Add a customizable log handler

The previous log handler wasn't actually hooked up to anything. Add a public
API for the log handler with priority filtering, defaulting to priority
'error' and stderr as output stream.

And to keep the diff down and convenience up, provide a few simple wrappers
for logging. The generic is log_msg(), but let's use log_info, log_error, etc.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>

src/libinput-private.h

@@ -74,6 +74,13 @@ typedef void (*libinput_source_dispatch_t)(void *data);
 
 struct libinput_source;
 
+#define log_debug(...) log_msg(LIBINPUT_LOG_PRIORITY_DEBUG, __VA_ARGS__)
+#define log_info(...) log_msg(LIBINPUT_LOG_PRIORITY_INFO, __VA_ARGS__)
+#define log_error(...) log_msg(LIBINPUT_LOG_PRIORITY_ERROR, __VA_ARGS__)
+
+void
+log_msg(enum libinput_log_priority priority, const char *format, ...);
+
 int
 libinput_init(struct libinput *libinput,
 	      const struct libinput_interface *interface,

src/libinput-util.c

@@ -35,26 +35,6 @@
 #include "libinput-util.h"
 #include "libinput-private.h"
 
-static FILE *g_log_file = NULL;
-
-void
-set_logging_enabled(int enabled)
-{
-	g_log_file = enabled ? stdout : NULL;
-}
-
-void
-log_info(const char *format, ...)
-{
-	va_list ap;
-
-	if (g_log_file) {
-		va_start(ap, format);
-		vfprintf(g_log_file, format, ap);
-		va_end(ap);
-	}
-}
-
 void
 list_init(struct list *list)
 {

src/libinput.c

@@ -77,6 +77,68 @@ struct libinput_event_touch {
 	enum libinput_touch_type touch_type;
 };
 
+static void
+libinput_default_log_func(enum libinput_log_priority priority,
+			  void *data,
+			  const char *format, va_list args)
+{
+	const char *prefix;
+
+	switch(priority) {
+	case LIBINPUT_LOG_PRIORITY_DEBUG: prefix = "debug"; break;
+	case LIBINPUT_LOG_PRIORITY_INFO: prefix = "info"; break;
+	case LIBINPUT_LOG_PRIORITY_ERROR: prefix = "error"; break;
+	default: prefix="<invalid priority>"; break;
+	}
+
+	fprintf(stderr, "libinput %s: ", prefix);
+	vfprintf(stderr, format, args);
+}
+
+struct log_data {
+	enum libinput_log_priority priority;
+	libinput_log_handler handler;
+	void *user_data;
+};
+
+static struct log_data log_data = {
+	.priority = LIBINPUT_LOG_PRIORITY_ERROR,
+	.handler = libinput_default_log_func,
+	.user_data = NULL,
+};
+
+void
+log_msg(enum libinput_log_priority priority, const char *format, ...)
+{
+	va_list args;
+
+	if (log_data.handler && log_data.priority <= priority) {
+		va_start(args, format);
+		log_data.handler(priority, log_data.user_data, format, args);
+		va_end(args);
+	}
+}
+
+LIBINPUT_EXPORT void
+libinput_log_set_priority(enum libinput_log_priority priority)
+{
+	log_data.priority = priority;
+}
+
+LIBINPUT_EXPORT enum libinput_log_priority
+libinput_log_get_priority(void)
+{
+	return log_data.priority;
+}
+
+LIBINPUT_EXPORT void
+libinput_log_set_handler(libinput_log_handler log_handler,
+			 void *user_data)
+{
+	log_data.handler = log_handler;
+	log_data.user_data = user_data;
+}
+
 static void
 libinput_post_event(struct libinput *libinput,
 		    struct libinput_event *event);

src/libinput.h

@@ -41,6 +41,15 @@
  */
 typedef int32_t li_fixed_t;
 
+/**
+ * Log priority for internal logging messages.
+ */
+enum libinput_log_priority {
+	LIBINPUT_LOG_PRIORITY_DEBUG = 10,
+	LIBINPUT_LOG_PRIORITY_INFO = 20,
+	LIBINPUT_LOG_PRIORITY_ERROR = 30,
+};
+
 /**
  * @ingroup device
  *
@@ -860,6 +869,73 @@ libinput_suspend(struct libinput *libinput);
 void
 libinput_destroy(struct libinput *libinput);
 
