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.

2 files changed, 11 insertions, 0 deletions

diff --git a/platform/iphone/os_iphone.cpp b/platform/iphone/os_iphone.cpp
index 0e3eeed114..3f57014515 100644
--- a/platform/iphone/os_iphone.cpp
+++ b/platform/iphone/os_iphone.cpp
@@ -42,6 +42,7 @@
 #include "core/os/dir_access.h"
 #include "core/os/file_access.h"
 #include "core/project_settings.h"
+#include "drivers/unix/syslog_logger.h"
 
 #include "sem_iphone.h"
 
@@ -99,6 +100,13 @@ void OSIPhone::initialize_core() {
 	SemaphoreIphone::make_default();
 };
 
+void OSIPhone::initialize_logger() {
+	Vector<Logger *> loggers;
+	loggers.push_back(memnew(SyslogLogger));
+	loggers.push_back(memnew(RotatedFileLogger("user://logs/log.txt")));
+	_set_logger(memnew(CompositeLogger(loggers)));
+}
+
 void OSIPhone::initialize(const VideoMode &p_desired, int p_video_driver, int p_audio_driver) {
 
 	supported_orientations = 0;
@@ -570,6 +578,8 @@ OSIPhone::OSIPhone(int width, int height) {
 	vm.resizable = false;
 	set_video_mode(vm);
 	event_count = 0;
+
+	_set_logger(memnew(SyslogLogger));
 };
 
 OSIPhone::~OSIPhone() {
diff --git a/platform/iphone/os_iphone.h b/platform/iphone/os_iphone.h
index 475dceebf2..7a95b50d05 100644
--- a/platform/iphone/os_iphone.h
+++ b/platform/iphone/os_iphone.h
@@ -91,6 +91,7 @@ private:
 
 	virtual VideoMode get_default_video_mode() const;
 
+	virtual void initialize_logger();
 	virtual void initialize_core();
 	virtual void initialize(const VideoMode &p_desired, int p_video_driver, int p_audio_driver);