First implementation of conditional order checking slot occupancy

(cherry picked from commit 524e3e56cb4a357ba60335f91dce1e00cb8d22f2)

Some code adjustments: serialisation/storage, formatting

See: #40

src/lang/english.txt

@@ -4437,6 +4437,7 @@ STR_ORDER_CONDITIONAL_CARGO_WAITING                             :Waiting cargo
 STR_ORDER_CONDITIONAL_ACCEPTANCE_DROPDOWN                       :Accepted cargo
 STR_ORDER_CONDITIONAL_FREE_PLATFORMS                            :Free platforms
 STR_ORDER_CONDITIONAL_PERCENT                                   :Percent of times
+STR_ORDER_CONDITIONAL_SLOT_OCCUPANCY                            :Slot occupancy
 
 STR_ORDER_CONDITIONAL_REQUIRES_SERVICE_ORDER                    :Requires service {STRING}
 STR_ORDER_CONDITIONAL_CARGO_WAITING_ORDER                       :Next station {STRING} {STRING} waiting
@@ -4458,6 +4459,7 @@ STR_ORDER_CONDITIONAL_COMPARATOR_IS_FALSE                       :is false
 
 STR_ORDER_CONDITIONAL_VALUE_TOOLTIP                             :{BLACK}The value to compare the vehicle data against
 STR_ORDER_CONDITIONAL_CARGO_TOOLTIP                             :{BLACK}The cargo to compare the station data against
+STR_ORDER_CONDITIONAL_SLOT_TOOLTIP                              :{BLACK}The train slot to check the occupancy of
 STR_ORDER_CONDITIONAL_VALUE_CAPT                                :{WHITE}Enter value to compare against
 
 STR_ORDER_CONDITIONAL_COMPARATOR_ACCEPTS                        :accepts
@@ -4468,6 +4470,8 @@ STR_ORDER_CONDITIONAL_COMPARATOR_HAS_LESS_THAN                  :has less than
 STR_ORDER_CONDITIONAL_COMPARATOR_HAS_LESS_EQUALS                :has less than or exactly
 STR_ORDER_CONDITIONAL_COMPARATOR_HAS_MORE_THAN                  :has more than
 STR_ORDER_CONDITIONAL_COMPARATOR_HAS_MORE_EQUALS                :has more than or exactly
+STR_ORDER_CONDITIONAL_COMPARATOR_FULLY_OCCUPIED                 :is fully occupied
+STR_ORDER_CONDITIONAL_COMPARATOR_NOT_YET_FULLY_OCCUPIED         :is not fully occupied
 
 STR_ORDERS_SKIP_BUTTON                                          :{BLACK}Skip
 STR_ORDERS_SKIP_TOOLTIP                                         :{BLACK}Skip the current order, and start the next. Ctrl+Click skips to the selected order
@@ -4577,6 +4581,8 @@ STR_ORDER_OUT_OF_RANGE                                          :{RED} (Next des
 STR_ORDER_CONDITIONAL_UNCONDITIONAL                             :Jump to order {COMMA}
 STR_ORDER_CONDITIONAL_NUM                                       :Jump to order {COMMA} when {STRING} {STRING} {COMMA}
 STR_ORDER_CONDITIONAL_CARGO                                     :Jump to order {COMMA} when {STRING} {STRING} {STRING}
+STR_ORDER_CONDITIONAL_SLOT                                      :Jump to order {COMMA} when {TRSLOT} {STRING}
+STR_ORDER_CONDITIONAL_INVALID_SLOT                              :Jump to order {COMMA} when {RED}{STRING} {PREVIOUS_COLOUR}{STRING}
 STR_ORDER_CONDITIONAL_TRUE_FALSE                                :Jump to order {COMMA} when {STRING} {STRING}
 
 STR_INVALID_ORDER                                               :{RED} (Invalid Order)

src/order_cmd.cpp

@@ -38,6 +38,7 @@
 #include "viewport_func.h"
 #include "order_cmd.h"
 #include "vehiclelist.h"
+#include "tracerestrict.h"
 
 #include "table/strings.h"
 
