Merging latest development

Signed-off-by: kberg-amzn <karlberg@amazon.com>

Code/Framework/AzCore/AzCore/Component/Entity.cpp

@@ -207,12 +207,6 @@ namespace AZ
             ActivateComponent(**it);
         }
 
-        // Cache the transform interface to the transform interface
-        // Generally this pattern is not recommended unless for component event buses
-        // As we have a guarantee (by design) that components can't change during active state)
-        // Even though technically they can connect disconnect from the bus.
-        m_transform = TransformBus::FindFirstHandler(m_id);
-
         SetState(State::Active);
 
         EBUS_EVENT_ID(m_id, EntityBus, OnEntityActivated, m_id);
@@ -1320,6 +1314,19 @@ namespace AZ
         return *processSignature;
     }
 
+    AZ::TransformInterface* Entity::GetTransform() const
+    {
+        // Lazy evaluation of the cached entity transform.
+        if(!m_transform)
+        {
+            // Generally this pattern is not recommended unless for component event buses
+            // As we have a guarantee (by design) that components can't change during active state)
+            // Even though technically they can connect disconnect from the bus.
+            m_transform = TransformBus::FindFirstHandler(m_id);
+        }
+        return m_transform;
+    }
+
     //=========================================================================
     // MakeId
     // Ids must be unique across a project at authoring time. Runtime doesn't matter

Code/Framework/AzCore/AzCore/Component/Entity.h

@@ -354,10 +354,9 @@ namespace AZ
         //! @return The Process Signature of the local machine.
         static AZ::u32 GetProcessSignature();
 
-        /// @cond EXCLUDE_DOCS 
-        //! @deprecated Use the TransformBus to communicate with the TransformInterface.
-        inline TransformInterface* GetTransform() const { return m_transform; }
-        /// @endcond
+        //! Gets the TransformInterface for the entity.
+        //! @return The TransformInterface for the entity.
+        TransformInterface* GetTransform() const;
 
         //! Sorts an entity's components based on the dependencies between components.
         //! If all dependencies are met, the required services can be activated
@@ -406,7 +405,7 @@ namespace AZ
         //! A cached pointer to the transform interface. 
         //! We recommend using AZ::TransformBus and caching locally instead of accessing
         //! the transform interface directly through this pointer.
-        TransformInterface* m_transform;
+        mutable TransformInterface* m_transform;
 
         //! A user-friendly name for the entity. This makes error messages easier to read.
         AZStd::string m_name;

Code/Framework/AzCore/AzCore/IO/FileReader.cpp

@@ -0,0 +1,200 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#include <AzCore/IO/FileReader.h>
+#include <AzCore/IO/FileIO.h>
+#include <AzCore/IO/Path/Path.h>
+
+namespace AZ::IO
+{
+    FileReader::FileReader() = default;
+
+    FileReader::FileReader(AZ::IO::FileIOBase* fileIoBase, const char* filePath)
+    {
+        Open(fileIoBase, filePath);
+    }
+
+    FileReader::~FileReader()
+    {
+        Close();
+    }
+
+    FileReader::FileReader(FileReader&& other)
+    {
+        AZStd::swap(m_file, other.m_file);
+        AZStd::swap(m_fileIoBase, other.m_fileIoBase);
+    }
+
+    FileReader& FileReader::operator=(FileReader&& other)
+    {
+        // Close the current file and take over other file
+        Close();
+        m_file = AZStd::move(other.m_file);
+        m_fileIoBase = AZStd::move(other.m_fileIoBase);
+        other.m_file = AZStd::monostate{};
+        other.m_fileIoBase = {};
+
+        return *this;
+    }
+
+    bool FileReader::Open(AZ::IO::FileIOBase* fileIoBase, const char* filePath)
+    {
+        // Close file if the FileReader has an instance open
+        Close();
+
+        if (fileIoBase != nullptr)
+        {
+            AZ::IO::HandleType fileHandle;
+            if (fileIoBase->Open(filePath, IO::OpenMode::ModeRead, fileHandle))
+            {
+                m_file = fileHandle;
+                m_fileIoBase = fileIoBase;
+                return true;
+            }
+        }
+        else
+        {
+            AZ::IO::SystemFile file;
+            if (file.Open(filePath, IO::SystemFile::OpenMode::SF_OPEN_READ_ONLY))
+            {
+                m_file = AZStd::move(file);
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    bool FileReader::IsOpen() const
+    {
+        if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
+        {
+            return *fileHandle != AZ::IO::InvalidHandle;
+        }
+        else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
+        {
+            return systemFile->IsOpen();
+        }
+
+        return false;
+    }
+
+    void FileReader::Close()
+    {
+        if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
+        {
+            if (AZ::IO::FileIOBase* fileIo = m_fileIoBase; fileIo != nullptr)
+            {
+                fileIo->Close(*fileHandle);
+            }
+        }
+
+        m_file = AZStd::monostate{};
+        m_fileIoBase = {};
+    }
+
+    auto FileReader::Length() const -> SizeType
+    {
+        if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
+        {
+            if (SizeType fileSize{}; m_fileIoBase->Size(*fileHandle, fileSize))
+            {
+                return fileSize;
+            }
+        }
+        else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
+        {
+            return systemFile->Length();
+        }
+
+        return 0;
+    }
+
+    auto FileReader::Read(SizeType byteSize, void* buffer) -> SizeType
+    {
+        if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
+        {
+            if (SizeType bytesRead{}; m_fileIoBase->Read(*fileHandle, buffer, byteSize, false, &bytesRead))
+            {
+                return bytesRead;
+            }
+        }
+        else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
+        {
+            return systemFile->Read(byteSize, buffer);
+        }
+
+        return 0;
+    }
+
+    auto FileReader::Tell() const -> SizeType
+    {
+        if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
+        {
+            if (SizeType fileOffset{}; m_fileIoBase->Tell(*fileHandle, fileOffset))
+            {
+                return fileOffset;
+            }
+        }
+        else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
+        {
+            return systemFile->Tell();
+        }
+
+        return 0;
+    }
+
+    bool FileReader::Seek(AZ::s64 offset, SeekType type)
+    {
+        if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
+        {
+            return m_fileIoBase->Seek(*fileHandle, offset, type);
+        }
+        else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
+        {
+            systemFile->Seek(offset, static_cast<AZ::IO::SystemFile::SeekMode>(type));
+            return true;
+        }
+
+        return false;
+    }
+
+    bool FileReader::Eof() const
+    {
+        if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
+        {
+            return m_fileIoBase->Eof(*fileHandle);
+        }
+        else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
+        {
+            return systemFile->Eof();
+        }
+
+        return false;
+    }
+
+    bool FileReader::GetFilePath(AZ::IO::FixedMaxPath& filePath) const
+    {
+        if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
+        {
+            AZ::IO::FixedMaxPathString& pathStringRef = filePath.Native();
+            if (m_fileIoBase->GetFilename(*fileHandle, pathStringRef.data(), pathStringRef.capacity()))
+            {
+                pathStringRef.resize_no_construct(AZStd::char_traits<char>::length(pathStringRef.data()));
+                return true;
+            }
+        }
+        else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
+        {
+            filePath = systemFile->Name();
+            return true;
+        }
+
+        return false;
+    }
+}

Code/Framework/AzCore/AzCore/IO/FileReader.h

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+#pragma once
+
+#include <AzCore/IO/Path/Path_fwd.h>
+#include <AzCore/IO/SystemFile.h>
+#include <AzCore/std/containers/variant.h>
+
+namespace AZ::IO
+{
+    class FileIOBase;
+    enum class SeekType : AZ::u32;
+
+    //! Structure which encapsulates delegates File Read operations
+    //! to either the FileIOBase or SystemFile classes based if a FileIOBase* instance has been supplied
+    //! to the FileSystemReader class
+    //! the SettingsRegistry option to use FileIO
+    class FileReader
+    {
+        using HandleType = AZ::u32;
+        using FileHandleType = AZStd::variant<AZStd::monostate, AZ::IO::SystemFile, HandleType>;
+    public:
+        using SizeType = AZ::u64;
+
+        //! Creates FileReader instance in the default state with no file opend
+        FileReader();
+        ~FileReader();
+
+        //! Creates a new FileReader instance and attempts to open the file at the supplied path
+        //! Uses the FileIOBase instance if supplied
+        //! @param fileIOBase pointer to fileIOBase instance
+        //! @param null-terminated filePath to open
+        FileReader(AZ::IO::FileIOBase* fileIoBase, const char* filePath);
+
+        //! Takes ownership of the supplied FileReader handle
+        FileReader(FileReader&& other);
+
+        //! Moves ownership of FileReader handle to this instance
+        FileReader& operator=(FileReader&& other);
+
+        //! Opens a File using the FileIOBase instance if non-nullptr
+        //! Otherwise fall back to use SystemFile
+        //! @param fileIOBase pointer to fileIOBase instance
+        //! @param null-terminated filePath to open
+        //! @return true if the File is opened successfully
+        bool Open(AZ::IO::FileIOBase* fileIoBase, const char* filePath);
+
+        //! Returns true if a file is currently open
+        //! @return true if the file is open
+        bool IsOpen() const;
+
+        //! Closes the File
+        void Close();
+
+        //! Retrieve the length of the OpenFile
+        SizeType Length() const;
+
+        //! Attempts to read up to byte size bytes into the supplied buffer
+        //! @param byteSize - Maximum number of bytes to read
+        //! @param buffer - Buffer to read bytes into
+        //! @returns the number of bytes read if the file is open, otherwise 0
+        SizeType Read(SizeType byteSize, void* buffer);
+
+        //! Returns the current file offset
+        //! @returns file offset if the file is open, otherwise 0
+        SizeType Tell() const;
+
+        //! Seeks within the open file to the offset supplied
+        //! @param offset File offset to seek to
+        //! @param type parameter to indicate the reference point to start the seek from
+        //! @returns true if the file is open and the seek succeeded
+        bool Seek(AZ::s64 offset, SeekType type);
+
+        //! Returns true if the file is open and in the EOF state
+        bool Eof() const;
+
+        //! Store the file path of the open file into the output file path parameter
+        //! The filePath reference is left unmodified, if the path was not stored
+        //! @return true if the filePath was stored
+        bool GetFilePath(AZ::IO::FixedMaxPath& filePath) const;
+
+    private:
+
+        FileHandleType m_file;
+        AZ::IO::FileIOBase* m_fileIoBase{};
+    };
+}

Code/Framework/AzCore/AzCore/IO/SystemFile.cpp

@@ -160,12 +160,12 @@ void SystemFile::Seek(SeekSizeType offset, SeekMode mode)
     Platform::Seek(m_handle, this, offset, mode);
 }
 
-SystemFile::SizeType SystemFile::Tell()
+SystemFile::SizeType SystemFile::Tell() const
 {
     return Platform::Tell(m_handle, this);
 }
 
-bool SystemFile::Eof()
+bool SystemFile::Eof() const
 {
     return Platform::Eof(m_handle, this);
 }

Code/Framework/AzCore/AzCore/IO/SystemFile.h

@@ -72,9 +72,9 @@ namespace AZ
             /// Seek in current file.
             void Seek(SeekSizeType offset, SeekMode mode);
             /// Get the cursor position in the current file.
-            SizeType Tell();
+            SizeType Tell() const;
             /// Is the cursor at the end of the file?
-            bool Eof();
+            bool Eof() const;
             /// Get the time the file was last modified.
             AZ::u64 ModificationTime();
             /// Read data from a file synchronous. Return number of bytes actually read in the buffer.

