Entity功能¶

如果把这个类传入带这个参数的函数，可以返回handle

        operator entt::entity() const { return m_EntityHandle; }

Addcomponent

        T& AddComponent(Args&&... args)
        {
            CORE_DEBUG_ASSERT(!HasComponent<T>(), "Entity already has component!");
            T& component = m_Scene->m_Registry.emplace<T>(m_EntityHandle, std::forward<Args>(args)...);
            m_Scene->OnComponentAdded<T>(*this, component);
            return component;
        }

Scene¶

    void Scene::DestroyEntity(Entity entity)
    {
        m_Registry.destroy(entity);
    }

    //-------------组件添加时触发的函数-------------------
    template<typename T>
    void Scene::OnComponentAdded(Entity entity, T& component)
    {
        static_assert(false);
    }

    //--------------特化模板-------------
    template<>
    void Scene::OnComponentAdded<TransformComponent>(Entity entity, TransformComponent& component)
    {
    }
    template<>
    void Scene::OnComponentAdded<CameraComponent>(Entity entity, CameraComponent& component)
    {
        component.Camera.SetViewportSize(m_ViewportWidth, m_ViewportHeight);
    }
    template<>
    void Scene::OnComponentAdded<SpriteRendererComponent>(Entity entity, SpriteRendererComponent& component)
    {
    }
    template<>
    void Scene::OnComponentAdded<TagComponent>(Entity entity, TagComponent& component)
    {
    }
    template<>
    void Scene::OnComponentAdded<NativeScriptComponent>(Entity entity, NativeScriptComponent& component)
    {
    }

IMGUI¶

创建实体¶

右键创建菜单，显示创建实体。如果有当前选中的实体（上下文） + 绘制 Add Component 按钮 + 打开addcoponent界面 + 如果打开了addconponent + 菜单选项camera + 菜单选项speiteRenderer

        if (ImGui::BeginPopupContextWindow(0, 1, false))
        {
            if (ImGui::MenuItem("Create Empty Entity"))
                m_Context->CreateEntity("Empty Entity");
            ImGui::EndPopup();
        }



        ImGui::End();
        ImGui::Begin("Properties");
        if (m_SelectionContext)
        {
            DrawComponents(m_SelectionContext);

            if (ImGui::Button("Add Component"))
                ImGui::OpenPopup("AddComponent");
            if (ImGui::BeginPopup("AddComponent"))
            {
                if (ImGui::MenuItem("Camera"))
                {
                    m_SelectionContext.AddComponent<CameraComponent>();
                    ImGui::CloseCurrentPopup();
                }
                if (ImGui::MenuItem("Sprite Renderer"))
                {
                    m_SelectionContext.AddComponent<SpriteRendererComponent>();
                    ImGui::CloseCurrentPopup();
                }
                ImGui::EndPopup();
            }
        }

删除实体¶

先建立一个创建的菜单

        bool entityDeleted = false;
        if (ImGui::BeginPopupContextItem())
        {
            if (ImGui::MenuItem("Delete Entity"))
                entityDeleted = true;
            ImGui::EndPopup();
        }

再判断这个条件来执行上下文操作

        if (entityDeleted)
        {
            m_Context->DestroyEntity(entity);
            if (m_SelectionContext == entity)
                m_SelectionContext = {};
        }

组件自己删除¶

添加一个组件自己删除的功能

        if (entity.HasComponent<SpriteRendererComponent>())
        {
            ImGui::PushStyleVar(ImGuiStyleVar_FramePadding, ImVec2{ 4, 4 });
            bool open = ImGui::TreeNodeEx((void*)typeid(SpriteRendererComponent).hash_code(), treeNodeFlags, "Sprite Renderer");
            ImGui::SameLine(ImGui::GetWindowWidth() - 25.0f);
            if (ImGui::Button("+", ImVec2{ 20, 20 }))
            {
                ImGui::OpenPopup("ComponentSettings");
            }
            ImGui::PopStyleVar();
            bool removeComponent = false;
            if (ImGui::BeginPopup("ComponentSettings"))
            {
                if (ImGui::MenuItem("Remove component"))
                    removeComponent = true;
                ImGui::EndPopup();
            }
            if (open)
            {
                auto& src = entity.GetComponent<SpriteRendererComponent>();
                ImGui::ColorEdit4("Color", glm::value_ptr(src.Color));
                ImGui::TreePop();
            }
            if (removeComponent)
                entity.RemoveComponent<SpriteRendererComponent>();
        }