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wayland-server: Add wl_client_add_event_dispatch_listener

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The patch adds a listener called after an event has been dispatched
by the server.

Wayland servers that incorporate the Wayland display into their own
event loops may dispatch multiple Wayland events to clients as they
work through their task queues.

For e.g. if system display state changes the Wayland server may
emit several output / surface Wayland events to connected clients.

Currently an explicit flush is performd immediately after each
individual Wayland event is dispatched to make sure these are
propagated to clients in a deterministic / reliable manner.

This results in hard to maintain / easy to break code. Contributors
must make sure to explicitly flush when dispatching Wayland events
to clients - or otherwise wait for some other server event to flush
the client buffer later on. In the latter case behavior is not
deterministic and makes testing the server code much harder.

The client event_dispatch_listener added in this patch allows the
server to track if the processing of a server event has resulted in
the dispatch of one or more Wayland events to clients - and ensure
the buffer is appropriately flushed.

This eliminates the need to flush in many different areas of the
codebase, making the server easier to maintain and test.

Signed-off-by: Thomas Lukaszewicz <thomaslukaszewicz@gmail.com>
This commit is contained in:
Thomas Lukaszewicz 2024-01-03 23:47:46 +00:00
parent 6626d4d98c
commit a86fd86b5e
3 changed files with 80 additions and 5 deletions
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4
src/wayland-server-core.h
View file

@ -342,6 +342,10 @@ struct wl_listener *
wl_client_get_destroy_late_listener(struct wl_client *client,
wl_notify_func_t notify);
void
wl_client_add_event_dispatch_listener(struct wl_client *client,
struct wl_listener *listener);
struct wl_resource *
wl_client_get_object(struct wl_client *client, uint32_t id);

37
src/wayland-server.c
View file

@ -80,6 +80,7 @@ struct wl_client {
struct wl_map objects;
struct wl_priv_signal destroy_signal;
struct wl_priv_signal destroy_late_signal;
struct wl_priv_signal event_dispatch_signal;
pid_t pid;
uid_t uid;
gid_t gid;
@ -212,12 +213,13 @@ handle_array(struct wl_resource *resource, uint32_t opcode,
{
struct wl_closure *closure;
struct wl_object *object = &resource->object;
struct wl_client *client = resource->client;
if (resource->client->error)
if (client->error)
return;
if (!verify_objects(resource, opcode, args)) {
resource->client->error = true;
client->error = true;
return;
}
@ -225,14 +227,17 @@ handle_array(struct wl_resource *resource, uint32_t opcode,
&object->interface->events[opcode]);
if (closure == NULL) {
resource->client->error = true;
client->error = true;
return;
}
log_closure(resource, closure, true);
if (send_func(closure, resource->client->connection))
resource->client->error = true;
if (send_func(closure, client->connection)) {
client->error = true;
} else {
wl_priv_signal_final_emit(&client->event_dispatch_signal, client);
}
wl_closure_destroy(closure);
}
@ -549,6 +554,7 @@ wl_client_create(struct wl_display *display, int fd)
wl_priv_signal_init(&client->destroy_signal);
wl_priv_signal_init(&client->destroy_late_signal);
wl_priv_signal_init(&client->event_dispatch_signal);
if (bind_display(client, display) < 0)
goto err_map;
@ -917,6 +923,27 @@ wl_client_get_destroy_late_listener(struct wl_client *client,
return wl_priv_signal_get(&client->destroy_late_signal, notify);
}
/** Add a listener to be called after successful event dispatch.
*
* \param client The client object.
* \param listener The listener to be added.
*
* After an event has been dispatched to this client, the listener will
* be notified.
*
* There is no requirement to remove the link of the wl_listener when the
* signal is emitted.
*
* \memberof wl_client
* \since 1.22.0
*/
WL_EXPORT void
wl_client_add_event_dispatch_listener(struct wl_client *client,
struct wl_listener *listener)
{
wl_priv_signal_add(&client->event_dispatch_signal, listener);
}
WL_EXPORT void
wl_client_destroy(struct wl_client *client)
{

44
tests/client-test.c
View file

@ -143,3 +143,47 @@ TEST(client_destroy_listener)
wl_display_destroy(display);
}
struct event_dispatch_listener {
struct wl_listener listener;
bool done;
};
static void
event_dispatch_notify(struct wl_listener *l, void *data)
{
struct event_dispatch_listener *listener =
wl_container_of(l, listener, listener);
listener->done = true;
}
TEST(event_dispatch_listener)
{
struct wl_display *display;
struct wl_client *client;
struct wl_resource *resource;
struct event_dispatch_listener dispatch_listener;
int s[2];
assert(socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, s) == 0);
display = wl_display_create();
assert(display);
client = wl_client_create(display, s[0]);
assert(client);
dispatch_listener.listener.notify = event_dispatch_notify;
dispatch_listener.done = false;
wl_client_add_event_dispatch_listener(client, &dispatch_listener.listener);
resource = wl_resource_create(client, &wl_seat_interface, 4, 0);
assert(resource);
wl_seat_send_name(resource, "default");
wl_event_loop_dispatch(wl_display_get_event_loop(display), 0);
assert(dispatch_listener.done);
close(s[1]);
wl_client_destroy(client);
wl_display_destroy(display);
}