Show manage slots in veh/group window drop down even when no vehicles.

src/group_gui.cpp

@@ -484,16 +484,16 @@ public:
 		this->vscroll->SetCount(this->vehicles.Length());
 
 		/* The drop down menu is out, *but* it may not be used, retract it. */
-		if (this->vehicles.Length() == 0 && this->IsWidgetLowered(WID_GL_MANAGE_VEHICLES_DROPDOWN)) {
+		if (!this->ShouldShowActionDropdownList() && this->IsWidgetLowered(WID_GL_MANAGE_VEHICLES_DROPDOWN)) {
 			this->RaiseWidget(WID_GL_MANAGE_VEHICLES_DROPDOWN);
 			HideDropDownMenu(this);
 		}
 
 		/* Disable all lists management button when the list is empty */
+		this->SetWidgetDisabledState(WID_GL_MANAGE_VEHICLES_DROPDOWN, !this->ShouldShowActionDropdownList() || _local_company != this->vli.company);
 		this->SetWidgetsDisabledState(this->vehicles.Length() == 0 || _local_company != this->vli.company,
 				WID_GL_STOP_ALL,
 				WID_GL_START_ALL,
-				WID_GL_MANAGE_VEHICLES_DROPDOWN,
 				WIDGET_LIST_END);
 
 		/* Disable the group specific function when we select the default group or all vehicles */
@@ -703,7 +703,7 @@ public:
 
 			case WID_GL_MANAGE_VEHICLES_DROPDOWN: {
 				DropDownList *list = this->BuildActionDropdownList(true, Group::IsValidID(this->vli.index));
-				ShowDropDownList(this, list, 0, WID_GL_MANAGE_VEHICLES_DROPDOWN);
+				ShowDropDownList(this, list, -1, WID_GL_MANAGE_VEHICLES_DROPDOWN);
 				break;
 			}
 
@@ -826,7 +826,7 @@ public:
 				break;
 
 			case WID_GL_MANAGE_VEHICLES_DROPDOWN:
-				assert(this->vehicles.Length() != 0);
+				assert(this->ShouldShowActionDropdownList());
 
 				switch (index) {
 					case ADI_REPLACE: // Replace window

src/vehicle_gui.cpp

@@ -161,6 +161,15 @@ Dimension BaseVehicleListWindow::GetActionDropdownSize(bool show_autoreplace, bo
 	return d;
 }
 
+/**
+ * Whether the Action dropdown window should be shown/available.
+ * @return Whether available
+ */
+bool BaseVehicleListWindow::ShouldShowActionDropdownList() const
+{
+	return this->vehicles.Length() != 0 || (this->vli.vtype == VEH_TRAIN && _settings_client.gui.show_adv_tracerestrict_features);
+}
+
 /**
  * Display the Action dropdown window.
  * @param show_autoreplace If true include the autoreplace item.
@@ -170,14 +179,15 @@ Dimension BaseVehicleListWindow::GetActionDropdownSize(bool show_autoreplace, bo
 DropDownList *BaseVehicleListWindow::BuildActionDropdownList(bool show_autoreplace, bool show_group)
 {
 	DropDownList *list = new DropDownList();
+	bool disable = this->vehicles.Length() == 0;
 
-	if (show_autoreplace) *list->Append() = new DropDownListStringItem(STR_VEHICLE_LIST_REPLACE_VEHICLES, ADI_REPLACE, false);
-	*list->Append() = new DropDownListStringItem(STR_VEHICLE_LIST_SEND_FOR_SERVICING, ADI_SERVICE, false);
-	*list->Append() = new DropDownListStringItem(this->vehicle_depot_name[this->vli.vtype], ADI_DEPOT, false);
+	if (show_autoreplace) *list->Append() = new DropDownListStringItem(STR_VEHICLE_LIST_REPLACE_VEHICLES, ADI_REPLACE, disable);
+	*list->Append() = new DropDownListStringItem(STR_VEHICLE_LIST_SEND_FOR_SERVICING, ADI_SERVICE, disable);
+	*list->Append() = new DropDownListStringItem(this->vehicle_depot_name[this->vli.vtype], ADI_DEPOT, disable);
 
 	if (show_group) {
-		*list->Append() = new DropDownListStringItem(STR_GROUP_ADD_SHARED_VEHICLE, ADI_ADD_SHARED, false);
-		*list->Append() = new DropDownListStringItem(STR_GROUP_REMOVE_ALL_VEHICLES, ADI_REMOVE_ALL, false);
+		*list->Append() = new DropDownListStringItem(STR_GROUP_ADD_SHARED_VEHICLE, ADI_ADD_SHARED, disable);
+		*list->Append() = new DropDownListStringItem(STR_GROUP_REMOVE_ALL_VEHICLES, ADI_REMOVE_ALL, disable);
 	}
 	if (this->vli.vtype == VEH_TRAIN && _settings_client.gui.show_adv_tracerestrict_features) {
 		*list->Append() = new DropDownListStringItem(STR_TRACE_RESTRICT_SLOT_MANAGE, ADI_TRACERESTRICT_SLOT_MGMT, false);
@@ -1590,7 +1600,7 @@ public:
 		this->BuildVehicleList();
 		this->SortVehicleList();
 
-		if (this->vehicles.Length() == 0 && this->IsWidgetLowered(WID_VL_MANAGE_VEHICLES_DROPDOWN)) {
+		if (!this->ShouldShowActionDropdownList() && this->IsWidgetLowered(WID_VL_MANAGE_VEHICLES_DROPDOWN)) {
 			HideDropDownMenu(this);
 		}
 
@@ -1604,8 +1614,8 @@ public:
 		}
 		if (this->owner == _local_company) {
 			this->SetWidgetDisabledState(WID_VL_AVAILABLE_VEHICLES, this->vli.type != VL_STANDARD);
+			this->SetWidgetDisabledState(WID_VL_MANAGE_VEHICLES_DROPDOWN, !this->ShouldShowActionDropdownList());
 			this->SetWidgetsDisabledState(this->vehicles.Length() == 0,
-				WID_VL_MANAGE_VEHICLES_DROPDOWN,
 				WID_VL_STOP_ALL,
 				WID_VL_START_ALL,
 				WIDGET_LIST_END);
@@ -1645,7 +1655,7 @@ public:
 
 			case WID_VL_MANAGE_VEHICLES_DROPDOWN: {
 				DropDownList *list = this->BuildActionDropdownList(VehicleListIdentifier::UnPack(this->window_number).type == VL_STANDARD, false);
-				ShowDropDownList(this, list, 0, WID_VL_MANAGE_VEHICLES_DROPDOWN);
+				ShowDropDownList(this, list, -1, WID_VL_MANAGE_VEHICLES_DROPDOWN);
 				break;
 			}
 
@@ -1663,7 +1673,7 @@ public:
 				this->vehicles.SetSortType(index);
 				break;
 			case WID_VL_MANAGE_VEHICLES_DROPDOWN:
-				assert(this->vehicles.Length() != 0);
+				assert(this->ShouldShowActionDropdownList());
 
 				switch (index) {
 					case ADI_REPLACE: // Replace window

src/vehicle_gui_base.h

@@ -48,6 +48,7 @@ struct BaseVehicleListWindow : public Window {
 	void SortVehicleList();
 	void BuildVehicleList();
 	Dimension GetActionDropdownSize(bool show_autoreplace, bool show_group);
+	bool ShouldShowActionDropdownList() const;
 	DropDownList *BuildActionDropdownList(bool show_autoreplace, bool show_group);
 };