[gtk+] reftests: Add a way to compare different runs

[Matthias Clasen <matthiasc src gnome org>]

commit 40bb2a1616f81262b893b543a8b0bd1bd48532c8
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Mar 20 16:39:36 2015 -0400

    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.

 testsuite/reftests/gtk-reftest.c |   32 +++++++++++++++++++++++++++++---
 1 files changed, 29 insertions(+), 3 deletions(-)
---
diff --git a/testsuite/reftests/gtk-reftest.c b/testsuite/reftests/gtk-reftest.c
index 19f3899..193fd03 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
     {