We've learned how to save our level designs, translating the in-memory state of actors and grid settings into a binary file using SDL's file I/O capabilities. Now, we need the ability to bring those saved designs back to life in the editor. This lesson focuses entirely on deserialization - the process of reading the binary data and reconstructing the original objects. We'll implement the `Level::Load()` function, carefully using `SDL_ReadU8()`, `SDL_ReadLE32()`, and other `SDL_RWops` functions to read data in the sequence it was saved. A major focus will be the **Factory Pattern**. Since we only store a type identifier (like `1` for `BlueBlock`), we need a way to invoke the correct constructor. We'll achieve this by: - Adding static `Construct()` methods to actor subclasses. - Storing pointers to these methods (using `std::function`). - Using the type identifier read from the file to select and call the right factory function. This ensures our loading logic is flexible and can handle different actor types correctly. By the end of this lesson, we'll have completed our level editor project! Screenshot showing our completed level editor

Screenshot showing our completed level editor

## Level Deserialization With the serialization logic in place, we can now turn our attention to the reverse process: deserialization. The `Level::Load()` function is where we'll read the binary data from a .bin file and reconstruct the level state within the editor. The first step mirrors saving: we need to open the file. We construct the filename using the `LoadedLevel` number and attempt to open it using `SDL_RWFromFile()`, this time with the mode "rb" for reading in binary. If the file doesn't exist or cannot be opened, `SDL_RWFromFile()` returns `nullptr`, which we check for. Before reading any data, we also call `Actors.clear()` to remove any existing actors from the level currently loaded in the editor. ```c++ // Editor/Source/Level.cpp // ... void Level::Load() { Actors.clear(); std::string FileName{std::format( "Assets/Level{}.bin", LoadedLevel )}; SDL_RWops* Handle{SDL_RWFromFile( FileName.c_str(), "rb")}; if (!Handle) { CheckSDLError("Loading Level"); return; } // TODO: Deserialize stuff SDL_RWclose(Handle); } ``` Our deserializing code must closely align with our serialization code. We must deserialize our objects respecting the size, order, and endianness in which they were serialized. Our serialized data has three `Uint8` values representing the version, grid width and grid height in that order, followed by a little-endian `Uint32` representing the number of actors in the level. Let's deserialize them in that order, and log out what we found: ```c++ // Editor/Source/Level.cpp // ... void Level::Load() { // Actors.clear(); std::string FileName{std::format( "Assets/Level{}.bin", LoadedLevel )}; SDL_RWops* Handle{SDL_RWFromFile( FileName.c_str(), "rb")}; if (!Handle) { CheckSDLError("Loading Level"); return; } // Uint8 FileVersion{SDL_ReadU8(Handle)}; if (FileVersion != VERSION) { // This file is from a different version of // our software - react as needed } Uint8 GridWidth{SDL_ReadU8(Handle)}; Uint8 GridHeight{SDL_ReadU8(Handle)}; Uint32 ActorCount{SDL_ReadLE32(Handle)}; std::cout << std::format( "Loading a version " "{} level ({}x{}) with {} actors\n", FileVersion, GridWidth, GridHeight, ActorCount ); // TODO: Load Actors SDL_RWclose(Handle); } ``` Currently, our loading code exists but isn't called automatically when the editor starts. To make the editor load Level 1 immediately on launch, we can call `Load()` directly from the `Level` class's constructor. Since the `LoadedLevel` member defaults to `1`, adding `Load()` inside the constructor body will trigger the loading sequence for "Assets/Level1.bin" as soon as the `Level` object is created within the `Scene`. ```c++ // Editor/Level.h // ... namespace Editor { // ... class Level { public: Level(Scene& ParentScene) : ParentScene{ParentScene} { Load(); } // ... }; } ``` If a "Level1.bin" file exists from a previous save, its data should now be read and logged. ```c++ // Loading a version 1 level (13x6) with 2 actors ``` ## Actor Factories To load our actors, let's use some of the techniques we covered in our lesson on function pointers. Each specific `Actor` subtype that can exist in our serialized data will have a function that is responsible for deserializing that data, constructing the object based on that data, and returning a pointer to it. The natural place to define these functions is alongside the types themselves, so we'll add them as a static functions to our `Actor` subtypes, like `BlueBlock` and `GreenBlock`. Let's start with `BlueBlock`. To construct a `BlueBlock`, we need two things: - A reference to the parent `Scene`. Our `Level` 's `Load()` function can pass this when it's calling our factory function. - An `SDL_Rect` representing its position and size. The position (`x`, `y`) can be calculated from the grid row and grid column values in the serialized data. The size (`w`, `h`) is the same for all `BlueBlock` instances, and is currently stored as static `WIDTH` and `HEIGHT` values. All of our block types will need to calculate this `SDL_Rect`, so let's add a helper function to the `Actor` base class that they can all use: ```c++ // Editor/Actor.h // ... namespace Editor { class Scene; class Actor { public: // ... static SDL_Rect GeneratePositionRectangle( SDL_RWops* Handle, int Width, int Height ) { using namespace Config::Editor; Uint8 GridRow{SDL_ReadU8(Handle)}; Uint8 GridCol{SDL_ReadU8(Handle)}; SDL_Rect R{0, 0, Width, Height}; R.x = GridCol * HORIZONTAL_GRID_SNAP; R.y = GridRow * VERTICAL_GRID_SNAP; return R; } // ... }; } ``` Back in `BlueBlock`, let's add our `static` `Construct()` function: ```c++ // Editor/Blocks.h // ... namespace Editor{ class BlueBlock : public Actor { public: // ... static std::unique_ptr Construct( SDL_RWops* Handle, Scene& ParentScene ) { return std::make_unique( ParentScene, GeneratePositionRectangle( Handle, WIDTH, HEIGHT)); } }; } ``` ### Deserializing Green Blocks `GreenBlock::Construct()` will be similar - we'll also just grab the contrived `SomeNumber` and `SomeArray` data from the file and apply it to the object we create: ```c++ // Editor/Blocks.h // ... namespace Editor{ // ... class GreenBlock : public Actor { public: // ... static std::unique_ptr Construct( SDL_RWops* Handle, Scene& ParentScene ) { auto NewActor{std::make_unique( ParentScene, GeneratePositionRectangle( Handle, WIDTH, HEIGHT))}; NewActor->SomeNumber = SDL_ReadLE16(Handle); Uint32 ArraySize{SDL_ReadLE32(Handle)}; NewActor->SomeArray.resize(ArraySize); for (int i{0}; i < ArraySize; ++i) { NewActor->SomeArray[i] = SDL_ReadLE32(Handle); } return NewActor; } }; } ``` ## Using the Factories Back in `Level::Load()`, let's use these factories to recreate our full level. We'll store our loaders as `std::function` wrappers. We only need them in our `Level.cpp` file, so let's add them in an anonymous namespace in that file, above our `Load()` function: ```c++ // Editor/Source/Level.cpp // ... #include // ... namespace{ using namespace Config; using ActorLoaderFunc = std::function< std::unique_ptr(SDL_RWops*, Scene&)>; std::vector ActorLoaders{ {}, // Index 0 BlueBlock::Construct, // Index 1 GreenBlock::Construct, // Index 2 }; } // ... ``` The effect of putting `ActorLoaders` in an anonymous namespace is that it can now only be accessed from within this same source file, `Level.cpp`. This prevents us from polluting our global scope with symbols that are only relevant to one area of our program. The indices of this `ActorLoaders` array corresponds to the numeric actor types in our serialized data. As a reminder, our `ActorType` enum is set up like this: ```c++ enum class ActorType : Uint8 { Actor = 0, BlueBlock = 1, GreenBlock = 2, }; ``` So, we store the loader for `BlueBlock` at index 1, and `GreenBlock` at index 2. Our program doesn't allow basic `Actor` instances to be added to the level, so we'll never need to deserialize those. As such, we just store an empty `std::functional` at the base `Actor` index (`0`).