Code/Framework/AzCore/AzCore/Math/Transform.cpp

@@ -353,6 +353,7 @@ namespace AZ
                 Method("CreateFromMatrix3x3AndTranslation", &Transform::CreateFromMatrix3x3AndTranslation)->
                 Method("CreateUniformScale", &Transform::CreateUniformScale)->
                 Method("CreateTranslation", &Transform::CreateTranslation)->
+                Method("CreateLookAt", &Transform::CreateLookAt)->
                 Method("ConstructFromValuesNumeric", &Internal::ConstructTransformFromValues);
         }
     }

Code/Framework/AzCore/AzCore/Settings/SettingsRegistryImpl.cpp

@@ -10,6 +10,7 @@
 #include <cerrno>
 #include <AzCore/Casting/numeric_cast.h>
 #include <AzCore/IO/FileIO.h>
+#include <AzCore/IO/FileReader.h>
 #include <AzCore/IO/Path/Path.h>
 #include <AzCore/JSON/error/en.h>
 #include <AzCore/NativeUI//NativeUIRequests.h>
@@ -1116,118 +1117,6 @@ namespace AZ
         }
     }
 
-    //! Structure which encapsulates Commands to either the FileIOBase or SystemFile classes based on
-    //! the SettingsRegistry option to use FileIO
-    struct SettingsRegistryFileReader
-    {
-        using FileHandleType = AZStd::variant<AZStd::monostate, AZ::IO::SystemFile, AZ::IO::HandleType>;
-
-        SettingsRegistryFileReader() = default;
-        SettingsRegistryFileReader(bool useFileIo, const char* filePath)
-        {
-            Open(useFileIo, filePath);
-        }
-
-        ~SettingsRegistryFileReader()
-        {
-            if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
-            {
-                if (AZ::IO::FileIOBase* fileIo = AZ::IO::FileIOBase::GetInstance(); fileIo != nullptr)
-                {
-                    fileIo->Close(*fileHandle);
-                }
-            }
-        }
-
-        bool Open(bool useFileIo, const char* filePath)
-        {
-            Close();
-            if (AZ::IO::FileIOBase* fileIo = useFileIo ? AZ::IO::FileIOBase::GetInstance() : nullptr; fileIo != nullptr)
-            {
-                AZ::IO::HandleType fileHandle;
-                if (fileIo->Open(filePath, IO::OpenMode::ModeRead, fileHandle))
-                {
-                    m_file = fileHandle;
-                    return true;
-                }
-            }
-            else
-            {
-                AZ::IO::SystemFile file;
-                if (file.Open(filePath, IO::SystemFile::OpenMode::SF_OPEN_READ_ONLY))
-                {
-                    m_file = AZStd::move(file);
-                    return true;
-                }
-            }
-
-            return false;
-        }
-
-        bool IsOpen() const
-        {
-            if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
-            {
-                return *fileHandle != AZ::IO::InvalidHandle;
-            }
-            else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
-            {
-                return systemFile->IsOpen();
-            }
-
-            return false;
-        }
-
-        void Close()
-        {
-            if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
-            {
-                if (AZ::IO::FileIOBase* fileIo = AZ::IO::FileIOBase::GetInstance(); fileIo != nullptr)
-                {
-                    fileIo->Close(*fileHandle);
-                }
-            }
-
-            m_file = AZStd::monostate{};
-        }
-
-        u64 Length() const
-        {
-            if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
-            {
-                if (u64 fileSize{}; AZ::IO::FileIOBase::GetInstance()->Size(*fileHandle, fileSize))
-                {
-                    return fileSize;
-                }
-            }
-            else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
-            {
-                return systemFile->Length();
-            }
-
-            return 0;
-        }
-
-        AZ::IO::SizeType Read(AZ::IO::SizeType byteSize, void* buffer)
-        {
-            if (auto fileHandle = AZStd::get_if<AZ::IO::HandleType>(&m_file); fileHandle != nullptr)
-            {
-                if (AZ::u64 bytesRead{}; AZ::IO::FileIOBase::GetInstance()->Read(*fileHandle, buffer, byteSize, false, &bytesRead))
-                {
-                    return bytesRead;
-                }
-            }
-            else if (auto systemFile = AZStd::get_if<AZ::IO::SystemFile>(&m_file); systemFile != nullptr)
-            {
-                return systemFile->Read(byteSize, buffer);
-            }
-
-            return 0;
-        }
-
-        FileHandleType m_file;
-    };
-
     bool SettingsRegistryImpl::MergeSettingsFileInternal(const char* path, Format format, AZStd::string_view rootKey,
         AZStd::vector<char>& scratchBuffer)
     {
@@ -1236,7 +1125,7 @@ namespace AZ
 
         Pointer pointer(AZ_SETTINGS_REGISTRY_HISTORY_KEY "/-");
 
-        SettingsRegistryFileReader fileReader(m_useFileIo, path);
+        FileReader fileReader(m_useFileIo ? AZ::IO::FileIOBase::GetInstance(): nullptr, path);
         if (!fileReader.IsOpen())
         {
             AZ_Error("Settings Registry", false, R"(Unable to open registry file "%s".)", path);

Code/Framework/AzCore/AzCore/Settings/SettingsRegistryMergeUtils.cpp

@@ -6,6 +6,8 @@
  *
  */
 
+#include <AzCore/IO/FileIO.h>
+#include <AzCore/IO/FileReader.h>
 #include <AzCore/IO/GenericStreams.h>
 #include <AzCore/IO/Path/Path.h>
 #include <AzCore/IO/TextStreamWriters.h>
@@ -388,8 +390,36 @@ namespace AZ::SettingsRegistryMergeUtils
         const ConfigParserSettings& configParserSettings)
     {
         auto configPath = FindEngineRoot(registry) / filePath;
-        IO::SystemFile configFile;
-        if (!configFile.Open(configPath.c_str(), IO::SystemFile::OpenMode::SF_OPEN_READ_ONLY))
+        IO::FileReader configFile;
+        bool configFileOpened{};
+        switch (configParserSettings.m_fileReaderClass)
+        {
+        case ConfigParserSettings::FileReaderClass::UseFileIOIfAvailableFallbackToSystemFile:
+        {
+            auto fileIo = AZ::IO::FileIOBase::GetInstance();
+            configFileOpened = configFile.Open(fileIo, configPath.c_str());
+            break;
+        }
+        case ConfigParserSettings::FileReaderClass::UseSystemFileOnly:
+        {
+            configFileOpened = configFile.Open(nullptr, configPath.c_str());
+            break;
+        }
+        case ConfigParserSettings::FileReaderClass::UseFileIOOnly:
+        {
+            auto fileIo = AZ::IO::FileIOBase::GetInstance();
+            if (fileIo == nullptr)
+            {
+                return false;
+            }
+            configFileOpened = configFile.Open(fileIo, configPath.c_str());
+            break;
+        }
+        default:
+            AZ_Error("SettingsRegistryMergeUtils", false, "An Invalid FileReaderClass enum value has been supplied");
+            return false;
+        }
+        if (!configFileOpened)
         {
             AZ_Warning("SettingsRegistryMergeUtils", false, R"(Unable to open file "%s")", configPath.c_str());
             return false;
@@ -480,7 +510,7 @@ namespace AZ::SettingsRegistryMergeUtils
                 AZ_Error("SettingsRegistryMergeUtils", false,
                     R"(The config file "%s" contains a line which is longer than the max line length of %zu.)" "\n"
                     R"(Parsing will halt. The line content so far is:)" "\n"
-                    R"("%.*s")" "\n", configFile.Name(), configBuffer.max_size(),
+                    R"("%.*s")" "\n", configPath.c_str(), configBuffer.max_size(),
                     aznumeric_cast<int>(configBuffer.size()), configBuffer.data());
                 configFileParsed = false;
                 break;

Code/Framework/AzCore/AzCore/Settings/SettingsRegistryMergeUtils.h

@@ -155,6 +155,15 @@ namespace AZ::SettingsRegistryMergeUtils
         //! structure which is forwarded to the SettingsRegistryInterface MergeCommandLineArgument function
         //! The structure contains a functor which returns true if a character is a valid delimiter
         SettingsRegistryInterface::CommandLineArgumentSettings m_commandLineSettings;
+
+        //! enumeration to indicate if AZ::IO::FileIOBase should be used to open the config file over AZ::IO::SystemFile
+        enum class FileReaderClass
+        {
+            UseFileIOIfAvailableFallbackToSystemFile,
+            UseSystemFileOnly,
+            UseFileIOOnly
+        };
+        FileReaderClass m_fileReaderClass = FileReaderClass::UseFileIOIfAvailableFallbackToSystemFile;
     };
     //! Loads basic configuration files which have structures similar to Windows INI files
     //! It is inspired by the Python configparser module: https://docs.python.org/3.10/library/configparser.html

Code/Framework/AzCore/AzCore/azcore_files.cmake

@@ -166,6 +166,8 @@ set(FILES
     IO/FileIO.cpp
     IO/FileIO.h
     IO/FileIOEventBus.h
+    IO/FileReader.cpp
+    IO/FileReader.h
     IO/IOUtils.h
     IO/IOUtils.cpp
     IO/IStreamer.h

Code/Framework/AzCore/Tests/IO/FileReaderTests.cpp

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+#include <AzCore/IO/FileReader.h>
+#include <FileIOBaseTestTypes.h>
+#include <AzCore/UnitTest/TestTypes.h>
+
+namespace UnitTest
+{
+    template <typename FileIOType>
+    class FileReaderTestFixture
+        : public ScopedAllocatorSetupFixture
+    {
+    public:
+        void SetUp() override
+        {
+            if constexpr (AZStd::is_same_v<FileIOType, TestFileIOBase>)
+            {
+                m_fileIo = AZStd::make_unique<TestFileIOBase>();
+            }
+        }
+
+        void TearDown() override
+        {
+            m_fileIo.reset();
+        }
+
+    protected:
+        AZStd::unique_ptr<AZ::IO::FileIOBase> m_fileIo{};
+    };
+
+    using FileIOTypes = ::testing::Types<void, TestFileIOBase>;
+
+    TYPED_TEST_CASE(FileReaderTestFixture, FileIOTypes);
+
+    TYPED_TEST(FileReaderTestFixture, ConstructorWithFilePath_OpensFileSuccessfully)
+    {
+        AZ::IO::FileReader fileReader(this->m_fileIo.get(), AZ::IO::SystemFile::GetNullFilename());
+        EXPECT_TRUE(fileReader.IsOpen());
+    }
+
+    TYPED_TEST(FileReaderTestFixture, Open_OpensFileSucessfully)
+    {
+        AZ::IO::FileReader fileReader;
+        fileReader.Open(this->m_fileIo.get(), AZ::IO::SystemFile::GetNullFilename());
+        EXPECT_TRUE(fileReader.IsOpen());
+    }
+
+    TYPED_TEST(FileReaderTestFixture, Eof_OnNULDeviceFile_Succeeds)
+    {
+        AZ::IO::FileReader fileReader(this->m_fileIo.get(), AZ::IO::SystemFile::GetNullFilename());
+        EXPECT_TRUE(fileReader.Eof());
+    }
+
+    TYPED_TEST(FileReaderTestFixture, GetFilePath_ReturnsNULDeviceFilename_Succeeds)
+    {
+        AZ::IO::FileReader fileReader(this->m_fileIo.get(), AZ::IO::SystemFile::GetNullFilename());
+        AZ::IO::FixedMaxPath filePath;
+        EXPECT_TRUE(fileReader.GetFilePath(filePath));
+        AZ::IO::FixedMaxPath nulFilename{ AZ::IO::SystemFile::GetNullFilename() };
+        if (this->m_fileIo)
+        {
+            EXPECT_TRUE(this->m_fileIo->ResolvePath(nulFilename, nulFilename));
+        }
+        EXPECT_EQ(nulFilename, filePath);
+    }
+
+}   // namespace UnitTest

Code/Framework/AzCore/Tests/azcoretests_files.cmake

@@ -37,6 +37,7 @@ set(FILES
     FileIOBaseTestTypes.h
     Geometry2DUtils.cpp
     Interface.cpp
+    IO/FileReaderTests.cpp
     IO/Path/PathTests.cpp
     IPC.cpp
     Jobs.cpp

Code/Framework/AzToolsFramework/AzToolsFramework/Application/ToolsApplication.cpp

@@ -28,6 +28,7 @@
 #include <AzToolsFramework/ToolsComponents/TransformComponent.h>
 #include <AzToolsFramework/Entity/EditorEntityContextComponent.h>
 #include <AzToolsFramework/Entity/EditorEntityInfoBus.h>
+#include <AzToolsFramework/FocusMode/FocusModeSystemComponent.h>
 #include <AzToolsFramework/Slice/SliceMetadataEntityContextComponent.h>
 #include <AzToolsFramework/Prefab/PrefabSystemComponent.h>
 #include <AzToolsFramework/UI/Prefab/PrefabIntegrationManager.h>
@@ -248,6 +249,7 @@ namespace AzToolsFramework
         components.insert(components.end(), {
                 azrtti_typeid<EditorEntityContextComponent>(),
                 azrtti_typeid<Components::EditorEntityUiSystemComponent>(),
+                azrtti_typeid<FocusModeSystemComponent>(),
                 azrtti_typeid<SliceMetadataEntityContextComponent>(),
                 azrtti_typeid<Prefab::PrefabSystemComponent>(),
                 azrtti_typeid<EditorEntityFixupComponent>(),

Code/Framework/AzToolsFramework/AzToolsFramework/AssetBrowser/AssetBrowserTableModel.cpp

@@ -138,7 +138,13 @@ namespace AzToolsFramework
                         m_indexMap[row] = index;
                         m_rowMap[index] = row;
                         ++row;
-                        ++m_displayedItemsCounter;
+
+                        // We only want to increase the displayed counter if it is a parent (Source)
+                        // so we don't cut children entries.
+                        if (entry->GetEntryType() == AssetBrowserEntry::AssetEntryType::Source)
+                        {
+                            ++m_displayedItemsCounter;
+                        }
                     }
 
                     if (model->hasChildren(index))

Code/Framework/AzToolsFramework/AzToolsFramework/AssetBrowser/Views/AssetBrowserTableView.cpp

@@ -29,20 +29,20 @@ namespace AzToolsFramework
     {
         AssetBrowserTableView::AssetBrowserTableView(QWidget* parent)
             : AzQtComponents::TableView(parent)
-            , m_delegate(new EntryDelegate(this))
+            , m_delegate(new SearchEntryDelegate(this))
         {
-            setSortingEnabled(true);
+            setSortingEnabled(false);
             setItemDelegate(m_delegate);
             setRootIsDecorated(false);
 
