bus/at-spi-bus-launcher.c

   1 /* -*- mode: c; c-basic-offset: 2; indent-tabs-mode: nil; -*-
   2  *
   3  * at-spi-bus-launcher: Manage the a11y bus as a child process
   4  *
   5  * Copyright 2011 Red Hat, Inc.
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Library General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Library General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Library General Public
  18  * License along with this library; if not, write to the
  19  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20  * Boston, MA 02111-1307, USA.
  21  */
  22
  23 #include "config.h"
  24
  25 #include <unistd.h>
  26 #include <string.h>
  27 #include <signal.h>
  28 #include <sys/wait.h>
  29 #include <errno.h>
  30 #include <stdio.h>
  31
  32 #include <gio/gio.h>
  33 #ifdef HAVE_X11
  34 #include <X11/Xlib.h>
  35 #include <X11/Xatom.h>
  36 #endif
  37
  38 typedef enum {
  39   A11Y_BUS_STATE_IDLE = 0,
  40   A11Y_BUS_STATE_READING_ADDRESS,
  41   A11Y_BUS_STATE_RUNNING,
  42   A11Y_BUS_STATE_ERROR
  43 } A11yBusState;
  44
  45 typedef struct {
  46   GMainLoop *loop;
  47   gboolean launch_immediately;
  48   gboolean a11y_enabled;
  49   gboolean screen_reader_enabled;
  50   GDBusConnection *session_bus;
  51   GSettings *a11y_schema;
  52   GSettings *interface_schema;
  53
  54   A11yBusState state;
  55   /* -1 == error, 0 == pending, > 0 == running */
  56   int a11y_bus_pid;
  57   char *a11y_bus_address;
  58   int pipefd[2];
  59   char *a11y_launch_error_message;
  60 } A11yBusLauncher;
  61
  62 static A11yBusLauncher *_global_app = NULL;
  63
  64 static const gchar introspection_xml[] =
  65   "<node>"
  66   "  <interface name='org.a11y.Bus'>"
  67   "    <method name='GetAddress'>"
  68   "      <arg type='s' name='address' direction='out'/>"
  69   "    </method>"
  70   "  </interface>"
  71   "<interface name='org.a11y.Status'>"
  72   "<property name='IsEnabled' type='b' access='readwrite'/>"
  73   "<property name='ScreenReaderEnabled' type='b' access='readwrite'/>"
  74   "</interface>"
  75   "</node>";
  76 static GDBusNodeInfo *introspection_data = NULL;
  77
  78 static void
  79 setup_bus_child (gpointer data)
  80 {
  81   A11yBusLauncher *app = data;
  82   (void) app;
  83
  84   close (app->pipefd[0]);
  85   dup2 (app->pipefd[1], 3);
  86   close (app->pipefd[1]);
  87
  88   /* On Linux, tell the bus process to exit if this process goes away */
  89 #ifdef __linux
  90 #include <sys/prctl.h>
  91   prctl (PR_SET_PDEATHSIG, 15);
  92 #endif
  93 }
  94
  95 /**
  96  * unix_read_all_fd_to_string:
  97  *
  98  * Read all data from a file descriptor to a C string buffer.
