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a11y: Watch EventListenerRegistered/Deregistered signals

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Assistive technologies using AT-SPI typically register themselves on the
accessibility bus through the org.a11y.atspi.Registry.RegisterEvent
method, which will emit the EventListenerRegistered signal. We can use
that signal (and its corresponding EventListenerDeregistered sibling) to
know whether there is at least an AT on the other side of the
accessibility bus.
This commit is contained in:
Emmanuele Bassi 2024-05-24 19:15:09 +01:00
parent 9d5652de64
commit 4ea4dc9176
2 changed files with 113 additions and 0 deletions
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110
gtk/a11y/gtkatspiroot.c
View File

@ -45,6 +45,7 @@
#define ATSPI_PATH_PREFIX "/org/a11y/atspi"
#define ATSPI_ROOT_PATH ATSPI_PATH_PREFIX "/accessible/root"
#define ATSPI_CACHE_PATH ATSPI_PATH_PREFIX "/cache"
#define ATSPI_REGISTRY_PATH ATSPI_PATH_PREFIX "/registry"
struct _GtkAtSpiRoot
{
@ -71,6 +72,9 @@ struct _GtkAtSpiRoot
GtkAtSpiCache *cache;
GListModel *toplevels;
/* HashTable<str, str> */
GHashTable *event_listeners;
};
enum
@ -90,6 +94,7 @@ gtk_at_spi_root_finalize (GObject *gobject)
GtkAtSpiRoot *self = GTK_AT_SPI_ROOT (gobject);
g_clear_handle_id (&self->register_id, g_source_remove);
g_clear_pointer (&self->event_listeners, g_hash_table_unref);
g_free (self->bus_address);
g_free (self->base_path);
@ -541,6 +546,81 @@ on_registration_reply (GObject *gobject,
g_free (data);
}
static void
on_event_listener_registered (GDBusConnection *connection,
const char *sender_name,
const char *object_path,
const char *interface_name,
const char *signal_name,
GVariant *parameters,
gpointer user_data)
{
GtkAtSpiRoot *self = user_data;
if (g_strcmp0 (object_path, ATSPI_REGISTRY_PATH) == 0 &&
g_strcmp0 (interface_name, "org.a11y.atspi.Registry") == 0 &&
g_strcmp0 (signal_name, "EventListenerRegistered") == 0)
{
char *sender = NULL;
char *event_name = NULL;
char **event_types = NULL;
if (self->event_listeners == NULL)
self->event_listeners = g_hash_table_new_full (g_str_hash, g_str_equal,
g_free,
NULL);
g_variant_get (parameters, "(ssas)", &sender, &event_name, &event_types);
GTK_DEBUG (A11Y, "Registering event listener (%s, %s) on the a11y bus",
sender,
event_name[0] != 0 ? event_name : "(none)");
g_hash_table_add (self->event_listeners, sender);
g_free (event_name);
g_strfreev (event_types);
}
}
static void
on_event_listener_deregistered (GDBusConnection *connection,
const char *sender_name,
const char *object_path,
const char *interface_name,
const char *signal_name,
GVariant *parameters,
gpointer user_data)
{
GtkAtSpiRoot *self = user_data;
if (g_strcmp0 (object_path, ATSPI_REGISTRY_PATH) == 0 &&
g_strcmp0 (interface_name, "org.a11y.atspi.Registry") == 0 &&
g_strcmp0 (signal_name, "EventListenerDeregistered") == 0)
{
const char *sender = NULL;
const char *event = NULL;
if (self->event_listeners == NULL)
{
g_critical ("Received org.a11y.atspi.Registry::EventListenerDeregistered without "
"a corresponding EventListenerRegistered signal.");
return;
}
g_variant_get (parameters, "(&s&s)", &sender, &event);
if (g_hash_table_contains (self->event_listeners, sender))
{
GTK_DEBUG (A11Y, "Deregistering event listener (%s, %s) on the a11y bus",
sender,
event[0] != 0 ? event : "(none)");
g_hash_table_remove (self->event_listeners, sender);
}
}
}
static gboolean
root_register (gpointer user_data)
{
@ -587,6 +667,27 @@ root_register (gpointer user_data)
NULL,
NULL);
g_dbus_connection_signal_subscribe (self->connection,
"org.a11y.atspi.Registry",
"org.a11y.atspi.Registry",
"EventListenerRegistered",
ATSPI_REGISTRY_PATH,
NULL,
G_DBUS_SIGNAL_FLAGS_NONE,
on_event_listener_registered,
self,
NULL);
g_dbus_connection_signal_subscribe (self->connection,
"org.a11y.atspi.Registry",
"org.a11y.atspi.Registry",
"EventListenerDeregistered",
ATSPI_REGISTRY_PATH,
NULL,
G_DBUS_SIGNAL_FLAGS_NONE,
on_event_listener_deregistered,
self,
NULL);
GTK_DEBUG (A11Y, "Registering (%s, %s) on the a11y bus",
unique_name,
self->root_path);
@ -818,3 +919,12 @@ gtk_at_spi_root_get_base_path (GtkAtSpiRoot *self)
return self->base_path;
}
gboolean
gtk_at_spi_root_has_event_listeners (GtkAtSpiRoot *self)
{
g_return_val_if_fail (GTK_IS_AT_SPI_ROOT (self), FALSE);
return self->event_listeners != NULL &&
g_hash_table_size (self->event_listeners) != 0;
}

3
gtk/a11y/gtkatspirootprivate.h
View File

@ -63,4 +63,7 @@ gtk_at_spi_root_child_changed (GtkAtSpiRoot *self,
GtkAccessibleChildChange change,
GtkAccessible *child);
gboolean
gtk_at_spi_root_has_event_listeners (GtkAtSpiRoot *self);
G_END_DECLS