Add a simple conformance test for alpha testing

This adds a simple test which sets an alpha test on a pipeline and
then renders a texture. It then verifies that the transparent parts of
the texture aren't drawn. This is currently failing with the GL3
driver because GL3 requires the alpha test to be implemented in GLSL
but the generated alpha test uniform is only updated for the GLES2
driver.

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

3 files changed, 77 insertions, 0 deletions

diff --git a/tests/conform/Makefile.am b/tests/conform/Makefile.am
index 8eeffd0b..eab0b94e 100644
--- a/tests/conform/Makefile.am
+++ b/tests/conform/Makefile.am
@@ -56,6 +56,7 @@ test_sources = \
 	test-gles2-context.c \
 	test-euler-quaternion.c \
 	test-layer-remove.c \
+	test-alpha-test.c \
 	$(NULL)
 
 test_conformance_SOURCES = $(common_sources) $(test_sources)
diff --git a/tests/conform/test-alpha-test.c b/tests/conform/test-alpha-test.c
new file mode 100644
index 00000000..285118b0
--- /dev/null
+++ b/tests/conform/test-alpha-test.c
@@ -0,0 +1,74 @@
+#include <cogl/cogl.h>
+#include <string.h>
+
+#include "test-utils.h"
+
+static CoglTexture2D *
+create_texture (CoglContext *context)
+{
+  static const uint8_t data[] =
+    {
+      0xff, 0x00, 0x00, 0xff,
+      0x00, 0xfa, 0x00, 0xfa
+    };
+
+  return cogl_texture_2d_new_from_data (context,
+                                        2, 1, /* width/height */
+                                        COGL_PIXEL_FORMAT_RGBA_8888_PRE,
+                                        COGL_PIXEL_FORMAT_ANY,
+                                        4, /* rowstride */
+                                        data,
+                                        NULL /* error */);
+}
+
+void
+test_alpha_test (void)
+{
+  CoglTexture *tex = COGL_TEXTURE (create_texture (test_ctx));
+  CoglPipeline *pipeline = cogl_pipeline_new (test_ctx);
+  int fb_width = cogl_framebuffer_get_width (test_fb);
+  int fb_height = cogl_framebuffer_get_height (test_fb);
+  CoglColor clear_color;
+
+  cogl_pipeline_set_layer_texture (pipeline, 0, tex);
+  cogl_pipeline_set_layer_filters (pipeline, 0,
+                                   COGL_PIPELINE_FILTER_NEAREST,
+                                   COGL_PIPELINE_FILTER_NEAREST);
+  cogl_pipeline_set_alpha_test_function (pipeline,
+                                         COGL_PIPELINE_ALPHA_FUNC_GEQUAL,
+                                         254 / 255.0f /* alpha reference */);
+
+  cogl_color_init_from_4ub (&clear_color, 0x00, 0x00, 0xff, 0xff);
+  cogl_framebuffer_clear (test_fb,
+                          COGL_BUFFER_BIT_COLOR,
+                          &clear_color);
+
+  cogl_framebuffer_draw_rectangle (test_fb,
+                                   pipeline,
+                                   -1, -1,
+                                   1, 1);
+
+  cogl_object_unref (pipeline);
+  cogl_object_unref (tex);
+
+  /* The left side of the framebuffer should use the first pixel from
+   * the texture which is red */
+  test_utils_check_region (test_fb,
+                           2, 2,
+                           fb_width / 2 - 4,
+                           fb_height - 4,
+                           0xff0000ff);
+  /* The right side of the framebuffer should use the clear color
+   * because the second pixel from the texture is clipped from the
+   * alpha test */
+  test_utils_check_region (test_fb,
+                           fb_width / 2 + 2,
+                           2,
+                           fb_width / 2 - 4,
+                           fb_height - 4,
+                           0x0000ffff);
+
+  if (cogl_test_verbose ())
+    g_print ("OK\n");
+}
+
diff --git a/tests/conform/test-conform-main.c b/tests/conform/test-conform-main.c
index 74756850..df9d2a5a 100644
--- a/tests/conform/test-conform-main.c
+++ b/tests/conform/test-conform-main.c
@@ -100,6 +100,8 @@ main (int argc, char **argv)
 
   ADD_TEST (test_version, 0);
 
+  ADD_TEST (test_alpha_test, 0);
+
   UNPORTED_TEST (test_viewport);
 
   ADD_TEST (test_gles2_context, TEST_REQUIREMENT_GLES2_CONTEXT);