  99  */
 100 static gboolean
 101 unix_read_all_fd_to_string (int      fd,
 102                             char    *buf,
 103                             ssize_t  max_bytes)
 104 {
 105   ssize_t bytes_read;
 106
 107   while (max_bytes > 1 && (bytes_read = read (fd, buf, MAX (4096, max_bytes - 1))))
 108     {
 109       if (bytes_read < 0)
 110         return FALSE;
 111       buf += bytes_read;
 112       max_bytes -= bytes_read;
 113     }
 114   *buf = '\0';
 115   return TRUE;
 116 }
 117
 118 static void
 119 on_bus_exited (GPid     pid,
 120                gint     status,
 121                gpointer data)
 122 {
 123   A11yBusLauncher *app = data;
 124
 125   app->a11y_bus_pid = -1;
 126   app->state = A11Y_BUS_STATE_ERROR;
 127   if (app->a11y_launch_error_message == NULL)
 128     {
 129       if (WIFEXITED (status))
 130         app->a11y_launch_error_message = g_strdup_printf ("Bus exited with code %d", WEXITSTATUS (status));
 131       else if (WIFSIGNALED (status))
 132         app->a11y_launch_error_message = g_strdup_printf ("Bus killed by signal %d", WTERMSIG (status));
 133       else if (WIFSTOPPED (status))
 134         app->a11y_launch_error_message = g_strdup_printf ("Bus stopped by signal %d", WSTOPSIG (status));
 135     }
 136   g_main_loop_quit (app->loop);
 137 }
 138
 139 static gboolean
 140 ensure_a11y_bus (A11yBusLauncher *app)
 141 {
 142   GPid pid;
 143   char *argv[] = { DBUS_DAEMON, NULL, "--nofork", "--print-address", "3", NULL };
 144   char addr_buf[2048];
 145   GError *error = NULL;
 146
 147   if (app->a11y_bus_pid != 0)
 148     return FALSE;
 149
 150   argv[1] = g_strdup_printf ("--config-file=%s/at-spi2/accessibility.conf", SYSCONFDIR);
 151
 152   if (pipe (app->pipefd) < 0)
 153     g_error ("Failed to create pipe: %s", strerror (errno));
 154
 155   if (!g_spawn_async (NULL,
 156                       argv,
 157                       NULL,
 158                       G_SPAWN_SEARCH_PATH | G_SPAWN_DO_NOT_REAP_CHILD,
 159                       setup_bus_child,
 160                       app,
 161                       &pid,
 162                       &error))
 163     {
 164       app->a11y_bus_pid = -1;
 165       app->a11y_launch_error_message = g_strdup (error->message);
 166       g_clear_error (&error);
 167       goto error;
 168     }
 169
 170   close (app->pipefd[1]);
 171   app->pipefd[1] = -1;
 172
 173   g_child_watch_add (pid, on_bus_exited, app);
 174
 175   app->state = A11Y_BUS_STATE_READING_ADDRESS;
 176   app->a11y_bus_pid = pid;
 177   g_debug ("Launched a11y bus, child is %ld", (long) pid);
 178   if (!unix_read_all_fd_to_string (app->pipefd[0], addr_buf, sizeof (addr_buf)))
 179     {
 180       app->a11y_launch_error_message = g_strdup_printf ("Failed to read address: %s", strerror (errno));
 181       kill (app->a11y_bus_pid, SIGTERM);
 182       goto error;
 183     }
 184   close (app->pipefd[0]);
 185   app->pipefd[0] = -1;
 186   app->state = A11Y_BUS_STATE_RUNNING;
 187
 188   /* Trim the trailing newline */
 189   app->a11y_bus_address = g_strchomp (g_strdup (addr_buf));
 190   g_debug ("a11y bus address: %s", app->a11y_bus_address);
 191
 192 #ifdef HAVE_X11
 193   {
 194     Display *display = XOpenDisplay (NULL);
 195     if (display)
 196       {
 197         Atom bus_address_atom = XInternAtom (display, "AT_SPI_BUS", False);
 198         XChangeProperty (display,
 199                          XDefaultRootWindow (display),
 200                          bus_address_atom,
 201                          XA_STRING, 8, PropModeReplace,
 202                          (guchar *) app->a11y_bus_address, strlen (app->a11y_bus_address));
 203         XFlush (display);
 204         XCloseDisplay (display);
 205       }
 206   }
 207 #endif
 208
 209   return TRUE;
 210
 211  error:
 212   close (app->pipefd[0]);
 213   close (app->pipefd[1]);
 214   app->state = A11Y_BUS_STATE_ERROR;
 215
 216   return FALSE;
 217 }
 218
 219 static void
 220 handle_method_call (GDBusConnection       *connection,
 221                     const gchar           *sender,
