Add shim xdg-open implementation

As many 3rd party applications rely on xdg-utils for interacting
with the desktop environment, it makes sense for runtimes to provide
the expected tools. However there's no good reason to ship the usual
shell scripts, as the desktop abstraction is already provided by the
portal layer when running in a sandbox. Just add a small command line
tool that directly calls out to the portal.

src/Makefile.am

@@ -0,0 +1,6 @@
+bin_PROGRAMS = xdg-open
+
+xdg_open_SOURCES = xdg-open.c
+
+xdg_open_CFLAGS = $(FLATPAK_XDG_UTILS_CFLAGS)
+xdg_open_LDADD  = $(FLATPAK_XDG_UTILS_LIBS)

src/xdg-open.c

@@ -0,0 +1,122 @@
+/*
+ * Copyright © 2017 Red Hat, Inc
+ *
+ * This program 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.
+ *
+ * This library 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 this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *       Florian Müllner <[email protected]>
+ */
+
+#include <gio/gio.h>
+
+#include <glib/gi18n.h>
+
+#define PORTAL_BUS_NAME    "org.freedesktop.portal.Desktop"
+#define PORTAL_OBJECT_PATH "/org/freedesktop/portal/desktop"
+#define PORTAL_IFACE_NAME  "org.freedesktop.portal.OpenURI"
+
+static char **uris = NULL;
+static gboolean show_help = FALSE;
+static gboolean show_version = FALSE;
+
+static GOptionEntry entries[] = {
+  /* Compat options with "real" xdg-open */
+  { "manual", 0, G_OPTION_FLAG_HIDDEN, G_OPTION_ARG_NONE, &show_help, NULL, NULL },
+  { "version", 0, 0, G_OPTION_ARG_NONE, &show_version, N_("Show program version"), NULL },
+
+  { G_OPTION_REMAINING, 0, 0, G_OPTION_ARG_FILENAME_ARRAY, &uris, NULL, NULL }
+};
+
+int
+main (int argc, char *argv[])
+{
+  GOptionContext *context;
+  GError *error = NULL;
+  GDBusConnection *connection;
+  GVariantBuilder opt_builder;
+
+  context = g_option_context_new ("{ file | URL }");
+
+  g_option_context_add_main_entries (context, entries, NULL);
+  g_option_context_parse (context, &argc, &argv, &error);
+
+  if (error != NULL)
+    {
+      g_printerr ("Error parsing commandline options: %s\n", error->message);
+      g_printerr ("\n");
+      g_printerr ("Try \"%s --help\" for more information.\n", g_get_prgname ());
+
+      g_error_free (error);
+      return 1;
+    }
+
+  if (show_version)
+    {
+      g_print ("%s\n", PACKAGE_VERSION);
+
+      return 0;
+    }
+
+  if (show_help || uris == NULL || g_strv_length (uris) > 1)
+    {
+      char *help = g_option_context_get_help (context, TRUE, NULL);
+      g_print ("%s\n", help);
+
+      g_free (help);
+      return 0;
+    }
+
+  connection = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &error);
+
+  if (connection == NULL)
+    {
+      if (error)
+        g_printerr ("Failed to connect to session bus: %s", error->message);
+      else
+        g_printerr ("Failed to connect to session bus");
+
+      g_clear_pointer (&error, g_error_free);
+      return 3;
+    }
+
+  g_variant_builder_init (&opt_builder, G_VARIANT_TYPE_VARDICT);
+
+  g_dbus_connection_call_sync (connection,
+                               PORTAL_BUS_NAME,
+                               PORTAL_OBJECT_PATH,
+                               PORTAL_IFACE_NAME,
+                               "OpenURI",
+                               g_variant_new ("(ss@a{sv})",
+                                              "", *uris,
+                                              g_variant_builder_end (&opt_builder)),
+                               NULL,
+                               G_DBUS_CALL_FLAGS_NONE,
+                               -1,
+                               NULL,
+                               &error);
+
+  if (error)
+    {
+      g_printerr ("Failed to call portal: %s\n", error->message);
+
+      g_object_unref (connection);
+      g_error_free (error);
+
+      return 4;
+    }
+
+  g_object_unref (connection);
+
+  return 0;
+}