snippet: Don't generate code for snippets that are replaced

The loop that generates code for a list of snippets now starts from
the first snippet that has a replace string. Any snippets before that
would be ignored so there's no point in generating code for them.

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

cogl/cogl-pipeline-snippet.c

@@ -40,17 +40,66 @@
 void
 _cogl_pipeline_snippet_generate_code (const CoglPipelineSnippetData *data)
 {
-  CoglPipelineSnippet *snippet;
+  CoglPipelineSnippet *first_snippet, *snippet;
   int snippet_num = 0;
   int n_snippets = 0;
 
+  first_snippet = COGL_LIST_FIRST (data->snippets);
+
   /* First count the number of snippets so we can easily tell when
      we're at the last one */
   COGL_LIST_FOREACH (snippet, data->snippets, list_node)
     if (snippet->snippet->hook == data->hook)
-      n_snippets++;
+      {
+        /* Don't bother processing any previous snippets if we reach
+           one that has a replacement */
+        if (snippet->snippet->replace)
+          {
+            n_snippets = 1;
+            first_snippet = snippet;
+          }
+        else
+          n_snippets++;
+      }
 
-  COGL_LIST_FOREACH (snippet, data->snippets, list_node)
+  /* If there weren't any snippets then generate a stub function with
+     the final name */
+  if (n_snippets == 0)
+    {
+      if (data->return_type)
+        g_string_append_printf (data->source_buf,
+                                "\n"
+                                "%s\n"
+                                "%s (%s)\n"
+                                "{\n"
+                                "  return %s (%s);\n"
+                                "}\n",
+                                data->return_type,
+                                data->final_name,
+                                data->argument_declarations ?
+                                data->argument_declarations : "",
+                                data->chain_function,
+                                data->arguments ? data->arguments : "");
+      else
+        g_string_append_printf (data->source_buf,
+                                "\n"
+                                "void\n"
+                                "%s (%s)\n"
+                                "{\n"
+                                "  %s (%s);\n"
+                                "}\n",
+                                data->final_name,
+                                data->argument_declarations ?
+                                data->argument_declarations : "",
+                                data->chain_function,
+                                data->arguments ? data->arguments : "");
+
+      return;
+    }
+
+  for (snippet = first_snippet, snippet_num = 0;
+       snippet_num < n_snippets;
+       snippet = COGL_LIST_NEXT (snippet, list_node), snippet_num++)
     if (snippet->snippet->hook == data->hook)
       {
         const char *source;
@@ -130,42 +179,7 @@ _cogl_pipeline_snippet_generate_code (const CoglPipelineSnippetData *data)
                                   data->return_variable);
 
         g_string_append (data->source_buf, "}\n");
-
-        snippet_num++;
       }
-
-  /* If there weren't any snippets then generate a stub function with
-     the final name */
-  if (snippet_num == 0)
-    {
-      if (data->return_type)
-        g_string_append_printf (data->source_buf,
-                                "\n"
-                                "%s\n"
-                                "%s (%s)\n"
-                                "{\n"
-                                "  return %s (%s);\n"
-                                "}\n",
-                                data->return_type,
-                                data->final_name,
-                                data->argument_declarations ?
-                                data->argument_declarations : "",
-                                data->chain_function,
-                                data->arguments ? data->arguments : "");
-      else
-        g_string_append_printf (data->source_buf,
-                                "\n"
-                                "void\n"
-                                "%s (%s)\n"
-                                "{\n"
-                                "  %s (%s);\n"
-                                "}\n",
-                                data->final_name,
-                                data->argument_declarations ?
-                                data->argument_declarations : "",
-                                data->chain_function,
-                                data->arguments ? data->arguments : "");
-    }
 }
 
 static void

tests/conform/test-snippets.c

@@ -232,6 +232,28 @@ paint (TestState *state)
 
   cogl_object_unref (snippet);
 
+  /* Test replacing a previous snippet */
+  pipeline = create_texture_pipeline ();
+
+  snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_FRAGMENT,
+                              NULL,
+                              "cogl_color_out = vec4 (0.5, 0.5, 0.5, 1.0);");
+  cogl_pipeline_add_snippet (pipeline, snippet);
+  cogl_object_unref (snippet);
+
+  snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_FRAGMENT, NULL, NULL);
+  cogl_snippet_set_pre (snippet, "cogl_color_out = vec4 (1.0, 1.0, 1.0, 1.0);");
+  cogl_snippet_set_replace (snippet,
+                            "cogl_color_out *= vec4 (1.0, 0.0, 0.0, 1.0);");
+  cogl_pipeline_add_snippet (pipeline, snippet);
+  cogl_object_unref (snippet);
+
+  cogl_push_source (pipeline);
+  cogl_rectangle_with_texture_coords (100, 0, 110, 10,
+                                      0, 0, 0, 0);
+  cogl_pop_source ();
+  cogl_object_unref (pipeline);
+
   /* Sanity check modifying the snippet */
   snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_FRAGMENT, "foo", "bar");
   g_assert_cmpstr (cogl_snippet_get_declarations (snippet), ==, "foo");
@@ -280,6 +302,7 @@ validate_result (void)
   test_utils_check_pixel (65, 5, 0x00ff00ff);
   test_utils_check_pixel (75, 5, 0x808000ff);
   test_utils_check_pixel (85, 5, 0x00ffffff);
+  test_utils_check_pixel (105, 5, 0xff0000ff);
 }
 
 void