gtkatspicontext.c

/* gtkatspicontext.c: AT-SPI GtkATContext implementation
 *
 * Copyright 2020  GNOME Foundation
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * This library 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 2.1 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/>.
 */

#include "config.h"

#include "gtkatspicontextprivate.h"

#include "gtkaccessibleprivate.h"

#include "gtkatspiactionprivate.h"
#include "gtkatspieditabletextprivate.h"
#include "gtkatspiprivate.h"
#include "gtkatspirootprivate.h"
#include "gtkatspiselectionprivate.h"
#include "gtkatspitextprivate.h"
#include "gtkatspiutilsprivate.h"
#include "gtkatspivalueprivate.h"
#include "gtkatspicomponentprivate.h"
#include "a11y/atspi/atspi-accessible.h"
#include "a11y/atspi/atspi-action.h"
#include "a11y/atspi/atspi-editabletext.h"
#include "a11y/atspi/atspi-text.h"
#include "a11y/atspi/atspi-value.h"
#include "a11y/atspi/atspi-selection.h"
#include "a11y/atspi/atspi-component.h"

#include "gtkdebug.h"
#include "gtkprivate.h"
#include "gtkeditable.h"
#include "gtkentryprivate.h"
#include "gtkroot.h"
#include "gtkstack.h"
#include "gtktextview.h"
#include "gtktypebuiltins.h"
#include "gtkwindow.h"

#include <gio/gio.h>

#include <locale.h>

#if defined(GDK_WINDOWING_WAYLAND)
# include <gdk/wayland/gdkwaylanddisplay.h>
#endif
#if defined(GDK_WINDOWING_X11)
# include <gdk/x11/gdkx11display.h>
# include <gdk/x11/gdkx11property.h>
#endif

/* We create a GtkAtSpiContext object for (almost) every widget.
 *
 * Each context implements a number of Atspi interfaces on a D-Bus
 * object. The context objects are connected into a tree by the
 * Parent property and GetChildAtIndex method of the Accessible
 * interface.
 *
 * The tree is an almost perfect mirror image of the widget tree,
 * with a few notable exceptions:
 *
 * - We don't create contexts for the GtkText widgets inside
 *   entry wrappers, since the Text functionality is represented
 *   on the entry contexts.
 *
 * - We insert non-widget backed context objects for each page
 *   of a stack. The main purpose of these extra context is to
 *   hold the TAB_PANEL role and be the target of the CONTROLS
 *   relation with their corresponding tabs (in the stack
 *   switcher or notebook).
 *
 * These are the exceptions implemented by GTK itself, but note that application
 * developers can customize the accessibility tree by implementing the
 * [iface@Gtk.Accessible] interface in any way they choose.
 */

struct _GtkAtSpiContext
{
  GtkATContext parent_instance;

  /* The root object, used as a entry point */
  GtkAtSpiRoot *root;

  /* The object path of the ATContext on the bus */
  char *context_path;

  /* Just a pointer; the connection is owned by the GtkAtSpiRoot
   * associated to the GtkATContext
   */
  GDBusConnection *connection;

  /* Accerciser refuses to work unless we implement a GetInterface
   * call that returns a list of all implemented interfaces. We
   * collect the answer here.
   */
  GVariant *interfaces;

  guint registration_ids[20];
  guint n_registered_objects;
};

G_DEFINE_TYPE (GtkAtSpiContext, gtk_at_spi_context, GTK_TYPE_AT_CONTEXT)

/* {{{ State handling */
static void
set_atspi_state (guint64        *states,
                 AtspiStateType  state)
{
  *states |= (G_GUINT64_CONSTANT (1) << state);
}

static void
unset_atspi_state (guint64        *states,
                   AtspiStateType  state)
{
  *states &= ~(G_GUINT64_CONSTANT (1) << state);
}

static void
collect_states (GtkAtSpiContext    *self,
                GVariantBuilder *builder)
{
  GtkATContext *ctx = GTK_AT_CONTEXT (self);
  GtkAccessibleValue *value;
  GtkAccessible *accessible;
  guint64 states = 0;

  accessible = gtk_at_context_get_accessible (ctx);

  set_atspi_state (&states, ATSPI_STATE_VISIBLE);

  if (ctx->accessible_role == GTK_ACCESSIBLE_ROLE_WINDOW)
    {
      set_atspi_state (&states, ATSPI_STATE_SHOWING);
      if (gtk_accessible_get_platform_state (accessible, GTK_ACCESSIBLE_PLATFORM_STATE_ACTIVE))
        set_atspi_state (&states, ATSPI_STATE_ACTIVE);
    }

