Started work on prefabs.

src/dawn/scene/Prefab.hpp

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+// Copyright (c) 2022 Dominic Masters
+// 
+// This software is released under the MIT License.
+// https://opensource.org/licenses/MIT
+
+#pragma once
+#include "SceneItem.hpp"
+#include "SceneItemComponent.hpp"
+#include "scene/components/Components.hpp"
+#include "util/array.hpp"
+
+namespace Dawn {
+  class Prefab {
+    public:
+      /**
+       * Returns a list of assets that this prefab requires to be loaded for the
+       * instanciation to work.
+       * 
+       * @param man Asset Manager to retreive the assets from.
+       * @return List of required assets, includes sibling/child assets.
+       */
+      static virtual std::vector<Asset*> getAssets(AssetManager *man) = 0;
+
+      /**
+       * Create a scene item from this prefab.
+       * 
+       * @param scene Scene to add the item to.
+       * @return The created scene item for this prefab.
+       */
+      static virtual SceneItem * create(Scene *scene) = 0;
+  };
+
+  template<class T>
+  class UIPrefab : public Prefab {
+    public:
+      /** @deprecated */
+      static SceneItem * create(Scene *scene) override {
+        assertUnreachable();
+      }
+
+      /**
+       * Applies a UI Prefab styling to an existing UI Element.
+       * 
+       * @param existing Existing item to apply styling to.
+       */
+      static virtual void uiApply(T *existing) = 0;
+      
+      /**
+       * Creates a UI Item from this prefab.
+       * 
+       * @param canvas Canvas to create this item on to.
+       * @return Pointer to the created UI Item.
+       */
+      static virtual T * uiCreate(UICanvas *canvas) {
+        auto item = canvas->addElement<T>();
+        uiApply(item);
+        return item;
+      }
+  }
+}