The collapsible element. (#294)

src/ftxui/component/collapsible.cpp

@@ -0,0 +1,55 @@
+#include <memory>  // for make_unique, __shared_ptr_access, __shared_ptr_access<>::element_type, shared_ptr
+#include <utility>  // for move
+
+#include "ftxui/component/component.hpp"       // for Make, Collapsible
+#include "ftxui/component/component_base.hpp"  // for ComponentBase, Component
+#include "ftxui/component/event.hpp"           // for Event
+#include "ftxui/dom/elements.hpp"              // for Element
+#include "ftxui/dom/node.hpp"                  // for Node
+
+namespace ftxui {
+
+/// @brief A collapsible component. It display a checkbox with an arrow. Once
+/// activated, the children is displayed.
+/// @params label The label of the checkbox.
+/// @params child The children to display.
+/// @params show Hold the state about whether the children is displayed or not.
+/// 
+/// ### Example
+/// ```cpp
+/// auto component = Collapsible("Show details", details);
+/// ```
+///
+/// ### Output
+/// ```
+/// 
+/// ▼ Show details
+/// <details component>
+/// ```
+Component Collapsible(ConstStringRef label,
+                      Component child,
+                      Ref<bool> show) {
+  class Impl : public ComponentBase {
+   public:
+    Impl(ConstStringRef label, Component child, Ref<bool> show)
+        : label_(label), show_(std::move(show)) {
+          CheckboxOption opt;
+          opt.style_checked = "▼ ";
+          opt.style_unchecked = "▶ ";
+          Add(Container::Vertical({
+              Checkbox(label_, show_.operator->(), opt),
+              Maybe(std::move(child), show_.operator->()),
+          }));
+    }
+    ConstStringRef label_;
+    Ref<bool> show_;
+  };
+
+  return Make<Impl>(label, std::move(child), std::move(show));
+}
+
+}  // namespace ftxui
+
+// Copyright 2021 Arthur Sonzogni. All rights reserved.
+// Use of this source code is governed by the MIT license that can be found in
+// the LICENSE file.

src/ftxui/component/maybe.cpp

@@ -9,10 +9,10 @@
 
 namespace ftxui {
 
-Component Maybe(Component child, bool* show) {
+Component Maybe(Component child, const bool* show) {
   class Impl : public ComponentBase {
    public:
-    Impl(bool* show) : show_(show) {}
+    Impl(const bool* show) : show_(show) {}
 
    private:
     Element Render() override {
@@ -25,7 +25,7 @@ Component Maybe(Component child, bool* show) {
       return *show_ && ComponentBase::OnEvent(event);
     }
 
-    bool* show_;
+    const bool* show_;
   };
 
   auto maybe = Make<Impl>(show);