@@ -1003,10 +1004,18 @@ CommandCost CmdInsertOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 			OrderConditionComparator occ = new_order.GetConditionComparator();
 			if (occ >= OCC_END) return CMD_ERROR;
 			switch (new_order.GetConditionVariable()) {
+				case OCV_SLOT_OCCUPANCY: {
+					TraceRestrictSlotID slot = new_order.GetXData();
+					if (slot != INVALID_TRACE_RESTRICT_SLOT_ID && !TraceRestrictSlot::IsValidID(slot)) return CMD_ERROR;
+					if (occ != OCC_IS_TRUE && occ != OCC_IS_FALSE) return CMD_ERROR;
+					break;
+				}
+
 				case OCV_CARGO_WAITING:
 				case OCV_CARGO_ACCEPTANCE:
 					if (!CargoSpec::Get(new_order.GetConditionValue())->IsValid()) return CMD_ERROR;
 					/* FALL THROUGH */
+
 				case OCV_REQUIRES_SERVICE:
 					if (occ != OCC_IS_TRUE && occ != OCC_IS_FALSE) return CMD_ERROR;
 					break;
@@ -1480,8 +1489,8 @@ CommandCost CmdMoveOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
  *                        the maximum vehicle order id is 254.
  * @param p2 various bitstuffed elements
  *  - p2 = (bit 0 -  3) - what data to modify (@see ModifyOrderFlags)
- *  - p2 = (bit 4 - 15) - the data to modify
+ *  - p2 = (bit 4 - 19) - the data to modify
- *  - p2 = (bit 16 - 23) - a CargoID for cargo type orders (MOF_CARGO_TYPE_UNLOAD or MOF_CARGO_TYPE_LOAD)
+ *  - p2 = (bit 20 - 27) - a CargoID for cargo type orders (MOF_CARGO_TYPE_UNLOAD or MOF_CARGO_TYPE_LOAD)
  * @param text unused
  * @return the cost of this operation or an error
  */
@@ -1490,8 +1499,8 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 	VehicleOrderID sel_ord = GB(p1, 20,  8);
 	VehicleID veh          = GB(p1,  0, 20);
 	ModifyOrderFlags mof   = Extract<ModifyOrderFlags, 0, 4>(p2);
-	uint16 data            = GB(p2,  4, 11);
+	uint16 data            = GB(p2,  4, 16);
-	CargoID cargo_id       = (mof == MOF_CARGO_TYPE_UNLOAD || mof == MOF_CARGO_TYPE_LOAD) ? (CargoID) GB(p2, 16, 8) : (CargoID) CT_INVALID;
+	CargoID cargo_id       = (mof == MOF_CARGO_TYPE_UNLOAD || mof == MOF_CARGO_TYPE_LOAD) ? (CargoID) GB(p2, 20, 8) : (CargoID) CT_INVALID;
 
 	if (mof >= MOF_END) return CMD_ERROR;
 
@@ -1583,6 +1592,7 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 				case OCV_REQUIRES_SERVICE:
 				case OCV_CARGO_ACCEPTANCE:
 				case OCV_CARGO_WAITING:
+				case OCV_SLOT_OCCUPANCY:
 					if (data != OCC_IS_TRUE && data != OCC_IS_FALSE) return CMD_ERROR;
 					break;
 
@@ -1604,6 +1614,10 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 					if (data > 100) return CMD_ERROR;
 					break;
 
+				case OCV_SLOT_OCCUPANCY:
+					if (data != INVALID_TRACE_RESTRICT_SLOT_ID && !TraceRestrictSlot::IsValidID(data)) return CMD_ERROR;
+					break;
+
 				case OCV_CARGO_ACCEPTANCE:
 				case OCV_CARGO_WAITING:
 					if (!(data < NUM_CARGO && CargoSpec::Get(data)->IsValid())) return CMD_ERROR;
@@ -1684,6 +1698,7 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 			case MOF_COND_VARIABLE: {
 				/* Check whether old conditional variable had a cargo as value */
 				bool old_var_was_cargo = (order->GetConditionVariable() == OCV_CARGO_ACCEPTANCE || order->GetConditionVariable() == OCV_CARGO_WAITING);
+				bool old_var_was_slot = (order->GetConditionVariable() == OCV_SLOT_OCCUPANCY);
 				order->SetConditionVariable((OrderConditionVariable)data);
 
