reftests: Allow minor differences to be tolerated

Based on an earlier patch by Michael Biebl, as used in Debian's GTK 3
packaging, with additional inspiration from librsvg's reftests.

Each .ui or .node reftest can have an accompanying .keyfile file
like this:

    [reftest]
    tolerated-diff-level=20
    tolerated-diff-pixels=1000

If the image differs, but the number of pixels that differ is no more
than tolerated-diff-pixels and the differences are no more than
tolerated-diff-level, then we treat it as a success with warnings, save
the .diff.png for analysis, and use g_test_incomplete() to record the
test-case as "TODO".

Signed-off-by: Simon McVittie <smcv@debian.org>
Forwarded: https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/3195
Applied-upstream: no, upstream want reftests to be a strict pass/fail with identical results required

Gbp-Pq: Name reftests-Allow-minor-differences-to-be-tolerated.patch

diff --git a/testsuite/gsk/compare-render.c b/testsuite/gsk/compare-render.c
index 9742358b5b0fcb73527eb2ebc6ec5add7bcfedc7..cd6bf50399b67b9057195d201c52e76f50164479 100644 (file)
--- a/testsuite/gsk/compare-render.c
+++ b/testsuite/gsk/compare-render.c
@@ -98,6 +98,12 @@ get_output_file (const char *file,
   return result;
 }
 
+static char *
+get_test_keyfile (const char *node_file)
+{
+  return file_replace_extension (node_file, ".node", ".keyfile");
+}
+
 static void
 save_image (cairo_surface_t *surface,
             const char      *test_name,
@@ -246,12 +252,35 @@ main (int argc, char **argv)
 
       if (diff_surface)
         {
+          char *keyfile_path = get_test_keyfile (node_file);
+          GKeyFile *keyfile = g_key_file_new ();
+          guint64 tolerated_diff = 0;
+          guint64 tolerated_pixels = 0;
+
+          if (keyfile_path != NULL && g_file_test (keyfile_path, G_FILE_TEST_EXISTS))
+            {
+              GError *error = NULL;
+              g_key_file_load_from_file (keyfile, keyfile_path, G_KEY_FILE_NONE, &error);
+              g_assert_no_error (error);
+              tolerated_diff = g_key_file_get_uint64 (keyfile, "reftest", "tolerated-diff-level", NULL);
+              g_print ("Maximum difference tolerated: %" G_GUINT64_FORMAT " levels\n", tolerated_diff);
+              tolerated_pixels = g_key_file_get_uint64 (keyfile, "reftest", "tolerated-diff-pixels", NULL);
+              g_print ("Different pixels tolerated: %" G_GUINT64_FORMAT "\n", tolerated_pixels);
+            }
+
           g_print ("%u (out of %u) pixels differ from reference by up to %u levels\n",
                    pixels_changed, pixels, max_diff);
 
           save_image (diff_surface, node_file, ".diff.png");
           cairo_surface_destroy (diff_surface);
-          success = FALSE;
+
+          if (max_diff <= tolerated_diff && pixels_changed <= tolerated_pixels)
+            g_print ("not right, but close enough?\n");
+          else
+            success = FALSE;
+
+          g_key_file_unref (keyfile);
+          g_free (keyfile_path);
         }
     }
 

diff --git a/testsuite/reftests/gtk-reftest.c b/testsuite/reftests/gtk-reftest.c
index 3ae54133bbe4218f3c365e9e35ad07264d3cf763..f2fd60e1b2220884e691439865c101920eee0331 100644 (file)
--- a/testsuite/reftests/gtk-reftest.c
+++ b/testsuite/reftests/gtk-reftest.c
@@ -292,6 +292,12 @@ save_image (cairo_surface_t *surface,
   g_free (filename);
 }
 
+static char *
+get_test_keyfile (const char *ui_file)
+{
+  return get_test_file (ui_file, ".keyfile", TRUE);
+}
+
 static void
 test_ui_file (GFile *file)
 {
@@ -328,11 +334,35 @@ test_ui_file (GFile *file)
 
   if (diff_image)
     {
+      char *keyfile_path = get_test_keyfile (ui_file);
+      GKeyFile *keyfile = g_key_file_new ();
+      guint64 tolerated_diff = 0;
+      guint64 tolerated_pixels = 0;
+
+      if (keyfile_path != NULL)
+        {
+          GError *error = NULL;
+          g_key_file_load_from_file (keyfile, keyfile_path, G_KEY_FILE_NONE, &error);
+          g_assert_no_error (error);
+          tolerated_diff = g_key_file_get_uint64 (keyfile, "reftest", "tolerated-diff-level", NULL);
+          g_test_message ("Maximum difference tolerated: %" G_GUINT64_FORMAT " levels", tolerated_diff);
+          tolerated_pixels = g_key_file_get_uint64 (keyfile, "reftest", "tolerated-diff-pixels", NULL);
+          g_test_message ("Different pixels tolerated: %" G_GUINT64_FORMAT, tolerated_pixels);
+        }
+
       g_test_message ("%u (out of %u) pixels differ from reference by up to %u levels",
                       pixels_changed, pixels, max_diff);
+
       save_image (diff_image, ui_file, ".diff.png");
       cairo_surface_destroy (diff_image);
-      g_test_fail ();
+
+      if (max_diff <= tolerated_diff && pixels_changed <= tolerated_pixels)
+        g_test_incomplete ("not right, but close enough?");
+      else
+        g_test_fail ();
+
+      g_key_file_unref (keyfile);
+      g_free (keyfile_path);
     }
 
   remove_extra_css (provider);

diff --git a/testsuite/reftests/image-compare.c b/testsuite/reftests/image-compare.c
index 07bb79e4e06ed9991e760ed269723f4b7351130b..714f4fcadcf9999c5589cb66694e2bac8c55db56 100644 (file)
--- a/testsuite/reftests/image-compare.c
+++ b/testsuite/reftests/image-compare.c
@@ -41,7 +41,7 @@ main (int argc, char **argv)
   image1 = cairo_image_surface_create_from_png (argv[1]);
   image2 = cairo_image_surface_create_from_png (argv[2]);
 
-  diff = reftest_compare_surfaces (image1, image2);
+  diff = reftest_compare_surfaces (image1, image2, NULL, NULL, NULL);
 
   if (opt_filename && diff)
     cairo_surface_write_to_png (diff, opt_filename);