Add fragment and vertex snippet hooks for global declarations

This adds hook points to add global function and variable declarations
to either the fragment or vertex shader. The declarations can then be
used by subsequent snippets. Only the ‘declarations’ string of the
snippet is used and the code is directly put in the global scope near
the top of the shader.

The reason this is necessary rather than just adding a normal snippet
with the declarations is that for the other hooks Cogl assumes that
the snippets are independent of each other. That means if a snippet
has a replace string then it will assume that it doesn't even need to
generate the code for earlier hooks which means the global
declarations would be lost.

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

(cherry picked from commit ebb82d5b0bc30487b7101dc66b769160b40f92ca)

1 files changed, 111 insertions, 3 deletions

diff --git a/tests/conform/test-snippets.c b/tests/conform/test-snippets.c
index 51bd090a..f27af80d 100644
--- a/tests/conform/test-snippets.c
+++ b/tests/conform/test-snippets.c
@@ -6,7 +6,7 @@
 
 typedef struct _TestState
 {
-  int padding;
+  int fb_width, fb_height;
 } TestState;
 
 typedef void (* SnippetTestFunc) (TestState *state);
@@ -533,6 +533,109 @@ test_vertex_transform_hook (TestState *state)
 }
 
 static void
+test_global_vertex_hook (TestState *state)
+{
+  CoglPipeline *pipeline;
+  CoglSnippet *snippet;
+
+  pipeline = cogl_pipeline_new (test_ctx);
+
+  /* Creates a function in the global declarations hook which is used
+   * by a subsequent snippet. The subsequent snippets replace any
+   * previous snippets but this shouldn't prevent the global
+   * declarations from being generated */
+
+  snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_VERTEX_GLOBALS,
+                              /* declarations */
+                              "float\n"
+                              "multiply_by_two (float number)\n"
+                              "{\n"
+                              "  return number * 2.0;\n"
+                              "}\n",
+                              /* post */
+                              "This string shouldn't be used so "
+                              "we can safely put garbage in here.");
+  cogl_snippet_set_pre (snippet,
+                        "This string shouldn't be used so "
+                        "we can safely put garbage in here.");
+  cogl_snippet_set_replace (snippet,
+                            "This string shouldn't be used so "
+                            "we can safely put garbage in here.");
+  cogl_pipeline_add_snippet (pipeline, snippet);
+  cogl_object_unref (snippet);
+
+  snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_VERTEX,
+                              NULL, /* declarations */
+                              NULL /* replace */);
+  cogl_snippet_set_replace (snippet,
+                            "cogl_color_out.r = multiply_by_two (0.5);\n"
+                            "cogl_color_out.gba = vec3 (0.0, 0.0, 1.0);\n"
+                            "cogl_position_out = cogl_position_in;\n");
+  cogl_pipeline_add_snippet (pipeline, snippet);
+  cogl_object_unref (snippet);
+
+  cogl_framebuffer_draw_rectangle (test_fb,
+                                   pipeline,
+                                   -1, 1,
+                                   10.0f * 2.0f / state->fb_width - 1.0f,
+                                   10.0f * 2.0f / state->fb_height - 1.0f);
+
+  cogl_object_unref (pipeline);
+
+  test_utils_check_pixel (test_fb, 5, 5, 0xff0000ff);
+}
+
+static void
+test_global_fragment_hook (TestState *state)
+{
+  CoglPipeline *pipeline;
+  CoglSnippet *snippet;
+
+  pipeline = cogl_pipeline_new (test_ctx);
+
+  /* Creates a function in the global declarations hook which is used
+   * by a subsequent snippet. The subsequent snippets replace any
+   * previous snippets but this shouldn't prevent the global
+   * declarations from being generated */
+
+  snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_FRAGMENT_GLOBALS,
+                              /* declarations */
+                              "float\n"
+                              "multiply_by_four (float number)\n"
+                              "{\n"
+                              "  return number * 4.0;\n"
+                              "}\n",
+                              /* post */
+                              "This string shouldn't be used so "
+                              "we can safely put garbage in here.");
+  cogl_snippet_set_pre (snippet,
+                        "This string shouldn't be used so "
+                        "we can safely put garbage in here.");
+  cogl_snippet_set_replace (snippet,
+                            "This string shouldn't be used so "
+                            "we can safely put garbage in here.");
+  cogl_pipeline_add_snippet (pipeline, snippet);
+  cogl_object_unref (snippet);
+
+  snippet = cogl_snippet_new (COGL_SNIPPET_HOOK_FRAGMENT,
+                              NULL, /* declarations */
+                              NULL /* replace */);
+  cogl_snippet_set_replace (snippet,
+                            "cogl_color_out.r = multiply_by_four (0.25);\n"
+                            "cogl_color_out.gba = vec3 (0.0, 0.0, 1.0);\n");
+  cogl_pipeline_add_snippet (pipeline, snippet);
+  cogl_object_unref (snippet);
+
+  cogl_framebuffer_draw_rectangle (test_fb,
+                                   pipeline,
+                                   0, 0, 10, 10);
+
+  cogl_object_unref (pipeline);
+
+  test_utils_check_pixel (test_fb, 5, 5, 0xff0000ff);
+}
+
+static void
 test_snippet_order (TestState *state)
 {
   CoglPipeline *pipeline;
@@ -668,6 +771,8 @@ tests[] =
     test_modify_vertex_layer,
     test_replace_vertex_layer,
     test_vertex_transform_hook,
+    test_global_fragment_hook,
+    test_global_vertex_hook,
     test_snippet_order,
     test_naming_texture_units,
     test_snippet_properties
@@ -693,10 +798,13 @@ test_snippets (void)
 {
   TestState state;
 
+  state.fb_width = cogl_framebuffer_get_width (test_fb);
+  state.fb_height = cogl_framebuffer_get_height (test_fb);
+
   cogl_framebuffer_orthographic (test_fb,
                                  0, 0,
-                                 cogl_framebuffer_get_width (test_fb),
-                                 cogl_framebuffer_get_height (test_fb),
+                                 state.fb_width,
+                                 state.fb_height,
                                  -1,
                                  100);