 				OrderConditionComparator occ = order->GetConditionComparator();
@@ -1693,13 +1708,18 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 						order->SetConditionValue(0);
 						break;
 
+					case OCV_SLOT_OCCUPANCY:
+						if (!old_var_was_slot) order->GetXDataRef() = INVALID_TRACE_RESTRICT_SLOT_ID;
+						if (occ != OCC_IS_TRUE && occ != OCC_IS_FALSE) order->SetConditionComparator(OCC_IS_TRUE);
+						break;
+
 					case OCV_CARGO_ACCEPTANCE:
 					case OCV_CARGO_WAITING:
 						if (!old_var_was_cargo) order->SetConditionValue((uint16) GetFirstValidCargo());
 						if (occ != OCC_IS_TRUE && occ != OCC_IS_FALSE) order->SetConditionComparator(OCC_IS_TRUE);
 						break;
 					case OCV_REQUIRES_SERVICE:
-						if (old_var_was_cargo) order->SetConditionValue(0);
+						if (old_var_was_cargo || old_var_was_slot) order->SetConditionValue(0);
 						if (occ != OCC_IS_TRUE && occ != OCC_IS_FALSE) order->SetConditionComparator(OCC_IS_TRUE);
 						order->SetConditionValue(0);
 						break;
@@ -1713,7 +1733,7 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 						FALLTHROUGH;
 
 					default:
-						if (old_var_was_cargo) order->SetConditionValue(0);
+						if (old_var_was_cargo || old_var_was_slot) order->SetConditionValue(0);
 						if (occ == OCC_IS_TRUE || occ == OCC_IS_FALSE) order->SetConditionComparator(OCC_EQUALS);
 						break;
 				}
@@ -1725,8 +1745,16 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 				break;
 
 			case MOF_COND_VALUE:
+				switch (order->GetConditionVariable()) {
+					case OCV_SLOT_OCCUPANCY:
+						order->GetXDataRef() = data;
+						break;
+
+					default:
 						order->SetConditionValue(data);
 						break;
+				}
+				break;
 
 			case MOF_COND_DESTINATION:
 				order->SetConditionSkipToOrder(data);
@@ -2349,6 +2377,7 @@ VehicleOrderID ProcessConditionalOrder(const Order *order, const Vehicle *v)
 	OrderConditionComparator occ = order->GetConditionComparator();
 	uint16 value = order->GetConditionValue();
 
+	// OrderConditionCompare ignores the last parameter for occ == OCC_IS_TRUE or occ == OCC_IS_FALSE.
 	switch (order->GetConditionVariable()) {
 		case OCV_LOAD_PERCENTAGE:    skip_order = OrderConditionCompare(occ, CalcPercentVehicleFilled(v, NULL), value); break;
 		case OCV_RELIABILITY:        skip_order = OrderConditionCompare(occ, ToPercent16(v->reliability),       value); break;
@@ -2366,6 +2395,11 @@ VehicleOrderID ProcessConditionalOrder(const Order *order, const Vehicle *v)
 			if (Station::IsValidID(next_station)) skip_order = OrderConditionCompare(occ, HasBit(Station::Get(next_station)->goods[value].status, GoodsEntry::GES_ACCEPTANCE), value);
 			break;
 		}
+		case OCV_SLOT_OCCUPANCY: {
+			const TraceRestrictSlot* slot = TraceRestrictSlot::GetIfValid(order->GetXData());
+			if (slot != nullptr) skip_order = OrderConditionCompare(occ, slot->occupants.size() >= slot->max_occupancy, value);
+			break;
+		}
 		case OCV_FREE_PLATFORMS: {
 			StationID next_station = GetNextRealStation(v, order);
 			if (Station::IsValidID(next_station)) skip_order = OrderConditionCompare(occ, GetFreeStationPlatforms(next_station), value);

src/order_gui.cpp

@@ -31,6 +31,7 @@
 #include "aircraft.h"
 #include "engine_func.h"
 #include "vehiclelist.h"
+#include "tracerestrict.h"
 
 #include "widgets/order_widget.h"
 
@@ -63,6 +64,8 @@ static const StringID _cargo_type_unload_order_drowdown[] = {
 };
 static const uint32 _cargo_type_unload_order_drowdown_hidden_mask = 0x8; // 01000
 
