[gegl] Drop cache if the node's output format has changed

[Daniel Sabo <daniels src gnome org>]

commit 9e86368826f3b1207fb104e70d70c6f9dfb0779e
Author: Daniel Sabo <DanielSabo gmail com>
Date:   Wed Jan 16 00:57:22 2013 -0800

    Drop cache if the node's output format has changed

 gegl/graph/gegl-node.c |   30 +++++++++++++++++++-----------
 1 files changed, 19 insertions(+), 11 deletions(-)
---
diff --git a/gegl/graph/gegl-node.c b/gegl/graph/gegl-node.c
index 1a7d507..1b24c88 100644
--- a/gegl/graph/gegl-node.c
+++ b/gegl/graph/gegl-node.c
@@ -2052,21 +2052,29 @@ gegl_node_computed_event (GeglCache *self,
 GeglCache *
 gegl_node_get_cache (GeglNode *node)
 {
+  GeglPad    *pad;
+  const Babl *format = NULL;
   g_return_val_if_fail (GEGL_IS_NODE (node), NULL);
 
-  if (!node->cache)
-    {
-      GeglPad    *pad;
-      const Babl *format;
+  /* XXX: it should be possible to have cache for other pads than
+   * only "output" pads
+   */
+  pad = gegl_node_get_pad (node, "output");
+  if (!pad)
+    return NULL;
 
-      /* XXX: it should be possible to have cache for other pads than
-       * only "output" pads
-       */
-      pad = gegl_node_get_pad (node, "output");
-      if (!pad)
-        return NULL;
+  format = gegl_pad_get_format (pad);
 
-      format = gegl_pad_get_format (pad);
+  if (node->cache && format &&
+      node->cache->format != format)
+  {
+    /* FIXME: Also cover output_format = NULL and cache->format != RGBA float */
+    g_object_unref(node->cache);
+    node->cache = NULL;
+  }
+
+  if (!node->cache)
+    {
       if (!format)
         {
           format = babl_format ("RGBA float");