Make component more functionnal

include/ftxui/component/component_base.hpp

@@ -0,0 +1,81 @@
+#ifndef FTXUI_COMPONENT_BASE_HPP
+#define FTXUI_COMPONENT_BASE_HPP
+
+#include <memory>  // for unique_ptr
+#include <vector>  // for vector
+
+#include "ftxui/component/captured_mouse.hpp"  // for CaptureMouse
+#include "ftxui/dom/elements.hpp"              // for Element
+
+namespace ftxui {
+
+class Delegate;
+class Focus;
+struct Event;
+
+class ComponentBase;
+using Component = std::shared_ptr<ComponentBase>;
+using Components = std::vector<Component>;
+
+/// @brief It implement rendering itself as ftxui::Element. It implement
+/// keyboard navigation by responding to ftxui::Event.
+/// @ingroup component
+class ComponentBase {
+ public:
+  // Constructor/Destructor.
+  ComponentBase() = default;
+  virtual ~ComponentBase();
+
+  // ComponentBase hierarchy.
+  ComponentBase* Parent();
+  void Add(Component children);
+
+  // Renders the component.
+  virtual Element Render();
+
+  // Handles an event.
+  // By default, reduce on children with a lazy OR.
+  //
+  // Returns whether the event was handled or not.
+  virtual bool OnEvent(Event);
+
+  // Focus management ----------------------------------------------------------
+  //
+  // If this component contains children, this indicates which one is active,
+  // nullptr if none is active.
+  //
+  // We say an element has the focus if the chain of ActiveChild() from the
+  // root component contains this object.
+  virtual Component ActiveChild();
+
+  // Whether this is the active child of its parent.
+  bool Active();
+  // Whether all the ancestors are active.
+  bool Focused();
+
+  // Make the |child| to be the "active" one.
+  virtual void SetActiveChild(ComponentBase* child);
+  void SetActiveChild(Component child);
+
+  // Configure all the ancestors to give focus to this component.
+  void TakeFocus();
+
+ protected:
+  CapturedMouse CaptureMouse(const Event& event);
+
+  std::vector<Component> children_;
+
+ private:
+  ComponentBase* parent_ = nullptr;
+  void Detach();
+};
+
+using Component = std::shared_ptr<ComponentBase>;
+
+}  // namespace ftxui
+
+#endif /* end of include guard: FTXUI_COMPONENT_BASE_HPP */
+
+// Copyright 2020 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.