+DropDownList* GetSlotDropDownList(Owner owner, TraceRestrictSlotID slot_id, int &selected);
+
 struct CargoTypeOrdersWindow : public Window {
 private:
 	CargoTypeOrdersWindowVariant variant;
@@ -244,7 +247,7 @@ public:
 			if (action_type == order_action_type) return;
 
 			ModifyOrderFlags mof = (this->variant == CTOWV_LOAD) ? MOF_CARGO_TYPE_LOAD : MOF_CARGO_TYPE_UNLOAD;
-			DoCommandP(this->vehicle->tile, this->vehicle->index + (this->order_id << 20), mof | (action_type << 4) | (cargo_id << 16), CMD_MODIFY_ORDER | CMD_MSG(STR_ERROR_CAN_T_MODIFY_THIS_ORDER));
+			DoCommandP(this->vehicle->tile, this->vehicle->index + (this->order_id << 20), mof | (action_type << 4) | (cargo_id << 20), CMD_MODIFY_ORDER | CMD_MSG(STR_ERROR_CAN_T_MODIFY_THIS_ORDER));
 
 			this->GetWidget<NWidgetCore>(widget)->SetDataTip(this->cargo_type_order_dropdown[this->GetOrderActionTypeForCargo(cargo_id)], STR_CARGO_TYPE_LOAD_ORDERS_DROP_TOOLTIP + this->variant);
 			this->SetWidgetDirty(widget);
@@ -602,6 +605,7 @@ static const OrderConditionVariable _order_conditional_variable[] = {
 	OCV_CARGO_WAITING,
 	OCV_CARGO_ACCEPTANCE,
 	OCV_FREE_PLATFORMS,
+	OCV_SLOT_OCCUPANCY,
 	OCV_PERCENT,
 	OCV_UNCONDITIONALLY,
 };
@@ -642,6 +646,18 @@ static const StringID _order_conditional_condition_accepts[] = {
 	INVALID_STRING_ID,
 };
 
+static const StringID _order_conditional_condition_is_fully_occupied[] = {
+	STR_NULL,
+	STR_NULL,
+	STR_NULL,
+	STR_NULL,
+	STR_NULL,
+	STR_NULL,
+	STR_ORDER_CONDITIONAL_COMPARATOR_FULLY_OCCUPIED,
+	STR_ORDER_CONDITIONAL_COMPARATOR_NOT_YET_FULLY_OCCUPIED,
+	INVALID_STRING_ID,
+};
+
 extern uint ConvertSpeedToDisplaySpeed(uint speed);
 extern uint ConvertDisplaySpeedToSpeed(uint speed);
 
@@ -813,6 +829,15 @@ void DrawOrderString(const Vehicle *v, const Order *order, int order_index, int
 				SetDParam(0, STR_CONDITIONAL_FREE_PLATFORMS );
 				SetDParam(2, STR_ORDER_CONDITIONAL_COMPARATOR_HAS + order->GetConditionComparator());
 				SetDParam(3, order->GetConditionValue());
+			} else if (ocv == OCV_SLOT_OCCUPANCY) {
+				if (TraceRestrictSlot::IsValidID(order->GetXData())) {
+					SetDParam(0, STR_ORDER_CONDITIONAL_SLOT);
+					SetDParam(2, order->GetXData());
+				} else {
+					SetDParam(0, STR_ORDER_CONDITIONAL_INVALID_SLOT);
+					SetDParam(2, STR_TRACE_RESTRICT_VARIABLE_UNDEFINED);
+				}
+				SetDParam(3, order->GetConditionComparator() == OCC_IS_TRUE ? STR_ORDER_CONDITIONAL_COMPARATOR_FULLY_OCCUPIED : STR_ORDER_CONDITIONAL_COMPARATOR_NOT_YET_FULLY_OCCUPIED);
 			} else {
 				OrderConditionComparator occ = order->GetConditionComparator();
 				bool is_cargo = ocv == OCV_CARGO_ACCEPTANCE || ocv == OCV_CARGO_WAITING;
@@ -1016,6 +1041,7 @@ private:
 		/* WID_O_SEL_COND_VALUE */
 		DP_COND_VALUE_NUMBER = 0, ///< Display number widget
 		DP_COND_VALUE_CARGO  = 1, ///< Display dropdown widget cargo types
+		DP_COND_VALUE_SLOT   = 2, ///< Display dropdown widget tracerestrict slots
 
 		DP_ROW_CONDITIONAL = 2, ///< Display the conditional order buttons in the top row of the ship/airplane order window.
 