             //Styling the header aligning text to the left and using a bold font.
             header()->setDefaultAlignment(Qt::AlignLeft);
-            header()->setStyleSheet("QHeaderView { font-weight: bold; }");
+            header()->setStyleSheet("QHeaderView { font-weight: bold; };");
+            
 
             setContextMenuPolicy(Qt::CustomContextMenu);
 
             setMouseTracking(true);
-            setSortingEnabled(false);
             setSelectionMode(QAbstractItemView::SingleSelection);
 
             connect(this, &AzQtComponents::TableView::customContextMenuRequested, this, &AssetBrowserTableView::OnContextMenu);
@@ -67,6 +67,8 @@ namespace AzToolsFramework
 
             header()->setSectionResizeMode(0, QHeaderView::ResizeMode::Stretch);
             header()->setSectionResizeMode(1, QHeaderView::ResizeMode::Stretch);
+            header()->setSortIndicatorShown(false);
+            header()->setSectionsClickable(false);
         }
 
         void AssetBrowserTableView::SetName(const QString& name)

Code/Framework/AzToolsFramework/AzToolsFramework/AssetBrowser/Views/AssetBrowserTableView.h

@@ -26,7 +26,7 @@ namespace AzToolsFramework
         class AssetBrowserEntry;
         class AssetBrowserTableModel;
         class AssetBrowserFilterModel;
-        class EntryDelegate;
+        class SearchEntryDelegate;
 
         class AssetBrowserTableView //! Table view that displays the asset browser entries in a list.
             : public AzQtComponents::TableView
@@ -67,9 +67,9 @@ namespace AzToolsFramework
 
         private:
             QString m_name;
-            QPointer<AssetBrowserTableModel> m_tableModel = nullptr;
-            QPointer<AssetBrowserFilterModel> m_sourceFilterModel = nullptr;
-            EntryDelegate* m_delegate = nullptr;
+            QPointer<AssetBrowserTableModel> m_tableModel;
+            QPointer<AssetBrowserFilterModel> m_sourceFilterModel;
+            SearchEntryDelegate* m_delegate = nullptr;
 
         private Q_SLOTS:
             void OnContextMenu(const QPoint& point);

Code/Framework/AzToolsFramework/AzToolsFramework/AssetBrowser/Views/EntryDelegate.cpp

@@ -11,12 +11,13 @@
 #include <AzToolsFramework/AssetBrowser/AssetBrowserModel.h>
 #include <AzToolsFramework/Thumbnails/ThumbnailerBus.h>
 #include <AzToolsFramework/AssetBrowser/Views/EntryDelegate.h>
-
+#include <AzCore/Utils/Utils.h>
 #include <AzQtComponents/Components/StyledBusyLabel.h>
 
 #include <QApplication>
 AZ_PUSH_DISABLE_WARNING(4251 4800, "-Wunknown-warning-option") // 4251: class 'QScopedPointer<QBrushData,QBrushDataPointerDeleter>' needs to have dll-interface to be used by clients of class 'QBrush'
                                                                // 4800: 'uint': forcing value to bool 'true' or 'false' (performance warning)
+#include <QAbstractItemView>
 #include <QPainter>
 AZ_POP_DISABLE_WARNING
 
@@ -24,8 +25,13 @@ namespace AzToolsFramework
 {
     namespace AssetBrowser
     {
-        const int ENTRY_SPACING_LEFT_PIXELS = 8;
-        const int ENTRY_ICON_MARGIN_LEFT_PIXELS = 2;
+        static constexpr const char* TreeIconPathFirst = "Assets/Editor/Icons/AssetBrowser/TreeBranch_First.svg";
+        static constexpr const char* TreeIconPathMiddle = "Assets/Editor/Icons/AssetBrowser/TreeBranch_Middle.svg";
+        static constexpr const char* TreeIconPathLast = "Assets/Editor/Icons/AssetBrowser/TreeBranch_Last.svg";
+        static constexpr const char* TreeIconPathOneChild = "Assets/Editor/Icons/AssetBrowser/TreeBranch_OneChild.svg";
+
+        const int EntrySpacingLeftPixels = 8;
+        const int EntryIconMarginLeftPixels = 2;
 
         EntryDelegate::EntryDelegate(QWidget* parent)
             : QStyledItemDelegate(parent)
@@ -62,7 +68,7 @@ namespace AzToolsFramework
 
                 // Draw main entry thumbnail.
                 QRect remainingRect(option.rect);
-                remainingRect.adjust(ENTRY_ICON_MARGIN_LEFT_PIXELS, 0, 0, 0); // bump it rightwards to give some margin to the icon.
+                remainingRect.adjust(EntryIconMarginLeftPixels, 0, 0, 0); // bump it rightwards to give some margin to the icon.
 
                 QSize iconSize(m_iconSize, m_iconSize);
                 // Note that the thumbnail might actually be smaller than the row if theres a lot of padding or font size
@@ -89,7 +95,7 @@ namespace AzToolsFramework
                     }
 
                     remainingRect.adjust(thumbX, 0, 0, 0); // bump it to the right by the size of the thumbnail
-                    remainingRect.adjust(ENTRY_SPACING_LEFT_PIXELS, 0, 0, 0); // bump it to the right by the spacing.
+                    remainingRect.adjust(EntrySpacingLeftPixels, 0, 0, 0); // bump it to the right by the spacing.
                 }
                 QString displayString = index.column() == aznumeric_cast<int>(AssetBrowserEntry::Column::Name)
                     ? qvariant_cast<QString>(entry->data(aznumeric_cast<int>(AssetBrowserEntry::Column::Name)))
@@ -148,7 +154,162 @@ namespace AzToolsFramework
             return m_iconSize;
         }
 
-    } // namespace Thumbnailer
+        SearchEntryDelegate::SearchEntryDelegate(QWidget* parent)
+            : EntryDelegate(parent)
+        {
+            LoadBranchPixMaps();
+        }
+
+        void SearchEntryDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
+        {
+            auto data = index.data(AssetBrowserModel::Roles::EntryRole);
+            if (data.canConvert<const AssetBrowserEntry*>())
+            {
+                bool isEnabled = (option.state & QStyle::State_Enabled) != 0;
+                bool isSelected = (option.state & QStyle::State_Selected) != 0;
+
+                QStyle* style = option.widget ? option.widget->style() : QApplication::style();
+
+                // draw the background
+                style->drawPrimitive(QStyle::PE_PanelItemViewItem, &option, painter, option.widget);
+
+                // Draw main entry thumbnail.
+                QRect remainingRect(option.rect);
+
+                QSize iconSize(m_iconSize, m_iconSize);
+                // Note that the thumbnail might actually be smaller than the row if theres a lot of padding or font size
+                // so it needs to center vertically with padding in that case:
+                QPoint iconTopLeft;
+                QPoint branchIconTopLeft = QPoint();
+
+                auto entry = qvariant_cast<const AssetBrowserEntry*>(data);
+                auto sourceEntry = azrtti_cast<const SourceAssetBrowserEntry*>(entry);
+
+                //If it is a SourceEntry or it is not the column name we don't want to add space for the branch Icon
+                if (sourceEntry || index.column() != aznumeric_cast<int>(AssetBrowserEntry::Column::Name))
+                {
+                    remainingRect.adjust(EntryIconMarginLeftPixels, 0, 0, 0); // bump it rightwards to give some margin to the icon.
+                    iconTopLeft = QPoint(remainingRect.x(), remainingRect.y() + (remainingRect.height() / 2) - (m_iconSize / 2));
+                }
+                else
+                {
+                    remainingRect.adjust(EntryIconMarginLeftPixels + m_iconSize, 0, 0, 0); // bump it rightwards to give some margin to the icon.
+                    iconTopLeft = QPoint(remainingRect.x() / 2 + m_iconSize, remainingRect.y() + (remainingRect.height() / 2) - (m_iconSize / 2));
+                    branchIconTopLeft = QPoint((remainingRect.x() / 2) - 2, remainingRect.y() + (remainingRect.height() / 2) - (m_iconSize / 2));
+                }
+
+                QPalette actualPalette(option.palette);
+
+                if (index.column() == aznumeric_cast<int>(AssetBrowserEntry::Column::Name))
+                {
+                    int thumbX = DrawThumbnail(painter, iconTopLeft, iconSize, entry->GetThumbnailKey());
+                    if (sourceEntry)
+                    {
+                        if (m_showSourceControl)
+                        {
+                            DrawThumbnail(painter, iconTopLeft, iconSize, sourceEntry->GetSourceControlThumbnailKey());
+                        }
+                        // sources with no children should be greyed out.
+                        if (sourceEntry->GetChildCount() == 0)
+                        {
+                            isEnabled = false; // draw in disabled style.
+                            actualPalette.setCurrentColorGroup(QPalette::Disabled);
+                        }
+                    }
+                    else
+                    {
+                        //Get the indexes above and below our entry to see what type are they.
+                        QAbstractItemView* view = qobject_cast<QAbstractItemView*>(option.styleObject);
+                        const QAbstractItemModel* viewModel = view->model();
+
+                        const QModelIndex indexBelow = viewModel->index(index.row() + 1, index.column());
+                        const QModelIndex indexAbove = viewModel->index(index.row() - 1, index.column());
+
+                        auto aboveEntry = qvariant_cast<const AssetBrowserEntry*>(indexBelow.data(AssetBrowserModel::Roles::EntryRole));
+                        auto belowEntry = qvariant_cast<const AssetBrowserEntry*>(indexAbove.data(AssetBrowserModel::Roles::EntryRole));
+
+                        auto aboveSourceEntry = azrtti_cast<const SourceAssetBrowserEntry*>(aboveEntry);
+                        auto belowSourceEntry = azrtti_cast<const SourceAssetBrowserEntry*>(belowEntry);
+
+                        // if current index is the last entry in the view
+                        // or the index above it is a Source Entry and
+                        // the index below is invalid or is valid but it is also a source entry
+                        // then the current index is the only child.
+                        if (index.row() == viewModel->rowCount() - 1 ||
+                            (indexBelow.isValid() && aboveSourceEntry &&
+                             (!indexAbove.isValid() || (indexAbove.isValid() && belowSourceEntry))))
+                        {
+                            DrawBranchPixMap(EntryBranchType::OneChild, painter, branchIconTopLeft, iconSize); // Draw One Child Icon
+                        }
+                        else if (indexBelow.isValid() && aboveSourceEntry) // The index above is a source entry
+                        {
+                            DrawBranchPixMap(EntryBranchType::Last, painter, branchIconTopLeft, iconSize); // Draw First child Icon
+                        }
+                        else if (indexAbove.isValid() && belowSourceEntry) // The index below is a source entry
+                        {
+                            DrawBranchPixMap(EntryBranchType::First, painter, branchIconTopLeft, iconSize); // Draw Last Child Icon
+                        }
+                        else //the index above and below are also child entries
+                        {
+                            DrawBranchPixMap(EntryBranchType::Middle, painter, branchIconTopLeft, iconSize); // Draw Default child Icon.
+                        }
+                    }
+
+                    remainingRect.adjust(thumbX, 0, 0, 0); // bump it to the right by the size of the thumbnail
+                    remainingRect.adjust(EntrySpacingLeftPixels, 0, 0, 0); // bump it to the right by the spacing.
+                }
+                QString displayString = index.column() == aznumeric_cast<int>(AssetBrowserEntry::Column::Name)
+                    ? qvariant_cast<QString>(entry->data(aznumeric_cast<int>(AssetBrowserEntry::Column::Name)))
+                    : qvariant_cast<QString>(entry->data(aznumeric_cast<int>(AssetBrowserEntry::Column::Path)));
+
+                style->drawItemText(
+                    painter, remainingRect, option.displayAlignment, actualPalette, isEnabled, displayString,
+                    isSelected ? QPalette::HighlightedText : QPalette::Text);
+            }
+        }
+
+        void SearchEntryDelegate::LoadBranchPixMaps()
+        {
+            AZ::IO::BasicPath<AZ::IO::FixedMaxPathString> absoluteIconPath;
+            for (int branchType = EntryBranchType::First; branchType != EntryBranchType::Count; ++branchType)
+            {
+                QPixmap pixmap;
+                switch (branchType)
+                {
+                case AzToolsFramework::AssetBrowser::EntryBranchType::First:
+                    absoluteIconPath = AZ::IO::FixedMaxPath(AZ::Utils::GetEnginePath()) / TreeIconPathFirst;
+                    break;
+                case AzToolsFramework::AssetBrowser::EntryBranchType::Middle:
+                    absoluteIconPath = AZ::IO::FixedMaxPath(AZ::Utils::GetEnginePath()) / TreeIconPathMiddle;
+                    break;
+                case AzToolsFramework::AssetBrowser::EntryBranchType::Last:
+                    absoluteIconPath = AZ::IO::FixedMaxPath(AZ::Utils::GetEnginePath()) / TreeIconPathLast;
+                    break;
+                case AzToolsFramework::AssetBrowser::EntryBranchType::OneChild:
+                default:
+                    absoluteIconPath = AZ::IO::FixedMaxPath(AZ::Utils::GetEnginePath()) / TreeIconPathOneChild;
+                    break;
+                }
+                bool pixmapLoadedSuccess = pixmap.load(absoluteIconPath.c_str()); 
+                AZ_Assert(pixmapLoadedSuccess, "Error loading Branch Icons in SearchEntryDelegate");
+
+                m_branchIcons[static_cast<EntryBranchType>(branchType)] = pixmap;
+
+            }
+        }
+
+        void SearchEntryDelegate::DrawBranchPixMap(
+            EntryBranchType branchType, QPainter* painter, const QPoint& point, const QSize& size) const
+        {
+            const QPixmap& pixmap = m_branchIcons[branchType];
+
+            pixmap.scaled(size, Qt::KeepAspectRatio, Qt::SmoothTransformation);
+            const QSize sizeDelta = size - pixmap.size();
+            const QPoint pointDelta = QPoint(sizeDelta.width() / 2, sizeDelta.height() / 2);
+            painter->drawPixmap(point + pointDelta, pixmap);
+        }
+
+    } // namespace AssetBrowser
 } // namespace AzToolsFramework
 
