Support reentrant screen. (#196)

examples/component/CMakeLists.txt

@@ -2,6 +2,7 @@ set(DIRECTORY_LIB component)
 
 example(button)
 example(checkbox)
+example(nested_screen)
 example(checkbox_in_frame)
 example(composition)
 example(gallery)

examples/component/nested_screen.cpp

@@ -0,0 +1,51 @@
+#include <memory>  // for shared_ptr, __shared_ptr_access
+#include <string>  // for operator+, to_wstring
+
+#include "ftxui/component/captured_mouse.hpp"  // for ftxui
+#include "ftxui/component/component.hpp"  // for Button, Horizontal, Renderer
+#include "ftxui/component/component_base.hpp"      // for ComponentBase
+#include "ftxui/component/component_options.hpp"   // for ButtonOption
+#include "ftxui/component/screen_interactive.hpp"  // for ScreenInteractive
+#include "ftxui/dom/elements.hpp"  // for separator, gauge, Element, operator|, vbox, border
+
+using namespace ftxui;
+
+void Nested(std::string path) {
+  auto screen = ScreenInteractive::FitComponent();
+  auto back_button = Button("Back", screen.ExitLoopClosure());
+  auto goto_1 = Button("Goto /1", [path] { Nested(path + "/1"); });
+  auto goto_2 = Button("Goto /2", [path] { Nested(path + "/2"); });
+  auto goto_3 = Button("Goto /3", [path] { Nested(path + "/3"); });
+  auto layout = Container::Vertical({
+      back_button,
+      goto_1,
+      goto_2,
+      goto_3,
+  });
+  auto renderer = Renderer(layout, [&] {
+    return vbox({
+        text("path: " + path),
+        separator(),
+        back_button->Render(),
+        goto_1->Render(),
+        goto_2->Render(),
+        goto_3->Render(),
+    }) | border;
+  });
+  screen.Loop(renderer);
+}
+
+int main(int argc, const char* argv[]) {
+  auto screen = ScreenInteractive::FitComponent();
+  auto button_quit = Button("Quit", screen.ExitLoopClosure());
+  auto button_nested = Button("Nested", [] { Nested(""); });
+  screen.Loop(Container::Vertical({
+    button_quit,
+    button_nested,
+  }));
+  return 0;
+}
+
+// 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.