(svn r7299) -CodeChange: Train and Aircraft Build window GUI code simplified a bit:

- using one engine list instead of 3
- removed engine filters (loco, wagons, helicopters, etc.)
- EngineList code isolated from GUI (moved to helpers.cpp - reusing CBlobT code which does exactly what is needed for EngineList)
- removed unnecessary  "optimization" (rebuild and sort engine list on each WE_PAINT)

10 files changed, 306 insertions, 392 deletions

diff --git a/Makefile b/Makefile
index 0da359dcc..5d29b8bcb 100644
--- a/Makefile
+++ b/Makefile
@@ -707,6 +707,7 @@ SRCS += gfx.c
 SRCS += gfxinit.c
 SRCS += graph_gui.c
 SRCS += heightmap.c
+SRCS += helpers.cpp
 SRCS += industry_cmd.c
 SRCS += industry_gui.c
 SRCS += intro_gui.c
diff --git a/build_vehicle_gui.c b/build_vehicle_gui.c
index cd8817920..32a4949f6 100644
--- a/build_vehicle_gui.c
+++ b/build_vehicle_gui.c
@@ -32,9 +32,6 @@ typedef enum BuildVehicleWidgets {
 	BUILD_VEHICLE_WIDGET_LIST,
 	BUILD_VEHICLE_WIDGET_SCROLLBAR,
 	BUILD_VEHICLE_WIDGET_PANEL,
-	BUILD_VEHICLE_WIDGET_PLANES,
-	BUILD_VEHICLE_WIDGET_JETS,
-	BUILD_VEHICLE_WIDGET_HELICOPTERS,
 	BUILD_VEHICLE_WIDGET_BUILD,
 	BUILD_VEHICLE_WIDGET_RENAME,
 	BUILD_VEHICLE_WIDGET_RESIZE,
@@ -50,13 +47,9 @@ static const Widget _build_vehicle_widgets[] = {
 	{  WWT_SCROLLBAR, RESIZE_BOTTOM,    14,   228,   239,    26,   121, 0x0,                     STR_0190_SCROLL_BAR_SCROLLS_LIST },
 	{      WWT_PANEL,     RESIZE_TB,    14,     0,   239,   122,   213, 0x0,                     STR_NULL },
 
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,     0,    79,   214,   225, STR_BLACK_PLANES,        STR_BUILD_PLANES_TIP },
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,    80,   159,   214,   225, STR_BLACK_JETS,          STR_BUILD_JETS_TIP },
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,   160,   239,   214,   225, STR_BLACK_HELICOPTERS,   STR_BUILD_HELICOPTERS_TIP },
-
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,     0,   114,   226,   237, STR_A006_BUILD_AIRCRAFT, STR_A026_BUILD_THE_HIGHLIGHTED_AIRCRAFT },
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,   115,   227,   226,   237, STR_A037_RENAME,         STR_A038_RENAME_AIRCRAFT_TYPE },
-	{  WWT_RESIZEBOX,     RESIZE_TB,    14,   228,   239,   226,   237, 0x0,                     STR_RESIZE_BUTTON },
+	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,     0,   114,   214,   225, STR_A006_BUILD_AIRCRAFT, STR_A026_BUILD_THE_HIGHLIGHTED_AIRCRAFT },
+	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,   115,   227,   214,   225, STR_A037_RENAME,         STR_A038_RENAME_AIRCRAFT_TYPE },
+	{  WWT_RESIZEBOX,     RESIZE_TB,    14,   228,   239,   214,   225, 0x0,                     STR_RESIZE_BUTTON },
 	{   WIDGETS_END},
 };
 
@@ -64,8 +57,6 @@ static bool _internal_sort_order; // descending/ascending
 static byte _last_sort_criteria = 0;
 static bool _last_sort_order = false;
 
-typedef int CDECL VehicleSortListingTypeFunction(const void*, const void*);
-
 static int CDECL EngineNumberSorter(const void *a, const void *b)
 {
 	const EngineID va = *(const EngineID*)a;
@@ -179,7 +170,7 @@ static int CDECL AircraftEngineCargoSorter(const void *a, const void *b)
 	return _internal_sort_order ? -r : r;
 }
 
