Make the focused button to take the focus inside frame. (#371)

This resolves:
https://github.com/ArthurSonzogni/FTXUI/issues/370

CHANGELOG.md

@@ -21,6 +21,7 @@ current (development)
 - `Menu` can now be used in the 4 directions, using `MenuOption.direction`.
 - `Menu` can display an animated underline, using
   `MenuOption.underline.enabled`.
+- `Button` is now taking the focus in frame.
 - **breaking** All the options are now using a transform function.
 - **breaking** The `Toggle` component is now implemented using `Menu`.
 - **bugfix** Container::Tab implements `Focusable()`.

examples/component/CMakeLists.txt

@@ -2,6 +2,7 @@ set(DIRECTORY_LIB component)
 
 example(button)
 example(button_animated)
+example(button_in_frame)
 example(button_style)
 example(canvas_animated)
 example(checkbox)

examples/component/button_in_frame.cpp

+#include <array>   // for array
+#include <memory>  // for shared_ptr, __shared_ptr_access
+#include <string>  // for operator+, to_string
+
+#include "ftxui/component/captured_mouse.hpp"  // for ftxui
+#include "ftxui/component/component.hpp"  // for Checkbox, Renderer, Vertical
+#include "ftxui/component/component_base.hpp"      // for ComponentBase
+#include "ftxui/component/screen_interactive.hpp"  // for ScreenInteractive
+#include "ftxui/dom/elements.hpp"  // for operator|, Element, size, border, frame, vscroll_indicator, HEIGHT, LESS_THAN
+
+using namespace ftxui;
+
+int main(int argc, const char* argv[]) {
+  int counter = 0;
+  auto on_click = [&] { counter++; };
+
+  auto button_style = ButtonOption::Animated(Color::Default, Color::GrayDark,
+                                             Color::Default, Color::White);
+
+  auto container = Container::Vertical({});
+  for (int i = 0; i < 30; ++i) {
+    auto button =
+        Button("Button " + std::to_string(i), on_click, &button_style);
+    container->Add(button);
+  }
+
+  auto renderer = Renderer(container, [&] {
+    return vbox({
+               hbox({
+                   text("Counter:"),
+                   text(std::to_string(counter)),
+               }),
+               separator(),
+               container->Render() | vscroll_indicator | frame |
+                   size(HEIGHT, LESS_THAN, 20),
+           }) |
+           border;
+  });
+
+  auto screen = ScreenInteractive::FitComponent();
+  screen.Loop(renderer);
+
+  return 0;
+}
+
+// Copyright 2022 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/button.cpp

@@ -69,22 +69,27 @@ Component Button(ConstStringRef label,
 
     // Component implementation:
     Element Render() override {
-      float target = Focused() ? 1.F : 0.F;  // NOLINT
+      const bool active = Active();
+      const bool focused = Focused();
+      const bool focused_or_hover = focused || mouse_hover_;
+
+      float target = focused_or_hover ? 1.F : 0.F;  // NOLINT
       if (target != animator_background_.to()) {
         SetAnimationTarget(target);
       }
 
+      auto focus_management = focused ? focus : active ? select : nothing;
       EntryState state = {
           *label_,
           false,
-          Active(),
-          Focused(),
+          active,
+          focused_or_hover,
       };
 
       auto element =
           (option_->transform ? option_->transform : DefaultTransform)  //
           (state);
-      return element | AnimatedColorStyle() | reflect(box_);
+      return element | AnimatedColorStyle() | focus_management | reflect(box_);
     }
 
     Decorator AnimatedColorStyle() {
@@ -151,10 +156,9 @@ Component Button(ConstStringRef label,
         return false;
       }
 
-      TakeFocus();
-
       if (event.mouse().button == Mouse::Left &&
           event.mouse().motion == Mouse::Pressed) {
+        TakeFocus();
         OnClick();
         return true;
       }