1e-5;
 
 
@@ -1122,6 +1133,176 @@ photos_utils_get_urns_from_paths (GList *paths, GtkTreeModel *model)
 }
 
 
+static void
+photos_utils_graph_to_xml_add_stack (GeglNode *head, gint indent, PhotosUtilsSerializeState *ss)
+{
+  if (GEGL_IS_NODE (head))
+    {
+      GeglNode *iter = head;
+
+      while (iter)
+        {
+          GeglPad     *input, *aux;
+          const gchar *id = NULL;
+          gchar       *class;
+          gegl_node_get (iter, "operation", &class, NULL);
+
+          input = gegl_node_get_pad (iter, "input");
+          aux   = gegl_node_get_pad (iter, "aux");
+
+          if (gegl_node_get_num_sinks (iter) > 1)
+            {
+              const gchar *new_id = g_hash_table_lookup (ss->clones, iter);
+              if (new_id)
+                {
+                  ind; g_string_append (ss->buf, "<clone ref='");
+                  g_string_append (ss->buf, new_id);
+                  g_string_append (ss->buf, "'/>\n");
+                  return; /* terminate the stack, the cloned part is already
+                             serialized */
+                }
+              else
+                {
+                  gchar temp_id[64];
+                  sprintf (temp_id, "clone%i", ss->clone_count++);
+                  id = g_strdup (temp_id);
+                  g_hash_table_insert (ss->clones, iter, (gchar *) id);
+                  /* the allocation is freed by the hash table */
+                }
+            }
+
+          if (!strcmp (class, "layer"))
+            {
+              serialize_layer (ss, indent, iter);
+            }
+          else
+            {
+              if (aux &&
+                  gegl_pad_get_connected_to (aux))
+                {
+                  GeglPad  *source_pad;
+                  GeglNode *source_node;
+                  source_pad  = gegl_pad_get_connected_to (aux);
+                  source_node = gegl_pad_get_node (source_pad);
+                  {
+                    GeglNode *graph = g_object_get_data (G_OBJECT (source_node),
+                                                         "graph");
+                    if (graph)
+                      source_node = graph;
+                  }
+                  ind; g_string_append (ss->buf, "<node");
+
+                  {
+                    gchar *class;
+                    gchar *name;
+                    gegl_node_get (iter, "operation", &class,
+                                   "name", &name,
+                                   NULL);
+                    if (name[0])
+                      {
+                        xml_attr (ss->buf, "name", name);
+                      }
+                    xml_attr (ss->buf, "operation", class);
+                    if (id != NULL)
+                      xml_attr (ss->buf, "id", id);
+                    g_free (name);
+                    g_free (class);
+                  }
+
+                  g_string_append (ss->buf, ">\n");
+                  serialize_properties (ss, indent + 4, iter);
+                  photos_utils_graph_to_xml_add_stack (source_node, indent + 4, ss);
+
+                  ind; g_string_append (ss->buf, "</node>\n");
+                }
+              else
+                {
+                  if (class)
+                    {
+                      if (strcmp (class, "nop") &&
+                          strcmp (class, "clone"))
+                        {
+                          ind; g_string_append (ss->buf, "<node");
+
+                          {
+                            gchar *class;
+                            gchar *name;
+                            gegl_node_get (iter, "operation", &class,
+                                           "name", &name,
+                                           NULL);
+                            if (name[0])
+                              {
+                                xml_attr (ss->buf, "name", name);
+                              }
+                            xml_attr (ss->buf, "operation", class);
+                            if (id != NULL)
+                              xml_attr (ss->buf, "id", id);
+                            g_free (name);
+                            g_free (class);
+                          }
+
+                          g_string_append (ss->buf, ">\n");
+                          serialize_properties (ss, indent + 4, iter);
+                          ind; g_string_append (ss->buf, "</node>\n");
+                        }
+                    }
+                }
+            }
+          id = NULL;
+          if (input)
+            {
+              GeglPad *source_pad;
+              source_pad = gegl_pad_get_connected_to (input);
+              if (source_pad)
+                {
+                  GeglNode *source_node = gegl_pad_get_node (source_pad);
+                  GeglNode *graph       = g_object_get_data (G_OBJECT (source_node),
+                                                             "graph");
+                  if (graph)
+                    source_node = graph;
+                  iter = source_node;
+                }
+              else
+                iter = NULL;
+            }
+          else
+            {
+              iter = NULL;
+            }
+
+          g_free (class);
+        }
+    }
+}
+
+
+gchar *
+photos_utils_graph_to_xml (GeglNode *head, GeglNode *tail, const gchar *path_root)
+{
+  PhotosUtilsSerializeState ss;
+  gchar *ret_val;
+
+  ss.buf = g_string_new ("");
+  ss.clones = g_hash_table_new (NULL, NULL);
+  ss.path_root = path_root;
+
+  head = gegl_node_get_output_proxy (head, "output");
+
+  g_string_append (ss.buf, "<?xml version='1.0' encoding='UTF-8'?>\n");
+  g_string_append (ss.buf, "<gegl>\n");
+
+  photos_utils_graph_to_xml_add_stack (head, 2, &ss);
+
+  g_string_append (ss->buf, "</gegl>\n");
+
+  g_hash_table_foreach (ss->clones, free_clone_id, NULL);
+  g_hash_table_destroy (ss->clones);
+
+  ret_val = g_string_free (ss.buf, FALSE);
+  return ret_val;
+}
+
+
 GIcon *
 photos_utils_icon_from_rdf_type (const gchar *type)
 {
diff --git a/src/photos-utils.h b/src/photos-utils.h
index cc63745..23b419b 100644
--- a/src/photos-utils.h
+++ b/src/photos-utils.h
@@ -1,6 +1,6 @@
 /*
  * Photos - access, organize and share your photos on GNOME
- * Copyright © 2012, 2013, 2014, 2015 Red Hat, Inc.
+ * Copyright © 2012, 2013, 2014, 2015, 2016 Red Hat, Inc.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -139,6 +139,8 @@ GtkBorder       *photos_utils_get_thumbnail_frame_border  (void);
 
 GList           *photos_utils_get_urns_from_paths         (GList *paths, GtkTreeModel *model);
 
+gchar           *photos_utils_graph_to_xml                 (GeglNode *head, GeglNode *tail, const gchar 
*path_root);
+
 GIcon           *photos_utils_icon_from_rdf_type          (const gchar *type);
 
 gboolean         photos_utils_make_directory_with_parents (GFile *file, GCancellable *cancellable, GError 
**error);