  if (ctx->accessible_role == GTK_ACCESSIBLE_ROLE_TEXT_BOX ||
      ctx->accessible_role == GTK_ACCESSIBLE_ROLE_SEARCH_BOX ||
      ctx->accessible_role == GTK_ACCESSIBLE_ROLE_SPIN_BUTTON)
    set_atspi_state (&states, ATSPI_STATE_EDITABLE);

  if (gtk_at_context_has_accessible_property (ctx, GTK_ACCESSIBLE_PROPERTY_READ_ONLY))
    {
      value = gtk_at_context_get_accessible_property (ctx, GTK_ACCESSIBLE_PROPERTY_READ_ONLY);
      if (gtk_boolean_accessible_value_get (value))
        {
          set_atspi_state (&states, ATSPI_STATE_READ_ONLY);
          unset_atspi_state (&states, ATSPI_STATE_EDITABLE);
        }
    }

  if (gtk_accessible_get_platform_state (accessible, GTK_ACCESSIBLE_PLATFORM_STATE_FOCUSABLE))
    set_atspi_state (&states, ATSPI_STATE_FOCUSABLE);

  if (gtk_accessible_get_platform_state (accessible, GTK_ACCESSIBLE_PLATFORM_STATE_FOCUSED))
    set_atspi_state (&states, ATSPI_STATE_FOCUSED);

  if (gtk_at_context_has_accessible_property (ctx, GTK_ACCESSIBLE_PROPERTY_ORIENTATION))
    {
      value = gtk_at_context_get_accessible_property (ctx, GTK_ACCESSIBLE_PROPERTY_ORIENTATION);
      if (gtk_orientation_accessible_value_get (value) == GTK_ORIENTATION_HORIZONTAL)
        set_atspi_state (&states, ATSPI_STATE_HORIZONTAL);
      else
        set_atspi_state (&states, ATSPI_STATE_VERTICAL);
    }

  if (gtk_at_context_has_accessible_property (ctx, GTK_ACCESSIBLE_PROPERTY_MODAL))
    {
      value = gtk_at_context_get_accessible_property (ctx, GTK_ACCESSIBLE_PROPERTY_MODAL);
      if (gtk_boolean_accessible_value_get (value))
        set_atspi_state (&states, ATSPI_STATE_MODAL);
    }

  if (gtk_at_context_has_accessible_property (ctx, GTK_ACCESSIBLE_PROPERTY_MULTI_LINE))
    {
      value = gtk_at_context_get_accessible_property (ctx, GTK_ACCESSIBLE_PROPERTY_MULTI_LINE);
      if (gtk_boolean_accessible_value_get (value))
        set_atspi_state (&states, ATSPI_STATE_MULTI_LINE);
    }

  if (gtk_at_context_has_accessible_state (ctx, GTK_ACCESSIBLE_STATE_BUSY))
    {
      value = gtk_at_context_get_accessible_state (ctx, GTK_ACCESSIBLE_STATE_BUSY);
      if (gtk_boolean_accessible_value_get (value))
        set_atspi_state (&states, ATSPI_STATE_BUSY);
    }

  if (gtk_at_context_has_accessible_state (ctx, GTK_ACCESSIBLE_STATE_CHECKED))
    {
      value = gtk_at_context_get_accessible_state (ctx, GTK_ACCESSIBLE_STATE_CHECKED);
      switch (gtk_tristate_accessible_value_get (value))
        {
        case GTK_ACCESSIBLE_TRISTATE_TRUE:
          set_atspi_state (&states, ATSPI_STATE_CHECKED);
          break;
        case GTK_ACCESSIBLE_TRISTATE_MIXED:
          set_atspi_state (&states, ATSPI_STATE_INDETERMINATE);
          break;
        case GTK_ACCESSIBLE_TRISTATE_FALSE:
        default:
          break;
        }
    }

  if (gtk_at_context_has_accessible_state (ctx, GTK_ACCESSIBLE_STATE_DISABLED))
    {
      value = gtk_at_context_get_accessible_state (ctx, GTK_ACCESSIBLE_STATE_DISABLED);
      if (!gtk_boolean_accessible_value_get (value))
        set_atspi_state (&states, ATSPI_STATE_SENSITIVE);
    }
  else
    set_atspi_state (&states, ATSPI_STATE_SENSITIVE);