@@ -1087,6 +1113,9 @@ private:
 			case OCV_CARGO_ACCEPTANCE:
 				return _order_conditional_condition_accepts;
 
+			case OCV_SLOT_OCCUPANCY:
+				return _order_conditional_condition_is_fully_occupied;
+
 			default:
 				return _order_conditional_condition;
 		}
@@ -1634,12 +1663,19 @@ public:
 					} else {
 						train_row_sel->SetDisplayedPlane(DP_GROUNDVEHICLE_ROW_CONDITIONAL);
 					}
-					OrderConditionVariable ocv = (order == NULL) ? OCV_LOAD_PERCENTAGE : order->GetConditionVariable();
+
+					OrderConditionVariable ocv = (order == nullptr) ? OCV_LOAD_PERCENTAGE : order->GetConditionVariable();
 					bool is_cargo = (ocv == OCV_CARGO_ACCEPTANCE || ocv == OCV_CARGO_WAITING);
+					bool is_slot_occupancy = (ocv == OCV_SLOT_OCCUPANCY);
 
 					if (is_cargo) {
 						this->GetWidget<NWidgetCore>(WID_O_COND_CARGO)->widget_data = cargo_names_list[(order == NULL) ? 0 : order->GetConditionValue()];
 						this->GetWidget<NWidgetStacked>(WID_O_SEL_COND_VALUE)->SetDisplayedPlane(DP_COND_VALUE_CARGO);
+					} else if (is_slot_occupancy) {
+						TraceRestrictSlotID slot_id = (order != nullptr && TraceRestrictSlot::IsValidID(order->GetXData()) ? order->GetXData() : INVALID_TRACE_RESTRICT_SLOT_ID);
+
+						this->GetWidget<NWidgetCore>(WID_O_COND_SLOT)->widget_data = (slot_id != INVALID_TRACE_RESTRICT_SLOT_ID) ? STR_TRACE_RESTRICT_SLOT_NAME : STR_TRACE_RESTRICT_VARIABLE_UNDEFINED;
+						this->GetWidget<NWidgetStacked>(WID_O_SEL_COND_VALUE)->SetDisplayedPlane(DP_COND_VALUE_SLOT);
 					} else {
 						this->GetWidget<NWidgetStacked>(WID_O_SEL_COND_VALUE)->SetDisplayedPlane(DP_COND_VALUE_NUMBER);
 					}
@@ -1797,6 +1833,17 @@ public:
 				break;
 			}
 
+			case WID_O_COND_SLOT: {
+				VehicleOrderID sel = this->OrderGetSel();
+				const Order *order = this->vehicle->GetOrder(sel);
+
+				if (order != nullptr && order->IsType(OT_CONDITIONAL)) {
+					TraceRestrictSlotID value = order->GetXData();
+					SetDParam(0, value);
+				}
+				break;
+			}
+
 			case WID_O_CAPTION:
 				SetDParam(0, this->vehicle->index);
 				break;
@@ -1958,6 +2005,14 @@ public:
 				}
 				break;
 
+			case WID_O_COND_SLOT: {
+				int selected;
+				TraceRestrictSlotID value = this->vehicle->GetOrder(this->OrderGetSel())->GetXData();
+				DropDownList *list = GetSlotDropDownList(this->vehicle->owner, value, selected);
+				if (list != nullptr) ShowDropDownList(this, list, selected, WID_O_COND_SLOT, 0, true);
+				break;
+			}
+
 			case WID_O_REVERSE: {
 				VehicleOrderID sel_ord = this->OrderGetSel();
 				const Order *order = this->vehicle->GetOrder(sel_ord);
@@ -1992,7 +2047,10 @@ public:
 				const Order *o = this->vehicle->GetOrder(this->OrderGetSel());
 				OrderConditionVariable cond_var = o->GetConditionVariable();
 				ShowDropDownMenu(this, GetComparatorStrings(o), o->GetConditionComparator(), WID_O_COND_COMPARATOR, 0,
-						(cond_var == OCV_REQUIRES_SERVICE || cond_var == OCV_CARGO_ACCEPTANCE || cond_var == OCV_CARGO_WAITING) ? 0x3F : 0xC0, 0, DDSF_LOST_FOCUS);
+					(cond_var == OCV_REQUIRES_SERVICE ||
+					 cond_var == OCV_CARGO_ACCEPTANCE ||
+					 cond_var == OCV_CARGO_WAITING ||
+					 cond_var == OCV_SLOT_OCCUPANCY) ? 0x3F : 0xC0, 0, DDSF_LOST_FOCUS);
 				break;
 			}
 