-static VehicleSortListingTypeFunction* const _aircraft_sorter[] = {
+static EngList_SortTypeFunction * const _aircraft_sorter[] = {
 	&EngineNumberSorter,
 	&AircraftEngineCostSorter,
 	&AircraftEngineSpeedSorter,
@@ -286,135 +277,87 @@ void CcBuildAircraft(bool success, TileIndex tile, uint32 p1, uint32 p2)
 	}
 }
 
-static inline void ExtendEngineListSize(EngineID **engine_list, uint16 *engine_list_length, uint16 step_size, uint16 max)
-{
-	*engine_list_length = min(*engine_list_length + step_size, max);
-	*engine_list = realloc((void*)*engine_list, (*engine_list_length) * sizeof((*engine_list)[0]));
-}
-
-static void GenerateBuildAircraftList(EngineID **planes, uint16 *num_planes, EngineID **jets, uint16 *num_jets, EngineID **helicopters, uint16 *num_helicopters)
+static void GenerateBuildAircraftList(Window *w)
 {
-	uint16 plane_length      = *num_planes;
-	uint16 jet_length        = *num_jets;
-	uint16 helicopter_length = *num_helicopters;
 	EngineID eid;
+	buildvehicle_d *bv = &WP(w, buildvehicle_d);
 
-	(*num_planes)      = 0;
-	(*num_jets)        = 0;
-	(*num_helicopters) = 0;
+	EngList_RemoveAll(&bv->eng_list);
 
 	for (eid = AIRCRAFT_ENGINES_INDEX; eid < AIRCRAFT_ENGINES_INDEX + NUM_AIRCRAFT_ENGINES; eid++) {
-
 		if (IsEngineBuildable(eid, VEH_Aircraft)) {
 			const AircraftVehicleInfo *avi = AircraftVehInfo(eid);
-
-			switch (avi->subtype) {
-				case AIR_CTOL: // Propeller planes
-					if (*num_planes == plane_length) ExtendEngineListSize(planes, &plane_length, 5, NUM_AIRCRAFT_ENGINES);
-					(*planes)[(*num_planes)++] = eid;
+			switch (bv->filter.acc_planes) {
+				case HELICOPTERS_ONLY:
+					if (avi->subtype != 0) continue; // if not helicopter
 					break;
 
-				case (AIR_CTOL | AIR_FAST): // Jet planes
-					if (*num_jets == jet_length) ExtendEngineListSize(jets, &jet_length, 5, NUM_AIRCRAFT_ENGINES);
-					(*jets)[(*num_jets)++] = eid;
+				case AIRCRAFT_ONLY:
+					if (avi->subtype == 0) continue; // if helicopter
 					break;
 
-				case 0: // Helicopters
-					if (*num_helicopters == helicopter_length) ExtendEngineListSize(helicopters, &helicopter_length, 5, NUM_AIRCRAFT_ENGINES);
-					(*helicopters)[(*num_helicopters)++] = eid;
+				case ALL:
 					break;
 			}
+			EngList_Add(&bv->eng_list, eid);
 		}
 	}
 }
 
 static void GenerateBuildList(Window *w)
 {
-	switch (WP(w, buildvehicle_d).vehicle_type) {
+	buildvehicle_d *bv = &WP(w, buildvehicle_d);
+
+	switch (bv->vehicle_type) {
 		case VEH_Aircraft:
-			GenerateBuildAircraftList(&WP(w, buildvehicle_d).list_a, &WP(w, buildvehicle_d).list_a_length,
-									  &WP(w, buildvehicle_d).list_b, &WP(w, buildvehicle_d).list_b_length,
-									  &WP(w, buildvehicle_d).list_c, &WP(w, buildvehicle_d).list_c_length);
+			GenerateBuildAircraftList(w);
+			_internal_sort_order = WP(w,buildvehicle_d).descending_sort_order;
+			EngList_Sort(&WP(w, buildvehicle_d).eng_list, _aircraft_sorter[WP(w,buildvehicle_d).sort_criteria]);
 			break;
 
