Extract logging logic

Previously logging logic was scattered over OS class implementations
with plenty of duplication. Major changes in this commit:

 - Extracted logging logic into a separate Logger hierarchy. It allows
   easy configuration of logging mechanism depending on compile-time or
   run-time configuration.

 - Implemented RotatedFileLogger which is usually used with StdLogger,
   providing persistency of logs. It is often important to be able to
   obtain logs of the game even in production to be able to understand
   what happened prior to some problem. On mobile there previously was
   no way to obtain the logs aside from having the device connected to
   your machine.

 - flush() is not performed in release mode for every logged line. It
   is only performed for errors.

6 files changed, 174 insertions, 57 deletions

diff --git a/drivers/unix/file_access_unix.cpp b/drivers/unix/file_access_unix.cpp
index 649f874cf..206f57d4a 100644
--- a/drivers/unix/file_access_unix.cpp
+++ b/drivers/unix/file_access_unix.cpp
@@ -223,6 +223,12 @@ Error FileAccessUnix::get_error() const {
 	return last_error;
 }
 
+void FileAccessUnix::flush() {
+
+	ERR_FAIL_COND(!f);
+	fflush(f);
+}
+
 void FileAccessUnix::store_8(uint8_t p_dest) {
 
 	ERR_FAIL_COND(!f);
diff --git a/drivers/unix/file_access_unix.h b/drivers/unix/file_access_unix.h
index e2848e412..96f2ff8e2 100644
--- a/drivers/unix/file_access_unix.h
+++ b/drivers/unix/file_access_unix.h
@@ -72,6 +72,7 @@ public:
 
 	virtual Error get_error() const; ///< get last error
 
+	virtual void flush();
 	virtual void store_8(uint8_t p_dest); ///< store a byte
 
 	virtual bool file_exists(const String &p_path); ///< return true if a file exists
diff --git a/drivers/unix/os_unix.cpp b/drivers/unix/os_unix.cpp
index 75c8a153f..29fe73f17 100644
--- a/drivers/unix/os_unix.cpp
+++ b/drivers/unix/os_unix.cpp
@@ -64,39 +64,7 @@
 #include <string.h>
 #include <sys/time.h>
 #include <sys/wait.h>
-
-extern bool _print_error_enabled;
-
-void OS_Unix::print_error(const char *p_function, const char *p_file, int p_line, const char *p_code, const char *p_rationale, ErrorType p_type) {
-
-	if (!_print_error_enabled)
-		return;
-
-	const char *err_details;
-	if (p_rationale && p_rationale[0])
-		err_details = p_rationale;
-	else
-		err_details = p_code;
-
-	switch (p_type) {
-		case ERR_ERROR:
-			print("\E[1;31mERROR: %s: \E[0m\E[1m%s\n", p_function, err_details);
-			print("\E[0;31m   At: %s:%i.\E[0m\n", p_file, p_line);
-			break;
-		case ERR_WARNING:
-			print("\E[1;33mWARNING: %s: \E[0m\E[1m%s\n", p_function, err_details);
-			print("\E[0;33m   At: %s:%i.\E[0m\n", p_file, p_line);
-			break;
-		case ERR_SCRIPT:
-			print("\E[1;35mSCRIPT ERROR: %s: \E[0m\E[1m%s\n", p_function, err_details);
-			print("\E[0;35m   At: %s:%i.\E[0m\n", p_file, p_line);
-			break;
-		case ERR_SHADER:
-			print("\E[1;36mSHADER ERROR: %s: \E[0m\E[1m%s\n", p_function, err_details);
-			print("\E[0;36m   At: %s:%i.\E[0m\n", p_file, p_line);
-			break;
-	}
-}
+#include <unistd.h>
 
 void OS_Unix::debug_break() {
 
@@ -165,29 +133,16 @@ void OS_Unix::initialize_core() {
 	}
 }
 
-void OS_Unix::finalize_core() {
+void OS_Unix::initialize_logger() {
+	Vector<Logger *> loggers;
+	loggers.push_back(memnew(UnixTerminalLogger));
+	loggers.push_back(memnew(RotatedFileLogger("user://logs/log.txt")));
+	_set_logger(memnew(CompositeLogger(loggers)));
 }
 
-void OS_Unix::vprint(const char *p_format, va_list p_list, bool p_stder) {
-
-	if (p_stder) {
-
-		vfprintf(stderr, p_format, p_list);
-		fflush(stderr);
-	} else {
-
-		vprintf(p_format, p_list);
-		fflush(stdout);
-	}
+void OS_Unix::finalize_core() {
 }
 
-void OS_Unix::print(const char *p_format, ...) {
-
-	va_list argp;
-	va_start(argp, p_format);
-	vprintf(p_format, argp);
-	va_end(argp);
-}
 void OS_Unix::alert(const String &p_alert, const String &p_title) {
 
 	fprintf(stderr, "ERROR: %s\n", p_alert.utf8().get_data());
@@ -559,4 +514,38 @@ String OS_Unix::get_executable_path() const {
 #endif
 }
 