 #include "AssetBrowser/Views/moc_EntryDelegate.cpp"

Code/Framework/AzToolsFramework/AzToolsFramework/AssetBrowser/Views/EntryDelegate.h

@@ -27,9 +27,19 @@ namespace AzToolsFramework
 {
     namespace AssetBrowser
     {
+        //! Type of branch icon the delegate should paint.
+        enum EntryBranchType
+        {
+            First,
+            Middle,
+            Last,
+            OneChild,
+            Count
+        };
+
         class AssetBrowserFilterModel;
 
-        //! EntryDelegate draws a single item in AssetBrowser
+        //! EntryDelegate draws a single item in AssetBrowser.
         class EntryDelegate
             : public QStyledItemDelegate
         {
@@ -52,5 +62,23 @@ namespace AzToolsFramework
             //! Draw a thumbnail and return its width
             int DrawThumbnail(QPainter* painter, const QPoint& point, const QSize& size, Thumbnailer::SharedThumbnailKey thumbnailKey) const;
         };
+
+        //! SearchEntryDelegate draws a single item in AssetBrowserTableView.
+        class SearchEntryDelegate
+            : public EntryDelegate
+        {
+            Q_OBJECT
+        public:
+            explicit SearchEntryDelegate(QWidget* parent = nullptr);
+
+            void paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const override;
+
+        private:
+            void LoadBranchPixMaps();
+            void DrawBranchPixMap(EntryBranchType branchType, QPainter* painter, const QPoint& point, const QSize& size) const;
+
+        private:
+            QMap<EntryBranchType, QPixmap> m_branchIcons;
+        };
     } // namespace AssetBrowser
 } // namespace AzToolsFramework

Code/Framework/AzToolsFramework/AzToolsFramework/AzToolsFrameworkModule.cpp

@@ -22,6 +22,7 @@
 #include <AzToolsFramework/Entity/EditorEntityModelComponent.h>
 #include <AzToolsFramework/Entity/EditorEntitySearchComponent.h>
 #include <AzToolsFramework/Entity/EditorEntitySortComponent.h>
+#include <AzToolsFramework/FocusMode/FocusModeSystemComponent.h>
 #include <AzToolsFramework/PropertyTreeEditor/PropertyTreeEditorComponent.h>
 #include <AzToolsFramework/Render/EditorIntersectorComponent.h>
 #include <AzToolsFramework/Slice/SliceDependencyBrowserComponent.h>
@@ -69,6 +70,7 @@ namespace AzToolsFramework
             Components::EditorSelectionAccentSystemComponent::CreateDescriptor(),
             EditorEntityContextComponent::CreateDescriptor(),
             EditorEntityFixupComponent::CreateDescriptor(),
+            FocusModeSystemComponent::CreateDescriptor(),
             SliceMetadataEntityContextComponent::CreateDescriptor(),
             SliceRequestComponent::CreateDescriptor(),
             Prefab::PrefabSystemComponent::CreateDescriptor(),

Code/Framework/AzToolsFramework/AzToolsFramework/FocusMode/FocusModeInterface.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#pragma once
+
+#include <AzCore/Interface/Interface.h>
+#include <AzCore/Serialization/SerializeContext.h>
+
+namespace AzToolsFramework
+{
+    //! FocusModeInterface
+    //! Interface to handle the Editor Focus Mode.
+    class FocusModeInterface
+    {
+    public:
+        AZ_RTTI(FocusModeInterface, "{437243B0-F86B-422F-B7B8-4A21CC000702}");
+
+        //! Sets the root entity the Editor should focus on.
+        //! The Editor will only allow the user to select entities that are descendants of the EntityId provided.
+        //! @param entityId The entityId that will become the new focus root.
+        virtual void SetFocusRoot(AZ::EntityId entityId) = 0;
+
+        //! Clears the Editor focus, allowing the user to select the whole level again.
+        virtual void ClearFocusRoot() = 0;
+
+        //! Returns the entity id of the root of the current Editor focus.
+        //! @return The entity id of the root of the Editor focus, or an invalid entity id if no focus is set.
+        virtual AZ::EntityId GetFocusRoot() = 0;
+
+        //! Returns whether the entity id provided is part of the focused sub-tree.
+        virtual bool IsInFocusSubTree(AZ::EntityId entityId) const = 0;
+    };
+
+} // namespace AzToolsFramework

Code/Framework/AzToolsFramework/AzToolsFramework/FocusMode/FocusModeSystemComponent.cpp

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#include <AzCore/Component/TransformBus.h>
+
+#include <AzToolsFramework/API/ViewportEditorModeTrackerInterface.h>
+#include <AzToolsFramework/FocusMode/FocusModeSystemComponent.h>
+
+namespace AzToolsFramework
+{
+    bool IsInFocusSubTree(AZ::EntityId entityId, AZ::EntityId focusRootId)
+    {
+        if (entityId == AZ::EntityId())
+        {
+            return false;
+        }
+
+        if (entityId == focusRootId)
+        {
+            return true;
+        }
+
+        AZ::EntityId parentId;
+        AZ::TransformBus::EventResult(parentId, entityId, &AZ::TransformInterface::GetParentId);
+
+        return IsInFocusSubTree(parentId, focusRootId);
+    }
+
+    void FocusModeSystemComponent::Init()
+    {
+    }
+
+    void FocusModeSystemComponent::Activate()
+    {
+        AZ::Interface<FocusModeInterface>::Register(this);
+    }
+
+    void FocusModeSystemComponent::Deactivate()
+    {
+        AZ::Interface<FocusModeInterface>::Unregister(this);
+    }
+
+    void FocusModeSystemComponent::Reflect([[maybe_unused]] AZ::ReflectContext* context)
+    {
+    }
+
+    void FocusModeSystemComponent::GetProvidedServices(AZ::ComponentDescriptor::DependencyArrayType& provided)
+    {
+        provided.push_back(AZ_CRC_CE("EditorFocusMode"));
+    }
+
+    void FocusModeSystemComponent::GetRequiredServices([[maybe_unused]] AZ::ComponentDescriptor::DependencyArrayType& required)
+    {
+    }
+
+    void FocusModeSystemComponent::GetIncompatibleServices([[maybe_unused]] AZ::ComponentDescriptor::DependencyArrayType& incompatible)
+    {
+    }
+
+    void FocusModeSystemComponent::SetFocusRoot(AZ::EntityId entityId)
+    {
+        m_focusRoot = entityId;
+
+        // TODO - If m_focusRoot != AZ::EntityId(), activate focus mode via ViewportEditorModeTrackerInterface; else, deactivate focus mode
+    }
+
+    void FocusModeSystemComponent::ClearFocusRoot()
+    {
+        SetFocusRoot(AZ::EntityId());
+    }
+
+    AZ::EntityId FocusModeSystemComponent::GetFocusRoot()
+    {
+        return m_focusRoot;
+    }
+
+    bool FocusModeSystemComponent::IsInFocusSubTree(AZ::EntityId entityId) const
+    {
+        if (m_focusRoot == AZ::EntityId())
+        {
+            return true;
+        }
+
+        return AzToolsFramework::IsInFocusSubTree(entityId, m_focusRoot);
+    }
+
+} // namespace AzToolsFramework

Code/Framework/AzToolsFramework/AzToolsFramework/FocusMode/FocusModeSystemComponent.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#pragma once
+
+#include <AzCore/Component/Component.h>
+#include <AzCore/Memory/SystemAllocator.h>
+
+#include <AzToolsFramework/FocusMode/FocusModeInterface.h>
+
+namespace AzToolsFramework
+{
+    bool IsInFocusSubTree(AZ::EntityId entityId, AZ::EntityId focusRootId);
+
+    //! System Component to handle the Editor Focus Mode system
+    class FocusModeSystemComponent final
+        : public AZ::Component
+        , private FocusModeInterface
+    {
+    public:
+        AZ_COMPONENT(FocusModeSystemComponent, "{6CE522FE-2057-4794-BD05-61E04BD8EA30}");
+
+        FocusModeSystemComponent() = default;
+        virtual ~FocusModeSystemComponent() = default;
+
+        // AZ::Component overrides ...
+        void Init() override;
+        void Activate() override;
+        void Deactivate() override;
+
+        static void Reflect(AZ::ReflectContext* context);
+        static void GetProvidedServices(AZ::ComponentDescriptor::DependencyArrayType& provided);
+        static void GetRequiredServices(AZ::ComponentDescriptor::DependencyArrayType& required);
+        static void GetIncompatibleServices(AZ::ComponentDescriptor::DependencyArrayType& incompatible);
+
+        // FocusModeInterface overrides ...
+        void SetFocusRoot(AZ::EntityId entityId) override;
+        void ClearFocusRoot() override;
+        AZ::EntityId GetFocusRoot() override;
+        bool IsInFocusSubTree(AZ::EntityId entityId) const override;
+
+    private:
+        AZ::EntityId m_focusRoot;
+    };
+
+} // namespace AzToolsFramework

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabFocusHandler.cpp

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#include <AzToolsFramework/Prefab/PrefabFocusHandler.h>
+
+#include <AzToolsFramework/Entity/PrefabEditorEntityOwnershipInterface.h>
+#include <AzToolsFramework/Prefab/Instance/Instance.h>
+#include <AzToolsFramework/Prefab/Instance/InstanceEntityMapperInterface.h>
+
+namespace AzToolsFramework::Prefab
+{
+    PrefabFocusHandler::PrefabFocusHandler()
+    {
+        m_instanceEntityMapperInterface = AZ::Interface<InstanceEntityMapperInterface>::Get();
+        AZ_Assert(
+            m_instanceEntityMapperInterface,
+            "Prefab - PrefabFocusHandler - "
+            "Instance Entity Mapper Interface could not be found. "
+            "Check that it is being correctly initialized.");
+
+        AZ::Interface<PrefabFocusInterface>::Register(this);
+    }
+
+    PrefabFocusHandler::~PrefabFocusHandler()
+    {
+        AZ::Interface<PrefabFocusInterface>::Unregister(this);
+    }
+
+    PrefabFocusOperationResult PrefabFocusHandler::FocusOnOwningPrefab(AZ::EntityId entityId)
+    {
+        InstanceOptionalReference focusedInstance;
+
+        if (!entityId.IsValid())
+        {
+            PrefabEditorEntityOwnershipInterface* prefabEditorEntityOwnershipInterface =
+                AZ::Interface<PrefabEditorEntityOwnershipInterface>::Get();
+
+            if(!prefabEditorEntityOwnershipInterface)
+            {
+                return AZ::Failure(AZStd::string("Could not focus on root prefab instance - internal error "
+                                                 "(PrefabEditorEntityOwnershipInterface unavailable)."));
+            }
+
+            focusedInstance = prefabEditorEntityOwnershipInterface->GetRootPrefabInstance();
+        }
+        else
+        {
+            focusedInstance = m_instanceEntityMapperInterface->FindOwningInstance(entityId);
+        }
+
+        if (!focusedInstance.has_value())
+        {
+            return AZ::Failure(AZStd::string(
+                "Prefab Focus Handler: Couldn't find owning instance of entityId provided."));
+        }
+
+        m_focusedInstance = focusedInstance;
+        m_focusedTemplateId = focusedInstance->get().GetTemplateId();
+
+        FocusModeInterface* focusModeInterface = AZ::Interface<FocusModeInterface>::Get();
+        if (focusModeInterface)
+        {
+            focusModeInterface->SetFocusRoot(focusedInstance->get().GetContainerEntityId());
+        }
+
+        return AZ::Success();
+    }
+    
+    TemplateId PrefabFocusHandler::GetFocusedPrefabTemplateId()
+    {
+        return m_focusedTemplateId;
+    }
+
+    InstanceOptionalReference PrefabFocusHandler::GetFocusedPrefabInstance()
+    {
+        return m_focusedInstance;
+    }
+
+    bool PrefabFocusHandler::IsOwningPrefabBeingFocused(AZ::EntityId entityId)
+    {
+        if (!m_focusedInstance.has_value())
+        {
+            // PrefabFocusHandler has not been initialized yet.
+            return false;
+        }
+
+        if (!entityId.IsValid())
+        {
+            return false;
+        }
+
+        InstanceOptionalReference instance = m_instanceEntityMapperInterface->FindOwningInstance(entityId);
+
+        return instance.has_value() && (&instance->get() == &m_focusedInstance->get());
+    }
+
+} // namespace AzToolsFramework::Prefab

