tests: Add "set_parent_exported" command

Add a "set_parent_exported" command to test the xdg-foreign support, so
that we can add a test which uses the GDK API for exported window:

  `gdk_wayland_window_set_transient_for_exported()`

That will allow to detect if transient is applied correctly between
foreign windows and detect possible crashes such as issue !174.

Related: https://gitlab.gnome.org/GNOME/mutter/issues/174

src/tests/test-client.c

@@ -20,6 +20,7 @@
 #include <gio/gunixinputstream.h>
 #include <gtk/gtk.h>
 #include <gdk/gdkx.h>
+#include <gdk/gdkwayland.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
@@ -31,6 +32,19 @@ GHashTable *windows;
 
 static void read_next_line (GDataInputStream *in);
 
+static void
+window_export_handle_cb (GdkWindow  *window,
+                         const char *handle_str,
+                         gpointer    user_data)
+{
+  GdkWindow *gdk_window = gtk_widget_get_window (GTK_WIDGET (user_data));
+
+  if (!gdk_wayland_window_set_transient_for_exported (gdk_window,
+                                                      (gchar *) handle_str))
+    g_print ("Fail to set transient_for exported window handle %s", handle_str);
+  gdk_window_set_modal_hint (gdk_window, TRUE);
+}
+
 static GtkWidget *
 lookup_window (const char *window_id)
 {
@@ -151,6 +165,35 @@ process_line (const char *line)
       gtk_window_set_transient_for (GTK_WINDOW (window),
                                     GTK_WINDOW (parent_window));
     }
+  else if (strcmp (argv[0], "set_parent_exported") == 0)
+    {
+      if (argc != 3)
+        {
+          g_print ("usage: set_parent_exported <window-id> <parent-id>");
+          goto out;
+        }
+
+      GtkWidget *window = lookup_window (argv[1]);
+      if (!window)
+        {
+          g_print ("unknown window %s", argv[1]);
+          goto out;
+        }
+
+      GtkWidget *parent_window = lookup_window (argv[2]);
+      if (!parent_window)
+        {
+          g_print ("unknown parent window %s", argv[2]);
+          goto out;
+        }
+
+      GdkWindow *parent_gdk_window = gtk_widget_get_window (parent_window);
+      if (!gdk_wayland_window_export_handle (parent_gdk_window,
+                                             window_export_handle_cb,
+                                             window,
+                                             NULL))
+        g_print ("Fail to export handle for window id %s", argv[2]);
+    }
   else if (strcmp (argv[0], "show") == 0)
     {
       if (argc != 2)

src/tests/test-runner.c

@@ -423,7 +423,8 @@ test_case_do (TestCase *test,
                            NULL))
         return FALSE;
     }
-  else if (strcmp (argv[0], "set_parent") == 0)
+  else if (strcmp (argv[0], "set_parent") == 0 ||
+           strcmp (argv[0], "set_parent_exported") == 0)
     {
       if (argc != 3)
         BAD_COMMAND("usage: %s <client-id>/<window-id> <parent-window-id>",
@@ -435,7 +436,7 @@ test_case_do (TestCase *test,
         return FALSE;
 
       if (!test_client_do (client, error,
-                           "set_parent", window_id,
+                           argv[0], window_id,
                            argv[2],
                            NULL))
         return FALSE;