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>

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);
+}