Make component more functionnal

src/ftxui/component/checkbox.cpp

@@ -9,29 +9,62 @@
 
 namespace ftxui {
 
-Element CheckBox::Render() {
+/// @brief Draw checkable element.
+/// @param label The label of the checkbox.
+/// @param checked Whether the checkbox is checked or not.
+/// @ingroup component
+/// @see CheckboxBase
+///
+/// ### Example
+///
+/// ```cpp
+/// auto screen = ScreenInteractive::FitComponent();
+/// std::wstring label = L"Make a sandwidth";
+/// bool checked = false;
+/// Component checkbox = Checkbox(&label, &checked);
+/// screen.Loop(checkbox)
+/// ```
+///
+/// ### Output
+///
+/// ```bash
+/// ☐ Make a sandwitch
+/// ```
+Component Checkbox(const std::wstring* label, bool* checked) {
+  return Make<CheckboxBase>(label, checked);
+}
+
+// static
+CheckboxBase* From(Component component) {
+  return static_cast<CheckboxBase*>(component.get());
+}
+
+CheckboxBase::CheckboxBase(const std::wstring* label, bool* state)
+    : label_(label), state_(state) {}
+
+Element CheckboxBase::Render() {
   bool is_focused = Focused();
   auto style = is_focused ? focused_style : unfocused_style;
-  auto focus_management = is_focused ? focus : state ? select : nothing;
-  return hbox(text(state ? checked : unchecked),
-              text(label) | style | focus_management) |
+  auto focus_management = is_focused ? focus : *state_ ? select : nothing;
+  return hbox(text(*state_ ? checked : unchecked),
+              text(*label_) | style | focus_management) |
          reflect(box_);
 }
 
-bool CheckBox::OnEvent(Event event) {
+bool CheckboxBase::OnEvent(Event event) {
   if (event.is_mouse())
     return OnMouseEvent(event);
 
   if (event == Event::Character(' ') || event == Event::Return) {
-    state = !state;
+    *state_ = !*state_;
     on_change();
     return true;
   }
   return false;
 }
 
-bool CheckBox::OnMouseEvent(Event event) {
-    if (!CaptureMouse(event))
+bool CheckboxBase::OnMouseEvent(Event event) {
+  if (!CaptureMouse(event))
     return false;
   if (!box_.Contain(event.mouse().x, event.mouse().y))
     return false;
@@ -40,7 +73,7 @@ bool CheckBox::OnMouseEvent(Event event) {
 
   if (event.mouse().button == Mouse::Left &&
       event.mouse().motion == Mouse::Pressed) {
-    state = !state;
+    *state_ = !*state_;
     on_change();
     return true;
   }