+/**
+ * @ingroup base
+ *
+ * Set the global log priority. Messages with priorities equal to or
+ * higher than the argument will be printed to the current log handler.
+ *
+ * The default log priority is LIBINPUT_LOG_PRIORITY_ERROR.
+ *
+ * @param priority The minimum priority of log messages to print.
+ *
+ * @see libinput_log_set_handler
+ */
+void
+libinput_log_set_priority(enum libinput_log_priority priority);
+
+/**
+ * @ingroup base
+ *
+ * Get the global log priority. Messages with priorities equal to or
+ * higher than the argument will be printed to the current log handler.
+ *
+ * The default log priority is LIBINPUT_LOG_PRIORITY_ERROR.
+ *
+ * @return The minimum priority of log messages to print.
+ *
+ * @see libinput_log_set_handler
+ */
+enum libinput_log_priority
+libinput_log_get_priority(void);
+
+/**
+ * @ingroup base
+ *
+ * Log handler type for custom logging.
+ *
+ * @param priority The priority of the current message
+ * @param user_data Caller-specific data pointer as previously passed into
+ * libinput_log_set_handler()
+ * @param format Message format in printf-style
+ * @param args Message arguments
+ *
+ * @see libinput_set_log_priority
+ * @see libinput_log_set_handler
+ */
+typedef void (*libinput_log_handler)(enum libinput_log_priority priority,
+				     void *user_data,
+				     const char *format, va_list args);
+
+/**
+ * @ingroup base
+ *
+ * Set the global log handler. Messages with priorities equal to or higher
+ * than the current log priority will be passed to the given
+ * log handler.
+ *
+ * The default log handler prints to stderr.
+ *
+ * @param log_handler The log handler for library messages.
+ * @param user_data Caller-specific data pointer, passed into the log
+ * handler.
+ *
+ * @see libinput_log_set_handler
+ */
+void
+libinput_log_set_handler(libinput_log_handler log_handler,
+			 void *user_data);
+
 /**
  * @defgroup seat Initialization and manipulation of seats
  *

src/path.c

@@ -264,7 +264,7 @@ libinput_path_add_device(struct libinput *libinput,
 	struct libinput_device *device;
 
 	if (libinput->interface_backend != &interface_backend) {
-		log_info("Mismatching backends. This is an application bug.\n");
+		log_error("Mismatching backends. This is an application bug.\n");
 		return NULL;
 	}
 
@@ -301,7 +301,7 @@ libinput_path_remove_device(struct libinput_device *device)
 	struct path_device *dev;
 
 	if (libinput->interface_backend != &interface_backend) {
-		log_info("Mismatching backends. This is an application bug.\n");
+		log_error("Mismatching backends. This is an application bug.\n");
 		return;
 	}
 

test/Makefile.am

@@ -16,7 +16,7 @@ liblitest_la_SOURCES = \
 	litest-wacom-touch.c \
 	litest.c
 
-run_tests = test-udev test-path test-pointer test-touch
+run_tests = test-udev test-path test-pointer test-touch test-log
 build_tests = test-build-linker test-build-pedantic-c99 test-build-std-gnuc90
 
 noinst_PROGRAMS = $(build_tests) $(run_tests)
@@ -42,6 +42,11 @@ test_touch_CFLAGS = $(AM_CPPFLAGS)
 test_touch_LDADD = $(TEST_LIBS)
 test_touch_LDFLAGS = -static
 
+test_log_SOURCES = log.c
+test_log_CFLAGS = $(AM_CPPFLAGS)
+test_log_LDADD = $(TEST_LIBS)
+test_log_LDFLAGS = -static
+
 # build-test only
 test_build_pedantic_c99_SOURCES = build-pedantic.c
 test_build_pedantic_c99_CFLAGS = $(AM_CPPFLAGS) -std=c99 -pedantic -Werror