  if (gtk_at_context_has_accessible_state (ctx, GTK_ACCESSIBLE_STATE_EXPANDED))
    {
      value = gtk_at_context_get_accessible_state (ctx, GTK_ACCESSIBLE_STATE_EXPANDED);
      if (value->value_class->type == GTK_ACCESSIBLE_VALUE_TYPE_BOOLEAN)
        {
          set_atspi_state (&states, ATSPI_STATE_EXPANDABLE);
          if (gtk_boolean_accessible_value_get (value))
            set_atspi_state (&states, ATSPI_STATE_EXPANDED);
        }
    }

  if (gtk_at_context_has_accessible_state (ctx, GTK_ACCESSIBLE_STATE_INVALID))
    {
      value = gtk_at_context_get_accessible_state (ctx, GTK_ACCESSIBLE_STATE_INVALID);
      switch (gtk_invalid_accessible_value_get (value))
        {
        case GTK_ACCESSIBLE_INVALID_TRUE:
        case GTK_ACCESSIBLE_INVALID_GRAMMAR:
        case GTK_ACCESSIBLE_INVALID_SPELLING:
          set_atspi_state (&states, ATSPI_STATE_INVALID);
          break;
        case GTK_ACCESSIBLE_INVALID_FALSE:
        default:
          break;
        }
    }

  if (gtk_at_context_has_accessible_state (ctx, GTK_ACCESSIBLE_STATE_PRESSED))
    {
      value = gtk_at_context_get_accessible_state (ctx, GTK_ACCESSIBLE_STATE_PRESSED);
      switch (gtk_tristate_accessible_value_get (value))
        {
        case GTK_ACCESSIBLE_TRISTATE_TRUE:
          set_atspi_state (&states, ATSPI_STATE_PRESSED);
          break;
        case GTK_ACCESSIBLE_TRISTATE_MIXED:
          set_atspi_state (&states, ATSPI_STATE_INDETERMINATE);
          break;
        case GTK_ACCESSIBLE_TRISTATE_FALSE:
        default:
          break;
        }
    }

  if (gtk_at_context_has_accessible_state (ctx, GTK_ACCESSIBLE_STATE_SELECTED))
    {
      value = gtk_at_context_get_accessible_state (ctx, GTK_ACCESSIBLE_STATE_SELECTED);
      if (value->value_class->type == GTK_ACCESSIBLE_VALUE_TYPE_BOOLEAN)
        {
          set_atspi_state (&states, ATSPI_STATE_SELECTABLE);
          if (gtk_boolean_accessible_value_get (value))
            set_atspi_state (&states, ATSPI_STATE_SELECTED);
        }
    }

  g_variant_builder_add (builder, "u", (guint32) (states & 0xffffffff));
  g_variant_builder_add (builder, "u", (guint32) (states >> 32));
}
/* }}} */
/* {{{ Relation handling */
static void
collect_relations (GtkAtSpiContext *self,
                   GVariantBuilder *builder)
{
  GtkATContext *ctx = GTK_AT_CONTEXT (self);
  struct {
    GtkAccessibleRelation r;
    AtspiRelationType s;
  } map[] = {
    { GTK_ACCESSIBLE_RELATION_LABELLED_BY, ATSPI_RELATION_LABELLED_BY },
    { GTK_ACCESSIBLE_RELATION_CONTROLS, ATSPI_RELATION_CONTROLLER_FOR },
    { GTK_ACCESSIBLE_RELATION_DESCRIBED_BY, ATSPI_RELATION_DESCRIBED_BY },
    { GTK_ACCESSIBLE_RELATION_FLOW_TO, ATSPI_RELATION_FLOWS_TO},
  };
  GtkAccessibleValue *value;
  GList *list, *l;
  GtkATContext *target_ctx;
  int i;

  for (i = 0; i < G_N_ELEMENTS (map); i++)
    {
      if (!gtk_at_context_has_accessible_relation (ctx, map[i].r))
        continue;

      GVariantBuilder b = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE ("a(so)"));

      value = gtk_at_context_get_accessible_relation (ctx, map[i].r);
      list = gtk_reference_list_accessible_value_get (value);

      for (l = list; l; l = l->next)
        {
          target_ctx = gtk_accessible_get_at_context (GTK_ACCESSIBLE (l->data));