 		default: NOT_REACHED();
 	}
-
-	/* Ensure that we do not have trailing unused blocks in the arrays. We will never be able to access them anyway since we are unaware that they are there */
-	WP(w, buildvehicle_d).list_a = realloc((void*)WP(w, buildvehicle_d).list_a, WP(w, buildvehicle_d).list_a_length * sizeof(WP(w, buildvehicle_d).list_a[0]));
-	WP(w, buildvehicle_d).list_b = realloc((void*)WP(w, buildvehicle_d).list_b, WP(w, buildvehicle_d).list_b_length * sizeof(WP(w, buildvehicle_d).list_b[0]));
-	WP(w, buildvehicle_d).list_c = realloc((void*)WP(w, buildvehicle_d).list_c, WP(w, buildvehicle_d).list_c_length * sizeof(WP(w, buildvehicle_d).list_c[0]));
-
-	WP(w, buildvehicle_d).data_invalidated = false; // No need to regenerate the list anymore. We just did it
 }
 
-static inline EngineID *GetEngineArray(Window *w)
+static inline const EngineID *GetEngineArray(Window *w)
 {
-	switch (WP(w,buildvehicle_d).show_engine_button) {
-		case 1: return WP(w, buildvehicle_d).list_a;
-		case 2: return WP(w, buildvehicle_d).list_b;
-		case 3: return WP(w, buildvehicle_d).list_c;
-		default: NOT_REACHED();
-	}
-	return NULL;
+	return WP(w, buildvehicle_d).eng_list;
 }
 
 static inline uint16 GetEngineArrayLength(Window *w)
 {
-	switch (WP(w,buildvehicle_d).show_engine_button) {
-		case 1: return WP(w, buildvehicle_d).list_a_length;
-		case 2: return WP(w, buildvehicle_d).list_b_length;
-		case 3: return WP(w, buildvehicle_d).list_c_length;
-		default: NOT_REACHED();
-	}
-	return 0;
-}
-
-static void SortAircraftBuildList(Window *w)
-{
-	_internal_sort_order = WP(w,buildvehicle_d).decenting_sort_order;
-	qsort((void*)GetEngineArray(w), GetEngineArrayLength(w), sizeof(GetEngineArray(w)[0]),
-		  _aircraft_sorter[WP(w,buildvehicle_d).sort_criteria]);
+	return EngList_Count(&WP(w, buildvehicle_d).eng_list);
 }
 
 static void DrawBuildAircraftWindow(Window *w)
 {
-	SetWindowWidgetLoweredState(w, BUILD_VEHICLE_WIDGET_PLANES,      WP(w,buildvehicle_d).show_engine_button == 1);
-	SetWindowWidgetLoweredState(w, BUILD_VEHICLE_WIDGET_JETS,        WP(w,buildvehicle_d).show_engine_button == 2);
-	SetWindowWidgetLoweredState(w, BUILD_VEHICLE_WIDGET_HELICOPTERS, WP(w,buildvehicle_d).show_engine_button == 3);
+	buildvehicle_d *bv = &WP(w, buildvehicle_d);
 
 	SetWindowWidgetDisabledState(w, BUILD_VEHICLE_WIDGET_BUILD, w->window_number == 0);
 
-	if (WP(w, buildvehicle_d).data_invalidated) {
-		GenerateBuildList(w);
+	GenerateBuildList(w);
 
-		if (WP(w,buildvehicle_d).sel_engine != INVALID_ENGINE) {
-			int i;
-			bool found = false;
-			if (HASBIT(WP(w,buildvehicle_d).show_engine_button, 0)) {
-				for (i = 0; i < GetEngineArrayLength(w); i++) {
-					if (WP(w,buildvehicle_d).sel_engine != GetEngineArray(w)[i]) continue;
-					found = true;
-					break;
-				}
-			}
-			if (!found) WP(w,buildvehicle_d).sel_engine = INVALID_ENGINE;
+	if (bv->sel_engine != INVALID_ENGINE) {
+		int i;
+		bool found = false;
+		int num_planes = GetEngineArrayLength(w);
+		for (i = 0; i < num_planes; i++) {
+			if (bv->sel_engine != GetEngineArray(w)[i]) continue;
+			found = true;
+			break;
 		}
+		if (!found) bv->sel_engine = INVALID_ENGINE;
 	}
 