test/log.c

@@ -0,0 +1,169 @@
+/*
+ * Copyright © 2014 Red Hat, Inc.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and
+ * its documentation for any purpose is hereby granted without fee, provided
+ * that the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation, and that the name of the copyright holders not be used in
+ * advertising or publicity pertaining to distribution of the software
+ * without specific, written prior permission.  The copyright holders make
+ * no representations about the suitability of this software for any
+ * purpose.  It is provided "as is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
+ * SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
+ * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
+ * CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <config.h>
+
+#include <check.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libinput.h>
+#include <libudev.h>
+#include <unistd.h>
+
+#include "litest.h"
+
+static int log_handler_called;
+static void *log_handler_userdata;
+
+static int open_restricted(const char *path, int flags, void *data)
+{
+	int fd;
+	fd = open(path, flags);
+	return fd < 0 ? -errno : fd;
+}
+static void close_restricted(int fd, void *data)
+{
+	close(fd);
+}
+
+const struct libinput_interface simple_interface = {
+	.open_restricted = open_restricted,
+	.close_restricted = close_restricted,
+};
+
+static void
+simple_log_handler(enum libinput_log_priority priority,
+		   void *userdata,
+		   const char *format,
+		   va_list args)
+{
+	log_handler_called++;
+	ck_assert(userdata == log_handler_userdata);
+	ck_assert(format != NULL);
+}
+
+START_TEST(log_default_priority)
+{
+	enum libinput_log_priority pri;
+
+	pri = libinput_log_get_priority();
+
+	ck_assert_int_eq(pri, LIBINPUT_LOG_PRIORITY_ERROR);
+}
+END_TEST
+
+START_TEST(log_handler_invoked)
+{
+	struct libinput *li;
+
+	libinput_log_set_priority(LIBINPUT_LOG_PRIORITY_DEBUG);
+	libinput_log_set_handler(simple_log_handler, NULL);
+	log_handler_userdata = NULL;
+
+	li = libinput_path_create_context(&simple_interface, NULL);
+	libinput_path_add_device(li, "/tmp");
+
+	ck_assert_int_gt(log_handler_called, 0);
+	log_handler_called = 0;
+}
+END_TEST
+
+START_TEST(log_userdata_NULL)
+{
+	struct libinput *li;
+
+	libinput_log_set_priority(LIBINPUT_LOG_PRIORITY_DEBUG);
+	libinput_log_set_handler(simple_log_handler, NULL);
+	log_handler_userdata = NULL;
+
+	li = libinput_path_create_context(&simple_interface, NULL);
+	libinput_path_add_device(li, "/tmp");
+
+	ck_assert_int_gt(log_handler_called, 0);
+	log_handler_called = 0;
+}
+END_TEST
+
+START_TEST(log_userdata)
+{
+	struct libinput *li;
+
+	libinput_log_set_priority(LIBINPUT_LOG_PRIORITY_DEBUG);
+	libinput_log_set_handler(simple_log_handler, &li);
+	log_handler_userdata = &li;
+
+	li = libinput_path_create_context(&simple_interface, NULL);
+	libinput_path_add_device(li, "/tmp");
+
+	ck_assert_int_gt(log_handler_called, 0);
+	log_handler_called = 0;
+}
+END_TEST
+
+START_TEST(log_handler_NULL)
+{
+	struct libinput *li;
+
+	libinput_log_set_priority(LIBINPUT_LOG_PRIORITY_DEBUG);
+	libinput_log_set_handler(NULL, NULL);
+	log_handler_userdata = NULL;
+
+	li = libinput_path_create_context(&simple_interface, NULL);
+	libinput_path_add_device(li, "/tmp");
+
+	ck_assert_int_eq(log_handler_called, 0);
+	log_handler_called = 0;
+	libinput_log_set_handler(simple_log_handler, NULL);
+}
+END_TEST
+
+START_TEST(log_priority)
+{
+	struct libinput *li;
+
+	libinput_log_set_priority(LIBINPUT_LOG_PRIORITY_ERROR);
+	libinput_log_set_handler(simple_log_handler, NULL);
+	log_handler_userdata = NULL;
+
+	li = libinput_path_create_context(&simple_interface, NULL);
+	libinput_path_add_device(li, "/tmp");
+
+	ck_assert_int_eq(log_handler_called, 0);
+
+	libinput_log_set_priority(LIBINPUT_LOG_PRIORITY_INFO);
+	libinput_path_add_device(li, "/tmp");
+	ck_assert_int_gt(log_handler_called, 0);
+
+	log_handler_called = 0;
+}
+END_TEST
+
+int main (int argc, char **argv) {
+	litest_add_no_device("log:defaults", log_default_priority);
+	litest_add_no_device("log:logging", log_handler_invoked);
+	litest_add_no_device("log:logging", log_handler_NULL);
+	litest_add_no_device("log:logging", log_userdata);
+	litest_add_no_device("log:logging", log_userdata_NULL);
+	litest_add_no_device("log:logging", log_priority);
+
+	return litest_run(argc, argv);
+}