pipeline: Add a snippet hook for the texture lookup

This adds a per-layer snippet hook for the texure lookup. Here the
snippet can modify the texture coordinates used for the lookup or
modify the texel resulting from the lookup. This is the first
per-layer hook so this also adds the
COGL_PIPELINE_LAYER_STATE_FRAGMENT_SNIPPETS state and all of the
boilerplate needed to make that work.

Most of the functions used by the pipeline state to manage the snippet
list has been moved into cogl-pipeline-snippet.c so that it can be
shared with the layer state.

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

cogl/cogl-pipeline-snippet.c

@@ -32,6 +32,8 @@
 #include <string.h>
 
 #include "cogl-pipeline-snippet-private.h"
+#include "cogl-snippet-private.h"
+#include "cogl-util.h"
 
 /* Helper functions that are used by both GLSL pipeline backends */
 
@@ -158,3 +160,101 @@ _cogl_pipeline_snippet_generate_code (const CoglPipelineSnippetData *data)
                                 data->arguments ? data->arguments : "");
     }
 }
+
+static void
+_cogl_pipeline_snippet_free (CoglPipelineSnippet *pipeline_snippet)
+{
+  cogl_object_unref (pipeline_snippet->snippet);
+  g_slice_free (CoglPipelineSnippet, pipeline_snippet);
+}
+
+void
+_cogl_pipeline_snippet_list_free (CoglPipelineSnippetList *list)
+{
+  CoglPipelineSnippet *pipeline_snippet, *tmp;
+
+  COGL_LIST_FOREACH_SAFE (pipeline_snippet, list, list_node, tmp)
+    _cogl_pipeline_snippet_free (pipeline_snippet);
+}
+
+void
+_cogl_pipeline_snippet_list_add (CoglPipelineSnippetList *list,
+                                 CoglPipelineSnippetHook hook,
+                                 CoglSnippet *snippet)
+{
+  CoglPipelineSnippet *pipeline_snippet = g_slice_new (CoglPipelineSnippet);
+
+  pipeline_snippet->hook = hook;
+  pipeline_snippet->snippet = cogl_object_ref (snippet);
+
+  _cogl_snippet_make_immutable (pipeline_snippet->snippet);
+
+  if (COGL_LIST_EMPTY (list))
+    COGL_LIST_INSERT_HEAD (list, pipeline_snippet, list_node);
+  else
+    {
+      CoglPipelineSnippet *tail;
+
+      for (tail = COGL_LIST_FIRST (list);
+           COGL_LIST_NEXT (tail, list_node);
+           tail = COGL_LIST_NEXT (tail, list_node));
+
+      COGL_LIST_INSERT_AFTER (tail, pipeline_snippet, list_node);
+    }
+}
+
+void
+_cogl_pipeline_snippet_list_copy (CoglPipelineSnippetList *dst,
+                                  const CoglPipelineSnippetList *src)
+{
+  CoglPipelineSnippet *tail = NULL;
+  const CoglPipelineSnippet *l;
+
+  COGL_LIST_INIT (dst);
+
+  COGL_LIST_FOREACH (l, src, list_node)
+    {
+      CoglPipelineSnippet *copy = g_slice_dup (CoglPipelineSnippet, l);
+
+      cogl_object_ref (copy->snippet);
+
+      if (tail)
+        COGL_LIST_INSERT_AFTER (tail, copy, list_node);
+      else
+        COGL_LIST_INSERT_HEAD (dst, copy, list_node);
+
+      tail = copy;
+    }
+}
+
+void
+_cogl_pipeline_snippet_list_hash (CoglPipelineSnippetList *list,
+                                  unsigned int *hash)
+{
+  CoglPipelineSnippet *l;
+
+  COGL_LIST_FOREACH (l, list, list_node)
+    {
+      *hash = _cogl_util_one_at_a_time_hash (*hash,
+                                             &l->hook,
+                                             sizeof (CoglPipelineSnippetHook));
+      *hash = _cogl_util_one_at_a_time_hash (*hash,
+                                             &l->snippet,
+                                             sizeof (CoglSnippet *));
+    }
+}
+
+gboolean
+_cogl_pipeline_snippet_list_equal (CoglPipelineSnippetList *list0,
+                                   CoglPipelineSnippetList *list1)
+{
+  CoglPipelineSnippet *l0, *l1;
+
+  for (l0 = COGL_LIST_FIRST (list0), l1 = COGL_LIST_FIRST (list1);
+       l0 && l1;
+       l0 = COGL_LIST_NEXT (l0, list_node), l1 = COGL_LIST_NEXT (l1, list_node))
+    if (l0->hook != l1->hook || l0->snippet != l1->snippet)
+      return FALSE;
+
+  return l0 == NULL && l1 == NULL;
+}