snippet: Add a 'replace' string

If present, the 'replace' string will be used instead of whatever code
would normally be invoked for that hook point. It will also replace
any previous snippets.

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

cogl/cogl-pipeline-fragend-glsl.c

@@ -957,8 +957,11 @@ _cogl_pipeline_fragend_glsl_end (CoglPipeline *pipeline,
             if ((source = cogl_snippet_get_pre (snippet->snippet)))
               g_string_append (shader_state->source, source);
 
-            /* Chain on to the next function */
-            if (snippet_num > 0)
+            /* Chain on to the next function, or bypass it if there is
+               a replace string */
+            if ((source = cogl_snippet_get_replace (snippet->snippet)))
+              g_string_append (shader_state->source, source);
+            else if (snippet_num > 0)
               g_string_append_printf (shader_state->source,
                                       "  cogl_snippet%i ();\n",
                                       snippet_num - 1);

cogl/cogl-pipeline-state.h

@@ -954,6 +954,11 @@ cogl_pipeline_set_uniform_matrix (CoglPipeline *pipeline,
  * The ‘pre’ string in @snippet will be inserted at the top of the
  * main() function before any vertex processing is done.
  *
+ * The ‘replace’ string in @snippet will be used instead of the
+ * generated vertex processing if it is present. This can be used if
+ * the application wants to provide a complete vertex shader and
+ * doesn't need the generated output from Cogl.
+ *
  * The ‘post’ string in @snippet will be inserted after all of the
  * standard vertex processing is done. This can be used to modify the
  * outputs.
@@ -982,6 +987,11 @@ cogl_pipeline_add_vertex_hook (CoglPipeline *pipeline,
  * The ‘pre’ string in @snippet will be inserted at the top of the
  * main() function before any fragment processing is done.
  *
+ * The ‘replace’ string in @snippet will be used instead of the
+ * generated fragment processing if it is present. This can be used if
+ * the application wants to provide a complete fragment shader and
+ * doesn't need the generated output from Cogl.
+ *
  * The ‘post’ string in @snippet will be inserted after all of the
  * standard fragment processing is done. At this point the generated
  * value for the rest of the pipeline state will already be in

cogl/cogl-pipeline-vertend-glsl.c

@@ -397,8 +397,11 @@ _cogl_pipeline_vertend_glsl_end (CoglPipeline *pipeline,
             if ((source = cogl_snippet_get_pre (snippet->snippet)))
               g_string_append (shader_state->source, source);
 
-            /* Chain on to the next function */
-            if (snippet_num > 0)
+            /* Chain on to the next function, or bypass it if there is
+               a replace string */
+            if ((source = cogl_snippet_get_replace (snippet->snippet)))
+              g_string_append (shader_state->source, source);
+            else if (snippet_num > 0)
               g_string_append_printf (shader_state->source,
                                       "  cogl_snippet%i ();\n",
                                       snippet_num - 1);

cogl/cogl-snippet-private.h

@@ -44,6 +44,7 @@ struct _CoglSnippet
 
   char *declarations;
   char *pre;
+  char *replace;
   char *post;
 };
 

cogl/cogl-snippet.c

@@ -108,6 +108,27 @@ cogl_snippet_get_pre (CoglSnippet *snippet)
   return snippet->pre;
 }
 
+void
+cogl_snippet_set_replace (CoglSnippet *snippet,
+                          const char *replace)
+{
+  _COGL_RETURN_IF_FAIL (cogl_is_snippet (snippet));
+
+  if (!_cogl_snippet_modify (snippet))
+    return;
+
+  g_free (snippet->replace);
+  snippet->replace = replace ? g_strdup (replace) : NULL;
+}
+
+const char *
+cogl_snippet_get_replace (CoglSnippet *snippet)
+{
+  _COGL_RETURN_VAL_IF_FAIL (cogl_is_snippet (snippet), NULL);
+
+  return snippet->replace;
+}
+
 void
 cogl_snippet_set_post (CoglSnippet *snippet,
                        const char *post)
@@ -140,6 +161,7 @@ _cogl_snippet_free (CoglSnippet *snippet)
 {
   g_free (snippet->declarations);
   g_free (snippet->pre);
+  g_free (snippet->replace);
   g_free (snippet->post);
   g_slice_free (CoglSnippet, snippet);
 }

cogl/cogl-snippet.h

@@ -154,6 +154,42 @@ cogl_snippet_set_pre (CoglSnippet *snippet,
 const char *
 cogl_snippet_get_pre (CoglSnippet *snippet);
 