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabFocusHandler.h

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#pragma once
+
+#include <AzCore/Memory/SystemAllocator.h>
+
+#include <AzToolsFramework/FocusMode/FocusModeInterface.h>
+#include <AzToolsFramework/Prefab/PrefabFocusInterface.h>
+#include <AzToolsFramework/Prefab/Template/Template.h>
+
+namespace AzToolsFramework::Prefab
+{
+    class InstanceEntityMapperInterface;
+
+    //! Handles Prefab Focus mode, determining which prefab file entity changes will target.
+    class PrefabFocusHandler final
+        : private PrefabFocusInterface
+    {
+    public:
+        AZ_CLASS_ALLOCATOR(PrefabFocusHandler, AZ::SystemAllocator, 0);
+
+        PrefabFocusHandler();
+        ~PrefabFocusHandler();
+
+        // PrefabFocusInterface override ...
+        PrefabFocusOperationResult FocusOnOwningPrefab(AZ::EntityId entityId) override;
+        TemplateId GetFocusedPrefabTemplateId() override;
+        InstanceOptionalReference GetFocusedPrefabInstance() override;
+        bool IsOwningPrefabBeingFocused(AZ::EntityId entityId) override;
+
+    private:
+        InstanceOptionalReference m_focusedInstance;
+        TemplateId m_focusedTemplateId;
+
+        InstanceEntityMapperInterface* m_instanceEntityMapperInterface;
+    };
+
+} // namespace AzToolsFramework::Prefab

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabFocusInterface.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#pragma once
+
+#include <AzCore/Interface/Interface.h>
+#include <AzCore/Serialization/SerializeContext.h>
+
+#include <AzToolsFramework/Prefab/Instance/Instance.h>
+#include <AzToolsFramework/Prefab/Template/Template.h>
+
+namespace AzToolsFramework::Prefab
+{
+    using PrefabFocusOperationResult = AZ::Outcome<void, AZStd::string>;
+
+    //! Interface to handle operations related to the Prefab Focus system.
+    class PrefabFocusInterface
+    {
+    public:
+        AZ_RTTI(PrefabFocusInterface, "{F3CFA37B-5FD8-436A-9C30-60EB54E350E1}");
+
+        //! Set the focused prefab instance to the owning instance of the entityId provided.
+        //! @param entityId The entityId of the entity whose owning instance we want the prefab system to focus on.
+        virtual PrefabFocusOperationResult FocusOnOwningPrefab(AZ::EntityId entityId) = 0;
+
+        //! Returns the template id of the instance the prefab system is focusing on.
+        virtual TemplateId GetFocusedPrefabTemplateId() = 0;
+
+        //! Returns a reference to the instance the prefab system is focusing on.
+        virtual InstanceOptionalReference GetFocusedPrefabInstance() = 0;
+
+        //! Returns whether the entity belongs to the instance that is being focused on, or one of its descendants.
+        //! @param entityId The entityId of the queried entity.
+        //! @return true if the entity belongs to the focused instance or one of its descendants, false otherwise.
+        virtual bool IsOwningPrefabBeingFocused(AZ::EntityId entityId) = 0;
+    };
+
+} // namespace AzToolsFramework::Prefab

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabPublicHandler.h

@@ -13,6 +13,7 @@
 #include <AzCore/std/string/string_view.h>
 
 #include <AzToolsFramework/Prefab/Instance/Instance.h>
+#include <AzToolsFramework/Prefab/PrefabFocusHandler.h>
 #include <AzToolsFramework/Prefab/PrefabPublicInterface.h>
 #include <AzToolsFramework/Prefab/PrefabSystemComponentInterface.h>
 #include <AzToolsFramework/Prefab/PrefabUndoCache.h>
@@ -189,6 +190,9 @@ namespace AzToolsFramework
             PrefabLoaderInterface* m_prefabLoaderInterface = nullptr;
             PrefabSystemComponentInterface* m_prefabSystemComponentInterface = nullptr;
 
+            // Handles the Prefab Focus API that determines what prefab is being edited.
+            PrefabFocusHandler m_prefabFocusHandler;
+
             // Caches entity states for undo/redo purposes
             PrefabUndoCache m_prefabUndoCache;
 

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabSystemComponent.h

@@ -369,7 +369,7 @@ namespace AzToolsFramework
             // A counter for generating unique Link Ids.
             AZStd::atomic<LinkId> m_linkIdCounter = 0u;
 
-            // Used for finding the owning instance of an arbitrary entity
+            // Used for finding the owning instance of an arbitrary entity.
             InstanceEntityMapper m_instanceEntityMapper;
 
             // Used for finding the Instances owned by an arbitrary Template.
@@ -378,16 +378,16 @@ namespace AzToolsFramework
             // Used for loading/saving Prefab Template files.
             PrefabLoader m_prefabLoader;
 
-            // Handler the public Prefab API used by UI and scripting
+            // Handles the public Prefab API used by UI and scripting.
             PrefabPublicHandler m_prefabPublicHandler;
 
             // Used for updating Instances of Prefab Template.
             InstanceUpdateExecutor m_instanceUpdateExecutor;
 
-            // Used for updating Templates when Instances are modified
+            // Used for updating Templates when Instances are modified.
             InstanceToTemplatePropagator m_instanceToTemplatePropagator;
 
-            // Handler of the public Prefab requests
+            // Handler of the public Prefab requests.
             PrefabPublicRequestHandler m_prefabPublicRequestHandler;
         };
     } // namespace Prefab

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Outliner/EntityOutliner.qss

@@ -18,18 +18,19 @@ AzToolsFramework--EntityOutlinerWidget QTreeView
     selection-background-color: transparent;
 }
 
+
+/* 	
+ *  Entity Outliner handles hover and selected state of items via code,
+ *  so we need to override the AzQtComponents::Treeview style.
+ */
 AzToolsFramework--EntityOutlinerWidget QTreeView::branch:hover
 , AzToolsFramework--EntityOutlinerWidget QTreeView::item:hover
-{
-    background: rgba(255, 255, 255, 30);
-}
-
-AzToolsFramework--EntityOutlinerWidget QTreeView::branch:selected
+, AzToolsFramework--EntityOutlinerWidget QTreeView::branch:selected
 , AzToolsFramework--EntityOutlinerWidget QTreeView::item:selected
 , AzToolsFramework--EntityOutlinerWidget QTreeView::branch:selected:active
 , AzToolsFramework--EntityOutlinerWidget QTreeView::item:selected:active
 {
-    background: rgba(255, 255, 255, 45);
+    background: transparent;
 }
 
 

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Outliner/EntityOutlinerListModel.cpp

@@ -44,6 +44,7 @@
 #include <AzToolsFramework/Entity/EditorEntityContextBus.h>
 #include <AzToolsFramework/Entity/EditorEntityHelpers.h>
 #include <AzToolsFramework/Entity/EditorEntityInfoBus.h>
+#include <AzToolsFramework/FocusMode/FocusModeInterface.h>
 #include <AzToolsFramework/ToolsComponents/ComponentAssetMimeDataContainer.h>
 #include <AzToolsFramework/ToolsComponents/ComponentMimeData.h>
 #include <AzToolsFramework/ToolsComponents/EditorEntityIdContainer.h>
@@ -102,10 +103,14 @@ namespace AzToolsFramework
         EntityCompositionNotificationBus::Handler::BusConnect();
         AZ::EntitySystemBus::Handler::BusConnect();
 
-        m_editorEntityFrameworkInterface = AZ::Interface<AzToolsFramework::EditorEntityUiInterface>::Get();
+        m_editorEntityUiInterface = AZ::Interface<AzToolsFramework::EditorEntityUiInterface>::Get();
+        AZ_Assert(m_editorEntityUiInterface != nullptr,
+            "EntityOutlinerListModel requires a EditorEntityUiInterface instance on Initialize.");
 
-        AZ_Assert(m_editorEntityFrameworkInterface != nullptr,
-            "EntityOutlinerListModel requires a EditorEntityFrameworkInterface instance on Initialize.");
+        m_focusModeInterface = AZ::Interface<FocusModeInterface>::Get();
+        AZ_Assert(
+            m_focusModeInterface != nullptr,
+            "EntityOutlinerListModel requires a FocusModeInterface instance on Initialize.");
     }
 
     int EntityOutlinerListModel::rowCount(const QModelIndex& parent) const
@@ -279,7 +284,7 @@ namespace AzToolsFramework
 
     QVariant EntityOutlinerListModel::GetEntityIcon(const AZ::EntityId& id) const
     {
-        auto entityUiHandler = m_editorEntityFrameworkInterface->GetHandler(id);
+        auto entityUiHandler = m_editorEntityUiInterface->GetHandler(id);
         QIcon icon;
 
         // Retrieve the icon from the handler
@@ -316,7 +321,7 @@ namespace AzToolsFramework
 
     QVariant EntityOutlinerListModel::GetEntityTooltip(const AZ::EntityId& id) const
     {
-        auto entityUiHandler = m_editorEntityFrameworkInterface->GetHandler(id);
+        auto entityUiHandler = m_editorEntityUiInterface->GetHandler(id);
         QString tooltip;
 
         // Retrieve the tooltip from the handler
@@ -349,7 +354,7 @@ namespace AzToolsFramework
     QVariant EntityOutlinerListModel::dataForVisibility(const QModelIndex& index, int role) const
     {
         auto entityId = GetEntityFromIndex(index);
-        auto entityUiHandler = m_editorEntityFrameworkInterface->GetHandler(entityId);
+        auto entityUiHandler = m_editorEntityUiInterface->GetHandler(entityId);
 
         if (!entityUiHandler || entityUiHandler->CanToggleLockVisibility(entityId))
         {
@@ -377,7 +382,7 @@ namespace AzToolsFramework
     QVariant EntityOutlinerListModel::dataForLock(const QModelIndex& index, int role) const
     {
         auto entityId = GetEntityFromIndex(index);
-        auto entityUiHandler = m_editorEntityFrameworkInterface->GetHandler(entityId);
+        auto entityUiHandler = m_editorEntityUiInterface->GetHandler(entityId);
 
         if (!entityUiHandler || entityUiHandler->CanToggleLockVisibility(entityId))
         {
@@ -436,7 +441,7 @@ namespace AzToolsFramework
             if (value.canConvert<Qt::CheckState>())
             {
                 const auto entityId = GetEntityFromIndex(index);
-                auto entityUiHandler = m_editorEntityFrameworkInterface->GetHandler(entityId);
+                auto entityUiHandler = m_editorEntityUiInterface->GetHandler(entityId);
 
                 if (!entityUiHandler || entityUiHandler->CanToggleLockVisibility(entityId))
                 {
@@ -532,6 +537,11 @@ namespace AzToolsFramework
             break;
         }
 
+        if (AZ::EntityId entityId = GetEntityFromIndex(index); !m_focusModeInterface->IsInFocusSubTree(entityId))
+        {
+            itemFlags &= !Qt::ItemIsEnabled;
+        }
+
         return itemFlags;
     }
 

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Outliner/EntityOutlinerListModel.hxx

@@ -36,6 +36,7 @@
 namespace AzToolsFramework
 {
     class EditorEntityUiInterface;
+    class FocusModeInterface;
 
     namespace EntityOutliner
     {
@@ -273,7 +274,8 @@ namespace AzToolsFramework
         QVariant GetEntityIcon(const AZ::EntityId& id) const;
         QVariant GetEntityTooltip(const AZ::EntityId& id) const;
         
-        EditorEntityUiInterface* m_editorEntityFrameworkInterface = nullptr;
+        EditorEntityUiInterface* m_editorEntityUiInterface = nullptr;
+        FocusModeInterface* m_focusModeInterface = nullptr;
     };
 
     class EntityOutlinerCheckBox

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Outliner/EntityOutlinerTreeView.cpp

@@ -38,6 +38,8 @@ namespace AzToolsFramework
 
         AZ_Assert((m_editorEntityFrameworkInterface != nullptr),
             "EntityOutlinerTreeView requires a EditorEntityFrameworkInterface instance on Construction.");
+
+        viewport()->setMouseTracking(true);
     }
 
     EntityOutlinerTreeView::~EntityOutlinerTreeView()
@@ -59,6 +61,11 @@ namespace AzToolsFramework
         }
     }
 
+    void EntityOutlinerTreeView::leaveEvent([[maybe_unused]] QEvent* event)
+    {
+        m_mousePosition = QPoint();
+    }
+
     void EntityOutlinerTreeView::mousePressEvent(QMouseEvent* event)
     {
         //postponing normal mouse pressed logic until mouse is released or dragged
@@ -112,6 +119,8 @@ namespace AzToolsFramework
             setSelectionMode(selectionModeBefore);
         }
 
+        m_mousePosition = event->pos();
+
         //process mouse movement as normal, potentially triggering drag and drop
         QTreeView::mouseMoveEvent(event);
     }
@@ -172,12 +181,45 @@ namespace AzToolsFramework
 
     void EntityOutlinerTreeView::drawBranches(QPainter* painter, const QRect& rect, const QModelIndex& index) const
     {
+        const bool isEnabled = (this->model()->flags(index) & Qt::ItemIsEnabled);
+
+        const bool isSelected = selectionModel()->isSelected(index);
+        const bool isHovered = (index == indexAt(m_mousePosition)) && isEnabled;
+
+        // Paint the branch Selection/Hover Rect
+        PaintBranchSelectionHoverRect(painter, rect, isSelected, isHovered);
+        
         // Paint the branch background as defined by the entity's handler, or its closes ancestor's.
         PaintBranchBackground(painter, rect, index);
 
