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