Add mouse implementation of most components.

src/ftxui/component/checkbox.cpp

@@ -9,10 +9,14 @@ Element CheckBox::Render() {
   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);
+              text(label) | style | focus_management) |
+         reflect(box_);
 }
 
 bool CheckBox::OnEvent(Event event) {
+  if (event.is_mouse())
+    return OnMouseEvent(event);
+
   if (event == Event::Character(' ') || event == Event::Return) {
     state = !state;
     on_change();
@@ -21,6 +25,24 @@ bool CheckBox::OnEvent(Event event) {
   return false;
 }
 
+bool CheckBox::OnMouseEvent(Event event) {
+  if (!box_.Contain(event.mouse_x(), event.mouse_y()))
+    return false;
+
+  if (event.is_mouse_move()) {
+    TakeFocus();
+    return true;
+  }
+
+  if (event.is_mouse_left_down()) {
+    state = !state;
+    on_change();
+    return true;
+  }
+
+  return false;
+}
+
 }  // namespace ftxui
 
 // Copyright 2020 Arthur Sonzogni. All rights reserved.