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GameStateManager

Code: include/managers/GameStateManager.hpp, src/managers/GameStateManager.cpp

Overview

GameStateManager owns the active game-state stack and transition order (push / pop / change / clear-stack). It is state-machine infrastructure: it lives under managers/ for historical layout reasons, but it is not a domain manager like AI or World.

Managers serve the states. Domain managers do not advance the state graph. States request transitions via this API; domain managers are called by states during enter / exit (or by this class only for the shared full-screen UI clear).

See ARCHITECTURE.md for the ownership table and transition model.

Transition model

Standard exit-then-enter for replaces:

API Behavior
changeState(id) Exit top → if stack empty, clear UI → enter new. On enter failure, re-enter previous top when possible.
changeStateClearingStack(id) Exit entire stack → clear UI → enter new. On enter failure, best-effort restore previous stack.
pushState(id) Pause top → enter overlay (no full UI clear).
popState() Exit top → resume new top (no full UI clear).

Full-screen UI clear uses UIManager::prepareForStateTransition() as a service after exits, before destination enter().

States are identified by GameStateId (not free-form strings).

API (current)

void addState(std::unique_ptr<GameState> state);
void pushState(GameStateId stateId);
void popState();
void changeState(GameStateId stateId);
void changeStateClearingStack(GameStateId stateId);

void update(float deltaTime);
void handleInput();
void recordGPUVertices(VoidLight::GPURenderer& gpuRenderer, float interpolationAlpha);
void renderGPUScene(VoidLight::GPURenderer& gpuRenderer, SDL_GPURenderPass* scenePass, float interpolationAlpha);
void renderGPUUI(VoidLight::GPURenderer& gpuRenderer, SDL_GPURenderPass* swapchainPass);

bool hasState(GameStateId stateId) const;
std::shared_ptr<GameState> getState(GameStateId stateId) const;
void removeState(GameStateId stateId);
void clearAllStates();

Usage sketch

GameStateManager gsm;
gsm.addState(std::make_unique<MainMenuState>());
gsm.addState(std::make_unique<GamePlayState>());
gsm.pushState(GameStateId::MAIN_MENU);

// Frame:
gsm.handleInput();
gsm.update(deltaTime);
// GPU path via GameEngine → gsm.recordGPUVertices / renderGPU*

// From a state:
mp_stateManager->changeState(GameStateId::GAME_PLAY);
// Pause over gameplay:
mp_stateManager->pushState(GameStateId::PAUSE);
// Leave gameplay stack to menu:
mp_stateManager->changeStateClearingStack(GameStateId::MAIN_MENU);

Thread safety

Not thread-safe. All transitions and updates run on the main thread.

See also