### Design Improvements and Maps When our design requires us to keep two values in sync, we should generally try to improve our approach. Inevitably we, or someone on our team, will make some change that breaks that link, thereby introducing a bug. We'll learn better techniques for implementing these patterns later, but one simple improvement is to use a `std::unordered_map` as an alternative to a `std::vector`. This lets make the mapping from `ActorType` values to their corresponding `std::functional` factory more explicit: ```c++ // Editor/Source/Level.cpp // ... #include // // ... namespace{ using namespace Config; using ActorLoaderFunc = std::function< std::unique_ptr(SDL_RWops*, Scene&)>; using enum ActorType;// std::unordered_map< ActorType, ActorLoaderFunc > ActorLoaders{ {Actor, {}},// {BlueBlock, BlueBlock::Construct},// {GreenBlock, GreenBlock::Construct}// }; } // ... ``` Our `Load()` function can use this `std::unordered_map` in much the same way it uses a `std::vector`, using the `[]` operator to access the correct loader. The only difference is that it needs to cast the `Uint8` representing the actor's type back to the `Config::ActorType` enum value it originated from: ```c++ Uint8 Type{SDL_ReadU8(Handle)}; auto Loader{ActorLoaders[ // When ActorLoaders is a vector: Type// // When ActorLoaders is an unordered_map: static_cast(Type)// ]}; ``` We cover maps in more detail later in the course.

All that's left to do is update our `Load()` function to loop `ActorCount` times, grab the type of each actor, call the corresponding `std::functional` to create it, and then add it to the level: ```c++ // Editor/Source/Level.cpp // ... void Level::Load() { // Actors.clear(); std::string FileName{std::format( "Assets/Level{}.bin", LoadedLevel )}; SDL_RWops* Handle{SDL_RWFromFile( FileName.c_str(), "rb")}; if (!Handle) { CheckSDLError("Loading Level"); return; } Uint8 FileVersion{SDL_ReadU8(Handle)}; if (FileVersion != VERSION) { // This file is from a different version of // our software - react as needed } Uint8 GridWidth{SDL_ReadU8(Handle)}; Uint8 GridHeight{SDL_ReadU8(Handle)}; Uint32 ActorCount{SDL_ReadLE32(Handle)}; std::cout << std::format( "Loading a version " "{} level ({}x{}) with {} actors\n", FileVersion, GridWidth, GridHeight, ActorCount ); // for (size_t i{0}; i < ActorCount; ++i) { Uint8 ActorType{SDL_ReadU8(Handle)}; auto Loader{ActorLoaders[ActorType]}; if (Loader) { ActorPtr NewActor{Loader(Handle, ParentScene)}; NewActor->SetLocation(ActorLocation::Level); AddToLevel(std::move(NewActor)); } else { std::cout << "Error: No Loader for Actor " "Type " << ActorType << '\n'; } } SDL_RWclose(Handle); } ``` With all our plumbing in place, we can just add new actors to our editor as needed. In the Complete Code section below, we've added `RedBlock`, `OrangeBlock`, and `YellowBlock` actors by following the exact same pattern. 1. Add our new types to the `ActorType` enum 2. Add new classes that inherit from `Actor` 3. Add our necessary functions - `Construct()`, `Clone()`, `GetActorType()`, and the constructor. This can be done manually of using our preprocessor macro if we created one 4. Add an instance of our new type to the `ActorMenu`. With that, our program is now be complete! We can create levels which get saved in the `Assets/` directory alongside our program executable. We can also load those levels later, and see them restored in our `Editor` for us to modify. Screenshot showing our completed level editor

## Complete Code Complete versions of the files we changed in this lesson are provided below: ```c++ #pragma once #include #include #include #include namespace UserEvents{ #ifdef WITH_EDITOR inline Uint32 ACTOR_DRAG{SDL_RegisterEvents(1)}; inline Uint32 LOAD_LEVEL{SDL_RegisterEvents(1)}; inline Uint32 SAVE_LEVEL{SDL_RegisterEvents(1)}; inline Uint32 SAVE_AND_PLAY_LEVEL{ SDL_RegisterEvents(1)}; inline Uint32 LEVEL_EDIT{SDL_RegisterEvents(1)}; #endif inline Uint32 LAUNCH_LEVEL{ SDL_RegisterEvents(1)}; } namespace Config { enum class ActorType : Uint8 { Actor = 0, BlueBlock = 1, GreenBlock = 2, CyanBlock = 3, OrangeBlock = 4, RedBlock = 5, YellowBlock = 6, }; inline const std::vector BUTTON_COLORS{ SDL_Color{15, 15, 15, 255}, // Normal SDL_Color{15, 155, 15, 255}, // Hover SDL_Color{225, 15, 15, 255}, // Active SDL_Color{60, 60, 60, 255} // Disabled }; inline constexpr SDL_Color FONT_COLOR{ 255, 255, 255, 255}; inline const std::string FONT{ "Assets/Rubik-SemiBold.ttf"}; } #ifdef WITH_EDITOR namespace Config::Editor { inline const Uint8 VERSION{1}; // Level inline const int HORIZONTAL_GRID_SNAP{50}; inline const int VERTICAL_GRID_SNAP{25}; inline const Uint8 GRID_WIDTH{13}; inline const Uint8 GRID_HEIGHT{6}; inline const int LEVEL_WIDTH{ HORIZONTAL_GRID_SNAP * GRID_WIDTH}; inline const int LEVEL_HEIGHT{ VERTICAL_GRID_SNAP * GRID_HEIGHT}; inline constexpr SDL_Color LEVEL_BACKGROUND{ 50, 50, 50, 255}; // ActorMenu inline const int ACTOR_MENU_WIDTH{70}; inline const int