          /* Realize the ATContext of the target, so we can ask for its ref */
          gtk_at_context_realize (target_ctx);

          g_variant_builder_add (&b, "@(so)",
                                 gtk_at_spi_context_to_ref (GTK_AT_SPI_CONTEXT (target_ctx)));
        }

      g_variant_builder_add (builder, "(ua(so))", map[i].s, &b);
    }
}
/* }}} */
/* {{{ Accessible implementation */
static int
get_index_in (GtkAccessible *parent,
              GtkAccessible *child)
{
  GtkAccessible *candidate;
  guint res;

  if (parent == NULL)
    return -1;

  res = 0;
  for (candidate = gtk_accessible_get_first_accessible_child (parent);
       candidate != NULL;
       candidate = gtk_accessible_get_next_accessible_sibling (candidate))
    {
      if (candidate == child)
        return res;

      if (!gtk_accessible_should_present (candidate))
        continue;

      res++;
    }

  return -1;
}

static int
get_index_in_parent (GtkAccessible *accessible)
{
  GtkAccessible *parent = gtk_accessible_get_accessible_parent (accessible);

  if (parent != NULL)
    return get_index_in (parent, accessible);

  return -1;
}

static int
get_index_in_toplevels (GtkWidget *widget)
{
  GListModel *toplevels = gtk_window_get_toplevels ();
  guint n_toplevels = g_list_model_get_n_items (toplevels);
  GtkWidget *window;
  int idx;

  idx = 0;
  for (guint i = 0; i < n_toplevels; i++)
    {
      window = g_list_model_get_item (toplevels, i);

      g_object_unref (window);

      if (window == widget)
        return idx;

      if (!gtk_accessible_should_present (GTK_ACCESSIBLE (window)))
        continue;

      idx += 1;
    }

  return -1;
}

static GVariant *
get_parent_context_ref (GtkAccessible *accessible)
{
  GVariant *res = NULL;

  GtkAccessible *parent = gtk_accessible_get_accessible_parent (accessible);

  if (parent == NULL)
    {
      GtkATContext *context = gtk_accessible_get_at_context (accessible);
      GtkAtSpiContext *self = GTK_AT_SPI_CONTEXT (context);

      res = gtk_at_spi_root_to_ref (self->root);
    }
  else
    {
      GtkATContext *parent_context = gtk_accessible_get_at_context (parent);
      gtk_at_context_realize (parent_context);

      res = gtk_at_spi_context_to_ref (GTK_AT_SPI_CONTEXT (parent_context));
    }

  if (res == NULL)
    res = gtk_at_spi_null_ref ();

  return res;
}

static void
handle_accessible_method (GDBusConnection       *connection,
                          const gchar           *sender,
                          const gchar           *object_path,
                          const gchar           *interface_name,
                          const gchar           *method_name,
                          GVariant              *parameters,
                          GDBusMethodInvocation *invocation,
                          gpointer               user_data)
{
  GtkAtSpiContext *self = user_data;

  GTK_DEBUG (A11Y, "handling %s on %s", method_name, object_path);

  if (g_strcmp0 (method_name, "GetRole") == 0)
    {
      guint atspi_role = gtk_atspi_role_for_context (GTK_AT_CONTEXT (self));

      g_dbus_method_invocation_return_value (invocation, g_variant_new ("(u)", atspi_role));
    }
  else if (g_strcmp0 (method_name, "GetRoleName") == 0)
    {
      GtkAccessibleRole role = gtk_at_context_get_accessible_role (GTK_AT_CONTEXT (self));
      const char *name = gtk_accessible_role_to_name (role, NULL);
      g_dbus_method_invocation_return_value (invocation, g_variant_new ("(s)", name));
    }
  else if (g_strcmp0 (method_name, "GetLocalizedRoleName") == 0)
    {
      GtkAccessibleRole role = gtk_at_context_get_accessible_role (GTK_AT_CONTEXT (self));
      const char *name = gtk_accessible_role_to_name (role, GETTEXT_PACKAGE);
      g_dbus_method_invocation_return_value (invocation, g_variant_new ("(s)", name));
    }
  else if (g_strcmp0 (method_name, "GetState") == 0)
    {
      GVariantBuilder builder = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE ("(au)"));

      g_variant_builder_open (&builder, G_VARIANT_TYPE ("au"));
      collect_states (self, &builder);
      g_variant_builder_close (&builder);

      g_dbus_method_invocation_return_value (invocation, g_variant_builder_end (&builder));
    }
  else if (g_strcmp0 (method_name, "GetAttributes") == 0)
    {
      GVariantBuilder builder = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE ("(a{ss})"));

      g_variant_builder_open (&builder, G_VARIANT_TYPE ("a{ss}"));
      g_variant_builder_add (&builder, "{ss}", "toolkit", "GTK");

      if (gtk_at_context_has_accessible_property (GTK_AT_CONTEXT (self), GTK_ACCESSIBLE_PROPERTY_PLACEHOLDER))
        {
          GtkAccessibleValue *value;