 222                     const gchar           *object_path,
 223                     const gchar           *interface_name,
 224                     const gchar           *method_name,
 225                     GVariant              *parameters,
 226                     GDBusMethodInvocation *invocation,
 227                     gpointer               user_data)
 228 {
 229   A11yBusLauncher *app = user_data;
 230
 231   if (g_strcmp0 (method_name, "GetAddress") == 0)
 232     {
 233       ensure_a11y_bus (app);
 234       if (app->a11y_bus_pid > 0)
 235         g_dbus_method_invocation_return_value (invocation,
 236                                                g_variant_new ("(s)", app->a11y_bus_address));
 237       else
 238         g_dbus_method_invocation_return_dbus_error (invocation,
 239                                                     "org.a11y.Bus.Error",
 240                                                     app->a11y_launch_error_message);
 241     }
 242 }
 243
 244 static GVariant *
 245 handle_get_property  (GDBusConnection       *connection,
 246                       const gchar           *sender,
 247                       const gchar           *object_path,
 248                       const gchar           *interface_name,
 249                       const gchar           *property_name,
 250                     GError **error,
 251                     gpointer               user_data)
 252 {
 253   A11yBusLauncher *app = user_data;
 254
 255   if (g_strcmp0 (property_name, "IsEnabled") == 0)
 256     return g_variant_new ("b", app->a11y_enabled);
 257   else if (g_strcmp0 (property_name, "ScreenReaderEnabled") == 0)
 258     return g_variant_new ("b", app->screen_reader_enabled);
 259   else
 260     return NULL;
 261 }
 262
 263 static void
 264 handle_a11y_enabled_change (A11yBusLauncher *app, gboolean enabled,
 265                                gboolean notify_gsettings)
 266 {
 267   GVariantBuilder builder;
 268   GVariantBuilder invalidated_builder;
 269
 270   if (enabled == app->a11y_enabled)
 271     return;
 272
 273   app->a11y_enabled = enabled;
 274
 275   if (notify_gsettings && app->interface_schema)
 276     {
 277       g_settings_set_boolean (app->interface_schema, "toolkit-accessibility",
 278                               enabled);
 279       g_settings_sync ();
 280     }
 281
 282   g_variant_builder_init (&builder, G_VARIANT_TYPE_ARRAY);
 283   g_variant_builder_init (&invalidated_builder, G_VARIANT_TYPE ("as"));
 284   g_variant_builder_add (&builder, "{sv}", "IsEnabled",
 285                          g_variant_new_boolean (enabled));
 286
 287   g_dbus_connection_emit_signal (app->session_bus, NULL, "/org/a11y/bus",
 288                                  "org.freedesktop.DBus.Properties",
 289                                  "PropertiesChanged",
 290                                  g_variant_new ("(sa{sv}as)", "org.a11y.Status",
 291                                                 &builder,
 292                                                 &invalidated_builder),
 293                                  NULL);
 294 }
 295
 296 static void
 297 handle_screen_reader_enabled_change (A11yBusLauncher *app, gboolean enabled,
 298                                gboolean notify_gsettings)
 299 {
 300   GVariantBuilder builder;
 301   GVariantBuilder invalidated_builder;
 302
 303   if (enabled == app->screen_reader_enabled)
 304     return;
 305
 306   /* If the screen reader is being enabled, we should enable accessibility
 307    * if it isn't enabled already */
 308   if (enabled)
 309     handle_a11y_enabled_change (app, enabled, notify_gsettings);
 310
 311   app->screen_reader_enabled = enabled;
 312
 313   if (notify_gsettings && app->a11y_schema)
 314     {
 315       g_settings_set_boolean (app->a11y_schema, "screen-reader-enabled",
 316                               enabled);
 317       g_settings_sync ();
 318     }
 319
 320   g_variant_builder_init (&builder, G_VARIANT_TYPE_ARRAY);
 321   g_variant_builder_init (&invalidated_builder, G_VARIANT_TYPE ("as"));
