[gimp] app: protect against calling a subclass' GimpItem::get_node() impl directly

[Michael Natterer <mitch src gnome org>]

commit 12aa801441226c7f8f1fa87416f22552b3eec292
Author: Michael Natterer <mitch gimp org>
Date:   Sun Feb 14 20:26:16 2010 +0100

    app: protect against calling a subclass' GimpItem::get_node() impl directly
    
    gimp_drawable_get_mode_node() was calling gimp_drawable_get_node()
    instead of gimp_item_get_node() if the mode_node didn't already exist.
    Fortunately that was never the case i nthe current code. Added
    warnings in the GimpItem::get_node() impls that would go off in such a
    situation.

 app/core/gimpchannel.c  |    6 ++++++
 app/core/gimpdrawable.c |    4 +++-
 app/core/gimplayer.c    |    2 ++
 3 files changed, 11 insertions(+), 1 deletions(-)
---
diff --git a/app/core/gimpchannel.c b/app/core/gimpchannel.c
index 7354976..ca7fd76 100644
--- a/app/core/gimpchannel.c
+++ b/app/core/gimpchannel.c
@@ -851,6 +851,8 @@ gimp_channel_get_node (GimpItem *item)
                        channel->color.b,
                        channel->color.a);
 
+  g_warn_if_fail (channel->color_node == NULL);
+
   channel->color_node = gegl_node_new_child (node,
                                              "operation", "gegl:color",
                                              "value",     color,
@@ -858,12 +860,16 @@ gimp_channel_get_node (GimpItem *item)
 
   g_object_unref (color);
 
+  g_warn_if_fail (channel->mask_node == NULL);
+
   channel->mask_node = gegl_node_new_child (node,
                                             "operation", "gegl:opacity",
                                             NULL);
   gegl_node_connect_to (channel->color_node, "output",
                         channel->mask_node,  "input");
 
+  g_warn_if_fail (channel->invert_node == NULL);
+
   channel->invert_node = gegl_node_new_child (node,
                                               "operation", "gegl:invert",
                                               NULL);
diff --git a/app/core/gimpdrawable.c b/app/core/gimpdrawable.c
index 5818c5b..af7dfe5 100644
--- a/app/core/gimpdrawable.c
+++ b/app/core/gimpdrawable.c
@@ -819,6 +819,8 @@ gimp_drawable_get_node (GimpItem *item)
 
   node = GIMP_ITEM_CLASS (parent_class)->get_node (item);
 
+  g_warn_if_fail (drawable->private->mode_node == NULL);
+
   drawable->private->mode_node = gegl_node_new_child (node,
                                                       "operation", "gegl:over",
                                                       NULL);
@@ -1533,7 +1535,7 @@ gimp_drawable_get_mode_node (GimpDrawable *drawable)
   g_return_val_if_fail (GIMP_IS_DRAWABLE (drawable), NULL);
 
   if (! drawable->private->mode_node)
-    gimp_drawable_get_node (GIMP_ITEM (drawable));
+    gimp_item_get_node (GIMP_ITEM (drawable));
 
   return drawable->private->mode_node;
 }
diff --git a/app/core/gimplayer.c b/app/core/gimplayer.c
index fe5892d..a99416f 100644
--- a/app/core/gimplayer.c
+++ b/app/core/gimplayer.c
@@ -761,6 +761,8 @@ gimp_layer_get_node (GimpItem *item)
   source = gimp_drawable_get_source_node (drawable);
   gegl_node_add_child (node, source);
 
+  g_warn_if_fail (layer->opacity_node == NULL);
+
   layer->opacity_node = gegl_node_new_child (node,
                                              "operation", "gegl:opacity",
                                              "value",     layer->opacity,