          value = gtk_at_context_get_accessible_property (GTK_AT_CONTEXT (self), GTK_ACCESSIBLE_PROPERTY_PLACEHOLDER);

          g_variant_builder_add (&builder, "{ss}",
                                 "placeholder-text", gtk_string_accessible_value_get (value));
        }

      g_variant_builder_close (&builder);

      g_dbus_method_invocation_return_value (invocation, g_variant_builder_end (&builder));
    }
  else if (g_strcmp0 (method_name, "GetApplication") == 0)
    {
      g_dbus_method_invocation_return_value (invocation,
                                             g_variant_new ("(@(so))", gtk_at_spi_root_to_ref (self->root)));
    }
  else if (g_strcmp0 (method_name, "GetChildAtIndex") == 0)
    {
      GtkATContext *context = NULL;
      GtkAccessible *accessible;
      int idx, presentable_idx;

      g_variant_get (parameters, "(i)", &idx);

      accessible = gtk_at_context_get_accessible (GTK_AT_CONTEXT (self));

      GtkAccessible *child;

      presentable_idx = 0;
      for (child = gtk_accessible_get_first_accessible_child (accessible);
           child != NULL;
           child = gtk_accessible_get_next_accessible_sibling (child))
        {
          if (!gtk_accessible_should_present (child))
              continue;

          if (presentable_idx == idx)
            break;
          presentable_idx++;

        }
      if (child)
        {
          context = gtk_accessible_get_at_context (child);
        }

      if (context == NULL)
        {
          g_dbus_method_invocation_return_error (invocation,
                                                 G_IO_ERROR,
                                                 G_IO_ERROR_INVALID_ARGUMENT,
                                                 "No child with index %d", idx);
          return;
        }

      /* Realize the child ATContext in order to get its ref */
      gtk_at_context_realize (context);

      GVariant *ref = gtk_at_spi_context_to_ref (GTK_AT_SPI_CONTEXT (context));

      g_dbus_method_invocation_return_value (invocation, g_variant_new ("(@(so))", ref));
    }
  else if (g_strcmp0 (method_name, "GetChildren") == 0)
    {
      GVariantBuilder builder = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE ("a(so)"));

      GtkAccessible *accessible = gtk_at_context_get_accessible (GTK_AT_CONTEXT (self));

      GtkAccessible *child;
      for (child = gtk_accessible_get_first_accessible_child (accessible);
           child != NULL;
           child = gtk_accessible_get_next_accessible_sibling (child))
      {
          if (!gtk_accessible_should_present (child))
            continue;

          GtkATContext *context = gtk_accessible_get_at_context (child);

          /* Realize the child ATContext in order to get its ref */
          gtk_at_context_realize (context);

          GVariant *ref = gtk_at_spi_context_to_ref (GTK_AT_SPI_CONTEXT (context));

          if (ref != NULL)
            g_variant_builder_add (&builder, "@(so)", ref);
        }

      g_dbus_method_invocation_return_value (invocation, g_variant_new ("(a(so))", &builder));
    }
  else if (g_strcmp0 (method_name, "GetIndexInParent") == 0)
    {
      int idx = gtk_at_spi_context_get_index_in_parent (self);

      if (idx == -1)
        g_dbus_method_invocation_return_error (invocation, G_DBUS_ERROR, G_DBUS_ERROR_FAILED, "Not found");
      else
        g_dbus_method_invocation_return_value (invocation, g_variant_new ("(i)", idx));
    }
  else if (g_strcmp0 (method_name, "GetRelationSet") == 0)
    {
      GVariantBuilder builder = G_VARIANT_BUILDER_INIT (G_VARIANT_TYPE ("a(ua(so))"));
      collect_relations (self, &builder);
      g_dbus_method_invocation_return_value (invocation, g_variant_new ("(a(ua(so)))", &builder));
    }
  else if (g_strcmp0 (method_name, "GetInterfaces") == 0)
    {
      g_dbus_method_invocation_return_value (invocation, g_variant_new ("(@as)", self->interfaces));
    }

}

static GVariant *
handle_accessible_get_property (GDBusConnection       *connection,
                                const gchar           *sender,
                                const gchar           *object_path,
                                const gchar           *interface_name,
                                const gchar           *property_name,
                                GError               **error,
                                gpointer               user_data)
{
  GtkAtSpiContext *self = user_data;
  GVariant *res = NULL;

  GtkAccessible *accessible = gtk_at_context_get_accessible (GTK_AT_CONTEXT (self));

