初始提交: UE5.3项目基础框架

Plugins/CesiumForUnreal/Source/CesiumRuntime/Public/CesiumSubLevelSwitcherComponent.h

@@ -0,0 +1,112 @@
+// Copyright 2020-2024 CesiumGS, Inc. and Contributors
+
+#pragma once
+
+#include "Components/ActorComponent.h"
+#include "CesiumSubLevelSwitcherComponent.generated.h"
+
+class ACesiumGeoreference;
+class ALevelInstance;
+class ULevelStreaming;
+class UWorld;
+
+/**
+ * Manages the asynchronous switching between sub-levels, making sure that a
+ * previous sub-level is hidden before the CesiumGeoreference is switched to a
+ * new location and the next sub-level is loaded.
+ */
+UCLASS(ClassGroup = "Cesium")
+class CESIUMRUNTIME_API UCesiumSubLevelSwitcherComponent
+    : public UActorComponent {
+  GENERATED_BODY()
+
+public:
+  UCesiumSubLevelSwitcherComponent();
+
+  /**
+   * Gets the list of sub-levels that are currently registered with this
+   * switcher.
+   */
+  UFUNCTION(BlueprintPure, Category = "Cesium|Sub-levels")
+  TArray<ALevelInstance*> GetRegisteredSubLevels() const noexcept;
+
+  /**
+   * Gets the list of sub-levels that are currently registered with this
+   * switcher. This is slightly more efficient than GetRegisteredSubLevels but
+   * is not accessible from Blueprints.
+   */
+  const TArray<TWeakObjectPtr<ALevelInstance>>&
+  GetRegisteredSubLevelsWeak() const noexcept {
+    return this->_sublevels;
+  }
+
+  /**
+   * Gets the sub-level that is currently active, or nullptr if none are active.
+   */
+  UFUNCTION(BlueprintPure, Category = "Cesium|Sub-levels")
+  ALevelInstance* GetCurrentSubLevel() const noexcept;
+
+  /**
+   * Gets the sub-level that is in the process of becoming active. If nullptr,
+   * the target is a state where no sub-levels are active.
+   */
+  UFUNCTION(BlueprintPure, Category = "Cesium|Sub-levels")
+  ALevelInstance* GetTargetSubLevel() const noexcept;
+
+  /**
+   * Sets the sub-level that should be active. The switcher will asynchronously
+   * load and show this sub-level.
+   */
+  UFUNCTION(BlueprintCallable, Category = "Cesium|Sub-levels")
+  void SetTargetSubLevel(ALevelInstance* LevelInstance) noexcept;
+
+private:
+  // To allow the sub-level to register/unregister itself with the functions
+  // below.
+  friend class UCesiumSubLevelComponent;
+  friend class CesiumEditorSubLevelMutex;
+
+  /**
+   * Registers a sub-level with this switcher. The switcher will ensure that
+   * no more than one of the registered sub-levels is active at any time.
+   */
+  void RegisterSubLevel(ALevelInstance* pSubLevel) noexcept;
+
+  /**
+   * Unregisters a sub-level from this switcher. This is primarily used if the
+   * sub-level is being destroyed or reparented.
+   */
+  void UnregisterSubLevel(ALevelInstance* pSubLevel) noexcept;
+
+  virtual void TickComponent(
+      float DeltaTime,
+      enum ELevelTick TickType,
+      FActorComponentTickFunction* ThisTickFunction) override;
+
+  void _updateSubLevelStateGame();
+#if WITH_EDITOR
+  void _updateSubLevelStateEditor();
+#endif
+
+  /**
+   * Finds the ULevelStreaming instance, if any, associated with a given
+   * sub-level.
+   */
+  ULevelStreaming*
+  _getLevelStreamingForSubLevel(ALevelInstance* SubLevel) const;
+
+  // Don't save/load or copy this.
+  UPROPERTY(Transient, DuplicateTransient, TextExportTransient)
+  TArray<TWeakObjectPtr<ALevelInstance>> _sublevels;
+
+  // Don't save/load or copy this.
+  UPROPERTY(Transient, DuplicateTransient, TextExportTransient)
+  TWeakObjectPtr<ALevelInstance> _pCurrent = nullptr;
+
+  // Save/load this, but don't copy it.
+  UPROPERTY(DuplicateTransient, TextExportTransient)
+  TWeakObjectPtr<ALevelInstance> _pTarget = nullptr;
+
+  bool _doExtraChecksOnNextTick = false;
+  bool _isTransitioningSubLevels = false;
+};