UI: Insert timestamps after log newlines

It was a bit weird seeing lines in the log without the associated
timestamps, so it should just insert it after every newline instead.

obs/obs-app.cpp

@@ -185,6 +185,37 @@ string CurrentDateTimeString()
 	return buf;
 }
 
+static inline void LogString(fstream &logFile, const char *timeString,
+		char *str)
+{
+	logFile << timeString << str << endl;
+}
+
+static inline void LogStringChunk(fstream &logFile, char *str)
+{
+	char *nextLine = str;
+	string timeString = CurrentTimeString();
+	timeString += ": ";
+
+	while (*nextLine) {
+		char *nextLine = strchr(str, '\n');
+		if (!nextLine)
+			break;
+
+		if (nextLine != str && nextLine[-1] == '\r') {
+			nextLine[-1] = 0;
+		} else {
+			nextLine[0] = 0;
+		}
+
+		LogString(logFile, timeString.c_str(), str);
+		nextLine++;
+		str = nextLine;
+	}
+
+	LogString(logFile, timeString.c_str(), str);
+}
+
 static void do_log(int log_level, const char *msg, va_list args, void *param)
 {
 	fstream &logFile = *static_cast<fstream*>(param);
@@ -205,7 +236,7 @@ static void do_log(int log_level, const char *msg, va_list args, void *param)
 #endif
 
 	if (log_level <= LOG_INFO)
-		logFile << CurrentTimeString() << ": " << str << endl;
+		LogStringChunk(logFile, str);
 
 #ifdef _WIN32
 	if (log_level <= LOG_ERROR && IsDebuggerPresent())