Add API to install protocol loggers on the server wl_display

The new wl_display_add_protocol_logger allows to set a function as
a logger, which will get called when a new request is received or an
event is sent.
This is akin to setting WAYLAND_DEBUG=1, but more powerful because it
can be enabled at run time and allows to show the log e.g. in a UI view.
A test is added for the new functionality.

Signed-off-by: Giulio Camuffo <giulio.camuffo@kdab.com>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Yong Bakos <ybakos@humanoriented.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

4 files changed, 272 insertions, 7 deletions

diff --git a/Makefile.am b/Makefile.am
index e684a87..3eb6fd5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -161,7 +161,8 @@ TESTS =						\
 	resources-test				\
 	message-test				\
 	headers-test				\
-	compositor-introspection-test
+	compositor-introspection-test		\
+	protocol-logger-test
 
 if ENABLE_CPP_TEST
 TESTS += cpp-compile-test
@@ -220,6 +221,8 @@ message_test_SOURCES = tests/message-test.c
 message_test_LDADD = libtest-runner.la
 compositor_introspection_test_SOURCES = tests/compositor-introspection-test.c
 compositor_introspection_test_LDADD = libtest-runner.la
+protocol_logger_test_SOURCES = tests/protocol-logger-test.c
+protocol_logger_test_LDADD = libtest-runner.la
 headers_test_SOURCES = tests/headers-test.c \
 		       tests/headers-protocol-test.c \
 		       tests/headers-protocol-core-test.c
diff --git a/src/wayland-server-core.h b/src/wayland-server-core.h
index 56e8d80..21465af 100644
--- a/src/wayland-server-core.h
+++ b/src/wayland-server-core.h
@@ -522,6 +522,30 @@ wl_shm_buffer_create(struct wl_client *client,
 void
 wl_log_set_handler_server(wl_log_func_t handler);
 
+enum wl_protocol_logger_type {
+	WL_PROTOCOL_LOGGER_REQUEST,
+	WL_PROTOCOL_LOGGER_EVENT,
+};
+
+struct wl_protocol_logger_message {
+	struct wl_resource *resource;
+	int message_opcode;
+	const struct wl_message *message;
+	int arguments_count;
+	const union wl_argument *arguments;
+};
+
+typedef void (*wl_protocol_logger_func_t)(void *user_data,
+					  enum wl_protocol_logger_type direction,
+					  const struct wl_protocol_logger_message *message);
+
+struct wl_protocol_logger *
+wl_display_add_protocol_logger(struct wl_display *display,
+			       wl_protocol_logger_func_t, void *user_data);
+
+void
+wl_protocol_logger_destroy(struct wl_protocol_logger *logger);
+
 #ifdef  __cplusplus
 }
 #endif
diff --git a/src/wayland-server.c b/src/wayland-server.c
index dd648ac..9ecfd97 100644
--- a/src/wayland-server.c
+++ b/src/wayland-server.c
@@ -95,6 +95,7 @@ struct wl_display {
 	struct wl_list global_list;
 	struct wl_list socket_list;
 	struct wl_list client_list;
+	struct wl_list protocol_loggers;
 
 	struct wl_signal destroy_signal;
 	struct wl_signal create_client_signal;
@@ -123,8 +124,42 @@ struct wl_resource {
 	wl_dispatcher_func_t dispatcher;
 };
 
+struct wl_protocol_logger {
+	struct wl_list link;
+	wl_protocol_logger_func_t func;
+	void *user_data;
+};
+
 static int debug_server = 0;
 