 	SetVScrollCount(w, GetEngineArrayLength(w));
 	DrawWindowWidgets(w);
 
-	if (WP(w,buildvehicle_d).sel_engine == INVALID_ENGINE && GetEngineArrayLength(w) != 0) {
-		WP(w,buildvehicle_d).sel_engine = GetEngineArray(w)[0];
-	}
-
 	{
 		int x = 2;
 		int y = 27;
-		EngineID selected_id = WP(w,buildvehicle_d).sel_engine;
+		EngineID selected_id = bv->sel_engine;
 		EngineID eid = w->vscroll.pos;
-		EngineID *list = GetEngineArray(w);
+		const EngineID *list = GetEngineArray(w);
 		uint16 list_length = GetEngineArrayLength(w);
 		uint16 max = min(w->vscroll.pos + w->vscroll.cap, list_length);
 
@@ -431,19 +374,19 @@ static void DrawBuildAircraftWindow(Window *w)
 			DrawAircraftPurchaseInfo(x, wi->top + 1, wi->right - wi->left - 2, selected_id);
 		}
 	}
-	DrawString(85, 15, _aircraft_sort_listing[WP(w,buildvehicle_d).sort_criteria], 0x10);
-	DoDrawString(WP(w,buildvehicle_d).decenting_sort_order ? DOWNARROW : UPARROW, 69, 15, 0x10);
+	DrawString(85, 15, _aircraft_sort_listing[bv->sort_criteria], 0x10);
+	DoDrawString(bv->descending_sort_order ? DOWNARROW : UPARROW, 69, 15, 0x10);
 }
 
 static void BuildAircraftClickEvent(Window *w, WindowEvent *e)
 {
-	byte click_state = 0;
+	buildvehicle_d *bv = &WP(w, buildvehicle_d);
 
 	switch (e->we.click.widget) {
 		case BUILD_VEHICLE_WIDGET_SORT_ASSENDING_DESCENDING:
-			WP(w,buildvehicle_d).decenting_sort_order = !WP(w,buildvehicle_d).decenting_sort_order;
-			_last_sort_order = WP(w,buildvehicle_d).decenting_sort_order;
-			SortAircraftBuildList(w);
+			bv->descending_sort_order = !bv->descending_sort_order;
+			_last_sort_order = bv->descending_sort_order;
+			GenerateBuildList(w);
 			SetWindowDirty(w);
 			break;
 
@@ -451,60 +394,46 @@ static void BuildAircraftClickEvent(Window *w, WindowEvent *e)
 			uint i = (e->we.click.pt.y - 26) / 24;
 			if (i < w->vscroll.cap) {
 				i += w->vscroll.pos;
-
-				if (i < GetEngineArrayLength(w)) {
-					WP(w,buildvehicle_d).sel_engine = GetEngineArray(w)[i];
-					SetWindowDirty(w);
-				}
+				bv->sel_engine = (i < GetEngineArrayLength(w)) ? GetEngineArray(w)[i] : INVALID_ENGINE;
+				SetWindowDirty(w);
 			}
-		} break;
+			break;
+		}
 
 		case BUILD_VEHICLE_WIDGET_SORT_TEXT: case BUILD_VEHICLE_WIDGET_SORT_DROPDOWN:/* Select sorting criteria dropdown menu */
-			ShowDropDownMenu(w, _aircraft_sort_listing, WP(w,buildvehicle_d).sort_criteria, BUILD_VEHICLE_WIDGET_SORT_DROPDOWN, 0, 0);
+			ShowDropDownMenu(w, _aircraft_sort_listing, bv->sort_criteria, BUILD_VEHICLE_WIDGET_SORT_DROPDOWN, 0, 0);
 			return;
 