+void UnixTerminalLogger::log_error(const char *p_function, const char *p_file, int p_line, const char *p_code, const char *p_rationale, ErrorType p_type) {
+	if (!should_log(true)) {
+		return;
+	}
+
+	const char *err_details;
+	if (p_rationale && p_rationale[0])
+		err_details = p_rationale;
+	else
+		err_details = p_code;
+
+	switch (p_type) {
+		case ERR_WARNING:
+			logf_error("\E[1;33mWARNING: %s: \E[0m\E[1m%s\n", p_function, err_details);
+			logf_error("\E[0;33m   At: %s:%i.\E[0m\n", p_file, p_line);
+			break;
+		case ERR_SCRIPT:
+			logf_error("\E[1;35mSCRIPT ERROR: %s: \E[0m\E[1m%s\n", p_function, err_details);
+			logf_error("\E[0;35m   At: %s:%i.\E[0m\n", p_file, p_line);
+			break;
+		case ERR_SHADER:
+			logf_error("\E[1;36mSHADER ERROR: %s: \E[0m\E[1m%s\n", p_function, err_details);
+			logf_error("\E[0;36m   At: %s:%i.\E[0m\n", p_file, p_line);
+			break;
+		case ERR_ERROR:
+		default:
+			logf_error("\E[1;31mERROR: %s: \E[0m\E[1m%s\n", p_function, err_details);
+			logf_error("\E[0;31m   At: %s:%i.\E[0m\n", p_file, p_line);
+			break;
+	}
+}
+
+UnixTerminalLogger::~UnixTerminalLogger() {}
+
 #endif
diff --git a/drivers/unix/os_unix.h b/drivers/unix/os_unix.h
index 19e79728f..1cc44c0ff 100644
--- a/drivers/unix/os_unix.h
+++ b/drivers/unix/os_unix.h
@@ -54,11 +54,11 @@ protected:
 	virtual int get_audio_driver_count() const;
 	virtual const char *get_audio_driver_name(int p_driver) const;
 
+	virtual void initialize_logger();
 	virtual void initialize_core();
 	virtual int unix_initialize_audio(int p_audio_driver);
 	//virtual void initialize(int p_video_driver,int p_audio_driver);
 
-	//virtual void finalize();
 	virtual void finalize_core();
 
 	String stdin_buf;
@@ -66,10 +66,6 @@ protected:
 	String get_global_settings_path() const;
 
 public:
-	virtual void print_error(const char *p_function, const char *p_file, int p_line, const char *p_code, const char *p_rationale, ErrorType p_type = ERR_ERROR);
-
-	virtual void print(const char *p_format, ...);
-	virtual void vprint(const char *p_format, va_list p_list, bool p_stder = false);
 	virtual void alert(const String &p_alert, const String &p_title = "ALERT!");
 	virtual String get_stdin_string(bool p_block);
 
@@ -120,6 +116,12 @@ public:
 	//virtual void run( MainLoop * p_main_loop );
 };
 
+class UnixTerminalLogger : public StdLogger {
+public:
+	virtual void log_error(const char *p_function, const char *p_file, int p_line, const char *p_code, const char *p_rationale, ErrorType p_type = ERR_ERROR);
+	virtual ~UnixTerminalLogger();
+};
+
 #endif
 
 #endif
diff --git a/drivers/unix/syslog_logger.cpp b/drivers/unix/syslog_logger.cpp
new file mode 100644
index 000000000..d57f39132
--- /dev/null
+++ b/drivers/unix/syslog_logger.cpp
@@ -0,0 +1,71 @@
+/*************************************************************************/
+/*  syslog_logger.cpp                                                    */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2017 Godot Engine contributors (cf. AUTHORS.md)    */
+/*                                                                       */
+/* 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 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.                */
+/*************************************************************************/
+
+#ifdef UNIX_ENABLED
+
+#include "syslog_logger.h"
+#include "print_string.h"
+#include <syslog.h>
+
+void SyslogLogger::logv(const char *p_format, va_list p_list, bool p_err) {
+	if (!should_log(p_err)) {
+		return;
+	}
+
+	vsyslog(p_err ? LOG_ERR : LOG_INFO, p_format, p_list);
+}
+
+void SyslogLogger::print_error(const char *p_function, const char *p_file, int p_line, const char *p_code, const char *p_rationale, ErrorType p_type) {
+	if (!should_log(true)) {
+		return;
+	}
+
+	const char *err_type = "**ERROR**";
+	switch (p_type) {
+		case ERR_ERROR: err_type = "**ERROR**"; break;
+		case ERR_WARNING: err_type = "**WARNING**"; break;
+		case ERR_SCRIPT: err_type = "**SCRIPT ERROR**"; break;
+		case ERR_SHADER: err_type = "**SHADER ERROR**"; break;
+		default: ERR_PRINT("Unknown error type"); break;
+	}
+
+	const char *err_details;
+	if (p_rationale && *p_rationale)
+		err_details = p_rationale;
+	else
+		err_details = p_code;
+
+	syslog(p_type == ERR_WARNING ? LOG_WARNING : LOG_ERR, "%s: %s\n   At: %s:%i:%s() - %s", err_type, err_details, p_file, p_line, p_function, p_code);
+}
+
+SyslogLogger::~SyslogLogger() {
+}
+
+#endif
\ No newline at end of file
diff --git a/drivers/unix/syslog_logger.h b/drivers/unix/syslog_logger.h
new file mode 100644
index 000000000..b3cf2f9e3
--- /dev/null
+++ b/drivers/unix/syslog_logger.h
@@ -0,0 +1,48 @@
+/*************************************************************************/
+/*  syslog_logger.h                                                      */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2017 Godot Engine contributors (cf. AUTHORS.md)    */
+/*                                                                       */
+/* 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 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.                */
+/*************************************************************************/
+
+#ifndef SYSLOG_LOGGER_H
+#define SYSLOG_LOGGER_H
+
+#ifdef UNIX_ENABLED
+
+#include "io/logger.h"
+
+class SyslogLogger : public Logger {
+public:
+	virtual void logv(const char *p_format, va_list p_list, bool p_err);
+	virtual void print_error(const char *p_function, const char *p_file, int p_line, const char *p_code, const char *p_rationale, ErrorType p_type);
+
+	virtual ~SyslogLogger();
+};
+
+#endif
+
+#endif
\ No newline at end of file