 322   g_variant_builder_add (&builder, "{sv}", "ScreenReaderEnabled",
 323                          g_variant_new_boolean (enabled));
 324
 325   g_dbus_connection_emit_signal (app->session_bus, NULL, "/org/a11y/bus",
 326                                  "org.freedesktop.DBus.Properties",
 327                                  "PropertiesChanged",
 328                                  g_variant_new ("(sa{sv}as)", "org.a11y.Status",
 329                                                 &builder,
 330                                                 &invalidated_builder),
 331                                  NULL);
 332 }
 333
 334 static gboolean
 335 handle_set_property  (GDBusConnection       *connection,
 336                       const gchar           *sender,
 337                       const gchar           *object_path,
 338                       const gchar           *interface_name,
 339                       const gchar           *property_name,
 340                       GVariant *value,
 341                     GError **error,
 342                     gpointer               user_data)
 343 {
 344   A11yBusLauncher *app = user_data;
 345   const gchar *type = g_variant_get_type_string (value);
 346   gboolean enabled;
 347
 348   if (g_strcmp0 (type, "b") != 0)
 349     {
 350       g_set_error (error, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
 351                        "org.a11y.Status.%s expects a boolean but got %s", property_name, type);
 352       return FALSE;
 353     }
 354
 355   enabled = g_variant_get_boolean (value);
 356
 357   if (g_strcmp0 (property_name, "IsEnabled") == 0)
 358     {
 359       handle_a11y_enabled_change (app, enabled, TRUE);
 360       return TRUE;
 361     }
 362   else if (g_strcmp0 (property_name, "ScreenReaderEnabled") == 0)
 363     {
 364       handle_screen_reader_enabled_change (app, enabled, TRUE);
 365       return TRUE;
 366     }
 367   else
 368     {
 369       g_set_error (error, G_DBUS_ERROR, G_DBUS_ERROR_INVALID_ARGS,
 370                        "Unknown property '%s'", property_name);
 371       return FALSE;
 372     }
 373 }
 374
 375 static const GDBusInterfaceVTable bus_vtable =
 376 {
 377   handle_method_call,
 378   NULL, /* handle_get_property, */
 379   NULL  /* handle_set_property */
 380 };
 381
 382 static const GDBusInterfaceVTable status_vtable =
 383 {
 384   NULL, /* handle_method_call */
 385   handle_get_property,
 386   handle_set_property
 387 };
 388
 389 static void
 390 on_bus_acquired (GDBusConnection *connection,
 391                  const gchar     *name,
 392                  gpointer         user_data)
 393 {
 394   A11yBusLauncher *app = user_data;
 395   GError *error;
 396   guint registration_id;
 397
 398   if (connection == NULL)
 399     {
 400       g_main_loop_quit (app->loop);
 401       return;
 402     }
 403   app->session_bus = connection;
 404
 405   if (app->launch_immediately)
 406     {
 407       ensure_a11y_bus (app);
 408       if (app->state == A11Y_BUS_STATE_ERROR)
 409         {
 410           g_main_loop_quit (app->loop);
 411           return;
 412         }
 413     }
 414
 415   error = NULL;
 416   registration_id = g_dbus_connection_register_object (connection,
 417                                                        "/org/a11y/bus",
 418                                                        introspection_data->interfaces[0],
 419                                                        &bus_vtable,
 420                                                        _global_app,
 421                                                        NULL,
 422                                                        &error);
 423   if (registration_id == 0)
 424     {
 425       g_error ("%s", error->message);
 426       g_clear_error (&error);
 427     }
 428
 429   g_dbus_connection_register_object (connection,
 430                                      "/org/a11y/bus",
 431                                      introspection_data->interfaces[1],