  GTK_DEBUG (A11Y, "handling GetProperty %s on %s", property_name, object_path);

  if (g_strcmp0 (property_name, "Name") == 0)
    {
      char *label = gtk_at_context_get_name (GTK_AT_CONTEXT (self));
      res = g_variant_new_string (label ? label : "");
      g_free (label);
    }
  else if (g_strcmp0 (property_name, "Description") == 0)
    {
      char *label = gtk_at_context_get_description (GTK_AT_CONTEXT (self));
      res = g_variant_new_string (label ? label : "");
      g_free (label);
    }
  else if (g_strcmp0 (property_name, "Locale") == 0)
    res = g_variant_new_string (setlocale (LC_MESSAGES, NULL));
  else if (g_strcmp0 (property_name, "AccessibleId") == 0)
    res = g_variant_new_string ("");
  else if (g_strcmp0 (property_name, "Parent") == 0)
    res = get_parent_context_ref (accessible);
  else if (g_strcmp0 (property_name, "ChildCount") == 0)
    res = g_variant_new_int32 (gtk_at_spi_context_get_child_count (self));
  else
    g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
                 "Unknown property '%s'", property_name);

  return res;
}

static const GDBusInterfaceVTable accessible_vtable = {
  handle_accessible_method,
  handle_accessible_get_property,
  NULL,
};
/* }}} */
/* {{{ Change notification */
static void
emit_text_changed (GtkAtSpiContext *self,
                   const char      *kind,
                   int              start,
                   int              end,
                   const char      *text)
{
  if (self->connection == NULL)
    return;

  g_dbus_connection_emit_signal (self->connection,
                                 NULL,
                                 self->context_path,
                                 "org.a11y.atspi.Event.Object",
                                 "TextChanged",
                                 g_variant_new ("(siiva{sv})",
                                                kind, start, end, g_variant_new_string (text), NULL),
                                 NULL);
}

static void
emit_text_selection_changed (GtkAtSpiContext *self,
                             const char      *kind,
                             int              cursor_position)
{
  if (self->connection == NULL)
    return;

  if (strcmp (kind, "text-caret-moved") == 0)
    g_dbus_connection_emit_signal (self->connection,
                                   NULL,
                                   self->context_path,
                                   "org.a11y.atspi.Event.Object",
                                   "TextCaretMoved",
                                   g_variant_new ("(siiva{sv})",
                                                  "", cursor_position, 0, g_variant_new_string (""), NULL),
                                 NULL);
  else
    g_dbus_connection_emit_signal (self->connection,
                                   NULL,
                                   self->context_path,
                                   "org.a11y.atspi.Event.Object",
                                   "TextSelectionChanged",
                                   g_variant_new ("(siiva{sv})",
                                                  "", 0, 0, g_variant_new_string (""), NULL),
                                   NULL);
}

static void
emit_selection_changed (GtkAtSpiContext *self,
                        const char      *kind)
{
  if (self->connection == NULL)
    return;

  g_dbus_connection_emit_signal (self->connection,
                                 NULL,
                                 self->context_path,
                                 "org.a11y.atspi.Event.Object",
                                 "SelectionChanged",
                                 g_variant_new ("(siiva{sv})",
                                                "", 0, 0, g_variant_new_string (""), NULL),
                                 NULL);
}

static void
emit_state_changed (GtkAtSpiContext *self,
                    const char      *name,
                    gboolean         enabled)
{
  if (self->connection == NULL)
    return;

  g_dbus_connection_emit_signal (self->connection,
                                 NULL,
                                 self->context_path,
                                 "org.a11y.atspi.Event.Object",
                                 "StateChanged",
                                 g_variant_new ("(siiva{sv})",
                                                name, enabled, 0, g_variant_new_string ("0"), NULL),
                                 NULL);
}

static void
emit_defunct (GtkAtSpiContext *self)
{
  if (self->connection == NULL)
    return;

  g_dbus_connection_emit_signal (self->connection,
                                 NULL,
                                 self->context_path,
                                 "org.a11y.atspi.Event.Object",
                                 "StateChanged",
                                 g_variant_new ("(siiva{sv})", "defunct", TRUE, 0, g_variant_new_string ("0"), NULL),
                                 NULL);
}

static void
emit_property_changed (GtkAtSpiContext *self,
                       const char      *name,
                       GVariant        *value)
{
  if (self->connection == NULL)
    return;

  g_dbus_connection_emit_signal (self->connection,
                                 NULL,
                                 self->context_path,
                                 "org.a11y.atspi.Event.Object",
                                 "PropertyChange",
                                 g_variant_new ("(siiva{sv})",
                                                name, 0, 0, value, NULL),
                                 NULL);
}

