rendernode tool: Add a compare command

This command can be used to compare the rendering of a node
to a reference image. It can also be used to compare the
renderings of two nodes, or to compare two images.

docs/reference/gtk/gtk4-rendernode-tool.rst

@@ -13,6 +13,7 @@ SYNOPSIS
 |   **gtk4-rendernode-tool** <COMMAND> [OPTIONS...] <FILE>
 |
 |   **gtk4-rendernode-tool** benchmark [OPTIONS...] <FILE>
+|   **gtk4-rendernode-tool** compare [OPTIONS...] <FILE1> <FILE2>
 |   **gtk4-rendernode-tool** info [OPTIONS...] <FILE>
 |   **gtk4-rendernode-tool** render [OPTIONS...] <FILE> [<FILE>]
 |   **gtk4-rendernode-tool** show [OPTIONS...] <FILE>
@@ -75,7 +76,21 @@ and prints the runtimes.
   the execution of the commands on the GPU. It can be useful to use this flag to test
   command submission performance.
 
+Compare
+^^^^^^^
 
+The ``compare`` command compares the rendering of a node with a reference image,
+or the renderings of two nodes, or two images. If any differences are found, the
+exit code is 1. If the images are identical, it is 0.
 
+``--renderer=RENDERER``
 
+  Use the given renderer.
 
+``--output=FILE``
+
+  Save the differences as a png image in ``FILE``.
+
+``--quiet``
+
+  Don't write results to stdout.`

tools/gtk-rendernode-tool-compare.c

@@ -0,0 +1,147 @@
+/*  Copyright 2024 Red Hat, Inc.
+ *
+ * GTK is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * GTK is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with GTK; see the file COPYING.  If not,
+ * see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Matthias Clasen
+ */
+
+#include "config.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include <glib/gi18n-lib.h>
+#include <glib/gprintf.h>
+#include <glib/gstdio.h>
+#include <gtk/gtk.h>
+#include "gtk-rendernode-tool.h"
+
+#include "testsuite/reftests/reftest-compare.h"
+
+static GdkTexture *
+texture_from_file (const char   *filename,
+                   GskRenderer  *renderer,
+                   GError      **error)
+{
+  GdkTexture *texture;
+
+  if (g_str_has_suffix (filename, ".node"))
+    {
+      GskRenderNode *node = load_node_file (filename);
+      texture = gsk_renderer_render_texture (renderer, node, NULL);
+      gsk_render_node_unref (node);
+    }
+  else
+    {
+      texture = gdk_texture_new_from_filename (filename, error);
+    }
+
+  return texture;
+}
+
+void
+do_compare (int          *argc,
+            const char ***argv)
+{
+  GOptionContext *context;
+  char *opt_filename = NULL;
+  gboolean opt_quiet = FALSE;
+  char **filenames = NULL;
+  char *renderer_name = NULL;
+  const GOptionEntry entries[] = {
+    { "renderer", 0, 0, G_OPTION_ARG_STRING, &renderer_name, N_("Renderer to use"), N_("RENDERER") },
+
+    { "output", 'o', 0, G_OPTION_ARG_FILENAME, &opt_filename, N_("Output file"), N_("FILE") },
+    { "quiet", 'q', 0, G_OPTION_ARG_NONE, &opt_quiet, "Don't talk", NULL },
+
+    { G_OPTION_REMAINING, 0, 0, G_OPTION_ARG_FILENAME_ARRAY, &filenames, NULL, N_("FILE1 FILE2") },
+    { NULL, }
+  };
+  GskRenderer *renderer;
+  GdkTexture *texture[2];
+  GdkTexture *diff;
+  GError *error = NULL;
+
+  g_set_prgname ("gtk4-rendernode-tool compare");
+  context = g_option_context_new (NULL);
+  g_option_context_set_translation_domain (context, GETTEXT_PACKAGE);
+  g_option_context_add_main_entries (context, entries, NULL);
+  g_option_context_set_summary (context, _("Compare .node or .png files."));
+
+  if (!g_option_context_parse (context, argc, (char ***)argv, &error))
+    {
+      g_printerr ("%s\n", error->message);
+      g_error_free (error);
+      exit (1);
+    }
+
+  g_option_context_free (context);
+
+  if (filenames == NULL || g_strv_length (filenames) != 2)
+    {
+      g_printerr (_("Must specify two files\n"));
+      exit (1);
+    }
+
+  renderer = create_renderer (renderer_name, &error);
+  if (renderer == NULL)
+    {
+      g_printerr (_("Failed to create renderer: %s\n"), error->message);
+      exit (1);
+    }
+
+  for (int i = 0; i < 2; i++)
+    {
+      texture[i] = texture_from_file (filenames[i], renderer, &error);
+      if (texture[i] == NULL)
+        {
+          g_printerr (_("Failed to load %s: %s\n"), filenames[i], error->message);
+          exit (1);
+        }
+    }
+
+  diff = reftest_compare_textures (texture[0], texture[1]);
+
+  if (opt_filename && diff)
+    {
+      if (!gdk_texture_save_to_png (diff, opt_filename))
+        {
+          g_printerr (_("Could not save diff image to %s\n"), opt_filename);
+          exit (1);
+        }
+    }
+
+  if (!opt_quiet)
+    {
+      if (diff)
+        {
+          if (opt_filename)
+            g_print (_("Differences witten to %s.\n"), opt_filename);
+          else
+            g_print (_("The images are different.\n"));
+        }
+      else
+        g_print (_("No differences.\n"));
+    }
+
+  if (diff)
+    exit (1);
+
+  g_strfreev (filenames);
+  g_object_unref (texture[0]);
+  g_object_unref (texture[1]);
+  g_object_unref (renderer);
+}