ACTOR_MENU_POSITION_X{LEVEL_WIDTH}; inline const SDL_Color ACTOR_MENU_BACKGROUND{ 15, 15, 15, 255}; inline const int PADDING{10}; // Window inline const std::string WINDOW_TITLE{"Editor"}; inline const int WINDOW_WIDTH{ LEVEL_WIDTH + ACTOR_MENU_WIDTH}; inline const int WINDOW_HEIGHT{LEVEL_HEIGHT + 50}; inline const SDL_Color WINDOW_BACKGROUND{ 35, 35, 35, 255}; } #endif inline void CheckSDLError( const std::string& Msg) { #ifdef CHECK_ERRORS const char* error = SDL_GetError(); if (*error != '\0') { std::cerr << Msg << " Error: " << error << '\n'; SDL_ClearError(); } #endif } ``` ```c++ #pragma once #include #include "Image.h" enum class ActorLocation { Level, Menu }; namespace Editor { class Scene; class Actor { public: Actor( Scene& ParentScene, const SDL_Rect& Rect, Image& Image ) : ParentScene{ParentScene}, Rect{Rect}, Art{Image} {} bool HasMouseFocus() const; virtual bool HandleEvent(const SDL_Event& E); void Tick(float DeltaTime) {} void Render(SDL_Surface* Surface) { if (isVisible) { Art.Render(Surface, Rect); } } const SDL_Rect& GetRect() const { return Rect; } const SDL_Point& GetDragOffset() const { return DragOffset; } const Image& GetArt() const { return Art; } SDL_Point GetPosition() const { return {Rect.x, Rect.y}; } void SetPosition(int x, int y) { Rect.x = x; Rect.y = y; } virtual std::unique_ptr Clone() const { return std::make_unique(*this); } ActorLocation GetLocation() const { return Location; } void SetLocation(ActorLocation NewLocation) { Location = NewLocation; } bool GetIsVisible() const { return isVisible; } void SetIsVisible(bool NewVisibility) { isVisible = NewVisibility; } virtual Config::ActorType GetActorType() const { return Config::ActorType::Actor; } virtual void Serialize(SDL_RWops* Handle) const { using namespace Config::Editor; Uint8 ActorType{static_cast(GetActorType())}; SDL_WriteU8(Handle, ActorType); Uint8 GridRow = Rect.y / VERTICAL_GRID_SNAP; SDL_WriteU8(Handle, GridRow); Uint8 GridCol = Rect.x / HORIZONTAL_GRID_SNAP; SDL_WriteU8(Handle, GridCol); } static SDL_Rect GeneratePositionRectangle( SDL_RWops* Handle, int Width, int Height ) { using namespace Config::Editor; Uint8 GridRow{SDL_ReadU8(Handle)}; Uint8 GridCol{SDL_ReadU8(Handle)}; SDL_Rect R{0, 0, Width, Height}; R.x = GridCol * HORIZONTAL_GRID_SNAP; R.y = GridRow * VERTICAL_GRID_SNAP; return R; } protected: Scene& ParentScene; SDL_Rect Rect; Image& Art; SDL_Point DragOffset{0, 0}; ActorLocation Location{ActorLocation::Menu}; bool isVisible{true}; }; } ``` ```c++ #pragma once #include #include #include #include "Actor.h" #include "Blocks.h" #include "Config.h" namespace Editor { class Scene; using ActorPtr = std::unique_ptr; using ActorPtrs = std::vector; class ActorMenu { public: ActorMenu(Scene& ParentScene) : ParentScene{ParentScene} { using namespace Config::Editor; Actors.emplace_back( std::make_unique( GetScene(), SDL_Rect{ ACTOR_MENU_POSITION_X + PADDING, PADDING, 0, 0 } ) ); Actors.emplace_back( std::make_unique( GetScene(), SDL_Rect{ ACTOR_MENU_POSITION_X + PADDING, BlueBlock::HEIGHT + PADDING * 2, 0, 0 } ) ); Actors.emplace_back( std::make_unique( GetScene(), SDL_Rect{ ACTOR_MENU_POSITION_X + PADDING, BlueBlock::HEIGHT * 2 + PADDING * 3, 0, 0 } ) ); Actors.emplace_back( std::make_unique( GetScene(), SDL_Rect{ ACTOR_MENU_POSITION_X + PADDING, BlueBlock::HEIGHT * 3 + PADDING * 4, 0, 0 } ) ); Actors.emplace_back( std::make_unique( GetScene(), SDL_Rect{ ACTOR_MENU_POSITION_X + PADDING, BlueBlock::HEIGHT * 4 + PADDING * 5, 0, 0 } ) ); } void HandleEvent(const SDL_Event& E) { for (ActorPtr& A : Actors) { A->HandleEvent(E); } } void Tick(float DeltaTime) { for (ActorPtr& A : Actors) { A->Tick(DeltaTime); } } void Render(SDL_Surface* Surface) { using namespace Config::Editor; auto [r, g, b, a]{ACTOR_MENU_BACKGROUND}; SDL_FillRect( Surface, &Rect, SDL_MapRGB(Surface->format, r, g, b) ); for (ActorPtr& A : Actors) { A->Render(Surface); } } Scene& GetScene() const { return ParentScene; } private: Scene& ParentScene; ActorPtrs Actors; SDL_Rect Rect{ Config::Editor::ACTOR_MENU_POSITION_X, 0, Config::Editor::ACTOR_MENU_WIDTH, Config::Editor::WINDOW_HEIGHT }; }; } ``` ```c++ #pragma once #include "Actor.h" namespace Editor{ class BlueBlock : public Actor { public: static constexpr int WIDTH{50}; static constexpr int HEIGHT{25}; BlueBlock( Scene& ParentScene, SDL_Rect Rect ); std::unique_ptr Clone() const override { return std::make_unique(*this); } Config::ActorType GetActorType() const override { return Config::ActorType::BlueBlock; } static std::unique_ptr Construct( SDL_RWops* Handle, Scene& ParentScene ) { return std::make_unique( ParentScene, GeneratePositionRectangle( Handle, WIDTH, HEIGHT)); } }; class GreenBlock : public Actor { public: static constexpr int WIDTH{50}; static constexpr int HEIGHT{25}; GreenBlock(Scene& ParentScene, SDL_Rect Rect); Config::ActorType GetActorType() const override { return Config::ActorType::GreenBlock; } std::unique_ptr Clone() const override { return std::make_unique< GreenBlock>(*this); } Sint16 