static void
emit_bounds_changed (GtkAtSpiContext *self,
                     int              x,
                     int              y,
                     int              width,
                     int              height)
{
  if (self->connection == NULL)
    return;

  g_dbus_connection_emit_signal (self->connection,
                                 NULL,
                                 self->context_path,
                                 "org.a11y.atspi.Event.Object",
                                 "BoundsChanged",
                                 g_variant_new ("(siiva{sv})",
                                                "", 0, 0, g_variant_new ("(iiii)", x, y, width, height), NULL),
                                 NULL);
}

static void
emit_children_changed (GtkAtSpiContext         *self,
                       GtkAtSpiContext         *child_context,
                       int                      idx,
                       GtkAccessibleChildState  state)
{
  /* If we don't have a connection on either contexts, we cannot emit a signal */
  if (self->connection == NULL || child_context->connection == NULL)
    return;

  GVariant *context_ref = gtk_at_spi_context_to_ref (self);
  GVariant *child_ref = gtk_at_spi_context_to_ref (child_context);

  gtk_at_spi_emit_children_changed (self->connection,
                                    self->context_path,
                                    state,
                                    idx,
                                    child_ref,
                                    context_ref);
}

static void
emit_focus (GtkAtSpiContext *self,
            gboolean         focus_in)
{
  if (self->connection == NULL)
    return;

  if (focus_in)
    g_dbus_connection_emit_signal (self->connection,
                                   NULL,
                                   self->context_path,
                                   "org.a11y.atspi.Event.Focus",
                                   "Focus",
                                   g_variant_new ("(siiva{sv})",
                                                  "", 0, 0, g_variant_new_string ("0"), NULL),
                                   NULL);
}

static void
emit_window_event (GtkAtSpiContext *self,
                   const char      *event_type)
{
  if (self->connection == NULL)
    return;

  g_dbus_connection_emit_signal (self->connection,
                                 NULL,
                                 self->context_path,
                                 "org.a11y.atspi.Event.Window",
                                 event_type,
                                 g_variant_new ("(siiva{sv})",
                                                "", 0, 0,
                                                g_variant_new_string("0"),
                                                NULL),
                                 NULL);
}

static void
gtk_at_spi_context_state_change (GtkATContext                *ctx,
                                 GtkAccessibleStateChange     changed_states,
                                 GtkAccessiblePropertyChange  changed_properties,
                                 GtkAccessibleRelationChange  changed_relations,
                                 GtkAccessibleAttributeSet   *states,
                                 GtkAccessibleAttributeSet   *properties,
                                 GtkAccessibleAttributeSet   *relations)
{
  GtkAtSpiContext *self = GTK_AT_SPI_CONTEXT (ctx);
  GtkAccessible *accessible = gtk_at_context_get_accessible (ctx);
  GtkAccessibleValue *value;

  if (GTK_IS_WIDGET (accessible) && !gtk_widget_get_realized (GTK_WIDGET (accessible)))
    return;

  if (changed_states & GTK_ACCESSIBLE_STATE_CHANGE_HIDDEN)
    {
      GtkAccessible *parent;
      GtkATContext *context;
      GtkAccessibleChildChange change;

      value = gtk_accessible_attribute_set_get_value (states, GTK_ACCESSIBLE_STATE_HIDDEN);
      if (gtk_boolean_accessible_value_get (value))
        change = GTK_ACCESSIBLE_CHILD_CHANGE_REMOVED;
      else
        change = GTK_ACCESSIBLE_CHILD_CHANGE_ADDED;

      if (GTK_IS_ROOT (accessible))
        {
          gtk_at_spi_root_child_changed (self->root, change, accessible);
          emit_state_changed (self, "showing", gtk_boolean_accessible_value_get (value));
        }
      else
        {
          parent = gtk_accessible_get_accessible_parent (accessible);

          context = gtk_accessible_get_at_context (parent);
          gtk_at_context_child_changed (context, change, accessible);
        }
    }

  if (changed_states & GTK_ACCESSIBLE_STATE_CHANGE_BUSY)
    {
      value = gtk_accessible_attribute_set_get_value (states, GTK_ACCESSIBLE_STATE_BUSY);
      emit_state_changed (self, "busy", gtk_boolean_accessible_value_get (value));
    }

  if (changed_states & GTK_ACCESSIBLE_STATE_CHANGE_CHECKED)
    {
      value = gtk_accessible_attribute_set_get_value (states, GTK_ACCESSIBLE_STATE_CHECKED);