@@ -2096,6 +2154,10 @@ public:
 			case WID_O_COND_CARGO:
 				DoCommandP(this->vehicle->tile, this->vehicle->index + (this->OrderGetSel() << 20), MOF_COND_VALUE | index << 4, CMD_MODIFY_ORDER | CMD_MSG(STR_ERROR_CAN_T_MODIFY_THIS_ORDER));
 				break;
+
+			case WID_O_COND_SLOT:
+				DoCommandP(this->vehicle->tile, this->vehicle->index + (this->OrderGetSel() << 20), MOF_COND_VALUE | index << 4, CMD_MODIFY_ORDER | CMD_MSG(STR_ERROR_CAN_T_MODIFY_THIS_ORDER));
+				break;
 		}
 	}
 
@@ -2318,6 +2380,8 @@ static const NWidgetPart _nested_orders_train_widgets[] = {
 															SetDataTip(STR_BLACK_COMMA, STR_ORDER_CONDITIONAL_VALUE_TOOLTIP), SetResize(1, 0),
 					NWidget(WWT_DROPDOWN, COLOUR_GREY, WID_O_COND_CARGO), SetMinimalSize(124, 12), SetFill(1, 0),
 															SetDataTip(STR_NULL, STR_ORDER_CONDITIONAL_CARGO_TOOLTIP), SetResize(1, 0),
+					NWidget(WWT_DROPDOWN, COLOUR_GREY, WID_O_COND_SLOT), SetMinimalSize(124, 12), SetFill(1, 0),
+															SetDataTip(STR_NULL, STR_ORDER_CONDITIONAL_SLOT_TOOLTIP), SetResize(1, 0),
 				EndContainer(),
 			EndContainer(),
 		EndContainer(),
@@ -2404,6 +2468,8 @@ static const NWidgetPart _nested_orders_widgets[] = {
 															SetDataTip(STR_BLACK_COMMA, STR_ORDER_CONDITIONAL_VALUE_TOOLTIP), SetResize(1, 0),
 					NWidget(WWT_DROPDOWN, COLOUR_GREY, WID_O_COND_CARGO), SetMinimalSize(124, 12), SetFill(1, 0),
 													SetDataTip(STR_NULL, STR_ORDER_CONDITIONAL_CARGO_TOOLTIP), SetResize(1, 0),
+					NWidget(WWT_DROPDOWN, COLOUR_GREY, WID_O_COND_SLOT), SetMinimalSize(124, 12), SetFill(1, 0),
+													SetDataTip(STR_NULL, STR_ORDER_CONDITIONAL_SLOT_TOOLTIP), SetResize(1, 0),
 				EndContainer(),
 			EndContainer(),
 		EndContainer(),

src/order_type.h

@@ -144,6 +144,7 @@ enum OrderConditionVariable {
 	OCV_CARGO_ACCEPTANCE,   ///< Skip if specified cargo is accepted at next station
 	OCV_FREE_PLATFORMS,     ///< Skip based on free platforms at next station
 	OCV_PERCENT,            ///< Skip xx percent of times
+	OCV_SLOT_OCCUPANCY,     ///< Test if train slot is fully occupied
 	OCV_END
 };
 