SomeNumber{32}; std::vector SomeArray{1, 2, 3}; void Serialize(SDL_RWops* Handle) const override { Actor::Serialize(Handle); SDL_WriteLE16(Handle, SomeNumber); SDL_WriteLE32(Handle, SomeArray.size()); for (Sint32 Num : SomeArray) { SDL_WriteLE32(Handle, Num); } } static std::unique_ptr Construct( SDL_RWops* Handle, Scene& ParentScene ) { auto NewActor{std::make_unique( ParentScene, GeneratePositionRectangle( Handle, WIDTH, HEIGHT))}; NewActor->SomeNumber = SDL_ReadLE16(Handle); Uint32 ArraySize{SDL_ReadLE32(Handle)}; NewActor->SomeArray.resize(ArraySize); for (int i{0}; i < ArraySize; ++i) { NewActor->SomeArray[i] = SDL_ReadLE32(Handle); } return NewActor; } }; class CyanBlock : public Actor { public: static constexpr int WIDTH{50}; static constexpr int HEIGHT{25}; CyanBlock(Scene& ParentScene, SDL_Rect Rect); Config::ActorType GetActorType() const override { return Config::ActorType::CyanBlock; } std::unique_ptr Clone() const override { return std::make_unique< CyanBlock>(*this); } void Serialize( SDL_RWops* Handle) const override { Actor::Serialize(Handle); } static std::unique_ptr Construct( SDL_RWops* Handle, Scene& ParentScene ) { using namespace Config::Editor; return std::make_unique( ParentScene, GeneratePositionRectangle( Handle, WIDTH, HEIGHT)); } }; class OrangeBlock : public Actor { public: static constexpr int WIDTH{50}; static constexpr int HEIGHT{25}; OrangeBlock(Scene& ParentScene, SDL_Rect Rect); Config::ActorType GetActorType() const override { return Config::ActorType::OrangeBlock; } std::unique_ptr Clone() const override { return std::make_unique< OrangeBlock>(*this); } void Serialize( SDL_RWops* Handle) const override { Actor::Serialize(Handle); } static std::unique_ptr Construct( SDL_RWops* Handle, Scene& ParentScene ) { using namespace Config::Editor; return std::make_unique( ParentScene, GeneratePositionRectangle( Handle, WIDTH, HEIGHT)); } }; class RedBlock : public Actor { public: static constexpr int WIDTH{50}; static constexpr int HEIGHT{25}; RedBlock(Scene& ParentScene, SDL_Rect Rect); Config::ActorType GetActorType() const override { return Config::ActorType::RedBlock; } std::unique_ptr Clone() const override { return std::make_unique< RedBlock>(*this); } void Serialize( SDL_RWops* Handle) const override { Actor::Serialize(Handle); } static std::unique_ptr Construct( SDL_RWops* Handle, Scene& ParentScene ) { using namespace Config::Editor; return std::make_unique( ParentScene, GeneratePositionRectangle( Handle, WIDTH, HEIGHT)); } }; class YellowBlock : public Actor { public: static constexpr int WIDTH{50}; static constexpr int HEIGHT{25}; YellowBlock(Scene& ParentScene, SDL_Rect Rect); Config::ActorType GetActorType() const override { return Config::ActorType::YellowBlock; } std::unique_ptr Clone() const override { return std::make_unique(*this); } void Serialize( SDL_RWops* Handle) const override { Actor::Serialize(Handle); } static std::unique_ptr Construct( SDL_RWops* Handle, Scene& ParentScene ) { using namespace Config::Editor; return std::make_unique( ParentScene, GeneratePositionRectangle( Handle, WIDTH, HEIGHT)); } }; } ``` ```c++ #include "Editor/Blocks.h" #include "Editor/Scene.h" using namespace Editor; BlueBlock::BlueBlock( Scene& ParentScene, SDL_Rect Rect) : Actor{ ParentScene, SDL_Rect{Rect.x, Rect.y, WIDTH, HEIGHT}, ParentScene.GetAssets().BlueBlock} {} GreenBlock::GreenBlock( Scene& ParentScene, SDL_Rect Rect) : Actor{ ParentScene, SDL_Rect{Rect.x, Rect.y, WIDTH, HEIGHT}, ParentScene.GetAssets().GreenBlock} {} CyanBlock::CyanBlock( Scene& ParentScene, SDL_Rect Rect) : Actor{ ParentScene, SDL_Rect{Rect.x, Rect.y, WIDTH, HEIGHT}, ParentScene.GetAssets().CyanBlock} {} OrangeBlock::OrangeBlock( Scene& ParentScene, SDL_Rect Rect) : Actor{ ParentScene, SDL_Rect{Rect.x, Rect.y, WIDTH, HEIGHT}, ParentScene.GetAssets().OrangeBlock} {} RedBlock::RedBlock( Scene& ParentScene, SDL_Rect Rect) : Actor{ ParentScene, SDL_Rect{Rect.x, Rect.y, WIDTH, HEIGHT}, ParentScene.GetAssets().RedBlock} {} YellowBlock::YellowBlock( Scene& ParentScene, SDL_Rect Rect) : Actor{ ParentScene, SDL_Rect{Rect.x, Rect.y, WIDTH, HEIGHT}, ParentScene.GetAssets().YellowBlock} {} ``` ```c++ #pragma once #include #include #include #include "Actor.h" namespace Editor { class Scene; using ActorPtr = std::unique_ptr; using ActorPtrs = std::vector; class Level { public: Level(Scene& ParentScene) : ParentScene{ParentScene} { Load(); } void HandleEvent(const SDL_Event& E); void HandleDrop(Actor* DragActor); void Tick(float DeltaTime); void Render(SDL_Surface* Surface); bool HasMouseFocus() const; void AddToLevel(ActorPtr NewActor); SDL_Point SnapToGridPosition(int x, int y); void DeleteAtPosition( int x, int y, const Actor* Unless); void Load(); void Save(); void SaveAndPlay(); private: Scene& ParentScene; ActorPtrs Actors; Actor* SelectedActor{nullptr}; int LoadedLevel{1}; SDL_Rect Rect{ 0, 0, Config::Editor::LEVEL_WIDTH, Config::Editor::LEVEL_HEIGHT }; }; } ``` ```c++ // Editor/Source/Level.cpp // ... #include #include #include "Editor/Level.h" #include #include "Editor/Scene.h" using namespace Editor; void Level::HandleEvent(const SDL_Event& E) { using namespace std::views; using namespace UserEvents; for (ActorPtr& A : reverse(Actors)) { if (A->HandleEvent(E)) { break; } } if ( E.type == SDL_MOUSEBUTTONDOWN && E.button.button == SDL_BUTTON_LEFT ) { SelectedActor = nullptr; } else if ( E.type == SDL_KEYDOWN && E.key.keysym.sym == SDLK_DELETE && SelectedActor ) { std::erase_if(Actors, [&](ActorPtr& Actor){ return Actor.get() == SelectedActor; } ); SelectedActor = nullptr; } else if (E.type == LOAD_LEVEL) { LoadedLevel = E.user.code; Load(); } else if (E.type == SAVE_LEVEL) { Save(); } else if (E.type == SAVE_AND_PLAY_LEVEL) { SaveAndPlay(); } } void Level::Tick(float DeltaTime) { for (ActorPtr& A : Actors) { A->Tick(DeltaTime); } } void Level::Render(SDL_Surface* Surface) { auto [r, g, b, a]{ Config::Editor::LEVEL_BACKGROUND }; SDL_FillRect(Surface, &Rect, SDL_MapRGB( Surface->format, r, g, b)); for (ActorPtr& A : Actors) { if (SelectedActor && A.get() == SelectedActor && SelectedActor->GetIsVisible() ) { auto [x, y, w, h]{ SelectedActor->GetRect() }; SDL_Rect Rect{x - 1, y - 1, w + 2, h + 2}; SDL_FillRect(Surface, &Rect, SDL_MapRGB( Surface->format, 255, 255, 255) ); } A->Render(Surface); } } void Level::HandleDrop(Actor* DragActor) { DragActor->SetIsVisible(true); if (!HasMouseFocus()) { return; } int MouseX, MouseY; SDL_GetMouseState(&MouseX, &MouseY); auto [GridX, GridY]{ SnapToGridPosition( MouseX, MouseY ) }; DeleteAtPosition(GridX, GridY, DragActor); using enum ActorLocation; if (DragActor->GetLocation() == Menu) { ActorPtr NewActor{DragActor->Clone()}; NewActor->SetPosition(GridX, GridY); SelectedActor = NewActor.get(); AddToLevel(std::move(NewActor)); } else { DragActor->SetPosition(GridX, GridY); SelectedActor = DragActor; } SDL_Event E{UserEvents::LEVEL_EDIT}; SDL_PushEvent(&E); } void Level::AddToLevel(ActorPtr NewActor) { NewActor->SetLocation(ActorLocation::Level); Actors.push_back(std::move(NewActor)); } bool Level::HasMouseFocus() const { if (!ParentScene.HasMouseFocus()) { return false; } int x, y; SDL_GetGlobalMouseState(&x, &y); auto [WinX, WinY]{ ParentScene.GetWindow().GetPosition() }; if ( x >= WinX + Config::Editor::LEVEL_WIDTH || y >= WinY + Config::Editor::LEVEL_HEIGHT ) { return false; } return true; } SDL_Point Level::SnapToGridPosition( int x, int y ) { using namespace Config::Editor; int sx{HORIZONTAL_GRID_SNAP}; int sy{VERTICAL_GRID_SNAP}; return { (x / sx) * sx, (y / sy) * sy, }; } void Level::DeleteAtPosition( int x, int y, const Actor* Unless ) { std::erase_if(Actors, [&](const ActorPtr& Actor){ auto [ax, ay]{Actor->GetPosition()}; return ax == x && ay == y && Actor.get() != Unless; } ); } namespace{ using namespace Config; using ActorLoaderFunc = std::function< std::unique_ptr(SDL_RWops*, Scene&)>; std::vector ActorLoaders{ {}, BlueBlock::Construct, GreenBlock::Construct, CyanBlock::Construct, OrangeBlock::Construct, RedBlock::Construct, YellowBlock::Construct, }; } void Level::Load() { Actors.clear(); std::string FileName{std::format( "Assets/Level{}.bin", LoadedLevel )}; SDL_RWops* Handle{SDL_RWFromFile( FileName.c_str(), "rb")}; if (!Handle) { CheckSDLError("Loading Level"); return; } Uint8 FileVersion{SDL_ReadU8(Handle)}; if (FileVersion != VERSION) { // This file is from a different version of // our software - react as needed } Uint8 GridWidth{SDL_ReadU8(Handle)}; Uint8 GridHeight{SDL_ReadU8(Handle)}; Uint32 ActorCount{SDL_ReadLE32(Handle)}; std::cout << std::format( "Loading a version " "{} level ({}x{}) with {} actors\n", FileVersion, GridWidth, GridHeight, ActorCount ); for (size_t i{0}; i < ActorCount; ++i) { Uint8 ActorType{SDL_ReadU8(Handle)}; auto Loader{ActorLoaders[ActorType]}; if (Loader) { ActorPtr NewActor{Loader(Handle, ParentScene)}; NewActor->SetLocation(ActorLocation::Level); AddToLevel(std::move(NewActor)); } else { std::cout << "Error: No Loader for Actor " "Type " << ActorType << '\n'; } } SDL_RWclose(Handle); } void Level::Save() { std::string FileName{ std::format("Assets/Level{}.bin", LoadedLevel) }; SDL_RWops* Handle{SDL_RWFromFile( FileName.c_str(), "wb") }; if (!Handle) { CheckSDLError("Saving Level"); Handle = SDL_RWFromFile( FileName.c_str(), "w+b" ); } using namespace Config::Editor; SDL_WriteU8(Handle, VERSION); SDL_WriteU8(Handle, GRID_WIDTH); SDL_WriteU8(Handle, GRID_HEIGHT); SDL_WriteLE32(Handle, Actors.size()); for (const ActorPtr& A : Actors) { A->Serialize(Handle); } SDL_RWclose(Handle); } void Level::SaveAndPlay() { Save(); SDL_Event E{UserEvents::LAUNCH_LEVEL}; E.user.code = LoadedLevel; SDL_PushEvent(&E); } ``` The remaining project files, which were not changed in this lesson, are available below: ```c++ #include "Editor/Actor.h" #include "Editor/Scene.h" using namespace Editor; bool Actor::HandleEvent(const SDL_Event& E) { if ( E.type == SDL_MOUSEBUTTONDOWN && E.button.button == SDL_BUTTON_LEFT && HasMouseFocus() ) { DragOffset.x = E.button.x - Rect.x; DragOffset.y = E.button.y - Rect.y; if (Location != ActorLocation::Menu) { SetIsVisible(false); } SDL_Event DragEvent{UserEvents::ACTOR_DRAG}; DragEvent.user.data1 = this; SDL_PushEvent(&DragEvent); return true; } return false; } bool Actor::HasMouseFocus() const { if (!ParentScene.HasMouseFocus()) { return false; } int x, y; SDL_GetMouseState(&x, &y); if ( x < Rect.x || x > Rect.x + Rect.w || y < Rect.y || y > Rect.y + Rect.h ) { return false; } return true; } ``` ```c++ #include "Editor/ActorTooltip.h" #include "Editor/Scene.h" using namespace Editor; ActorTooltip::ActorTooltip(Scene& ParentScene) : ParentScene{ParentScene} { SDLWindow = SDL_CreateWindow( "Tooltip", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 100, 100, SDL_WINDOW_HIDDEN | SDL_WINDOW_TOOLTIP | SDL_WINDOW_BORDERLESS | SDL_WINDOW_SKIP_TASKBAR | SDL_WINDOW_ALWAYS_ON_TOP ); CheckSDLError("Creating Tooltip Window"); DenyCursor = SDL_CreateSystemCursor( SDL_SYSTEM_CURSOR_NO ); CheckSDLError("Creating DenyCursor"); } ActorTooltip::~ActorTooltip() { if (!SDL_WasInit(SDL_INIT_VIDEO)) return; if (SDLWindow) { SDL_DestroyWindow(SDLWindow); } if (DenyCursor) { SDL_FreeCursor(DenyCursor); } } void ActorTooltip::Render() { if (!isVisible) return; DragActor->GetArt().Render( GetSurface(), SDL_Rect{ 0, 0, DragActor->GetRect().w, DragActor->GetRect().h }); SDL_UpdateWindowSurface(SDLWindow); } void ActorTooltip::Tick(float DeltaTime) { if (!isVisible) return; auto Buttons{ SDL_GetGlobalMouseState( nullptr, nullptr)}; if (!(Buttons & SDL_BUTTON_LEFT)) { SetIsVisible(false); ParentScene.GetLevel().HandleDrop(DragActor); } else { PositionWindow(); } } void ActorTooltip::PositionWindow() { int x, y; SDL_GetGlobalMouseState(&x, &y); if (ParentScene.GetLevel().HasMouseFocus()) { SDL_SetWindowOpacity(SDLWindow, 1); SDL_SetCursor(SDL_GetDefaultCursor()); auto [WinX, WinY]{ ParentScene.GetWindow().GetPosition() }; auto [GridX, GridY]{ ParentScene.GetLevel().SnapToGridPosition( x - WinX, y - WinY ) }; SDL_SetWindowPosition( SDLWindow, WinX + GridX, WinY + GridY ); } else { auto [DragOffsetX, DragOffsetY]{ DragActor->GetDragOffset() }; SDL_SetWindowPosition( SDLWindow, x - DragOffsetX, y - DragOffsetY ); SDL_SetWindowOpacity(SDLWindow, 0.5); SDL_SetCursor(DenyCursor); } } void ActorTooltip::HandleEvent( const SDL_Event& E) { using namespace UserEvents; if (E.type == ACTOR_DRAG) { DragActor = static_cast( E.user.data1 ); SDL_SetWindowSize( SDLWindow, DragActor->GetRect().w, DragActor->GetRect().h ); SetIsVisible(true); } } void ActorTooltip::SetIsVisible(bool Visible) { isVisible = Visible; if (isVisible) { SDL_ShowWindow(SDLWindow); } else { SDL_HideWindow(SDLWindow); SDL_SetCursor(SDL_GetDefaultCursor()); SDL_SetWindowOpacity(SDLWindow, 1); } } ``` ```c++ #include "Editor/Button.h" #include "Editor/Scene.h" using namespace Editor; void Button::HandleEvent(const SDL_Event& E) { using enum ButtonState; if (E.type == SDL_MOUSEBUTTONDOWN && E.button.button == SDL_BUTTON_LEFT && State == Hover ) { HandleLeftClick(); } else if ( E.type == SDL_MOUSEMOTION && ParentScene.HasMouseFocus() ) { SDL_Point Pos{E.motion.x, E.motion.y}; bool Hovering(SDL_PointInRect(&Pos, &Rect)); if (State == Normal && Hovering) { State = Hover; } else if (State == Hover && !Hovering) { State = Normal; } } } void Button::Render(SDL_Surface* Surface) { using namespace Config; auto [r, g, b, a]{ BUTTON_COLORS[static_cast(State)]}; SDL_FillRect(Surface, &Rect, SDL_MapRGB( Surface->format, r, g, b )); ButtonText.Render(Surface, &Rect); } ``` ```c++ #pragma once #include #include "Actor.h" namespace Editor{ class Scene; class ActorTooltip { public: ActorTooltip(Scene& ParentScene); ~ActorTooltip(); ActorTooltip(const ActorTooltip&) = delete; ActorTooltip& operator=(const ActorTooltip&) = delete; void Render(); void Tick(float DeltaTime); void PositionWindow(); void HandleEvent(const SDL_Event& E); void SetIsVisible(bool NewVisibility); SDL_Surface* GetSurface() const { return SDL_GetWindowSurface(SDLWindow); } private: bool isVisible{false}; SDL_Window* SDLWindow{nullptr}; Actor* DragActor{nullptr}; Scene& ParentScene; SDL_Cursor* DenyCursor{nullptr}; }; } ``` ```c++ #pragma once #include "Image.h" namespace Editor { struct AssetManager { Image BlueBlock{"Assets/Brick_Blue_A.png"}; Image GreenBlock{"Assets/Brick_Green_A.png"}; Image CyanBlock{"Assets/Brick_Cyan_A.png"}; Image OrangeBlock{"Assets/Brick_Orange_A.png"}; Image RedBlock{"Assets/Brick_Red_A.png"}; Image YellowBlock{"Assets/Brick_Yellow_A.png"}; }; } ``` ```c++ #pragma once #include #include #include "Text.h" enum class ButtonState { Normal = 0, Hover = 1, Active = 2, Disabled = 3 }; namespace Editor{ class Scene; class Button { public: Button( Scene& ParentScene, const std::string& Text, SDL_Rect Rect ) : ButtonText{Text, 20}, Rect{Rect}, ParentScene{ParentScene} {} virtual void HandleLeftClick() {} void HandleEvent(const SDL_Event& E); void Render(SDL_Surface* Surface); void Tick(float DeltaTime) {} ButtonState