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03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Sequencer/CommandLineID/CommandLineID.md

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+# CommandLineID
+
+- **功能描述：** 标记UMovieSceneCaptureProtocolBase的子类的协议类型。
+- **使用位置：** UCLASS
+- **引擎模块：** Sequencer
+- **元数据类型：** string="abc"
+- **限制类型：** UMovieSceneCaptureProtocolBase的子类上
+- **常用程度：** ★★
+
+标记UMovieSceneCaptureProtocolBase的子类的协议类型。
+
+用来在Sequcencer渲染导出的时候选择到正确的处理类。一般也就引擎内部使用，除非想自己自定义渲染输出的格式协议类。
+
+## 测试效果：
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+简单来说就是通过选择的格式名字来找到相关的ProtocolType Class
+
+```cpp
+void UMovieSceneCapture::Initialize(TSharedPtr<FSceneViewport> InSceneViewport, int32 PIEInstance)
+{
+			FString ImageProtocolOverrideString;
+			if (   FParse::Value( FCommandLine::Get(), TEXT( "-MovieFormat=" ), ImageProtocolOverrideString )
+			|| FParse::Value( FCommandLine::Get(), TEXT( "-ImageCaptureProtocol=" ), ImageProtocolOverrideString ) )
+			{
+				static const TCHAR* const CommandLineIDString = TEXT("CommandLineID");
+				TArray<UClass*> AllProtocolTypes = FindAllCaptureProtocolClasses();
+				for (UClass* Class : AllProtocolTypes)
+				{
+					bool bMetaDataMatch = Class->GetMetaData(CommandLineIDString) == ImageProtocolOverrideString;
+					if ( bMetaDataMatch || Class->GetName() == ImageProtocolOverrideString )
+					{
+						OverrideClass = Class;
+					}
+				}
+				ImageCaptureProtocolType = OverrideClass;		
+			}
+			
+		if (FParse::Value( FCommandLine::Get(), TEXT( "-AudioCaptureProtocol=" ), AudioProtocolOverrideString ) )
+		{
+			static const TCHAR* const CommandLineIDString = TEXT("CommandLineID");
+		}
+	}
+```

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Sequencer/SequencerBindingResolverLibrary/SequencerBindingResolverLibrary.md