+#define cogl_snippet_set_replace cogl_snippet_set_replace_EXP
+/**
+ * cogl_snippet_set_replace:
+ * @snippet: A #CoglSnippet
+ * @replace: The new source string for the replace section of this snippet.
+ *
+ * Sets a source string that will be used instead of any generated
+ * source code or any previous snippets for this hook point. Please
+ * see the documentation of each hook point in #CoglPipeline for a
+ * description of how this string should be used.
+ *
+ * This function should only be called before the snippet is attached
+ * to its first pipeline. After that the snippet should be considered
+ * immutable.
+ *
+ * Since: 1.10
+ * Stability: Unstable
+ */
+void
+cogl_snippet_set_replace (CoglSnippet *snippet,
+                          const char *replace);
+
+#define cogl_snippet_get_replace cogl_snippet_get_replace_EXP
+/**
+ * cogl_snippet_get_replace:
+ * @snippet: A #CoglSnippet
+ *
+ * Return value: the source string that was set with
+ *   cogl_snippet_set_replace() or %NULL if none was set.
+ *
+ * Since: 1.10
+ * Stability: Unstable
+ */
+const char *
+cogl_snippet_get_replace (CoglSnippet *snippet);
+
 #define cogl_snippet_set_post cogl_snippet_set_post_EXP
 /**
  * cogl_snippet_set_post:

tests/conform/test-snippets.c

@@ -150,25 +150,55 @@ paint (TestState *state)
 
   cogl_object_unref (snippet);
 
+  /* Check the replace string */
+  snippet = cogl_snippet_new (NULL, NULL);
+  cogl_snippet_set_pre (snippet,
+                        "cogl_color_out = vec4 (0.0, 0.5, 0.0, 1.0);");
+  /* Remove the generated output. If the replace string isn't working
+     then the code from the pre string would get overwritten with
+     white */
+  cogl_snippet_set_replace (snippet, "/* do nothing */");
+  cogl_snippet_set_post (snippet,
+                         "cogl_color_out += vec4 (0.5, 0.0, 0.0, 1.0);");
+
+  pipeline = cogl_pipeline_new ();
+  cogl_pipeline_add_fragment_hook (pipeline, snippet);
+  cogl_push_source (pipeline);
+  cogl_rectangle (70, 0, 80, 10);
+  cogl_pop_source ();
+  cogl_object_unref (pipeline);
+
+  cogl_object_unref (snippet);
+
   /* Sanity check modifying the snippet */
   snippet = cogl_snippet_new ("foo", "bar");
   g_assert_cmpstr (cogl_snippet_get_declarations (snippet), ==, "foo");
   g_assert_cmpstr (cogl_snippet_get_post (snippet), ==, "bar");
+  g_assert_cmpstr (cogl_snippet_get_replace (snippet), ==, NULL);
   g_assert_cmpstr (cogl_snippet_get_pre (snippet), ==, NULL);
 
   cogl_snippet_set_declarations (snippet, "fu");
   g_assert_cmpstr (cogl_snippet_get_declarations (snippet), ==, "fu");
   g_assert_cmpstr (cogl_snippet_get_post (snippet), ==, "bar");
+  g_assert_cmpstr (cogl_snippet_get_replace (snippet), ==, NULL);
   g_assert_cmpstr (cogl_snippet_get_pre (snippet), ==, NULL);
 
   cogl_snippet_set_post (snippet, "ba");
   g_assert_cmpstr (cogl_snippet_get_declarations (snippet), ==, "fu");
   g_assert_cmpstr (cogl_snippet_get_post (snippet), ==, "ba");
+  g_assert_cmpstr (cogl_snippet_get_replace (snippet), ==, NULL);
   g_assert_cmpstr (cogl_snippet_get_pre (snippet), ==, NULL);
 
   cogl_snippet_set_pre (snippet, "fuba");
   g_assert_cmpstr (cogl_snippet_get_declarations (snippet), ==, "fu");
   g_assert_cmpstr (cogl_snippet_get_post (snippet), ==, "ba");
+  g_assert_cmpstr (cogl_snippet_get_replace (snippet), ==, NULL);
+  g_assert_cmpstr (cogl_snippet_get_pre (snippet), ==, "fuba");
+
+  cogl_snippet_set_replace (snippet, "baba");
+  g_assert_cmpstr (cogl_snippet_get_declarations (snippet), ==, "fu");
+  g_assert_cmpstr (cogl_snippet_get_post (snippet), ==, "ba");
+  g_assert_cmpstr (cogl_snippet_get_replace (snippet), ==, "baba");
   g_assert_cmpstr (cogl_snippet_get_pre (snippet), ==, "fuba");
 }
 
@@ -182,6 +212,7 @@ validate_result (void)
   test_utils_check_pixel (45, 5, 0xff0000ff);
   test_utils_check_pixel (55, 5, 0x00ff00ff);
   test_utils_check_pixel (65, 5, 0x00ff00ff);
+  test_utils_check_pixel (75, 5, 0x808000ff);
 }
 
 void