tools/gtk-rendernode-tool.c

@@ -39,6 +39,7 @@ usage (void)
              "\n"
              "Commands:\n"
              "  benchmark    Benchmark rendering of a node\n"
+             "  compare      Compare nodes or images\n"
              "  info         Provide information about the node\n"
              "  show         Show the node\n"
              "  render       Take a screenshot of the node\n"
@@ -116,6 +117,8 @@ main (int argc, const char *argv[])
     do_info (&argc, &argv);
   else if (strcmp (argv[0], "benchmark") == 0)
     do_benchmark (&argc, &argv);
+  else if (strcmp (argv[0], "compare") == 0)
+    do_compare (&argc, &argv);
   else
     usage ();
 

tools/gtk-rendernode-tool.h

@@ -2,6 +2,7 @@
 #pragma once
 
 void do_benchmark   (int *argc, const char ***argv);
+void do_compare     (int *argc, const char ***argv);
 void do_info        (int *argc, const char ***argv);
 void do_show        (int *argc, const char ***argv);
 void do_render      (int *argc, const char ***argv);

tools/meson.build

@@ -42,10 +42,12 @@ gtk_tools = [
                          'fake-scope.c'], [libgtk_dep] ],
   ['gtk4-rendernode-tool', ['gtk-rendernode-tool.c',
                         'gtk-rendernode-tool-benchmark.c',
+                        'gtk-rendernode-tool-compare.c',
                         'gtk-rendernode-tool-info.c',
                         'gtk-rendernode-tool-render.c',
                         'gtk-rendernode-tool-show.c',
-                        'gtk-rendernode-tool-utils.c'], [libgtk_dep] ],
+                        'gtk-rendernode-tool-utils.c',
+                        '../testsuite/reftests/reftest-compare.c'], [libgtk_dep] ],
   ['gtk4-update-icon-cache', ['updateiconcache.c', '../gtk/gtkiconcachevalidator.c' ] + extra_update_icon_cache_objs, [ libgtk_dep ] ],
   ['gtk4-encode-symbolic-svg', ['encodesymbolic.c'], [ libgtk_static_dep ] ],
 ]