reftests: Add a way to compare different runs

gtk-reftest already had an --output=DIR option to tell it where
to save all the resulting images. Now you can combine this with
the --compare-with=DIR option in a second run to make gtk-reftest
compare the .out.png files from the first run with the .out.png
files of the current run, instead of producing .ref.png files.

The intended use for this is to verify that changes do not affect
the generated output.

1 files changed, 29 insertions, 3 deletions

diff --git a/testsuite/reftests/gtk-reftest.c b/testsuite/reftests/gtk-reftest.c
index 19f3899def..193fd0341a 100644
--- a/testsuite/reftests/gtk-reftest.c
+++ b/testsuite/reftests/gtk-reftest.c
@@ -39,6 +39,7 @@ typedef enum {
 static char *arg_output_dir = NULL;
 static char *arg_base_dir = NULL;
 static char *arg_direction = NULL;
+static char *arg_compare_dir = NULL;
 
 static const GOptionEntry test_args[] = {
   { "output",         'o', 0, G_OPTION_ARG_FILENAME, &arg_output_dir,
@@ -47,6 +48,8 @@ static const GOptionEntry test_args[] = {
     "Directory to run tests from", "DIR" },
   { "direction",       0, 0, G_OPTION_ARG_STRING, &arg_direction,
     "Set text direction", "ltr|rtl" },
+  { "compare-with",    0, 0, G_OPTION_ARG_FILENAME, &arg_compare_dir,
+    "Directory to compare with", "DIR" },
   { NULL }
 };
 
@@ -175,6 +178,28 @@ get_test_file (const char *test_file,
   return g_string_free (file, FALSE);
 }
 
+static char *
+get_reference_image (const char *ui_file)
+{
+  char *base;
+  char *reference_image;
+
+  if (!arg_compare_dir)
+    return NULL;
+
+  get_components_of_test_file (ui_file, NULL, &base);
+  reference_image = g_strconcat (arg_compare_dir, G_DIR_SEPARATOR_S, base, ".out.png", NULL);
+  g_free (base);
+
+  if (!g_file_test (reference_image, G_FILE_TEST_EXISTS))
+    {
+      g_free (reference_image);
+      return NULL;
+    }
+
+  return reference_image;
+}
+
 static GtkStyleProvider *
 add_extra_css (const char *testname,
                const char *extension)
@@ -234,9 +259,10 @@ test_ui_file (GFile *file)
   provider = add_extra_css (ui_file, ".css");
 
   ui_image = reftest_snapshot_ui_file (ui_file);
-  
-  reference_file = get_test_file (ui_file, ".ref.ui", TRUE);
-  if (reference_file)
+
+  if ((reference_file = get_reference_image (ui_file)) != NULL)
+    reference_image = cairo_image_surface_create_from_png (reference_file);
+  else if ((reference_file = get_test_file (ui_file, ".ref.ui", TRUE)) != NULL)
     reference_image = reftest_snapshot_ui_file (reference_file);
   else
     {