GUI2/Menu Button: allow changing selections with the scrollwheel (closes

 #3251)'

The changelog entry is under 1.14.3+dev since this is going to be backported.

changelog.md

@@ -4,6 +4,7 @@
      * Fixed missing prisoners and loss of recallable units in 'Captured'.
  ### User interface
    * Improved the layout of the Statistics dialog.
+   * Allow changing dropdown menu selections with the scrollwheel (FR #3251).
  ### Graphics
    * Tweaked the Ruffian's attack animation timing.
    * New attack animation for the Peasant.

src/gui/widgets/menu_button.cpp

@@ -48,16 +48,27 @@ menu_button::menu_button(const implementation::builder_menu_button& builder)
 	values_.emplace_back(::config {"label", this->get_label()});
 
 	connect_signal<event::MOUSE_ENTER>(
-			std::bind(&menu_button::signal_handler_mouse_enter, this, _2, _3));
+		std::bind(&menu_button::signal_handler_mouse_enter, this, _2, _3));
+
 	connect_signal<event::MOUSE_LEAVE>(
-			std::bind(&menu_button::signal_handler_mouse_leave, this, _2, _3));
+		std::bind(&menu_button::signal_handler_mouse_leave, this, _2, _3));
+
+	connect_signal<event::LEFT_BUTTON_DOWN>(
+		std::bind(&menu_button::signal_handler_left_button_down, this, _2, _3));
 
-	connect_signal<event::LEFT_BUTTON_DOWN>(std::bind(
-			&menu_button::signal_handler_left_button_down, this, _2, _3));
 	connect_signal<event::LEFT_BUTTON_UP>(
-			std::bind(&menu_button::signal_handler_left_button_up, this, _2, _3));
-	connect_signal<event::LEFT_BUTTON_CLICK>(std::bind(
-			&menu_button::signal_handler_left_button_click, this, _2, _3));
+		std::bind(&menu_button::signal_handler_left_button_up, this, _2, _3));
+
+	connect_signal<event::LEFT_BUTTON_CLICK>(
+		std::bind(&menu_button::signal_handler_left_button_click, this, _2, _3));
+
+	connect_signal<event::SDL_WHEEL_UP>(
+		std::bind(&menu_button::signal_handler_sdl_wheel_up, this, _2, _3),
+		event::dispatcher::back_post_child);
+
+	connect_signal<event::SDL_WHEEL_DOWN>(
+		std::bind(&menu_button::signal_handler_sdl_wheel_down, this, _2, _3),
+		event::dispatcher::back_post_child);
 }
 
 void menu_button::set_active(const bool active)
@@ -148,6 +159,30 @@ void menu_button::signal_handler_left_button_click(const event::ui_event event,
 	handled = true;
 }
 
+void menu_button::signal_handler_sdl_wheel_up(const event::ui_event event, bool& handled)
+{
+	DBG_GUI_E << LOG_HEADER << ' ' << event << ".\n";
+
+	// TODO: should values wrap?
+	if(selected_ > 0) {
+		set_selected(selected_ - 1);
+	}
+
+	handled = true;
+}
+
+void menu_button::signal_handler_sdl_wheel_down(const event::ui_event event, bool& handled)
+{
+	DBG_GUI_E << LOG_HEADER << ' ' << event << ".\n";
+
+	// TODO: should values wrap?
+	if(selected_ < values_.size() - 1) {
+		set_selected(selected_ + 1);
+	}
+
+	handled = true;
+}
+
 void menu_button::set_values(const std::vector<::config>& values, int selected)
 {
 	assert(static_cast<size_t>(selected) < values.size());

src/gui/widgets/menu_button.hpp

@@ -129,6 +129,10 @@ class menu_button : public styled_widget, public selectable_item
 	void signal_handler_left_button_up(const event::ui_event event, bool& handled);
 
 	void signal_handler_left_button_click(const event::ui_event event, bool& handled);
+
+	void signal_handler_sdl_wheel_up(const event::ui_event event, bool& handled);
+
+	void signal_handler_sdl_wheel_down(const event::ui_event event, bool& handled);
 };
 
 // }---------- DEFINITION ---------{