[cogl] test-utils: Add some fuzz to the pixel comparison routine

[Neil Roberts <nroberts src gnome org>]

commit 4c8966122f0e5bc6866f14dc5eeadad3142ff9a0
Author: Neil Roberts <neil linux intel com>
Date:   Wed Dec 7 12:38:38 2011 +0000

    test-utils: Add some fuzz to the pixel comparison routine
    
    When comparing a pixel, the comparison routines now allow each
    component to be off by +/- 1. This is to compensate for varying
    rounding across drivers.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=665723
    
    Reviewed-by: Robert Bragg <robert linux intel com>

 tests/conform/test-utils.c |   51 ++++++++++++++++++++++++++-----------------
 1 files changed, 31 insertions(+), 20 deletions(-)
---
diff --git a/tests/conform/test-utils.c b/tests/conform/test-utils.c
index 1c0d5b5..9d4d7e9 100644
--- a/tests/conform/test-utils.c
+++ b/tests/conform/test-utils.c
@@ -79,24 +79,43 @@ test_utils_fini (TestUtilsGTestFixture *fixture,
     cogl_object_unref (state->ctx);
 }
 
+static gboolean
+compare_component (int a, int b)
+{
+  return ABS (a - b) <= 1;
+}
+
+static void
+compare_pixel (const guint8 *screen_pixel, guint32 expected_pixel)
+{
+  /* Compare each component with a small fuzz factor */
+  if (!compare_component (screen_pixel[0], expected_pixel >> 24) ||
+      !compare_component (screen_pixel[1], (expected_pixel >> 16) & 0xff) ||
+      !compare_component (screen_pixel[2], (expected_pixel >> 8) & 0xff))
+    {
+      guint32 screen_pixel_num = GUINT32_FROM_BE (*(guint32 *) screen_pixel);
+      char *screen_pixel_string =
+        g_strdup_printf ("#%06x", screen_pixel_num >> 8);
+      char *expected_pixel_string =
+        g_strdup_printf ("#%06x", expected_pixel >> 8);
+
+      g_assert_cmpstr (screen_pixel_string, ==, expected_pixel_string);
+
+      g_free (screen_pixel_string);
+      g_free (expected_pixel_string);
+    }
+}
+
 void
 test_utils_check_pixel (int x, int y, guint32 expected_pixel)
 {
-  guint32 pixel;
-  char *screen_pixel;
-  char *intended_pixel;
+  guint8 pixel[4];
 
   cogl_read_pixels (x, y, 1, 1, COGL_READ_PIXELS_COLOR_BUFFER,
                     COGL_PIXEL_FORMAT_RGBA_8888_PRE,
-                    (guint8 *) &pixel);
-
-  screen_pixel = g_strdup_printf ("#%06x", GUINT32_FROM_BE (pixel) >> 8);
-  intended_pixel = g_strdup_printf ("#%06x", expected_pixel >> 8);
-
-  g_assert_cmpstr (screen_pixel, ==, intended_pixel);
+                    pixel);
 
-  g_free (screen_pixel);
-  g_free (intended_pixel);
+  compare_pixel (pixel, expected_pixel);
 }
 
 void
@@ -110,7 +129,6 @@ test_utils_check_region (int x, int y,
                          int width, int height,
                          guint32 expected_rgba)
 {
-  guint32 reference = expected_rgba >> 8;
   guint8 *pixels, *p;
 
   pixels = p = g_malloc (width * height * 4);
@@ -126,14 +144,7 @@ test_utils_check_region (int x, int y,
   for (y = 0; y < height; y++)
     for (x = 0; x < width; x++)
       {
-        guint32 current = GUINT32_FROM_BE (*((guint32 *)p)) >> 8;
-        if (current != reference)
-          {
-            /* Ensure we have a meaningful error message... */
-            char *screen_pixel = g_strdup_printf ("#%06x", current);
-            char *intended_pixel = g_strdup_printf ("#%06x", reference);
-            g_assert_cmpstr (screen_pixel, == ,intended_pixel);
-          }
+        compare_pixel (p, expected_rgba);
         p += 4;
       }