Add "frame" : scrollable area.

examples/component/radiobox_in_frame.cpp

@@ -0,0 +1,34 @@
+#include "ftxui/component/checkbox.hpp"
+#include "ftxui/component/container.hpp"
+#include "ftxui/component/input.hpp"
+#include "ftxui/component/menu.hpp"
+#include "ftxui/component/radiobox.hpp"
+#include "ftxui/component/screen_interactive.hpp"
+#include "ftxui/component/toggle.hpp"
+#include "ftxui/screen/string.hpp"
+
+using namespace ftxui;
+
+class MyComponent : public Component {
+  RadioBox radiobox;
+
+ public:
+  MyComponent() {
+    for(int i = 0; i<30; ++i) {
+      radiobox.entries.push_back(L"RadioBox " + to_wstring(i));
+    }
+    Add(&radiobox);
+  }
+
+  Element Render() override {
+    return radiobox.Render() | frame | size(20,10) | border;
+  }
+};
+
+int main(int argc, const char* argv[]) {
+  auto screen = ScreenInteractive::FitComponent();
+  MyComponent component;
+  screen.Loop(&component);
+
+  return 0;
+}