         QTreeView::drawBranches(painter, rect, index);
     }
 
+    void EntityOutlinerTreeView::PaintBranchSelectionHoverRect(
+        QPainter* painter, const QRect& rect, bool isSelected, bool isHovered) const
+    {
+        painter->save();
+        painter->setRenderHint(QPainter::Antialiasing, false);
+
+        if (isSelected || isHovered)
+        {
+            QPainterPath backgroundPath;
+            QRect backgroundRect(rect);
+
+            backgroundPath.addRect(backgroundRect);
+
+            QColor backgroundColor = m_hoverColor;
+            if (isSelected)
+            {
+                backgroundColor = m_selectedColor;
+            }
+
+            painter->fillPath(backgroundPath, backgroundColor);
+        }
+
+        painter->restore();
+    }
+
     void EntityOutlinerTreeView::PaintBranchBackground(QPainter* painter, const QRect& rect, const QModelIndex& index) const
     {
         // Go through ancestors and add them to the stack

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Outliner/EntityOutlinerTreeView.hxx

@@ -59,6 +59,7 @@ namespace AzToolsFramework
         void startDrag(Qt::DropActions supportedActions) override;
         void dragMoveEvent(QDragMoveEvent* event) override;
         void dropEvent(QDropEvent* event) override;
+        void leaveEvent(QEvent* event) override;
 
         //! Renders the left side of the item: appropriate background, branch lines, icons.
         void drawBranches(QPainter* painter, const QRect& rect, const QModelIndex& index) const override;
@@ -72,8 +73,10 @@ namespace AzToolsFramework
         void StartCustomDrag(const QModelIndexList& indexList, Qt::DropActions supportedActions) override;
 
         void PaintBranchBackground(QPainter* painter, const QRect& rect, const QModelIndex& index) const;
+        void PaintBranchSelectionHoverRect(QPainter* painter, const QRect& rect, bool isSelected, bool isHovered) const;
         
         QMouseEvent* m_queuedMouseEvent;
+        QPoint m_mousePosition;
         bool m_draggingUnselectedItem; // This is set when an item is dragged outside its bounding box.
 
         int m_expandOnlyDelay = -1;

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/LevelRootUiHandler.cpp

@@ -8,7 +8,6 @@
 
 #include <AzToolsFramework/UI/Prefab/LevelRootUiHandler.h>
 
-#include <AzToolsFramework/UI/Prefab/PrefabEditInterface.h>
 #include <AzToolsFramework/Prefab/PrefabPublicInterface.h>
 #include <AzToolsFramework/UI/Outliner/EntityOutlinerListModel.hxx>
 
@@ -24,14 +23,6 @@ namespace AzToolsFramework
 
     LevelRootUiHandler::LevelRootUiHandler()
     {
-        m_prefabEditInterface = AZ::Interface<Prefab::PrefabEditInterface>::Get();
-
-        if (m_prefabEditInterface == nullptr)
-        {
-            AZ_Assert(false, "LevelRootUiHandler - could not get PrefabEditInterface on LevelRootUiHandler construction.");
-            return;
-        }
-
         m_prefabPublicInterface = AZ::Interface<Prefab::PrefabPublicInterface>::Get();
 
         if (m_prefabPublicInterface == nullptr)

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/LevelRootUiHandler.h

@@ -14,7 +14,6 @@ namespace AzToolsFramework
 {
     namespace Prefab
     {
-        class PrefabEditInterface;
         class PrefabPublicInterface;
     };
 
@@ -36,7 +35,6 @@ namespace AzToolsFramework
         void PaintItemBackground(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const override;
 
     private:
-        Prefab::PrefabEditInterface* m_prefabEditInterface = nullptr;
         Prefab::PrefabPublicInterface* m_prefabPublicInterface = nullptr;
 
         static constexpr int m_levelRootBorderThickness = 1;

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/PrefabEditInterface.h

@@ -1,43 +0,0 @@
-/*
- * Copyright (c) Contributors to the Open 3D Engine Project.
- * For complete copyright and license terms please see the LICENSE at the root of this distribution.
- *
- * SPDX-License-Identifier: Apache-2.0 OR MIT
- *
- */
-
-#pragma once
-
-#include <AzCore/Interface/Interface.h>
-#include <AzCore/Serialization/SerializeContext.h>
-
-namespace AzToolsFramework
-{
-    namespace Prefab
-    {
-        /*!
-         * PrefabEditInterface
-         * Interface to expose the API to Edit Prefabs in the Editor.
-         */
-        class PrefabEditInterface
-        {
-        public:
-            AZ_RTTI(PrefabEditInterface, "{DABB1D43-3760-420E-9F1E-5104F0AFF167}");
-
-            /**
-             * Sets the prefab for the instance owning the entity provided as the prefab being edited.
-             * @param entityId The entity whose owning prefab should be edited.
-             */
-            virtual void EditOwningPrefab(AZ::EntityId entityId) = 0;
-            
-            /**
-             * Queries the Edit Manager to know if the provided entity is part of the prefab currently being edited.
-             * @param entityId The entity whose prefab editing state we want to query.
-             * @return True if the prefab owning this entity is being edited, false otherwise.
-             */
-            virtual bool IsOwningPrefabBeingEdited(AZ::EntityId entityId) = 0;
-        };
-
-    } // namespace Prefab
-} // namespace AzToolsFramework
-

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/PrefabEditManager.cpp

@@ -1,46 +0,0 @@
-/*
- * Copyright (c) Contributors to the Open 3D Engine Project.
- * For complete copyright and license terms please see the LICENSE at the root of this distribution.
- *
- * SPDX-License-Identifier: Apache-2.0 OR MIT
- *
- */
-
-#include <AzToolsFramework/UI/Prefab/PrefabEditManager.h>
-
-#include <AzCore/Serialization/SerializeContext.h>
-
-namespace AzToolsFramework
-{
-    namespace Prefab
-    {
-        PrefabEditManager::PrefabEditManager()
-        {
-            m_prefabPublicInterface = AZ::Interface<PrefabPublicInterface>::Get();
-
-            if (m_prefabPublicInterface == nullptr)
-            {
-                AZ_Assert(false, "Prefab - could not get PrefabPublicInterface on PrefabEditManager construction.");
-                return;
-            }
-
-            AZ::Interface<PrefabEditInterface>::Register(this);
-        }
-
-        PrefabEditManager::~PrefabEditManager()
-        {
-            AZ::Interface<PrefabEditInterface>::Unregister(this);
-        }
-
-        void PrefabEditManager::EditOwningPrefab(AZ::EntityId entityId)
-        {
-            m_instanceBeingEdited = m_prefabPublicInterface->GetInstanceContainerEntityId(entityId);
-        }
-
-        bool PrefabEditManager::IsOwningPrefabBeingEdited(AZ::EntityId entityId)
-        {
-            AZ::EntityId containerEntity = m_prefabPublicInterface->GetInstanceContainerEntityId(entityId);
-            return m_instanceBeingEdited == containerEntity;
-        }
-    }
-}

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/PrefabEditManager.h

@@ -1,40 +0,0 @@
-/*
- * Copyright (c) Contributors to the Open 3D Engine Project.
- * For complete copyright and license terms please see the LICENSE at the root of this distribution.
- *
- * SPDX-License-Identifier: Apache-2.0 OR MIT
- *
- */
-
-#pragma once
-
-#include <AzCore/Component/EntityId.h>
-#include <AzCore/Memory/SystemAllocator.h>
-
-#include <AzToolsFramework/Prefab/PrefabPublicInterface.h>
-#include <AzToolsFramework/UI/Prefab/PrefabEditInterface.h>
-
-namespace AzToolsFramework
-{
-    namespace Prefab
-    {
-        class PrefabEditManager final
-            : private PrefabEditInterface
-        {
-        public:
-            AZ_CLASS_ALLOCATOR(PrefabEditManager, AZ::SystemAllocator, 0);
-
-            PrefabEditManager();
-            ~PrefabEditManager();
-
-        private:
-            // PrefabEditInterface...
-            void EditOwningPrefab(AZ::EntityId entityId) override;
-            bool IsOwningPrefabBeingEdited(AZ::EntityId entityId) override;
-
-            AZ::EntityId m_instanceBeingEdited;
-
-            PrefabPublicInterface* m_prefabPublicInterface;
-        };
-    }
-}

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/PrefabIntegrationManager.cpp

@@ -22,6 +22,7 @@
 #include <AzToolsFramework/AssetBrowser/AssetBrowserBus.h>
 #include <AzToolsFramework/AssetBrowser/AssetSelectionModel.h>
 #include <AzToolsFramework/AssetBrowser/Entries/SourceAssetBrowserEntry.h>
+#include <AzToolsFramework/Prefab/PrefabFocusInterface.h>
 #include <AzToolsFramework/Prefab/PrefabLoaderInterface.h>
 #include <AzToolsFramework/ToolsComponents/EditorLayerComponentBus.h>
 #include <AzToolsFramework/UI/EditorEntityUi/EditorEntityUiInterface.h>
@@ -57,9 +58,9 @@ namespace AzToolsFramework
     {
         
         EditorEntityUiInterface* PrefabIntegrationManager::s_editorEntityUiInterface = nullptr;
-        PrefabPublicInterface* PrefabIntegrationManager::s_prefabPublicInterface = nullptr;
-        PrefabEditInterface* PrefabIntegrationManager::s_prefabEditInterface = nullptr;
+        PrefabFocusInterface* PrefabIntegrationManager::s_prefabFocusInterface = nullptr;
         PrefabLoaderInterface* PrefabIntegrationManager::s_prefabLoaderInterface = nullptr;
+        PrefabPublicInterface* PrefabIntegrationManager::s_prefabPublicInterface = nullptr;
         PrefabSystemComponentInterface* PrefabIntegrationManager::s_prefabSystemComponentInterface = nullptr;
 
         const AZStd::string PrefabIntegrationManager::s_prefabFileExtension = ".prefab";
@@ -102,13 +103,6 @@ namespace AzToolsFramework
                 return;
             }
 
-            s_prefabEditInterface = AZ::Interface<PrefabEditInterface>::Get();
-            if (s_prefabEditInterface == nullptr)
-            {
-                AZ_Assert(false, "Prefab - could not get PrefabEditInterface on PrefabIntegrationManager construction.");
-                return;
-            }
-
             s_prefabLoaderInterface = AZ::Interface<PrefabLoaderInterface>::Get();
             if (s_prefabLoaderInterface == nullptr)
             {
@@ -123,6 +117,13 @@ namespace AzToolsFramework
                 return;
             }
 
+            s_prefabFocusInterface = AZ::Interface<PrefabFocusInterface>::Get();
+            if (s_prefabFocusInterface == nullptr)
+            {
+                AZ_Assert(false, "Prefab - could not get PrefabFocusInterface on PrefabIntegrationManager construction.");
+                return;
+            }
+
             EditorContextMenuBus::Handler::BusConnect();
             PrefabInstanceContainerNotificationBus::Handler::BusConnect();
             AZ::Interface<PrefabIntegrationInterface>::Register(this);
@@ -224,7 +225,7 @@ namespace AzToolsFramework
                         // Edit Prefab
                         if (prefabWipFeaturesEnabled)
                         {
-                            bool beingEdited = s_prefabEditInterface->IsOwningPrefabBeingEdited(selectedEntity);
+                            bool beingEdited = s_prefabFocusInterface->IsOwningPrefabBeingFocused(selectedEntity);
 
                             if (!beingEdited)
                             {
@@ -428,7 +429,7 @@ namespace AzToolsFramework
 
         void PrefabIntegrationManager::ContextMenu_EditPrefab(AZ::EntityId containerEntity)
         {
-            s_prefabEditInterface->EditOwningPrefab(containerEntity);
+            s_prefabFocusInterface->FocusOnOwningPrefab(containerEntity);
         }
 
         void PrefabIntegrationManager::ContextMenu_SavePrefab(AZ::EntityId containerEntity)

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/PrefabIntegrationManager.h

@@ -17,7 +17,7 @@
 #include <AzToolsFramework/Prefab/PrefabPublicInterface.h>
 #include <AzToolsFramework/Prefab/PrefabSystemComponentInterface.h>
 #include <AzToolsFramework/UI/Prefab/LevelRootUiHandler.h>
-#include <AzToolsFramework/UI/Prefab/PrefabEditManager.h>
+
 #include <AzToolsFramework/UI/Prefab/PrefabIntegrationBus.h>
 #include <AzToolsFramework/UI/Prefab/PrefabIntegrationInterface.h>
 #include <AzToolsFramework/UI/Prefab/PrefabUiHandler.h>
@@ -28,7 +28,7 @@ namespace AzToolsFramework
 {
     namespace Prefab
     {
-
+        class PrefabFocusInterface;
         class PrefabLoaderInterface;
 
