vault backup: 2024-10-12 17:19:45

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Path/RelativeToGameDir/RelativeToGameDir.md

@@ -0,0 +1,136 @@
+# RelativeToGameDir
+
+- **功能描述：** 如果系统目录选择框的结果为Project的子目录，则转换为相对路径，否则返回绝对路径。
+- **使用位置：** UPROPERTY
+- **引擎模块：** Path Property
+- **元数据类型：** bool
+- **限制类型：** FFilePath 
+- **常用程度：** ★★★
+
+如果系统目录选择框的结果为Project的子目录，则转换为相对路径，否则返回绝对路径。
+
+## 测试代码：
+
+```cpp
+public:
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = FilePath)
+	FFilePath MyFilePath_Default;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = FilePath, meta = (LongPackageName))
+	FFilePath MyFilePath_LongPackageName;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = FilePath, meta = (RelativeToGameDir))
+	FFilePath MyFilePath_RelativeToGameDir;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = FilePath, meta = (FilePathFilter = "umap"))
+	FFilePath MyFilePath_FilePathFilter;
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = FilePath, meta = (FilePathFilter = "My Config Files|*.ini"))
+	FFilePath MyFilePath_FilePathFilter_INI;
+```
+
+## 测试结果：
+
+- FFilePath弹出的都为Windows系统的默认文件选择对话框。
+- MyFilePath_Default，弹出默认的系统文件选择对话框，可以选择任何路径的任何文件。
+- MyFilePath_LongPackageName，限制选择范围为Content下的资产，否则会弹出报错。结果路径会被转换为/Game/ObjectPath这种长的包名。
+- MyFilePath_RelativeToGameDir，如果选择结果为Project目录（uproject所在的目录）下的子文件，则返回结果会相对路径。否则直接返回绝对路径。
+- MyFilePath_FilePathFilter，可以选择任何目录下的指定后缀名的文件。代码里示例为umap，则只能选择关卡文件。
+- MyFilePath_FilePathFilter_INI，演示了只能选取ini文件。FilePathFilter 支持我们采用“描述 | *.后缀名”的格式自己书写过滤方式，规则同windows系统选取规则一样，也可以同时写多个后缀名。
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+在下面代码就可以看见FilePathFilter，bLongPackageName ，bRelativeToGameDir 的处理逻辑。
+
+- FileTypeFilter 设定扩展名到SFilePathPicker里
+- bLongPackageName 触发TryConvertFilenameToLongPackageName来转换路径。
+- bRelativeToGameDir 触发AbsolutePickedPath.RightChop(AbsoluteProjectDir.Len());来变成相对路径。
+
+```cpp
+USTRUCT(BlueprintType)
+struct FFilePath
+{
+	GENERATED_BODY()
+
+	/**
+	* The path to the file.
+	*/
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = FilePath)
+	FString FilePath;
+};
+
+void FFilePathStructCustomization::CustomizeHeader( TSharedRef<IPropertyHandle> StructPropertyHandle, class FDetailWidgetRow& HeaderRow, IPropertyTypeCustomizationUtils& StructCustomizationUtils )
+{
+	const FString& MetaData = StructPropertyHandle->GetMetaData(TEXT("FilePathFilter"));
+	bLongPackageName = StructPropertyHandle->HasMetaData(TEXT("LongPackageName"));
+	bRelativeToGameDir = StructPropertyHandle->HasMetaData(TEXT("RelativeToGameDir"));
+	
+	if (MetaData.IsEmpty())
+	{
+		FileTypeFilter = TEXT("All files (*.*)|*.*");
+	}
+	else
+	{
+		if (MetaData.Contains(TEXT("|"))) // If MetaData follows the Description|ExtensionList format, use it as is
+		{
+			FileTypeFilter = MetaData;
+		}
+		else
+		{
+			FileTypeFilter = FString::Printf(TEXT("%s files (*.%s)|*.%s"), *MetaData, *MetaData, *MetaData);
+		}
+	}
+}
+
+void FFilePathStructCustomization::HandleFilePathPickerPathPicked( const FString& PickedPath )
+{
+	FString FinalPath = PickedPath;
+	if (bLongPackageName)
+	{
+		FString LongPackageName;
+		FString StringFailureReason;
+		if (FPackageName::TryConvertFilenameToLongPackageName(PickedPath, LongPackageName, &StringFailureReason) == false)
+		{
+			FMessageDialog::Open(EAppMsgType::Ok, FText::FromString(StringFailureReason));
+		}
+		FinalPath = LongPackageName;
+	}
+	else if (bRelativeToGameDir && !PickedPath.IsEmpty())
+	{
+		//A filepath under the project directory will be made relative to the project directory
+		//Otherwise, the absolute path will be returned unless it doesn't exist, the current path will
+		//be kept. This can happen if it's already relative to project dir (tabbing when selected)
+
+		const FString ProjectDir = FPaths::ProjectDir();
+		const FString AbsoluteProjectDir = FPaths::ConvertRelativePathToFull(ProjectDir);
+		const FString AbsolutePickedPath = FPaths::ConvertRelativePathToFull(PickedPath);
+
+		//Verify if absolute path to file exists. If it was already relative to content directory
+		//the absolute will be to binaries and will possibly be garbage
+		if (FPaths::FileExists(AbsolutePickedPath))
+		{
+			//If file is part of the project dir, chop the project dir part
+			//Otherwise, use the absolute path
+			if (AbsolutePickedPath.StartsWith(AbsoluteProjectDir))
+			{
+				FinalPath = AbsolutePickedPath.RightChop(AbsoluteProjectDir.Len());
+			}
+			else
+			{
+				FinalPath = AbsolutePickedPath;
+			}
+		}
+		else
+		{
+			//If absolute file doesn't exist, it might already be relative to project dir
+			//If not, then it might be a manual entry, so keep it untouched either way
+			FinalPath = PickedPath;
+		}
+	}
+
+	PathStringProperty->SetValue(FinalPath);
+	FEditorDirectories::Get().SetLastDirectory(ELastDirectory::GENERIC_OPEN, FPaths::GetPath(PickedPath));
+}
+```