show better changesite for floodfill/terrain frill/item place

src/scenedit/scen.undo.cpp

@@ -291,7 +291,7 @@ aPlaceEraseItem::aPlaceEraseItem(std::string name, bool place, size_t index, cTo
 {}
 
 aPlaceEraseItem::aPlaceEraseItem(std::string name, bool place, item_changes_t items)
-	: cTerrainAction(name, items.begin()->second.loc, !place)
+	: cTerrainAction(name, closest_to_view(items), !place)
 	, items(items)
 {}
 
@@ -1249,3 +1249,19 @@ bool aCreateAreaRect::redo_me() {
 	area->area_desc[which] = rect;
 	return true;
 }
+
+location closest_to_view(stroke_ter_changes_t changes) {
+	std::vector<location> locs;
+	for(auto& it : changes){
+		locs.push_back(it.first);
+	}
+	return closest_point(locs, loc(cen_x, cen_y));
+}
+
+location closest_to_view(item_changes_t changes) {
+	std::vector<location> locs;
+	for(auto& it : changes){
+		locs.push_back(it.second.loc);
+	}
+	return closest_point(locs, loc(cen_x, cen_y));
+}

src/scenedit/scen.undo.hpp

@@ -45,6 +45,9 @@ typedef std::map<location,cOutdoors*,loc_compare> outdoor_sections_t;
 typedef std::map<location,std::vector<eFieldType>,loc_compare> clear_field_stroke_t;
 typedef std::set<location,loc_compare> field_stroke_t;
 
+location closest_to_view(stroke_ter_changes_t changes);
+location closest_to_view(item_changes_t changes);
+
 // Action that modified something in town or outdoor terrain, so we should show the modified area when undoing or redoing
 class cTerrainAction : public cAction {
 public:
@@ -100,7 +103,7 @@ public:
 class aDrawTerrain : public cTerrainAction {
 public:
 	aDrawTerrain(std::string name, stroke_ter_changes_t stroke_changes) :
-		cTerrainAction(name, stroke_changes.begin()->first), // Use arbitrary changed tile as site of change
+		cTerrainAction(name, closest_to_view(stroke_changes)),
 		changes(stroke_changes) {}
 	bool undo_me() override;
 	bool redo_me() override;