         //! Structure for saving/retrieving user settings related to prefab workflows.
@@ -80,9 +80,6 @@ namespace AzToolsFramework
             void ExecuteSavePrefabDialog(TemplateId templateId, bool useSaveAllPrefabsPreference) override;
 
         private:
-            // Manages the Edit Mode UI for prefabs
-            PrefabEditManager m_prefabEditManager;
-
             // Used to handle the UI for the level root
             LevelRootUiHandler m_levelRootUiHandler;
 
@@ -135,13 +132,12 @@ namespace AzToolsFramework
             AZStd::unique_ptr<QDialog> ConstructSavePrefabDialog(TemplateId templateId, bool useSaveAllPrefabsPreference);
             void SavePrefabsInDialog(QDialog* unsavedPrefabsDialog);
 
-
             static const AZStd::string s_prefabFileExtension;
 
             static EditorEntityUiInterface* s_editorEntityUiInterface;
-            static PrefabPublicInterface* s_prefabPublicInterface;
-            static PrefabEditInterface* s_prefabEditInterface;
+            static PrefabFocusInterface* s_prefabFocusInterface;
             static PrefabLoaderInterface* s_prefabLoaderInterface;
+            static PrefabPublicInterface* s_prefabPublicInterface;
             static PrefabSystemComponentInterface* s_prefabSystemComponentInterface;
         };
     }

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/PrefabUiHandler.cpp

@@ -8,7 +8,7 @@
 
 #include <AzToolsFramework/UI/Prefab/PrefabUiHandler.h>
 
-#include <AzToolsFramework/UI/Prefab/PrefabEditInterface.h>
+#include <AzToolsFramework/Prefab/PrefabFocusInterface.h>
 #include <AzToolsFramework/Prefab/PrefabPublicInterface.h>
 #include <AzToolsFramework/UI/Outliner/EntityOutlinerListModel.hxx>
 
@@ -26,21 +26,19 @@ namespace AzToolsFramework
 
     PrefabUiHandler::PrefabUiHandler()
     {
-        m_prefabEditInterface = AZ::Interface<Prefab::PrefabEditInterface>::Get();
-
-        if (m_prefabEditInterface == nullptr)
-        {
-            AZ_Assert(false, "PrefabUiHandler - could not get PrefabEditInterface on PrefabUiHandler construction.");
-            return;
-        }
-
         m_prefabPublicInterface = AZ::Interface<Prefab::PrefabPublicInterface>::Get();
-
         if (m_prefabPublicInterface == nullptr)
         {
             AZ_Assert(false, "PrefabUiHandler - could not get PrefabPublicInterface on PrefabUiHandler construction.");
             return;
         }
+
+        m_prefabFocusInterface = AZ::Interface<Prefab::PrefabFocusInterface>::Get();
+        if (m_prefabFocusInterface == nullptr)
+        {
+            AZ_Assert(false, "PrefabUiHandler - could not get PrefabFocusInterface on PrefabUiHandler construction.");
+            return;
+        }
     }
 
     QString PrefabUiHandler::GenerateItemInfoString(AZ::EntityId entityId) const
@@ -83,7 +81,7 @@ namespace AzToolsFramework
 
     QIcon PrefabUiHandler::GenerateItemIcon(AZ::EntityId entityId) const
     {
-        if (m_prefabEditInterface->IsOwningPrefabBeingEdited(entityId))
+        if (m_prefabFocusInterface->IsOwningPrefabBeingFocused(entityId))
         {
             return QIcon(m_prefabEditIconPath);
         }
@@ -105,7 +103,7 @@ namespace AzToolsFramework
         const bool hasVisibleChildren = index.data(EntityOutlinerListModel::ExpandedRole).value<bool>() && index.model()->hasChildren(index);
 
         QColor backgroundColor = m_prefabCapsuleColor;
-        if (m_prefabEditInterface->IsOwningPrefabBeingEdited(entityId))
+        if (m_prefabFocusInterface->IsOwningPrefabBeingFocused(entityId))
         {
             backgroundColor = m_prefabCapsuleEditColor;
         }
@@ -191,7 +189,7 @@ namespace AzToolsFramework
         const bool isLastColumn = descendantIndex.column() == EntityOutlinerListModel::ColumnLockToggle;
 
         QColor borderColor = m_prefabCapsuleColor;
-        if (m_prefabEditInterface->IsOwningPrefabBeingEdited(entityId))
+        if (m_prefabFocusInterface->IsOwningPrefabBeingFocused(entityId))
         {
             borderColor = m_prefabCapsuleEditColor;
         }

Code/Framework/AzToolsFramework/AzToolsFramework/UI/Prefab/PrefabUiHandler.h

@@ -12,9 +12,10 @@
 
 namespace AzToolsFramework
 {
+
     namespace Prefab
     {
-        class PrefabEditInterface;
+        class PrefabFocusInterface;
         class PrefabPublicInterface;
     };
 
@@ -37,7 +38,7 @@ namespace AzToolsFramework
             const QModelIndex& descendantIndex) const override;
 
     private:
-        Prefab::PrefabEditInterface* m_prefabEditInterface = nullptr;
+        Prefab::PrefabFocusInterface* m_prefabFocusInterface = nullptr;
         Prefab::PrefabPublicInterface* m_prefabPublicInterface = nullptr;
 
         static bool IsLastVisibleChild(const QModelIndex& parent, const QModelIndex& child);

Code/Framework/AzToolsFramework/AzToolsFramework/ViewportSelection/EditorHelpers.cpp

@@ -13,6 +13,7 @@
 #include <AzFramework/Viewport/CameraState.h>
 #include <AzFramework/Viewport/ViewportScreen.h>
 #include <AzFramework/Visibility/BoundsBus.h>
+#include <AzToolsFramework/FocusMode/FocusModeInterface.h>
 #include <AzToolsFramework/API/EditorViewportIconDisplayInterface.h>
 #include <AzToolsFramework/ToolsComponents/EditorEntityIconComponentBus.h>
 #include <AzToolsFramework/Viewport/ViewportMessages.h>
@@ -112,6 +113,17 @@ namespace AzToolsFramework
         }
     }
 
+    EditorHelpers::EditorHelpers(const EditorVisibleEntityDataCache* entityDataCache)
+        : m_entityDataCache(entityDataCache)
+    {
+        m_focusModeInterface = AZ::Interface<FocusModeInterface>::Get();
+        AZ_Assert(
+            m_focusModeInterface,
+            "EditorHelpers - "
+            "Focus Mode Interface could not be found. "
+            "Check that it is being correctly initialized.");
+    }
+
     AZ::EntityId EditorHelpers::HandleMouseInteraction(
         const AzFramework::CameraState& cameraState, const ViewportInteraction::MouseInteractionEvent& mouseInteraction)
     {
@@ -173,6 +185,12 @@ namespace AzToolsFramework
             }
         }
 
+        // Verify if the entity Id corresponds to an entity that is focused; if not, halt selection.
+        if (!m_focusModeInterface->IsInFocusSubTree(entityIdUnderCursor))
+        {
+            return AZ::EntityId();
+        }
+
         return entityIdUnderCursor;
     }
 

Code/Framework/AzToolsFramework/AzToolsFramework/ViewportSelection/EditorHelpers.h

@@ -22,6 +22,7 @@ namespace AzFramework
 namespace AzToolsFramework
 {
     class EditorVisibleEntityDataCache;
+    class FocusModeInterface;
 
     namespace ViewportInteraction
     {
@@ -38,10 +39,7 @@ namespace AzToolsFramework
 
         //! An EditorVisibleEntityDataCache must be passed to EditorHelpers to allow it to
         //! efficiently read entity data without resorting to EBus calls.
-        explicit EditorHelpers(const EditorVisibleEntityDataCache* entityDataCache)
-            : m_entityDataCache(entityDataCache)
-        {
-        }
+        explicit EditorHelpers(const EditorVisibleEntityDataCache* entityDataCache);
         EditorHelpers(const EditorHelpers&) = delete;
         EditorHelpers& operator=(const EditorHelpers&) = delete;
         ~EditorHelpers() = default;
@@ -62,5 +60,6 @@ namespace AzToolsFramework
 
     private:
         const EditorVisibleEntityDataCache* m_entityDataCache = nullptr; //!< Entity Data queried by the EditorHelpers.
+        const FocusModeInterface* m_focusModeInterface = nullptr;
     };
 } // namespace AzToolsFramework

Code/Framework/AzToolsFramework/AzToolsFramework/ViewportSelection/EditorTransformComponentSelection.cpp

@@ -3642,7 +3642,7 @@ namespace AzToolsFramework
         }
     }
 
-    void EditorTransformComponentSelection::OnViewportViewEntityChanged(const AZ::EntityId& newViewId)
+    void EditorTransformComponentSelection::OnViewportViewEntityChanged(const AZ::EntityId& viewEntityId)
     {
         AZ_PROFILE_FUNCTION(AzToolsFramework);
 
@@ -3650,12 +3650,12 @@ namespace AzToolsFramework
         // match the editor camera translation/orientation), record the entity id if we have
         // a manipulator tracking it (entity id exists in m_entityIdManipulator lookups)
         // and remove it when recreating manipulators (see InitializeManipulators)
-        if (newViewId.IsValid())
+        if (viewEntityId.IsValid())
         {
-            const auto entityIdLookupIt = m_entityIdManipulators.m_lookups.find(newViewId);
+            const auto entityIdLookupIt = m_entityIdManipulators.m_lookups.find(viewEntityId);
             if (entityIdLookupIt != m_entityIdManipulators.m_lookups.end())
             {
-                m_editorCameraComponentEntityId = newViewId;
+                m_editorCameraComponentEntityId = viewEntityId;
                 RegenerateManipulators();
             }
         }

Code/Framework/AzToolsFramework/AzToolsFramework/ViewportSelection/EditorTransformComponentSelection.h

@@ -270,7 +270,7 @@ namespace AzToolsFramework
         void OnTransformChanged(const AZ::Transform& localTM, const AZ::Transform& worldTM) override;
 
         // Camera::EditorCameraNotificationBus overrides ...
-        void OnViewportViewEntityChanged(const AZ::EntityId& newViewId) override;
+        void OnViewportViewEntityChanged(const AZ::EntityId& viewEntityId) override;
 
         // EditorContextVisibilityNotificationBus overrides ...
         void OnEntityVisibilityChanged(bool visibility) override;

Code/Framework/AzToolsFramework/AzToolsFramework/aztoolsframework_files.cmake

@@ -149,6 +149,9 @@ set(FILES
     Entity/SliceEditorEntityOwnershipServiceBus.h
     Fingerprinting/TypeFingerprinter.h
     Fingerprinting/TypeFingerprinter.cpp
+    FocusMode/FocusModeInterface.h
+    FocusMode/FocusModeSystemComponent.h
+    FocusMode/FocusModeSystemComponent.cpp
     Logger/TraceLogger.cpp
     Logger/TraceLogger.h
     Manipulators/AngularManipulator.cpp
@@ -629,6 +632,9 @@ set(FILES
     Prefab/PrefabDomTypes.h
     Prefab/PrefabDomUtils.h
     Prefab/PrefabDomUtils.cpp
+    Prefab/PrefabFocusHandler.h
+    Prefab/PrefabFocusHandler.cpp
+    Prefab/PrefabFocusInterface.h
     Prefab/PrefabIdTypes.h
     Prefab/PrefabLoader.h
     Prefab/PrefabLoader.cpp
@@ -721,9 +727,6 @@ set(FILES
     UI/Layer/LayerUiHandler.cpp
     UI/Prefab/LevelRootUiHandler.h
     UI/Prefab/LevelRootUiHandler.cpp
-    UI/Prefab/PrefabEditInterface.h
-    UI/Prefab/PrefabEditManager.h
-    UI/Prefab/PrefabEditManager.cpp
     UI/Prefab/PrefabIntegrationBus.h
     UI/Prefab/PrefabIntegrationManager.h
     UI/Prefab/PrefabIntegrationManager.cpp

