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, 29 insertions, 16 deletions

diff --git a/platform/android/file_access_android.cpp b/platform/android/file_access_android.cpp
index c7b0d9afcd..0fdf9002d7 100644
--- a/platform/android/file_access_android.cpp
+++ b/platform/android/file_access_android.cpp
@@ -146,6 +146,11 @@ Error FileAccessAndroid::get_error() const {
 	return eof ? ERR_FILE_EOF : OK; //not sure what else it may happen
 }
 
+void FileAccessAndroid::flush() {
+
+	ERR_FAIL();
+}
+
 void FileAccessAndroid::store_8(uint8_t p_dest) {
 
 	ERR_FAIL();
diff --git a/platform/android/file_access_android.h b/platform/android/file_access_android.h
index beccf494dd..c8fedbe684 100644
--- a/platform/android/file_access_android.h
+++ b/platform/android/file_access_android.h
@@ -63,6 +63,7 @@ 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/platform/android/file_access_jandroid.cpp b/platform/android/file_access_jandroid.cpp
index fe934c89fb..980afd8f46 100644
--- a/platform/android/file_access_jandroid.cpp
+++ b/platform/android/file_access_jandroid.cpp
@@ -157,6 +157,9 @@ Error FileAccessJAndroid::get_error() const {
 	return OK;
 }
 
+void FileAccessJAndroid::flush() {
+}
+
 void FileAccessJAndroid::store_8(uint8_t p_dest) {
 }
 
diff --git a/platform/android/file_access_jandroid.h b/platform/android/file_access_jandroid.h
index 75a6a21335..368d2c98fa 100644
--- a/platform/android/file_access_jandroid.h
+++ b/platform/android/file_access_jandroid.h
@@ -67,6 +67,7 @@ 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/platform/android/os_android.cpp b/platform/android/os_android.cpp
index dbea2d7531..0eb14f6af3 100644
--- a/platform/android/os_android.cpp
+++ b/platform/android/os_android.cpp
@@ -47,6 +47,15 @@
 #include "file_access_jandroid.h"
 #endif
 
+class AndroidLogger : public Logger {
+public:
+	virtual void logv(const char *p_format, va_list p_list, bool p_err) {
+		__android_log_vprint(p_err ? ANDROID_LOG_ERROR : ANDROID_LOG_INFO, "godot", p_format, p_list);
+	}
+
+	virtual ~AndroidLogger() {}
+};
+
 int OS_Android::get_video_driver_count() const {
 
 	return 1;
@@ -111,6 +120,13 @@ void OS_Android::initialize_core() {
 #endif
 }
 
+void OS_Android::initialize_logger() {
+	Vector<Logger *> loggers;
+	loggers.push_back(memnew(AndroidLogger));
+	loggers.push_back(memnew(RotatedFileLogger("user://logs/log.txt")));
+	_set_logger(memnew(CompositeLogger(loggers)));
+}
+
 void OS_Android::set_opengl_extensions(const char *p_gl_extensions) {
 
 	ERR_FAIL_COND(!p_gl_extensions);
@@ -162,23 +178,9 @@ void OS_Android::delete_main_loop() {
 }
 
 void OS_Android::finalize() {
-
 	memdelete(input);
 }
 
-void OS_Android::vprint(const char *p_format, va_list p_list, bool p_stderr) {
-
-	__android_log_vprint(p_stderr ? ANDROID_LOG_ERROR : ANDROID_LOG_INFO, "godot", p_format, p_list);
-}
-
-void OS_Android::print(const char *p_format, ...) {
-
-	va_list argp;
-	va_start(argp, p_format);
-	__android_log_vprint(ANDROID_LOG_INFO, "godot", p_format, argp);
-	va_end(argp);
-}
-
 void OS_Android::alert(const String &p_alert, const String &p_title) {
 
 	//print("ALERT: %s\n", p_alert.utf8().get_data());
@@ -737,6 +739,8 @@ OS_Android::OS_Android(GFXInitFunc p_gfx_init_func, void *p_gfx_init_ud, OpenURI
 	set_keep_screen_on_func = p_set_keep_screen_on_func;
 	alert_func = p_alert_func;
 	use_reload_hooks = false;
+
+	_set_logger(memnew(AndroidLogger));
 }
 
 OS_Android::~OS_Android() {
diff --git a/platform/android/os_android.h b/platform/android/os_android.h
index 119c14bff3..a614bb8067 100644
--- a/platform/android/os_android.h
+++ b/platform/android/os_android.h
@@ -149,6 +149,7 @@ public:
 	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 void initialize(const VideoMode &p_desired, int p_video_driver, int p_audio_driver);
 
@@ -161,8 +162,6 @@ public:
 
 	static OS *get_singleton();
 
-	virtual void vprint(const char *p_format, va_list p_list, bool p_stderr = false);
-	virtual void print(const char *p_format, ...);
 	virtual void alert(const String &p_alert, const String &p_title = "ALERT!");
 
 	virtual void set_mouse_show(bool p_show);