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+# SequencerBindingResolverLibrary
+
+- **功能描述：** 把具有SequencerBindingResolverLibrary标记的UBlueprintFunctionLibrary作为动态绑定的类。
+- **使用位置：** UCLASS
+- **引擎模块：** Sequencer
+- **元数据类型：** bool
+- **限制类型：** UClass上，但一般是UBlueprintFunctionLibrary
+- **常用程度：** ★★
+
+把具有SequencerBindingResolverLibrary标记的UBlueprintFunctionLibrary作为动态绑定的类。只把它里面的函数添加到右键菜单里。
+
+动态绑定是Sequencer的一个新功能，简单来说就是允许设定好的轨迹变化动态应用到运行时的其他Actor上，用来做Gameplay和Sequence的过度切换会很有用。更细致用法可以参考官方文档：[https://dev.epicgames.com/documentation/zh-cn/unreal-engine/dynamic-binding-in-sequencer](https://dev.epicgames.com/documentation/zh-cn/unreal-engine/dynamic-binding-in-sequencer)
+
+## 测试代码：
+
+```cpp
+UCLASS(meta=(SequencerBindingResolverLibrary), MinimalAPI)
+class UMySequencerBindingResolverLibrary : public UBlueprintFunctionLibrary
+{
+	GENERATED_BODY()
+
+public:
+
+	/** Resolve the bound object to the player's pawn */
+	UFUNCTION(BlueprintPure, Category="Sequencer|Insider", meta=(WorldContext="WorldContextObject"))
+	static FMovieSceneDynamicBindingResolveResult ResolveToMyActor(UObject* WorldContextObject, FString ActorTag);
+};
+```
+
+源码：
+
+```cpp
+UCLASS(meta=(SequencerBindingResolverLibrary), MinimalAPI)
+class UBuiltInDynamicBindingResolverLibrary : public UBlueprintFunctionLibrary
+{
+	GENERATED_BODY()
+
+public:
+
+	/** Resolve the bound object to the player's pawn */
+	UFUNCTION(BlueprintPure, Category="Sequencer|Dynamic Binding", meta=(WorldContext="WorldContextObject"))
+	static MOVIESCENE_API FMovieSceneDynamicBindingResolveResult ResolveToPlayerPawn(UObject* WorldContextObject, int32 PlayerControllerIndex = 0);
+};
+
+```
+
+## 测试结果：
+
+在没有定义UMySequencerBindingResolverLibrary 之前，引擎里有个内建的ResolveToPlayerPawn，可以把PlayerControllerIndex 解析为Pawn来动态绑定到玩家的Pawn。
+
+因此我们也可以定义自己的动态绑定函数，来解析一个FString为一个Actor，如代码里ResolveToMyActor所示。
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+FMovieSceneDynamicBindingCustomization会搜索引擎里的所有类，但为了缩减范围，因此只有在标有SequencerBindingResolverLibrary的类下面才去发现Resolver函数。
+
+```cpp
+void FMovieSceneDynamicBindingCustomization::CollectResolverLibraryBindActions(UBlueprint* Blueprint, FBlueprintActionMenuBuilder& MenuBuilder, bool bIsRebinding)
+{
+	// Add any class that has the "SequencerBindingResolverLibrary" meta as a target class.
+//
+// We don't consider *all* blueprint function libraries because there are many, many of them that expose
+// functions that are, technically speaking, compatible with bound object resolution (i.e. they return
+// a UObject pointer) but that are completely non-sensical in this context.
+const static FName SequencerBindingResolverLibraryMeta("SequencerBindingResolverLibrary");
+for (TObjectIterator<UClass> ClassIt; ClassIt; ++ClassIt)
+{
+	UClass* CurrentClass = *ClassIt;
+	if (CurrentClass->HasMetaData(SequencerBindingResolverLibraryMeta))
+	{
+		FBlueprintActionFilter::Add(MenuFilter.TargetClasses, CurrentClass);
+	}
+}
+}
+```

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Sequencer/TakeRecorderDisplayName/TakeRecorderDisplayName.md

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+# TakeRecorderDisplayName
+
+- **功能描述：** 指定UTakeRecorderSource的显示名字。
+- **使用位置：** UCLASS
+- **引擎模块：** Sequencer
+- **元数据类型：** string="abc"
+- **限制类型：** UTakeRecorderSource的子类上
+- **常用程度：** ★★
+
+指定UTakeRecorderSource的显示名字。
+
+这个一般是引擎内部自己用，除非想自己自定义UTakeRecorderSource才会派上用场。因为原理和展示过于简单，因此就不自己构建测试代码。
+
+## 源码例子：
+
+```cpp
+UCLASS(Category="Actors", meta = (TakeRecorderDisplayName = "Player"))
+class UTakeRecorderPlayerSource : public UTakeRecorderSource
+{}
+```
+
+## 测试效果：
+
+在引擎源码中可见有多个UTakeRecorderSource，其上都标了名字。
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+用TakeRecorderDisplayName指定的名字来作为菜单项的名字。
+
+```cpp
+TSharedRef<SWidget> SLevelSequenceTakeEditor::OnGenerateSourcesMenu()
+{
+		for (UClass* Class : SourceClasses)
+		{
+			TSubclassOf<UTakeRecorderSource> SubclassOf = Class;
+		
+			MenuBuilder.AddMenuEntry(
+				FText::FromString(Class->GetMetaData(TEXT("TakeRecorderDisplayName"))),
+				Class->GetToolTipText(true),
+				FSlateIconFinder::FindIconForClass(Class),
+				FUIAction(
+					FExecuteAction::CreateSP(this, &SLevelSequenceTakeEditor::AddSourceFromClass, SubclassOf),
+					FCanExecuteAction::CreateSP(this, &SLevelSequenceTakeEditor::CanAddSourceFromClass, SubclassOf)
+				)
+			);
+		}
+}
+```