GetState() const { return State; } void SetState(ButtonState NewState) { State = NewState; } private: Scene& ParentScene; ButtonState State{ButtonState::Normal}; Text ButtonText; SDL_Rect Rect; }; } ``` ```c++ #pragma once; #include "Button.h" namespace Editor{ using namespace Config::Editor; class LoadLevelButton : public Button { public: constexpr static int WIDTH{40}; LoadLevelButton(Scene& ParentScene, int Level) : Level{Level}, Button { ParentScene, std::to_string(Level), { PADDING * Level + WIDTH * (Level-1), LEVEL_HEIGHT + PADDING, WIDTH, 30 } } { if (Level == 1) { SetState(ButtonState::Active); } } void HandleEvent(const SDL_Event& E) { Button::HandleEvent(E); if (E.type == UserEvents::LOAD_LEVEL) { if (E.user.code == Level) { SetState(ButtonState::Active); } else { SetState(ButtonState::Normal); } } } void HandleLeftClick() override { SDL_Event E{UserEvents::LOAD_LEVEL}; E.user.code = Level; SDL_PushEvent(&E); } private: int Level; }; class PlayLevelButton : public Button { public: constexpr static int WIDTH{70}; PlayLevelButton(Scene& ParentScene) : Button { ParentScene, "PLAY", { LEVEL_WIDTH - WIDTH - PADDING, LEVEL_HEIGHT + PADDING, WIDTH, 30 } } {} void HandleLeftClick() override { using namespace UserEvents; SDL_Event E{SAVE_AND_PLAY_LEVEL}; SDL_PushEvent(&E); } }; class SaveLevelButton : public Button { public: constexpr static int WIDTH{70}; SaveLevelButton(Scene& ParentScene) : Button { ParentScene, "SAVE", { LEVEL_WIDTH - WIDTH - PlayLevelButton::WIDTH - PADDING * 2, LEVEL_HEIGHT + PADDING, WIDTH, 30 } } { SetState(ButtonState::Disabled); } void HandleEvent(const SDL_Event& E) { Button::HandleEvent(E); using namespace UserEvents; if (E.type == LEVEL_EDIT) { SetState(ButtonState::Normal); } else if ( E.type == LOAD_LEVEL || E.type == SAVE_LEVEL || E.type == SAVE_AND_PLAY_LEVEL ) { SetState(ButtonState::Disabled); } } void HandleLeftClick() override { SDL_Event E{UserEvents::SAVE_LEVEL}; SDL_PushEvent(&E); } }; } ``` ```c++ #pragma once #include #include #include #include "Config.h" namespace Editor{ class Image { public: Image() = default; Image(const std::string& Path) : ImageSurface{IMG_Load(Path.c_str()) } { CheckSDLError("Loading Image"); } void Render( SDL_Surface* Surface, SDL_Rect Rect ) const { SDL_BlitScaled( ImageSurface, nullptr, Surface, &Rect); } Image(Image&& Other) noexcept : ImageSurface(Other.ImageSurface) { Other.ImageSurface = nullptr; } ~Image() { if (ImageSurface) { SDL_FreeSurface(ImageSurface); } } Image(const Image&) = delete; Image& operator=(const Image&) = delete; private: SDL_Surface* ImageSurface{nullptr}; }; } ``` ```c++ #pragma once #include #include "ActorMenu.h" #include "ActorTooltip.h" #include "AssetManager.h" #include "Level.h" #include "Window.h" #include "EditorButtons.h" namespace Editor{ class Scene { public: Scene(Window& ParentWindow) : ParentWindow{ParentWindow} {} void HandleEvent(const SDL_Event& E) { ActorShelf.HandleEvent(E); TooltipWindow.HandleEvent(E); CurrentLevel.HandleEvent(E); LoadButton1.HandleEvent(E); LoadButton2.HandleEvent(E); LoadButton3.HandleEvent(E); SaveButton.HandleEvent(E); PlayButton.HandleEvent(E); } void Tick(float DeltaTime) { ActorShelf.Tick(DeltaTime); TooltipWindow.Tick(DeltaTime); CurrentLevel.Tick(DeltaTime); LoadButton1.Tick(DeltaTime); LoadButton2.Tick(DeltaTime); LoadButton3.Tick(DeltaTime); SaveButton.Tick(DeltaTime); PlayButton.Tick(DeltaTime); } void Render(SDL_Surface* Surface) { ActorShelf.Render(Surface); TooltipWindow.Render(); CurrentLevel.Render(Surface); LoadButton1.Render(Surface); LoadButton2.Render(Surface); LoadButton3.Render(Surface); SaveButton.Render(Surface); PlayButton.Render(Surface); } AssetManager& GetAssets() { return Assets; } bool HasMouseFocus() const { return ParentWindow.HasMouseFocus(); } Window& GetWindow() const { return ParentWindow; } Level& GetLevel() { return CurrentLevel; } private: ActorMenu ActorShelf{*this}; ActorTooltip TooltipWindow{*this}; Level CurrentLevel{*this}; Window& ParentWindow; AssetManager Assets; LoadLevelButton LoadButton1{*this, 1}; LoadLevelButton LoadButton2{*this, 2}; LoadLevelButton LoadButton3{*this, 3}; SaveLevelButton SaveButton{*this}; PlayLevelButton PlayButton{*this}; }; } ``` ```c++ #pragma once #include #include #include #include "Config.h" namespace Editor{ class Text { public: Text( const std::string& InitialText, int FontSize ) : Content(InitialText) { Font = TTF_OpenFont( Config::FONT.c_str(), FontSize); CheckSDLError("Opening Font"); SetText(InitialText); } ~Text() { if (!SDL_WasInit(SDL_INIT_VIDEO)) { return; } if (TextSurface) { SDL_FreeSurface(TextSurface); } if (Font) { TTF_CloseFont(Font); } } Text(const Text&) = delete; Text& operator=(const Text&) = delete; void SetText(const std::string& NewText) { Content = NewText; if (TextSurface) { SDL_FreeSurface(TextSurface); } TextSurface = TTF_RenderText_Blended(Font, Content.c_str(), Config::FONT_COLOR); CheckSDLError("Creating Text Surface"); } void Render( SDL_Surface* Surface, SDL_Rect* Rect ) { if (!TextSurface) return; int TextW{TextSurface->w}; int TextH{TextSurface->h}; // Center the text SDL_Rect Destination { Rect->x + (Rect->w - TextW) / 2, Rect->y + (Rect->h - TextH) / 2, TextW, TextH }; SDL_BlitSurface( TextSurface, nullptr, Surface, &Destination ); } private: std::string Content; TTF_Font* Font{nullptr}; SDL_Surface* TextSurface{nullptr}; }; } ``` ```c++ #pragma once #include #include "Config.h" namespace Editor{ class Window { public: Window() { SDLWindow = SDL_CreateWindow( Config::Editor::WINDOW_TITLE.c_str(), SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, Config::Editor::WINDOW_WIDTH, Config::Editor::WINDOW_HEIGHT, 0 ); CheckSDLError("Creating Editor Window"); } ~Window() { if (SDLWindow && SDL_WasInit(SDL_INIT_VIDEO)) { SDL_DestroyWindow(SDLWindow); } } Window(const Window&) = delete; Window& operator=(const Window&) = delete; void Render() { auto [r, g, b, a]{ Config::Editor::WINDOW_BACKGROUND }; SDL_FillRect( GetSurface(), nullptr, SDL_MapRGB(GetSurface()->format, r, g, b)); } void Update() { SDL_UpdateWindowSurface(SDLWindow); } SDL_Surface* GetSurface() const { return SDL_GetWindowSurface(SDLWindow); } bool HasMouseFocus() const { int x, y, w, h, MouseX, MouseY; SDL_GetWindowPosition(SDLWindow, &x, &y); SDL_GetWindowSize(SDLWindow, &w, &h); SDL_GetGlobalMouseState(&MouseX, &MouseY); if ( MouseX < x || MouseX > x + w || MouseY < y || MouseY > y + h ) { return false; } return true; } SDL_Point GetPosition() const { int x, y; SDL_GetWindowPosition(SDLWindow, &x, &y); return {x, y}; } SDL_Point GetSize() const { int x, y; SDL_GetWindowSize(SDLWindow, &x, &y); return {x, y}; } private: SDL_Window* SDLWindow{nullptr}; }; } ``` ```c++ #include #include #include #include "Config.h" #ifdef WITH_EDITOR #include "Editor/Scene.h" #include "Editor/Window.h" #endif int main(int argc, char** argv) { SDL_Init(SDL_INIT_VIDEO); CheckSDLError("SDL_Init"); IMG_Init(IMG_INIT_PNG); CheckSDLError("IMG_Init"); TTF_Init(); CheckSDLError("TTF_Init"); #ifdef WITH_EDITOR Editor::Window EditorWindow; Editor::Scene EditorScene{EditorWindow}; #endif Uint64 LastTick{SDL_GetPerformanceCounter()}; SDL_Event E; while (true) { while (SDL_PollEvent(&E)) { #ifdef WITH_EDITOR EditorScene.HandleEvent(E); #endif if ( E.type == SDL_QUIT || E.type == SDL_WINDOWEVENT && E.window.event == SDL_WINDOWEVENT_CLOSE ) { TTF_Quit(); IMG_Quit(); SDL_Quit(); return 0; } } Uint64 CurrentTick{SDL_GetPerformanceCounter()}; float DeltaTime{ static_cast(CurrentTick - LastTick) / SDL_GetPerformanceFrequency() }; LastTick = CurrentTick; #ifdef WITH_EDITOR EditorScene.Tick(DeltaTime); EditorWindow.Render(); EditorScene.Render(EditorWindow.GetSurface()); EditorWindow.Update(); #endif } return 0; } ``` ```c++ // cmake_minimum_required(VERSION 3.16) set(CMAKE_CXX_STANDARD 20) project(Editor VERSION 1.0.0) add_executable(Editor "main.cpp" "Editor/Source/Button.cpp" "Editor/Source/Blocks.cpp" "Editor/Source/Actor.cpp" "Editor/Source/ActorTooltip.cpp" "Editor/Source/Level.cpp" ) target_compile_definitions( Editor PUBLIC WITH_EDITOR CHECK_ERRORS ) target_include_directories( Editor PUBLIC ${PROJECT_SOURCE_DIR} ) add_subdirectory(external/SDL) add_subdirectory(external/SDL_image) add_subdirectory(external/SDL_ttf) target_link_libraries(Editor PRIVATE SDL2 SDL2_image SDL2_ttf ) if (WIN32) target_link_libraries( Editor PRIVATE SDL2main ) endif() set(AssetDirectory "${PROJECT_SOURCE_DIR}/Assets") add_custom_command( TARGET Editor POST_BUILD COMMAND ${CMAKE_COMMAND} -E copy_if_different "$" "$" "$" "$" COMMAND ${CMAKE_COMMAND} -E copy_directory_if_different "${AssetDirectory}" "$/Assets" VERBATIM ) ``` ## Summary In this final part of the editor's core implementation, we focused on deserialization - loading the saved level data back into the editor. We implemented the `Level::Load()` method, using `SDL_RWops` to read the binary file created in the previous lesson. We emphasized matching the read operations (`SDL_ReadU8()`, `SDL_ReadLE32()`, etc) to the write operations used during serialization. To handle reconstructing actors of unknown types, we introduced static factory methods (`Construct`) within each actor class. These factories read the necessary data from the file handle and returned a `unique_ptr`. A `std::vector` was used to map the serialized actor type ID to the corresponding factory function. Key Takeaways: - Loading involves opening files with "rb" mode using `SDL_RWFromFile()`. - Error check the result of `SDL_RWFromFile()`. - Read data in the exact sequence and format it was written. - Static factory methods provide a clean way to handle object construction during deserialization. - `std::function` allows storing pointers to these static methods for dynamic dispatch. - Remember to convert grid coordinates back to rendering coordinates when setting actor positions.

Loading Saved Levels

Understanding the Basics

Practical Applications

Common Mistakes

Next Steps

Additional Resources

Assessment Preparation