+static void
+log_closure(struct wl_resource *resource,
+	    struct wl_closure *closure, int send)
+{
+	struct wl_object *object = &resource->object;
+	struct wl_display *display = resource->client->display;
+	struct wl_protocol_logger *protocol_logger;
+	struct wl_protocol_logger_message message;
+
+	if (debug_server)
+		wl_closure_print(closure, object, send);
+
+	if (!wl_list_empty(&display->protocol_loggers)) {
+		message.resource = resource;
+		message.message_opcode = closure->opcode;
+		message.message = closure->message;
+		message.arguments_count = closure->count;
+		message.arguments = closure->args;
+		wl_list_for_each(protocol_logger,
+				 &display->protocol_loggers, link) {
+			protocol_logger->func(protocol_logger->user_data,
+					      send ? WL_PROTOCOL_LOGGER_EVENT :
+						     WL_PROTOCOL_LOGGER_REQUEST,
+					      &message);
+		}
+	}
+}
+
 WL_EXPORT void
 wl_resource_post_event_array(struct wl_resource *resource, uint32_t opcode,
 			     union wl_argument *args)
@@ -143,8 +178,7 @@ wl_resource_post_event_array(struct wl_resource *resource, uint32_t opcode,
 	if (wl_closure_send(closure, resource->client->connection))
 		resource->client->error = 1;
 
-	if (debug_server)
-		wl_closure_print(closure, object, true);
+	log_closure(resource, closure, true);
 
 	wl_closure_destroy(closure);
 }
@@ -183,8 +217,7 @@ wl_resource_queue_event_array(struct wl_resource *resource, uint32_t opcode,
 	if (wl_closure_queue(closure, resource->client->connection))
 		resource->client->error = 1;
 
-	if (debug_server)
-		wl_closure_print(closure, object, true);
+	log_closure(resource, closure, true);
 
 	wl_closure_destroy(closure);
 }
@@ -331,8 +364,7 @@ wl_client_connection_data(int fd, uint32_t mask, void *data)
 			break;
 		}
 
-		if (debug_server)
-			wl_closure_print(closure, object, false);
+		log_closure(resource, closure, false);
 
 		if ((resource_flags & WL_MAP_ENTRY_LEGACY) ||
 		    resource->dispatcher == NULL) {
@@ -885,6 +917,7 @@ wl_display_create(void)
 	wl_list_init(&display->socket_list);
 	wl_list_init(&display->client_list);
 	wl_list_init(&display->registry_resource_list);
+	wl_list_init(&display->protocol_loggers);
 
 	wl_signal_init(&display->destroy_signal);
 	wl_signal_init(&display->create_client_signal);
@@ -961,6 +994,8 @@ wl_display_destroy(struct wl_display *display)
 
 	wl_array_release(&display->additional_shm_formats);
 
+	wl_list_remove(&display->protocol_loggers);
+
 	free(display);
 }
 
@@ -1481,6 +1516,61 @@ wl_log_set_handler_server(wl_log_func_t handler)
 	wl_log_handler = handler;
 }
 