src/saveload/extended_ver_sl.cpp

@@ -49,6 +49,7 @@ static const uint32 _sl_xv_slxi_chunk_version = 0;          ///< current version
 const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_TRACE_RESTRICT,         XSCF_NULL,                8,   8, "tracerestrict",             NULL, NULL, "TRRM,TRRP,TRRS" },
 	{ XSLFI_TRACE_RESTRICT_OWNER,   XSCF_NULL,                1,   1, "tracerestrict_owner",       NULL, NULL, NULL        },
+	{ XSLFI_TRACE_RESTRICT_ORDRCND, XSCF_NULL,                1,   1, "tracerestrict_order_cond",  NULL, NULL, NULL        },
 	{ XSLFI_PROG_SIGS,              XSCF_NULL,                1,   1, "programmable_signals",      NULL, NULL, "SPRG"      },
 	{ XSLFI_ADJACENT_CROSSINGS,     XSCF_NULL,                1,   1, "adjacent_crossings",        NULL, NULL, NULL        },
 	{ XSLFI_SAFER_CROSSINGS,        XSCF_NULL,                1,   1, "safer_crossings",           NULL, NULL, NULL        },

src/saveload/extended_ver_sl.h

@@ -23,6 +23,7 @@ enum SlXvFeatureIndex {
 	XSLFI_NULL                          = 0,      ///< Unused value, to indicate that no extended feature test is in use
 	XSLFI_TRACE_RESTRICT,                         ///< Trace restrict
 	XSLFI_TRACE_RESTRICT_OWNER,                   ///< Trace restrict: train owner test
+	XSLFI_TRACE_RESTRICT_ORDRCND,                 ///< Trace restrict: slot conditional order
 	XSLFI_PROG_SIGS,                              ///< programmable signals patch
 	XSLFI_ADJACENT_CROSSINGS,                     ///< Adjacent level crossings closure patch
 	XSLFI_SAFER_CROSSINGS,                        ///< Safer level crossings

src/tracerestrict.cpp

@@ -1661,6 +1661,7 @@ CommandCost CmdDeleteTraceRestrictSlot(TileIndex tile, DoCommandFlag flags, uint
 
 		InvalidateWindowClassesData(WC_TRACE_RESTRICT);
 		InvalidateWindowClassesData(WC_TRACE_RESTRICT_SLOTS);
+		InvalidateWindowClassesData(WC_VEHICLE_ORDERS);
 	}
 
 	return CommandCost();
@@ -1707,6 +1708,7 @@ CommandCost CmdAlterTraceRestrictSlot(TileIndex tile, DoCommandFlag flags, uint3
 		// update windows
 		InvalidateWindowClassesData(WC_TRACE_RESTRICT);
 		InvalidateWindowClassesData(WC_TRACE_RESTRICT_SLOTS);
+		InvalidateWindowClassesData(WC_VEHICLE_ORDERS);
 	}
 
 	return CommandCost();

src/tracerestrict_gui.cpp

@@ -457,7 +457,7 @@ static int CDECL SlotNameSorter(const TraceRestrictSlot * const *a, const TraceR
 /**
  * Get a DropDownList of the group list
  */
-static DropDownList *GetSlotDropDownList(Owner owner, TraceRestrictSlotID slot_id, int &selected)
+DropDownList *GetSlotDropDownList(Owner owner, TraceRestrictSlotID slot_id, int &selected)
 {
 	GUIList<const TraceRestrictSlot*> list;
 

src/widgets/order_widget.h

@@ -35,8 +35,9 @@ enum OrderWidgets {
 	WID_O_COND_VARIABLE,             ///< Choose condition variable.
 	WID_O_COND_COMPARATOR,           ///< Choose condition type.
 	WID_O_COND_VALUE,                ///< Choose condition value.
-	WID_O_COND_CARGO,
+	WID_O_COND_CARGO,                ///< Choose condition cargo.
-	WID_O_SEL_COND_VALUE,            ///< widget for conditional value or conditional cargo type.
+	WID_O_COND_SLOT,                 ///< Choose condition slot.
+	WID_O_SEL_COND_VALUE,            ///< Widget for conditional value or conditional cargo type.
 	WID_O_SEL_TOP_LEFT,              ///< #NWID_SELECTION widget for left part of the top row of the 'your train' order window.
 	WID_O_SEL_TOP_MIDDLE,            ///< #NWID_SELECTION widget for middle part of the top row of the 'your train' order window.
 	WID_O_SEL_TOP_RIGHT,             ///< #NWID_SELECTION widget for right part of the top row of the 'your train' order window.