-		case BUILD_VEHICLE_WIDGET_HELICOPTERS: click_state++;
-		case BUILD_VEHICLE_WIDGET_JETS:        click_state++;
-		case BUILD_VEHICLE_WIDGET_PLANES:      click_state++;
-
-			if (WP(w,buildvehicle_d).show_engine_button == click_state) break; // We clicked the pressed button
-
-				WP(w,buildvehicle_d).sel_engine = INVALID_ENGINE;
-			WP(w,buildvehicle_d).show_engine_button = click_state;
-			w->vscroll.pos = 0;
-			SortAircraftBuildList(w);
-			SetWindowDirty(w);
-			break;
-
 		case BUILD_VEHICLE_WIDGET_BUILD: {
-			EngineID sel_eng = WP(w,buildvehicle_d).sel_engine;
+			EngineID sel_eng = bv->sel_engine;
 			if (sel_eng != INVALID_ENGINE)
 				DoCommandP(w->window_number, sel_eng, 0, CcBuildAircraft, CMD_BUILD_AIRCRAFT | CMD_MSG(STR_A008_CAN_T_BUILD_AIRCRAFT));
-		} break;
+			break;
+		}
 
 		case BUILD_VEHICLE_WIDGET_RENAME: {
-			EngineID sel_eng = WP(w,buildvehicle_d).sel_engine;
+			EngineID sel_eng = bv->sel_engine;
 			if (sel_eng != INVALID_ENGINE) {
-				WP(w,buildvehicle_d).rename_engine = sel_eng;
+				bv->rename_engine = sel_eng;
 				ShowQueryString(GetCustomEngineName(sel_eng),
 								STR_A039_RENAME_AIRCRAFT_TYPE, 31, 160, w->window_class, w->window_number, CS_ALPHANUMERAL);
 			}
-		} break;
+			break;
+		}
 	}
 }
 
 static void NewAircraftWndProc(Window *w, WindowEvent *e)
 {
+	buildvehicle_d *bv = &WP(w, buildvehicle_d);
+
 	switch (e->event) {
 		case WE_INVALIDATE_DATA:
-			WP(w,buildvehicle_d).data_invalidated = true;
 			SetWindowDirty(w);
 			break;
 
 		case WE_DESTROY:
-			free((void*)WP(w, buildvehicle_d).list_a);
-			free((void*)WP(w, buildvehicle_d).list_b);
-			free((void*)WP(w, buildvehicle_d).list_c);
+			EngList_Destroy(&bv->eng_list);
 			break;
 
 		case WE_PAINT:
@@ -518,16 +447,17 @@ static void NewAircraftWndProc(Window *w, WindowEvent *e)
 		case WE_ON_EDIT_TEXT: {
 			if (e->we.edittext.str[0] != '\0') {
 				_cmd_text = e->we.edittext.str;
-				DoCommandP(0, WP(w, buildvehicle_d).rename_engine, 0, NULL,
+				DoCommandP(0, bv->rename_engine, 0, NULL,
 						   CMD_RENAME_ENGINE | CMD_MSG(STR_A03A_CAN_T_RENAME_AIRCRAFT_TYPE));
 			}
-		} break;
+			break;
+		}
 
 		case WE_DROPDOWN_SELECT: /* we have selected a dropdown item in the list */
-			if (WP(w,buildvehicle_d).sort_criteria != e->we.dropdown.index) {
-				WP(w,buildvehicle_d).sort_criteria = e->we.dropdown.index;
+			if (bv->sort_criteria != e->we.dropdown.index) {
+				bv->sort_criteria = e->we.dropdown.index;
 				_last_sort_criteria = e->we.dropdown.index;
-				SortAircraftBuildList(w);
+				GenerateBuildList(w);
 			}
 			SetWindowDirty(w);
 				break;
@@ -540,83 +470,48 @@ static void NewAircraftWndProc(Window *w, WindowEvent *e)
 }
 
 static const WindowDesc _build_vehicle_desc = {
-	WDP_AUTO, WDP_AUTO, 240, 238,
+	WDP_AUTO, WDP_AUTO, 240, 226,
 	WC_BUILD_VEHICLE,0,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS | WDF_RESIZABLE,
 	_build_vehicle_widgets,
 	NewAircraftWndProc
 };
 
