Add a CoglSnippet type

This adds a CoglObject called CoglSnippet which will be used to store
strings used as GLSL snippets to be attached at hook points to a
CoglPipeline. The snippets can currently contain three strings:

declarations - This will be placed in the global scope and is intended
               to be used to declare uniforms, attributes and
               functions.

pre           - This will be inserted before the hook point.

post          - This will be inserted after the hook point.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

cogl/cogl-snippet.c

@@ -0,0 +1,145 @@
+/*
+ * Cogl
+ *
+ * An object oriented GL/GLES Abstraction/Utility Layer
+ *
+ * Copyright (C) 2011 Intel Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ *
+ *
+ * Authors:
+ *   Neil Roberts <neil@linux.intel.com>
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "cogl-snippet-private.h"
+#include "cogl-util.h"
+
+static void
+_cogl_snippet_free (CoglSnippet *snippet);
+
+COGL_OBJECT_DEFINE (Snippet, snippet);
+
+CoglSnippet *
+cogl_snippet_new (const char *declarations,
+                  const char *post)
+{
+  CoglSnippet *snippet = g_slice_new0 (CoglSnippet);
+
+  _cogl_snippet_object_new (snippet);
+
+  cogl_snippet_set_declarations (snippet, declarations);
+  cogl_snippet_set_post (snippet, post);
+
+  return snippet;
+}
+
+static gboolean
+_cogl_snippet_modify (CoglSnippet *snippet)
+{
+  if (snippet->immutable)
+    {
+      g_warning ("A CoglSnippet should not be modified once it has been "
+                 "attached to a pipeline. Any modifications after that point "
+                 "will be ignored.");
+
+      return FALSE;
+    }
+
+  return TRUE;
+}
+
+void
+cogl_snippet_set_declarations (CoglSnippet *snippet,
+                               const char *declarations)
+{
+  _COGL_RETURN_IF_FAIL (cogl_is_snippet (snippet));
+
+  if (!_cogl_snippet_modify (snippet))
+    return;
+
+  g_free (snippet->declarations);
+  snippet->declarations = declarations ? g_strdup (declarations) : NULL;
+}
+
+const char *
+cogl_snippet_get_declarations (CoglSnippet *snippet)
+{
+  _COGL_RETURN_VAL_IF_FAIL (cogl_is_snippet (snippet), NULL);
+
+  return snippet->declarations;
+}
+
+void
+cogl_snippet_set_pre (CoglSnippet *snippet,
+                      const char *pre)
+{
+  _COGL_RETURN_IF_FAIL (cogl_is_snippet (snippet));
+
+  if (!_cogl_snippet_modify (snippet))
+    return;
+
+  g_free (snippet->pre);
+  snippet->pre = pre ? g_strdup (pre) : NULL;
+}
+
+const char *
+cogl_snippet_get_pre (CoglSnippet *snippet)
+{
+  _COGL_RETURN_VAL_IF_FAIL (cogl_is_snippet (snippet), NULL);
+
+  return snippet->pre;
+}
+
+void
+cogl_snippet_set_post (CoglSnippet *snippet,
+                       const char *post)
+{
+  _COGL_RETURN_IF_FAIL (cogl_is_snippet (snippet));
+
+  if (!_cogl_snippet_modify (snippet))
+    return;
+
+  g_free (snippet->post);
+  snippet->post = post ? g_strdup (post) : NULL;
+}
+
+const char *
+cogl_snippet_get_post (CoglSnippet *snippet)
+{
+  _COGL_RETURN_VAL_IF_FAIL (cogl_is_snippet (snippet), NULL);
+
+  return snippet->post;
+}
+
+void
+_cogl_snippet_make_immutable (CoglSnippet *snippet)
+{
+  snippet->immutable = TRUE;
+}
+
+static void
+_cogl_snippet_free (CoglSnippet *snippet)
+{
+  g_free (snippet->declarations);
+  g_free (snippet->pre);
+  g_free (snippet->post);
+  g_slice_free (CoglSnippet, snippet);
+}