Menu: keep the previously focused element with mouse. (#462)

This resolves:
https://github.com/ArthurSonzogni/FTXUI/issues/453

CHANGELOG.md

@@ -15,6 +15,8 @@ current (development)
 ### Component:
 - Feature: Add the `Modal` component.
 - Feature: `Slider` supports taking references for all its arguments.
+- Improvement: The `Menu` keeps the focus when an entry is selected with the
+  mouse.
 
 ### Screen
 - Feature: add `Box::Union(a,b) -> Box`

src/ftxui/component/menu.cpp

@@ -83,8 +83,13 @@ class MenuBase : public ComponentBase {
   }
 
   void Clamp() {
+    if (*selected_ != selected_previous_) {
+      SelectedTakeFocus();
+    }
     boxes_.resize(size());
     *selected_ = util::clamp(*selected_, 0, size() - 1);
+    selected_previous_ = util::clamp(selected_previous_, 0, size() - 1);
+    selected_focus_ = util::clamp(selected_focus_, 0, size() - 1);
     focused_entry() = util::clamp(focused_entry(), 0, size() - 1);
   }
 
@@ -115,9 +120,6 @@ class MenuBase : public ComponentBase {
       bool is_focused = (focused_entry() == i) && is_menu_focused;
       bool is_selected = (*selected_ == i);
 
-      auto focus_management = !is_selected      ? nothing
-                              : is_menu_focused ? focus
-                                                : nothing;
       EntryState state = {
           entries_[i],
           false,
@@ -125,6 +127,9 @@ class MenuBase : public ComponentBase {
           is_focused,
       };
 
+      auto focus_management =
+          is_menu_focused && (selected_focus_ == i) ? focus : nothing;
+
       Element element =
           (option_->entries.transform ? option_->entries.transform
                                       : DefaultOptionTransform)  //
@@ -166,6 +171,11 @@ class MenuBase : public ComponentBase {
     }
   }
 
+  void SelectedTakeFocus() {
+    selected_previous_ = *selected_;
+    selected_focus_ = *selected_;
+  }
+
   void OnUp() {
     switch (option_->direction) {
       case MenuOption::Direction::Up:
@@ -270,6 +280,7 @@ class MenuBase : public ComponentBase {
 
       if (*selected_ != old_selected) {
         focused_entry() = *selected_;
+        SelectedTakeFocus();
         OnChange();
         return true;
       }
@@ -307,6 +318,7 @@ class MenuBase : public ComponentBase {
           event.mouse().motion == Mouse::Released) {
         if (*selected_ != i) {
           *selected_ = i;
+          selected_previous_ = *selected_;
           OnChange();
         }
         return true;
@@ -331,6 +343,7 @@ class MenuBase : public ComponentBase {
     *selected_ = util::clamp(*selected_, 0, size() - 1);
 
     if (*selected_ != old_selected) {
+      SelectedTakeFocus();
       OnChange();
     }
     return true;
@@ -449,7 +462,9 @@ class MenuBase : public ComponentBase {
 
  protected:
   ConstStringListRef entries_;
-  int* selected_ = nullptr;
+  int* selected_;
+  int selected_previous_ = *selected_;
+  int selected_focus_= *selected_;
   Ref<MenuOption> option_;
 
   std::vector<Box> boxes_;

src/ftxui/component/slider.cpp

@@ -23,10 +23,10 @@ class SliderBase : public ComponentBase {
              ConstRef<T> max,
              ConstRef<T> increment)
       : label_(std::move(label)),
-        value_(std::move(value)),
-        min_(std::move(min)),
-        max_(std::move(max)),
-        increment_(std::move(increment)) {}
+        value_(value),
+        min_(min),
+        max_(max),
+        increment_(increment) {}
 
   Element Render() override {
     auto gauge_color =
@@ -81,8 +81,9 @@ class SliderBase : public ComponentBase {
     }
 
     if (captured_mouse_) {
-      value_() = min_() + (event.mouse().x - gauge_box_.x_min) * (max_() - min_()) /
-                           (gauge_box_.x_max - gauge_box_.x_min);
+      value_() = min_() + (event.mouse().x - gauge_box_.x_min) *
+                              (max_() - min_()) /
+                              (gauge_box_.x_max - gauge_box_.x_min);
       value_() = std::max(min_(), std::min(max_(), value_()));
       return true;
     }
@@ -129,24 +130,21 @@ Component Slider(ConstStringRef label,
                  ConstRef<int> min,
                  ConstRef<int> max,
                  ConstRef<int> increment) {
-  return Make<SliderBase<int>>(std::move(label), std::move(value), std::move(min),
-                             std::move(max), std::move(increment));
+  return Make<SliderBase<int>>(std::move(label), value, min, max, increment);
 }
 Component Slider(ConstStringRef label,
                  Ref<float> value,
                  ConstRef<float> min,
                  ConstRef<float> max,
                  ConstRef<float> increment) {
-  return Make<SliderBase<float>>(std::move(label), std::move(value), std::move(min),
-                             std::move(max), std::move(increment));
+  return Make<SliderBase<float>>(std::move(label), value, min, max, increment);
 }
 Component Slider(ConstStringRef label,
                  Ref<long> value,
                  ConstRef<long> min,
                  ConstRef<long> max,
                  ConstRef<long> increment) {
-  return Make<SliderBase<long>>(std::move(label), std::move(value), std::move(min),
-                             std::move(max), std::move(increment));
+  return Make<SliderBase<long>>(std::move(label), value, min, max, increment);
 }
 
 }  // namespace ftxui