-/* Disable the aircraft subtype buttons for the types, that can't be build at the current airport */
-static void CreateAircraftWindow(Window *w)
-{
-	TileIndex tile = w->window_number;
-
-	if (tile == 0) {
-		WP(w, buildvehicle_d).show_engine_button = 1;
-	} else {
-		byte acc_planes = GetAirport(GetStationByTile(tile)->airport_type)->acc_planes;
-
-		WP(w, buildvehicle_d).show_engine_button = 0;
-		if (acc_planes == HELICOPTERS_ONLY || acc_planes == ALL) {
-			WP(w, buildvehicle_d).show_engine_button = 3;
-		} else {
-			DisableWindowWidget(w, BUILD_VEHICLE_WIDGET_HELICOPTERS);
-		}
-
-		if (acc_planes == AIRCRAFT_ONLY || acc_planes == ALL) {
-			/* Set the start clicked button to jets if the list isn't empty. If not, then show propeller planes */
-			WP(w, buildvehicle_d).show_engine_button = WP(w, buildvehicle_d).list_b_length == 0 ? 1 : 2;
-		} else {
-			DisableWindowWidget(w, BUILD_VEHICLE_WIDGET_JETS);
-			DisableWindowWidget(w, BUILD_VEHICLE_WIDGET_PLANES);
-		}
-
-		if (WP(w, buildvehicle_d).show_engine_button == 0) {
-			/* No plane type are buildable here */
-			NOT_REACHED();
-			WP(w, buildvehicle_d).show_engine_button = 1;
-		}
-	}
-}
-
 void ShowBuildVehicleWindow(TileIndex tile, byte type)
 {
+	buildvehicle_d *bv;
 	Window *w;
 
 	DeleteWindowById(WC_BUILD_VEHICLE, tile);
-
 	w = AllocateWindowDescFront(&_build_vehicle_desc, tile);
-
 	if (w == NULL) return;
 
-	WP(w, buildvehicle_d).vehicle_type = type;
-
-	w->resize.step_height = GetVehicleListHeight(type);
-	w->vscroll.cap = 4;
-	w->widget[BUILD_VEHICLE_WIDGET_LIST].data = (w->vscroll.cap << 8) + 1;
-
 	if (tile != 0) {
 		w->caption_color = GetTileOwner(tile);
 	} else {
 		w->caption_color = _local_player;
 	}
 
-	WP(w, buildvehicle_d).list_a_length = 0;
-	WP(w, buildvehicle_d).list_b_length = 0;
-	WP(w, buildvehicle_d).list_c_length = 0;
-	WP(w, buildvehicle_d).list_a        = NULL;
-	WP(w, buildvehicle_d).list_b        = NULL;
-	WP(w, buildvehicle_d).list_c        = NULL;
-	WP(w, buildvehicle_d).sel_engine           = INVALID_ENGINE;
-	WP(w, buildvehicle_d).sort_criteria        = _last_sort_criteria;
-	WP(w, buildvehicle_d).decenting_sort_order = _last_sort_order;
+	w->resize.step_height = GetVehicleListHeight(type);
+	w->vscroll.cap = 4;
+	w->widget[BUILD_VEHICLE_WIDGET_LIST].data = (w->vscroll.cap << 8) + 1;
+
+	bv = &WP(w, buildvehicle_d);
+	EngList_Create(&bv->eng_list);
+	bv->sel_engine           = INVALID_ENGINE;
+	bv->sort_criteria        = _last_sort_criteria;
+	bv->descending_sort_order = _last_sort_order;
+
+	bv->vehicle_type = type;
 
-	GenerateBuildList(w);
 	switch (type) {
-		case VEH_Aircraft: CreateAircraftWindow(w); break;
+		case VEH_Aircraft: {
+			byte acc_planes = GetAirport(GetStationByTile(tile)->airport_type)->acc_planes;
+			bv->filter.acc_planes = acc_planes;
+			break;
+		}
 		default: NOT_REACHED();
 	}
 
-	SortAircraftBuildList(w);
+	GenerateBuildList(w);
 }
diff --git a/engine.h b/engine.h
index 6fff71368..adb07cf44 100644
--- a/engine.h
+++ b/engine.h
@@ -293,4 +293,15 @@ int32 AddEngineReplacement(EngineRenewList* erl, EngineID old_engine, EngineID n
  */
 int32 RemoveEngineReplacement(EngineRenewList* erl, EngineID engine, uint32 flags);
 