Code/Framework/AzToolsFramework/Tests/FocusMode/EditorFocusModeTests.cpp

@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#include <AzTest/AzTest.h>
+#include <AzCore/UserSettings/UserSettingsComponent.h>
+#include <AzCore/Component/TransformBus.h>
+#include <AzToolsFramework/FocusMode/FocusModeInterface.h>
+#include <AzToolsFramework/UnitTest/AzToolsFrameworkTestHelpers.h>
+
+namespace AzToolsFramework
+{
+    class EditorFocusModeTests
+        : public ::testing::Test
+    {
+    protected:
+        void SetUp() override
+        {
+            m_app.Start(m_descriptor);
+
+            // Without this, the user settings component would attempt to save on finalize/shutdown. Since the file is
+            // shared across the whole engine, if multiple tests are run in parallel, the saving could cause a crash 
+            // in the unit tests.
+            AZ::UserSettingsComponentRequestBus::Broadcast(&AZ::UserSettingsComponentRequests::DisableSaveOnFinalize);
+
+            GenerateTestHierarchy();
+        }
+
+        void GenerateTestHierarchy() 
+        {
+            /*
+            *   City
+            *   |_  Street
+            *       |_  Car
+            *       |   |_ Passenger
+            *       |_  SportsCar
+            *           |_ Passenger
+            */
+
+            m_entityMap["cityId"] =         CreateEditorEntity("City",      AZ::EntityId());
+            m_entityMap["streetId"] =       CreateEditorEntity("Street",    m_entityMap["cityId"]);
+            m_entityMap["carId"] =          CreateEditorEntity("Car",       m_entityMap["streetId"]);
+            m_entityMap["passengerId1"] =   CreateEditorEntity("Passenger", m_entityMap["carId"]);
+            m_entityMap["sportsCarId"] =    CreateEditorEntity("SportsCar", m_entityMap["streetId"]);
+            m_entityMap["passengerId2"] =   CreateEditorEntity("Passenger", m_entityMap["sportsCarId"]);
+        }
+
+        AZ::EntityId CreateEditorEntity(const char* name, AZ::EntityId parentId)
+        {
+            AZ::Entity* entity = nullptr;
+            UnitTest::CreateDefaultEditorEntity(name, &entity);
+
+            // Parent
+            AZ::TransformBus::Event(entity->GetId(), &AZ::TransformInterface::SetParent, parentId);
+
+            return entity->GetId();
+        }
+
+        void TearDown() override
+        {
+            m_app.Stop();
+        }
+
+        UnitTest::ToolsTestApplication m_app{ "EditorFocusModeTests" };
+        AZ::ComponentApplication::Descriptor m_descriptor;
+        AZStd::unordered_map<AZStd::string, AZ::EntityId> m_entityMap;
+    };
+
+    TEST_F(EditorFocusModeTests, EditorFocusModeTests_SetFocus)
+    {
+        FocusModeInterface* focusModeInterface = AZ::Interface<FocusModeInterface>::Get();
+        EXPECT_TRUE(focusModeInterface != nullptr);
+
+        focusModeInterface->SetFocusRoot(m_entityMap["carId"]);
+        EXPECT_EQ(focusModeInterface->GetFocusRoot(), m_entityMap["carId"]);
+
+        focusModeInterface->ClearFocusRoot();
+        EXPECT_EQ(focusModeInterface->GetFocusRoot(), AZ::EntityId());
+    }
+
+    TEST_F(EditorFocusModeTests, EditorFocusModeTests_IsInFocusSubTree)
+    {
+        FocusModeInterface* focusModeInterface = AZ::Interface<FocusModeInterface>::Get();
+        EXPECT_TRUE(focusModeInterface != nullptr);
+
+        focusModeInterface->ClearFocusRoot();
+        
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["cityId"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["streetId"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["carId"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["passengerId1"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["sportsCarId"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["passengerId2"]), true);
+
+        focusModeInterface->SetFocusRoot(m_entityMap["streetId"]);
+
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["cityId"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["streetId"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["carId"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["passengerId1"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["sportsCarId"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["passengerId2"]), true);
+
+        focusModeInterface->SetFocusRoot(m_entityMap["carId"]);
+
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["cityId"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["streetId"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["carId"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["passengerId1"]), true);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["sportsCarId"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["passengerId2"]), false);
+
+        focusModeInterface->SetFocusRoot(m_entityMap["passengerId2"]);
+
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["cityId"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["streetId"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["carId"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["passengerId1"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["sportsCarId"]), false);
+        EXPECT_EQ(focusModeInterface->IsInFocusSubTree(m_entityMap["passengerId2"]), true);
+
+        focusModeInterface->ClearFocusRoot();
+    }
+}

Code/Framework/AzToolsFramework/Tests/Prefab/PrefabFocus/PrefabFocusTests.cpp

@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#include <AzCore/Component/EntityId.h>
+#include <AzToolsFramework/Entity/EditorEntityHelpers.h>
+#include <AzToolsFramework/Entity/PrefabEditorEntityOwnershipInterface.h>
+#include <AzToolsFramework/Prefab/PrefabFocusInterface.h>
+#include <Prefab/PrefabTestFixture.h>
+
+namespace UnitTest
+{
+    class PrefabFocusTests
+        : public PrefabTestFixture
+    {
+    protected:
+        void GenerateTestHierarchy()
+        {
+            /*
+             *  City (Prefab Container)
+             *  |_  City
+             *  |_  Street (Prefab Container)
+             *      |_  Car (Prefab Container)
+             *      |   |_ Passenger
+             *      |_  SportsCar (Prefab Container)
+             *          |_ Passenger
+             */
+
+            m_entityMap["passenger1"] = CreateEntity("Passenger1");
+            m_entityMap["passenger2"] = CreateEntity("Passenger2");
+            m_entityMap["city"] = CreateEntity("City");
+
+            AzToolsFramework::EditorEntityContextRequestBus::Broadcast(
+                &AzToolsFramework::EditorEntityContextRequests::HandleEntitiesAdded,
+                AzToolsFramework::EntityList{ m_entityMap["passenger1"], m_entityMap["passenger2"], m_entityMap["city"] });
+
+            AZStd::unique_ptr<AzToolsFramework::Prefab::Instance> carInstance =
+                m_prefabSystemComponent->CreatePrefab({ m_entityMap["passenger1"] }, {}, "test/car");
+            ASSERT_TRUE(carInstance);
+            m_instanceMap["car"] = carInstance.get();
+
+            AZStd::unique_ptr<AzToolsFramework::Prefab::Instance> sportsCarInstance =
+                m_prefabSystemComponent->CreatePrefab({ m_entityMap["passenger2"] }, {}, "test/sportsCar");
+            ASSERT_TRUE(sportsCarInstance);
+            m_instanceMap["sportsCar"] = sportsCarInstance.get();
+
+            AZStd::unique_ptr<AzToolsFramework::Prefab::Instance> streetInstance =
+                m_prefabSystemComponent->CreatePrefab({}, MakeInstanceList( AZStd::move(carInstance), AZStd::move(sportsCarInstance) ), "test/street");
+            ASSERT_TRUE(streetInstance);
+            m_instanceMap["street"] = streetInstance.get();
+
+            m_rootInstance =
+                m_prefabSystemComponent->CreatePrefab({ m_entityMap["city"] }, MakeInstanceList(AZStd::move(streetInstance)), "test/city");
+            ASSERT_TRUE(m_rootInstance);
+            m_instanceMap["city"] = m_rootInstance.get();
+        }
+
+        AZStd::unordered_map<AZStd::string, AZ::Entity*> m_entityMap;
+        AZStd::unordered_map<AZStd::string, Instance*> m_instanceMap;
+
+        AZStd::unique_ptr<AzToolsFramework::Prefab::Instance> m_rootInstance;
+    };
+
+    TEST_F(PrefabFocusTests, PrefabFocus_FocusOnOwningPrefab)
+    {
+        GenerateTestHierarchy();
+
+        PrefabFocusInterface* prefabFocusInterface = AZ::Interface<PrefabFocusInterface>::Get();
+        EXPECT_TRUE(prefabFocusInterface != nullptr);
+        
+        // Verify FocusOnOwningPrefab works when passing the container entity of the root prefab.
+        {
+            prefabFocusInterface->FocusOnOwningPrefab(m_instanceMap["city"]->GetContainerEntityId());
+            EXPECT_EQ(prefabFocusInterface->GetFocusedPrefabTemplateId(), m_instanceMap["city"]->GetTemplateId());
+
+            auto instance = prefabFocusInterface->GetFocusedPrefabInstance();
+            EXPECT_TRUE(instance.has_value());
+            EXPECT_EQ(&instance->get(), m_instanceMap["city"]);
+        }
+
+        // Verify FocusOnOwningPrefab works when passing a nested entity of the root prefab.
+        {
+            prefabFocusInterface->FocusOnOwningPrefab(m_entityMap["city"]->GetId());
+            EXPECT_EQ(prefabFocusInterface->GetFocusedPrefabTemplateId(), m_instanceMap["city"]->GetTemplateId());
+
+            auto instance = prefabFocusInterface->GetFocusedPrefabInstance();
+            EXPECT_TRUE(instance.has_value());
+            EXPECT_EQ(&instance->get(), m_instanceMap["city"]);
+        }
+
+        // Verify FocusOnOwningPrefab works when passing the container entity of a nested prefab.
+        {
+            prefabFocusInterface->FocusOnOwningPrefab(m_instanceMap["car"]->GetContainerEntityId());
+            EXPECT_EQ(prefabFocusInterface->GetFocusedPrefabTemplateId(), m_instanceMap["car"]->GetTemplateId());
+
+            auto instance = prefabFocusInterface->GetFocusedPrefabInstance();
+            EXPECT_TRUE(instance.has_value());
+            EXPECT_EQ(&instance->get(), m_instanceMap["car"]);
+        }
+
+        // Verify FocusOnOwningPrefab works when passing a nested entity of the a nested prefab.
+        {
+            prefabFocusInterface->FocusOnOwningPrefab(m_entityMap["passenger1"]->GetId());
+            EXPECT_EQ(prefabFocusInterface->GetFocusedPrefabTemplateId(), m_instanceMap["car"]->GetTemplateId());
+
+            auto instance = prefabFocusInterface->GetFocusedPrefabInstance();
+            EXPECT_TRUE(instance.has_value());
+            EXPECT_EQ(&instance->get(), m_instanceMap["car"]);
+        }
+
+        // Verify FocusOnOwningPrefab points to the root prefab when the focus is cleared.
+        {
+            AzToolsFramework::PrefabEditorEntityOwnershipInterface* prefabEditorEntityOwnershipInterface =
+                AZ::Interface<AzToolsFramework::PrefabEditorEntityOwnershipInterface>::Get();
+            AzToolsFramework::Prefab::InstanceOptionalReference rootPrefabInstance =
+                prefabEditorEntityOwnershipInterface->GetRootPrefabInstance();
+            EXPECT_TRUE(rootPrefabInstance.has_value());
+
+            prefabFocusInterface->FocusOnOwningPrefab(AZ::EntityId());
+            EXPECT_EQ(prefabFocusInterface->GetFocusedPrefabTemplateId(), rootPrefabInstance->get().GetTemplateId());
+
+            auto instance = prefabFocusInterface->GetFocusedPrefabInstance();
+            EXPECT_TRUE(instance.has_value());
+            EXPECT_EQ(&instance->get(), &rootPrefabInstance->get());
+        }
+
+        m_rootInstance.release();
+    }
+
+    TEST_F(PrefabFocusTests, PrefabFocus_IsOwningPrefabBeingFocused)
+    {
+        GenerateTestHierarchy();
+
+        PrefabFocusInterface* prefabFocusInterface = AZ::Interface<PrefabFocusInterface>::Get();
+        EXPECT_TRUE(prefabFocusInterface != nullptr);
+
+        // Verify IsOwningPrefabBeingFocused returns true for all entities in a focused prefab (container/nested)
+        {
+            prefabFocusInterface->FocusOnOwningPrefab(m_instanceMap["city"]->GetContainerEntityId());
+
+            EXPECT_TRUE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_instanceMap["city"]->GetContainerEntityId()));
+            EXPECT_TRUE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_entityMap["city"]->GetId()));
+        }
+
+        // Verify IsOwningPrefabBeingFocused returns false for all entities not in a focused prefab (ancestors/descendants)
+        {
+            prefabFocusInterface->FocusOnOwningPrefab(m_instanceMap["street"]->GetContainerEntityId());
+
+            EXPECT_TRUE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_instanceMap["street"]->GetContainerEntityId()));
+            EXPECT_FALSE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_instanceMap["city"]->GetContainerEntityId()));
+            EXPECT_FALSE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_entityMap["city"]->GetId()));
+            EXPECT_FALSE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_instanceMap["car"]->GetContainerEntityId()));
+            EXPECT_FALSE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_entityMap["passenger1"]->GetId()));
+        }
+
+        // Verify IsOwningPrefabBeingFocused returns false for all entities not in a focused prefab (siblings)
+        {
+            prefabFocusInterface->FocusOnOwningPrefab(m_instanceMap["sportsCar"]->GetContainerEntityId());
+
+            EXPECT_TRUE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_instanceMap["sportsCar"]->GetContainerEntityId()));
+            EXPECT_TRUE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_entityMap["passenger2"]->GetId()));
+            EXPECT_FALSE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_instanceMap["car"]->GetContainerEntityId()));
+            EXPECT_FALSE(prefabFocusInterface->IsOwningPrefabBeingFocused(m_entityMap["passenger1"]->GetId()));
+        }
+
+        m_rootInstance.release();
+    }
+
+}

Code/Framework/AzToolsFramework/Tests/aztoolsframeworktests_files.cmake

@@ -34,6 +34,7 @@ set(FILES
     EntityTestbed.h
     FileFunc.cpp
     FingerprintingTests.cpp
+    FocusMode/EditorFocusModeTests.cpp
     GenericComponentWrapperTest.cpp
     InstanceDataHierarchy.cpp
     IntegerPrimtitiveTestConfig.h
@@ -50,6 +51,7 @@ set(FILES
     Prefab/Benchmark/PrefabLoadBenchmarks.cpp
     Prefab/Benchmark/PrefabUpdateInstancesBenchmarks.cpp
     Prefab/Benchmark/SpawnableCreateBenchmarks.cpp
+    Prefab/PrefabFocus/PrefabFocusTests.cpp
     Prefab/MockPrefabFileIOActionValidator.cpp
     Prefab/MockPrefabFileIOActionValidator.h
     Prefab/PrefabDuplicateTests.cpp