 432                                      &status_vtable,
 433                                      _global_app,
 434                                      NULL,
 435                                      NULL);
 436 }
 437
 438 static void
 439 on_name_lost (GDBusConnection *connection,
 440               const gchar     *name,
 441               gpointer         user_data)
 442 {
 443   A11yBusLauncher *app = user_data;
 444   if (app->session_bus == NULL
 445       && connection == NULL
 446       && app->a11y_launch_error_message == NULL)
 447     app->a11y_launch_error_message = g_strdup ("Failed to connect to session bus");
 448   g_main_loop_quit (app->loop);
 449 }
 450
 451 static void
 452 on_name_acquired (GDBusConnection *connection,
 453                   const gchar     *name,
 454                   gpointer         user_data)
 455 {
 456   A11yBusLauncher *app = user_data;
 457   (void) app;
 458 }
 459
 460 static int sigterm_pipefd[2];
 461
 462 static void
 463 sigterm_handler (int signum)
 464 {
 465   write (sigterm_pipefd[1], "X", 1);
 466 }
 467
 468 static gboolean
 469 on_sigterm_pipe (GIOChannel  *channel,
 470                  GIOCondition condition,
 471                  gpointer     data)
 472 {
 473   A11yBusLauncher *app = data;
 474
 475   g_main_loop_quit (app->loop);
 476
 477   return FALSE;
 478 }
 479
 480 static void
 481 init_sigterm_handling (A11yBusLauncher *app)
 482 {
 483   GIOChannel *sigterm_channel;
 484
 485   if (pipe (sigterm_pipefd) < 0)
 486     g_error ("Failed to create pipe: %s", strerror (errno));
 487   signal (SIGTERM, sigterm_handler);
 488
 489   sigterm_channel = g_io_channel_unix_new (sigterm_pipefd[0]);
 490   g_io_add_watch (sigterm_channel,
 491                   G_IO_IN | G_IO_ERR | G_IO_HUP,
 492                   on_sigterm_pipe,
 493                   app);
 494 }
 495
 496 static gboolean
 497 already_running ()
 498 {
 499 #ifdef HAVE_X11
 500   Atom AT_SPI_BUS;
 501   Atom actual_type;
 502   Display *bridge_display;
 503   int actual_format;
 504   unsigned char *data = NULL;
 505   unsigned long nitems;
 506   unsigned long leftover;
 507   gboolean result = FALSE;
 508
 509   bridge_display = XOpenDisplay (NULL);
 510   if (!bridge_display)
 511               return FALSE;
 512
 513   AT_SPI_BUS = XInternAtom (bridge_display, "AT_SPI_BUS", False);
 514   XGetWindowProperty (bridge_display,
 515                       XDefaultRootWindow (bridge_display),
 516                       AT_SPI_BUS, 0L,
 517                       (long) BUFSIZ, False,
 518                       (Atom) 31, &actual_type, &actual_format,
 519                       &nitems, &leftover, &data);
 520
 521   if (data)
 522   {
 523     GDBusConnection *bus;
 524     const gchar *old_session = g_getenv ("DBUS_SESSION_BUS_ADDRESS");
 525     /* TODO: Is there a better way to connect? This is really hacky */
 526     g_setenv ("DBUS_SESSION_BUS_ADDRESS", data, TRUE);
 527     bus = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL);
 528     g_setenv ("DBUS_SESSION_BUS_ADDRESS", old_session, TRUE);
 529     if (bus != NULL)
 530       {
 531         result = TRUE;
 532         g_object_unref (bus);
 533       }
 534   }
 535
 536   XCloseDisplay (bridge_display);
 537   return result;
 538 #else
 539   return FALSE;
 540 #endif
 541 }
 542
 543 static GSettings *
 544 get_schema (const gchar *name)
 545 {
 546   const char * const *schemas = NULL;
 547   gint i;
 548
 549   schemas = g_settings_list_schemas ();
 550   for (i = 0; schemas[i]; i++)
 551   {
 552     if (!strcmp (schemas[i], name))
 553       return g_settings_new (schemas[i]);
 554   }
 555
 556   return NULL;
 557 }
 558
 559 static void
 560 gsettings_key_changed (GSettings *gsettings, const gchar *key, void *user_data)
 561 {
 562   gboolean new_val = g_settings_get_boolean (gsettings, key);
 563   A11yBusLauncher *app = user_data;
 564
 565   if (!strcmp (key, "toolkit-accessibility"))
 566     handle_a11y_enabled_change (_global_app, new_val, FALSE);
 567   else if (!strcmp (key, "screen-reader-enabled"))