+/* Engine list manipulators - current implementation is only C wrapper of CBlobT<EngineID> class (helpers.cpp) */
+void EngList_Create(EngineList *el);            ///< Creates engine list
+void EngList_Destroy(EngineList *el);           ///< Deallocate and destroy engine list
+uint EngList_Count(const EngineList *el);       ///< Returns number of items in the engine list
+void EngList_Add(EngineList *el, EngineID eid); ///< Append one item at the end of engine list
+EngineID* EngList_Items(EngineList *el);        ///< Returns engine list items as C array
+void EngList_RemoveAll(EngineList *el);         ///< Removes all items from engine list
+typedef int CDECL EngList_SortTypeFunction(const void*, const void*); ///< argument type for EngList_Sort()
+void EngList_Sort(EngineList *el, EngList_SortTypeFunction compare); ///< qsort of the engine list
+void EngList_SortPartial(EngineList *el, EngList_SortTypeFunction compare, uint begin, uint num_items); ///< qsort of specified portion of the engine list
+
 #endif /* ENGINE_H */
diff --git a/helpers.cpp b/helpers.cpp
new file mode 100644
index 000000000..f8f6aa24f
--- /dev/null
+++ b/helpers.cpp
@@ -0,0 +1,69 @@
+#include "stdafx.h"

+

+EXTERN_C_BEGIN

+#include "openttd.h"

+#include "engine.h"

+EXTERN_C_END

+

+#include <new>

+#include "yapf/blob.hpp"

+

+/* Engine list manipulators - current implementation is only C wrapper around CBlobT<EngineID> (see yapf/blob.hpp) */

+

+/* we cannot expose CBlobT directly to C so we must cast EngineList* to CBlobT<EngineID>* always when we are called from C */

+#define B (*(CBlobT<EngineID>*)el)

+

+/** Create Engine List (and initialize it to empty) */

+void EngList_Create(EngineList *el)

+{

+	// call CBlobT constructor explicitly

+	new (&B) CBlobT<EngineID>();

+}

+

+/** Destroy Engine List (and free its contents) */

+void EngList_Destroy(EngineList *el)

+{

+	// call CBlobT destructor explicitly

+	B.~CBlobT<EngineID>();

+}

+

+/** Return number of items stored in the Engine List */

+uint EngList_Count(const EngineList *el)

+{

+	return B.Size();

+}

+

+/** Add new item at the end of Engine List */

+void EngList_Add(EngineList *el, EngineID eid)

+{

+	B.Append(eid);

+}

+

+/** Return pointer to the items array held by Engine List */

+EngineID* EngList_Items(EngineList *el)

+{

+	return B.Data();

+}

+

+/** Clear the Engine List (by invalidating all its items == reseting item count to zero) */

+void EngList_RemoveAll(EngineList *el)

+{

+	B.Clear();

+}

+

+/** Sort all items using qsort() and given 'CompareItems' function */

+void EngList_Sort(EngineList *el, EngList_SortTypeFunction compare)

+{

+	qsort(B.Data(), B.Size(), sizeof(**el), compare);

+}

+

+/** Sort selected range of items (on indices @ <begin, begin+num_items-1>) */

+void EngList_SortPartial(EngineList *el, EngList_SortTypeFunction compare, uint begin, uint num_items)

+{

+	assert(begin <= (uint)B.Size());

+	assert(begin + num_items <= (uint)B.Size());

+	qsort(B.Data() + begin, num_items, sizeof(**el), compare);