      if (value->value_class->type == GTK_ACCESSIBLE_VALUE_TYPE_TRISTATE)
        {
          switch (gtk_tristate_accessible_value_get (value))
            {
            case GTK_ACCESSIBLE_TRISTATE_TRUE:
              emit_state_changed (self, "checked", TRUE);
              emit_state_changed (self, "indeterminate", FALSE);
              break;
            case GTK_ACCESSIBLE_TRISTATE_MIXED:
              emit_state_changed (self, "checked", FALSE);
              emit_state_changed (self, "indeterminate", TRUE);
              break;
            case GTK_ACCESSIBLE_TRISTATE_FALSE:
              emit_state_changed (self, "checked", FALSE);
              emit_state_changed (self, "indeterminate", FALSE);
              break;
            default:
              break;
            }
        }
      else
        {
          emit_state_changed (self, "checked", FALSE);
          emit_state_changed (self, "indeterminate", TRUE);
        }
    }

  if (changed_states & GTK_ACCESSIBLE_STATE_CHANGE_DISABLED)
    {
      value = gtk_accessible_attribute_set_get_value (states, GTK_ACCESSIBLE_STATE_DISABLED);
      emit_state_changed (self, "sensitive", !gtk_boolean_accessible_value_get (value));
    }

  if (changed_states & GTK_ACCESSIBLE_STATE_CHANGE_EXPANDED)
    {
      value = gtk_accessible_attribute_set_get_value (states, GTK_ACCESSIBLE_STATE_EXPANDED);
      if (value->value_class->type == GTK_ACCESSIBLE_VALUE_TYPE_BOOLEAN)
        {
          emit_state_changed (self, "expandable", TRUE);
          emit_state_changed (self, "expanded",gtk_boolean_accessible_value_get (value));
        }
      else
        emit_state_changed (self, "expandable", FALSE);
    }

  if (changed_states & GTK_ACCESSIBLE_STATE_CHANGE_INVALID)
    {
      value = gtk_accessible_attribute_set_get_value (states, GTK_ACCESSIBLE_STATE_INVALID);
      switch (gtk_invalid_accessible_value_get (value))
        {
        case GTK_ACCESSIBLE_INVALID_TRUE:
        case GTK_ACCESSIBLE_INVALID_GRAMMAR:
        case GTK_ACCESSIBLE_INVALID_SPELLING:
          emit_state_changed (self, "invalid", TRUE);
          break;
        case GTK_ACCESSIBLE_INVALID_FALSE:
          emit_state_changed (self, "invalid", FALSE);
          break;
        default:
          break;
        }
    }

  if (changed_states & GTK_ACCESSIBLE_STATE_CHANGE_PRESSED)
    {
      value = gtk_accessible_attribute_set_get_value (states, GTK_ACCESSIBLE_STATE_PRESSED);

      if (value->value_class->type == GTK_ACCESSIBLE_VALUE_TYPE_TRISTATE)
        {
          switch (gtk_tristate_accessible_value_get (value))
            {
            case GTK_ACCESSIBLE_TRISTATE_TRUE:
              emit_state_changed (self, "pressed", TRUE);
              emit_state_changed (self, "indeterminate", FALSE);
              break;
            case GTK_ACCESSIBLE_TRISTATE_MIXED:
              emit_state_changed (self, "pressed", FALSE);
              emit_state_changed (self, "indeterminate", TRUE);
              break;
            case GTK_ACCESSIBLE_TRISTATE_FALSE:
              emit_state_changed (self, "pressed", FALSE);
              emit_state_changed (self, "indeterminate", FALSE);
              break;
            default:
              break;
            }
        }
      else
        {
          emit_state_changed (self, "pressed", FALSE);
          emit_state_changed (self, "indeterminate", TRUE);
        }
    }

  if (changed_states & GTK_ACCESSIBLE_STATE_CHANGE_SELECTED)
    {
      value = gtk_accessible_attribute_set_get_value (states, GTK_ACCESSIBLE_STATE_SELECTED);
      if (value->value_class->type == GTK_ACCESSIBLE_VALUE_TYPE_BOOLEAN)
        {
          emit_state_changed (self, "selectable", TRUE);
          emit_state_changed (self, "selected",gtk_boolean_accessible_value_get (value));
        }
      else
        emit_state_changed (self, "selectable", FALSE);
    }

  if (changed_properties & GTK_ACCESSIBLE_PROPERTY_CHANGE_READ_ONLY)
    {
      gboolean readonly;

      value = gtk_accessible_attribute_set_get_value (properties, GTK_ACCESSIBLE_PROPERTY_READ_ONLY);
      readonly = gtk_boolean_accessible_value_get (value);

      emit_state_changed (self, "read-only", readonly);