allow multi-select for ships/stations, mixable with scrap

src/lib/eventsystem/event/CMakeLists.txt

@@ -4,7 +4,7 @@ SET(HDRS
 	${CMAKE_CURRENT_SOURCE_DIR}/TickAdvancedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BuildingBlocksChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/ExpansionCostChangedEvent.h
-	${CMAKE_CURRENT_SOURCE_DIR}/EntitySelectedEvent.h
+	${CMAKE_CURRENT_SOURCE_DIR}/EntitySelectionChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/GameSpeedChangedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/BossWaveUpdatedEvent.h
 	${CMAKE_CURRENT_SOURCE_DIR}/SchematicChoicesAvailableEvent.h

src/lib/eventsystem/event/EntitySelectedEvent.h

@@ -1,21 +0,0 @@
-#ifndef ENTITY_SELECTED_EVENT_H
-#define ENTITY_SELECTED_EVENT_H
-
-#include <optional>
-
-#include "entt/entity/entity.hpp"
-
-#include "Event.h"
-
-class EntitySelectedEvent : public Event
-{
-public:
-	explicit EntitySelectedEvent(std::optional<entt::entity> entity)
-		: entity(entity)
-	{
-	}
-
-	const std::optional<entt::entity> entity;
-};
-
-#endif // ENTITY_SELECTED_EVENT_H

src/lib/eventsystem/event/EntitySelectionChangedEvent.h

@@ -0,0 +1,25 @@
+#ifndef ENTITY_SELECTION_CHANGED_EVENT_H
+#define ENTITY_SELECTION_CHANGED_EVENT_H
+
+#include <vector>
+
+#include "entt/entity/entity.hpp"
+
+#include "Event.h"
+
+// The set of currently selected ships and/or defence stations. An empty list means
+// no actor is selected. Actors share the "field" selection category with scrap piles
+// (REQ-UI-SELECTION-CATEGORIES): they can be selected together, but never together with
+// buildings.
+class EntitySelectionChangedEvent : public Event
+{
+public:
+	explicit EntitySelectionChangedEvent(std::vector<entt::entity> entities)
+		: entities(std::move(entities))
+	{
+	}
+
+	const std::vector<entt::entity> entities;
+};
+
+#endif // ENTITY_SELECTION_CHANGED_EVENT_H