tests: Check that X11 selections handle Xwayland disappearing

It works by using an X11 client to set the clipboard content, using a
mimetype that on purpose is not handled by the clipboard manager. The
test then makes sure we don't crash when trying to transfer data from
the old X11 selection source.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2364>

src/tests/meson.build

@@ -295,6 +295,13 @@ if have_native_tests
         wayland_test_utils,
       ],
     },
+    {
+      'name': 'xwayland',
+      'suite': 'wayland',
+      'sources': [
+        'xwayland-tests.c',
+      ],
+    },
   ]
 
   foreach test_case: test_cases

src/tests/xwayland-tests.c

@@ -0,0 +1,190 @@
+/*
+ * Copyright (C) 2022 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ *
+ */
+
+#include "config.h"
+
+#include "meta/meta-selection.h"
+#include "meta-test/meta-context-test.h"
+#include "tests/meta-test-utils.h"
+#include "wayland/meta-wayland.h"
+#include "wayland/meta-xwayland.h"
+#include "x11/meta-x11-display-private.h"
+
+static MetaContext *test_context;
+
+static void
+test_client_do_check (MetaTestClient *test_client,
+                      ...)
+{
+  g_autoptr (GError) error = NULL;
+  va_list vap;
+  gboolean retval;
+
+  va_start (vap, test_client);
+  retval = meta_test_client_dov (test_client, &error, vap);
+  va_end (vap);
+
+  if (!retval)
+    g_error ("Failed to process test client command: %s", error->message);
+}
+
+static void
+test_client_wait_check (MetaTestClient *test_client)
+{
+  g_autoptr (GError) error = NULL;
+
+  if (!meta_test_client_wait (test_client, &error))
+    g_error ("Failed to wait for test client: %s", error->message);
+}
+
+static void
+transfer_ready_cb (GObject      *source_object,
+                   GAsyncResult *res,
+                   gpointer      user_data)
+{
+  GMainLoop *loop = user_data;
+  g_autoptr (GError) error = NULL;
+
+  if (!meta_selection_transfer_finish (META_SELECTION (source_object), res,
+                                       &error))
+    g_warning ("Failed to transfer: %s", error->message);
+
+  g_main_loop_quit (loop);
+}
+
+static gboolean
+tests_alarm_filter (MetaX11Display        *x11_display,
+                    XSyncAlarmNotifyEvent *event,
+                    gpointer               user_data)
+{
+  MetaTestClient *test_client = user_data;
+  return meta_test_client_process_x11_event (test_client,
+                                             x11_display, event);
+}
+
+static void
+ensure_xwayland (MetaContext *context)
+{
+  MetaDisplay *display = meta_context_get_display (test_context);
+
+  if (meta_display_get_x11_display (display))
+    return;
+
+  while (!meta_display_get_x11_display (display))
+    g_main_context_iteration (NULL, TRUE);
+}
+
+static void
+meta_test_xwayland_restart_selection (void)
+{
+  MetaWaylandCompositor *wayland_compositor =
+    meta_context_get_wayland_compositor (test_context);
+  MetaXWaylandManager *xwayland_manager =
+    meta_wayland_compositor_get_xwayland_manager (wayland_compositor);
+  MetaDisplay *display = meta_context_get_display (test_context);
+  MetaSelection *selection = meta_display_get_selection (display);
+  MetaX11Display *x11_display;
+  MetaTestClient *test_client;
+  static int client_count = 0;
+  g_autofree char *client_name = NULL;
+  g_autoptr (GError) error = NULL;
+  g_autoptr (GMainLoop) loop = NULL;
+  g_autoptr (GOutputStream) output = NULL;
+  const char *window_name = "clipboard-window";
+
+  client_name = g_strdup_printf ("test_client_%d", client_count++);
+  test_client = meta_test_client_new (test_context,
+                                      client_name, META_WINDOW_CLIENT_TYPE_X11,
+                                      &error);
+  if (!test_client)
+    g_error ("Failed to launch test client: %s", error->message);
+
+  ensure_xwayland (test_context);
+  x11_display = meta_display_get_x11_display (display);
+  meta_x11_display_set_alarm_filter (x11_display,
+                                     tests_alarm_filter,
+                                     test_client);
+
+  test_client_do_check (test_client,
+                        "create", window_name,
+                        NULL);
+  test_client_do_check (test_client,
+                        "clipboard-set", "application/mutter-test", "hello",
+                        NULL);
+  test_client_wait_check (test_client);
+
+  g_test_expect_message ("libmutter", G_LOG_LEVEL_WARNING,
+                         "*Connection to xwayland lost*");
+  g_test_expect_message ("libmutter", G_LOG_LEVEL_WARNING,
+                         "X Wayland crashed*; attempting to recover");
+
+  if (!meta_xwayland_signal (xwayland_manager, SIGKILL, &error))
+    g_error ("Failed to signal SIGSEGV to Xwayland");
+
+  while (meta_display_get_x11_display (display))
+    g_main_context_iteration (NULL, TRUE);
+
+  g_test_assert_expected_messages ();
+
+  loop = g_main_loop_new (NULL, FALSE);
+  output = g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_WARNING,
+                         "*Tried to transfer from NULL selection source");
+  meta_selection_transfer_async (selection,
+                                 META_SELECTION_CLIPBOARD,
+                                 "text/plain",
+                                 -1,
+                                 output,
+                                 NULL,
+                                 transfer_ready_cb,
+                                 loop);
+
+  g_main_loop_run (loop);
+
+  g_test_assert_expected_messages ();
+
+  meta_test_client_destroy (test_client);
+}
+
+static void
+init_tests (void)
+{
+  g_test_add_func ("/backends/xwayland/restart/selection",
+                   meta_test_xwayland_restart_selection);
+}
+
+int
+main (int    argc,
+      char **argv)
+{
+  g_autoptr (MetaContext) context = NULL;
+  g_autoptr (GError) error = NULL;
+
+  context = test_context =
+    meta_create_test_context (META_CONTEXT_TEST_TYPE_HEADLESS,
+                              META_CONTEXT_TEST_FLAG_TEST_CLIENT);
+  g_assert (meta_context_configure (context, &argc, &argv, NULL));
+
+  init_tests ();
+
+  return meta_context_test_run_tests (META_CONTEXT_TEST (context),
+                                      META_TEST_RUN_FLAG_NONE);
+}