+/** Adds a new protocol logger.
+ *
+ * When a new protocol message arrives or is sent from the server
+ * all the protocol logger functions will be called, carrying the
+ * \a user_data pointer, the type of the message (request or
+ * event) and the actual message.
+ * The lifetime of the messages passed to the logger function ends
+ * when they return so the messages cannot be stored and accessed
+ * later.
+ *
+ * \a errno is set on error.
+ *
+ * \param func The function to call to log a new protocol message
+ * \param user_data The user data pointer to pass to \a func
+ *
+ * \return The protol logger object on success, NULL on failure.
+ *
+ * \sa wl_protocol_logger_destroy
+ *
+ * \memberof wl_display
+ */
+WL_EXPORT struct wl_protocol_logger *
+wl_display_add_protocol_logger(struct wl_display *display,
+			       wl_protocol_logger_func_t func, void *user_data)
+{
+	struct wl_protocol_logger *logger;
+
+	logger = malloc(sizeof *logger);
+	if (!logger)
+		return NULL;
+
+	logger->func = func;
+	logger->user_data = user_data;
+	wl_list_insert(&display->protocol_loggers, &logger->link);
+
+	return logger;
+}
+
+/** Destroys a protocol logger.
+ *
+ * This function destroys a protocol logger and removes it from the display
+ * it was added to with \a wl_display_add_protocol_logger.
+ * The \a logger object becomes invalid after calling this function.
+ *
+ * \sa wl_display_add_protocol_logger
+ *
+ * \memberof wl_protocol_logger
+ */
+WL_EXPORT void
+wl_protocol_logger_destroy(struct wl_protocol_logger *logger)
+{
+	wl_list_remove(&logger->link);
+	free(logger);
+}
+
 /** Add support for a wl_shm pixel format
  *
  * \param display The display object
diff --git a/tests/protocol-logger-test.c b/tests/protocol-logger-test.c
new file mode 100644
index 0000000..80c74aa
--- /dev/null
+++ b/tests/protocol-logger-test.c
@@ -0,0 +1,148 @@
+/*
+ * Copyright © 2016 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include "wayland-client.h"
+#include "wayland-server.h"
+#include "test-runner.h"
+
+/* Ensure the connection doesn't fail due to lack of XDG_RUNTIME_DIR. */
+static const char *
+require_xdg_runtime_dir(void)
+{
+	char *val = getenv("XDG_RUNTIME_DIR");
+	assert(val && "set $XDG_RUNTIME_DIR to run this test");
+
+	return val;
+}
+
+struct compositor {
+	struct wl_display *display;
+	struct wl_event_loop *loop;
+	int message;
+	struct wl_client *client;
+};
+
+struct message {
+	enum wl_protocol_logger_type type;
+	const char *class;
+	int opcode;
+	const char *message_name;
+	int args_count;
+} messages[] = {
+	{
+		.type = WL_PROTOCOL_LOGGER_REQUEST,
+		.class = "wl_display",
+		.opcode = 0,
+		.message_name = "sync",
+		.args_count = 1,
+	},
+	{
+		.type = WL_PROTOCOL_LOGGER_EVENT,
+		.class = "wl_callback",
+		.opcode = 0,
+		.message_name = "done",
+		.args_count = 1,
+	},
+	{
+		.type = WL_PROTOCOL_LOGGER_EVENT,
+		.class = "wl_display",
+		.opcode = 1,
+		.message_name = "delete_id",
+		.args_count = 1,
+	},
+};
+
+static void
+logger_func(void *user_data, enum wl_protocol_logger_type type,
+	    const struct wl_protocol_logger_message *message)
+{
+	struct compositor *c = user_data;
+	struct message *msg = &messages[c->message++];
+
+	assert(msg->type == type);
+	assert(strcmp(msg->class, wl_resource_get_class(message->resource)) == 0);
+	assert(msg->opcode == message->message_opcode);
+	assert(strcmp(msg->message_name, message->message->name) == 0);
+	assert(msg->args_count == message->arguments_count);
+
+	c->client = wl_resource_get_client(message->resource);
+}
+
+static void
+callback_done(void *data, struct wl_callback *cb, uint32_t time)
+{
+	wl_callback_destroy(cb);
+}
+
+static const struct wl_callback_listener callback_listener = {
+	callback_done,
+};
+
+TEST(logger)
+{
+	test_set_timeout(1);
+
+	const char *socket;
+	struct compositor compositor = { 0 };
+	struct {
+		struct wl_display *display;
+		struct wl_callback *cb;
+	} client;
+	struct wl_protocol_logger *logger;
+
+	require_xdg_runtime_dir();
+
+	compositor.display = wl_display_create();
+	compositor.loop = wl_display_get_event_loop(compositor.display);
+	socket = wl_display_add_socket_auto(compositor.display);
+
+	logger = wl_display_add_protocol_logger(compositor.display,
+						logger_func, &compositor);
+
+	client.display = wl_display_connect(socket);
+	client.cb = wl_display_sync(client.display);
+	wl_callback_add_listener(client.cb, &callback_listener, NULL);
+	wl_display_flush(client.display);
+
+	while (compositor.message < 3) {
+		wl_event_loop_dispatch(compositor.loop, -1);
+		wl_display_flush_clients(compositor.display);
+	}
+
+	wl_display_dispatch(client.display);
+	wl_display_disconnect(client.display);
+
+	wl_client_destroy(compositor.client);
+	wl_protocol_logger_destroy(logger);
+	wl_display_destroy(compositor.display);
+}