 568     handle_screen_reader_enabled_change (_global_app, new_val, FALSE);
 569 }
 570
 571 int
 572 main (int    argc,
 573       char **argv)
 574 {
 575   GError *error = NULL;
 576   GMainLoop *loop;
 577   GDBusConnection *session_bus;
 578   int name_owner_id;
 579   gboolean a11y_set = FALSE;
 580   gboolean screen_reader_set = FALSE;
 581   gint i;
 582
 583   g_type_init ();
 584
 585   if (already_running ())
 586     return 0;
 587
 588   _global_app = g_slice_new0 (A11yBusLauncher);
 589   _global_app->loop = g_main_loop_new (NULL, FALSE);
 590
 591   for (i = 1; i < argc; i++)
 592     {
 593       if (!strcmp (argv[i], "--launch-immediately"))
 594         _global_app->launch_immediately = TRUE;
 595       else if (sscanf (argv[i], "--a11y=%d", &_global_app->a11y_enabled) == 2)
 596         a11y_set = TRUE;
 597       else if (sscanf (argv[i], "--screen-reader=%d",
 598                        &_global_app->screen_reader_enabled) == 2)
 599         screen_reader_set = TRUE;
 600     else
 601       g_error ("usage: %s [--launch-immediately] [--a11y=0|1] [--screen-reader=0|1]", argv[0]);
 602     }
 603
 604   _global_app->interface_schema = get_schema ("org.gnome.desktop.interface");
 605   _global_app->a11y_schema = get_schema ("org.gnome.desktop.a11y.applications");
 606
 607   if (!a11y_set)
 608     {
 609       _global_app->a11y_enabled = _global_app->interface_schema
 610                                   ? g_settings_get_boolean (_global_app->interface_schema, "toolkit-accessibility")
 611                                   : _global_app->launch_immediately;
 612     }
 613
 614   if (!screen_reader_set)
 615     {
 616       _global_app->screen_reader_enabled = _global_app->a11y_schema
 617                                   ? g_settings_get_boolean (_global_app->a11y_schema, "screen-reader-enabled")
 618                                   : FALSE;
 619     }
 620
 621   if (_global_app->interface_schema)
 622     g_signal_connect (_global_app->interface_schema,
 623                       "changed::toolkit-accessibility",
 624                       G_CALLBACK (gsettings_key_changed), _global_app);
 625
 626   if (_global_app->a11y_schema)
 627     g_signal_connect (_global_app->a11y_schema,
 628                       "changed::screen-reader-enabled",
 629                       G_CALLBACK (gsettings_key_changed), _global_app);
 630
 631   init_sigterm_handling (_global_app);
 632
 633   introspection_data = g_dbus_node_info_new_for_xml (introspection_xml, NULL);
 634   g_assert (introspection_data != NULL);
 635
 636   name_owner_id = g_bus_own_name (G_BUS_TYPE_SESSION,
 637                                   "org.a11y.Bus",
 638                                   G_BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT,
 639                                   on_bus_acquired,
 640                                   on_name_acquired,
 641                                   on_name_lost,
 642                                   _global_app,
 643                                   NULL);
 644
 645   g_main_loop_run (_global_app->loop);
 646
 647   if (_global_app->a11y_bus_pid > 0)
 648     kill (_global_app->a11y_bus_pid, SIGTERM);
 649
 650   /* Clear the X property if our bus is gone; in the case where e.g.
 651    * GDM is launching a login on an X server it was using before,
 652    * we don't want early login processes to pick up the stale address.
 653    */
 654 #ifdef HAVE_X11
 655   {
 656     Display *display = XOpenDisplay (NULL);
 657     if (display)
 658       {
 659         Atom bus_address_atom = XInternAtom (display, "AT_SPI_BUS", False);
 660         XDeleteProperty (display,
 661                          XDefaultRootWindow (display),
 662                          bus_address_atom);
 663
 664         XFlush (display);
 665         XCloseDisplay (display);
 666       }
 667   }
 668 #endif
 669
 670   if (_global_app->a11y_launch_error_message)
 671     {
 672       g_printerr ("Failed to launch bus: %s", _global_app->a11y_launch_error_message);
 673       return 1;
 674     }
 675   return 0;
 676 }