UE4：Log显示级别

Log Verbosity Levels

Log的输出级别有四个地方控制

1. CompileTime verbosity
2. Default verbosity
3. ini verbosity
4. Runtime verbosity

CompileTime Verbosity和Default Verbosity指的就是

DECLARE_LOG_CATEGORY_EXTERN(CategoryName, DefaultVerbosity, CompileTimeVerbosity)

的参数
在源码里定义如下

/** 
	 * A macro to declare a logging category as a C++ "extern", usually declared in the header and paired with DEFINE_LOG_CATEGORY in the source. Accessible by all files that include the header.
	 * @param CategoryName, category to declare
	 * @param DefaultVerbosity, default run time verbosity
	 * @param CompileTimeVerbosity, maximum verbosity to compile into the code
	 **/
	#define DECLARE_LOG_CATEGORY_EXTERN(CategoryName, DefaultVerbosity, CompileTimeVerbosity) \
		extern struct FLogCategory##CategoryName : public FLogCategory<ELogVerbosity::DefaultVerbosity, ELogVerbosity::CompileTimeVerbosity> \
		{ \
			FORCEINLINE FLogCategory##CategoryName() : FLogCategory(TEXT(#CategoryName)) {} \
		} CategoryName;

编译时如果Default Verbosity甚至大于CompileTime Verbosity，这个log就不会被编译进代码，运行时就不存在这个log
Default Verbosity就是运行时默认的log级别
Ini verbosity是在DefaultEngine.ini添加配置来控制对应的log级别。在DefaultEngine.ini中添加section ：[Core.log]，可以控制log的显示级别.
eg:
log使用的时候是
UE_LOG(CategoryName, Verbosity, Format, …)
在配置文件中加上log的section
[Core.Log]
global=Log
LogAnimMontage = VeryVerbose
在ini中配置的级别会覆盖DefaultVerbosity
用控制台启动游戏时可以通过参数来调整log级别
比如: -LogCmds=“foo verbose, bar off”
在游戏运行时还可以通过控制台命令修改显示级别
比如：Log [cat] [level]
会覆盖ini中的配置

LogAnimMontage 是CategoryName，那么这个Category的log的输出级别控制就会被改为VeryVerbose
global则是其他没有单独指定的Category的输出级别
log的显示级别定义在LogVerbosity.h中，log输出的时候，只会输出小于等于设置的最高级别的log

eg:
我在一个函数里写了一堆log：

void AMyCharacter::BeginPlay()
{
	Super::BeginPlay();
	UE_LOG(LogMylog, VeryVerbose, TEXT("Display Log."));
	UE_LOG(LogMylog, Verbose, TEXT("Display Log."));
	UE_LOG(LogMylog, Display, TEXT("Display Log."));
	UE_LOG(LogMylog, Warning, TEXT("Display Log."));
	UE_LOG(LogMylog, Error, TEXT("Display Log."));
}

默认情况下打印出来的是这样：

然后修改ini配置
[Core.Log]
global= Error
LogMylog = VeryVerbose
启动后的log：

官方文档ELogVerbosity

namespace ELogVerbosity
{
	enum Type : uint8
	{
		/** Not used */
		NoLogging		= 0,

		/** Always prints a fatal error to console (and log file) and crashes (even if logging is disabled) */
		Fatal,

		/** 
		 * Prints an error to console (and log file). 
		 * Commandlets and the editor collect and report errors. Error messages result in commandlet failure.
		 */
		Error,

		/** 
		 * Prints a warning to console (and log file).
		 * Commandlets and the editor collect and report warnings. Warnings can be treated as an error.
		 */
		Warning,

		/** Prints a message to console (and log file) */
		Display,

		/** Prints a message to a log file (does not print to console) */
		Log,

		/** 
		 * Prints a verbose message to a log file (if Verbose logging is enabled for the given category, 
		 * usually used for detailed logging) 
		 */
		Verbose,

		/** 
		 * Prints a verbose message to a log file (if VeryVerbose logging is enabled, 
		 * usually used for detailed logging that would otherwise spam output) 
		 */
		VeryVerbose,

		// Log masks and special Enum values

		All				= VeryVerbose,
		NumVerbosity,
		VerbosityMask	= 0xf,
		SetColor		= 0x40, // not actually a verbosity, used to set the color of an output device 
		BreakOnLog		= 0x80
	};
}