+}

+

+#undef B

+

diff --git a/lang/english.txt b/lang/english.txt
index 4d57418f8..6e1374914 100644
--- a/lang/english.txt
+++ b/lang/english.txt
@@ -2508,10 +2508,13 @@ STR_8816                                                        :{BLACK}-
 STR_8819_TRAIN_TOO_LONG                                         :{WHITE}Train too long
 STR_881A_TRAINS_CAN_ONLY_BE_ALTERED                             :{WHITE}Trains can only be altered when stopped inside a depot
 STR_881B_TRAINS                                                 :{WHITE}{COMPANY} - {COMMA} Train{P "" s}
+
 STR_881C_NEW_RAIL_VEHICLES                                      :{WHITE}New Rail Vehicles
 STR_NEW_ELRAIL_VEHICLES                                         :{WHITE}New Electric Rail Vehicles
 STR_881D_NEW_MONORAIL_VEHICLES                                  :{WHITE}New Monorail Vehicles
 STR_881E_NEW_MAGLEV_VEHICLES                                    :{WHITE}New Maglev Vehicles
+STR_ALL_AVAIL_RAIL_VEHICLES                                     :{WHITE}Rail Vehicles
+
 STR_881F_BUILD_VEHICLE                                          :{BLACK}Build Vehicle
 STR_CLONE_ROAD_VEHICLE                                          :{BLACK}Clone Vehicle
 STR_CLONE_ROAD_VEHICLE_INFO                                     :{BLACK}This will build a copy of the road vehicle. Control-click will share the orders
@@ -2560,12 +2563,6 @@ STR_8840_BUILD_NEW_TRAIN_VEHICLE                                :{BLACK}Build ne
 STR_8841_DRAG_TRAIN_VEHICLE_TO_HERE                             :{BLACK}Drag train vehicle to here to sell it
 STR_8842_CENTER_MAIN_VIEW_ON_TRAIN                              :{BLACK}Centre main view on train depot location
 STR_8843_TRAIN_VEHICLE_SELECTION                                :{BLACK}Train vehicle selection list - click on vehicle for information
-STR_BLACK_ENGINES                                               :{BLACK}Engines
-STR_BLACK_WAGONS                                                :{BLACK}Wagons
-STR_BLACK_BOTH                                                  :{BLACK}Both
-STR_BUILD_TRAIN_ENGINES_TIP                                     :{BLACK}Click to see engines only
-STR_BUILD_TRAIN_WAGONS_TIP                                      :{BLACK}Click to see wagons only
-STR_BUILD_TRAIN_BOTH_TIP                                        :{BLACK}Click to see both engines and wagons
 STR_8844_BUILD_THE_HIGHLIGHTED_TRAIN                            :{BLACK}Build the highlighted train vehicle
 STR_8845_RENAME_TRAIN_VEHICLE_TYPE                              :{BLACK}Rename train vehicle type
 STR_8846_CURRENT_TRAIN_ACTION_CLICK                             :{BLACK}Current train action - click here to stop/start train
@@ -2794,12 +2791,6 @@ STR_A01E_BUILD_AIRPORT                                          :{BLACK}Build ai
 STR_A01F_AIRCRAFT_CLICK_ON_AIRCRAFT                             :{BLACK}Aircraft - click on aircraft for information
 STR_A020_BUILD_NEW_AIRCRAFT_REQUIRES                            :{BLACK}Build new aircraft (requires airport with hangar)
 STR_A021_AIRCRAFT_CLICK_ON_AIRCRAFT                             :{BLACK}Aircraft - click on aircraft for information
-STR_BLACK_PLANES                                                :{BLACK}Propellers
-STR_BLACK_JETS                                                  :{BLACK}Jets
-STR_BLACK_HELICOPTERS                                           :{BLACK}Helicopters
-STR_BUILD_PLANES_TIP                                            :{BLACK}Click to see propeller planes
-STR_BUILD_JETS_TIP                                              :{BLACK}Click to see jet planes
-STR_BUILD_HELICOPTERS_TIP                                       :{BLACK}Click to see helicopters
 STR_A022_BUILD_NEW_AIRCRAFT                                     :{BLACK}Build new aircraft
 STR_A023_DRAG_AIRCRAFT_TO_HERE_TO                               :{BLACK}Drag aircraft to here to sell it
 STR_A024_CENTER_MAIN_VIEW_ON_HANGAR                             :{BLACK}Centre main view on hangar location
diff --git a/openttd.h b/openttd.h
index 204392741..277b3690b 100644
--- a/openttd.h
+++ b/openttd.h
@@ -55,6 +55,7 @@ typedef uint32 CursorID;
 typedef uint16 EngineID;
 typedef uint16 UnitID;
 typedef uint16 StringID;
+typedef EngineID *EngineList; ///< engine list type placeholder acceptable for C code (see helpers.cpp)
 
 /* IDs used in Pools */
 typedef uint16 VehicleID;
diff --git a/openttd.vcproj b/openttd.vcproj
index 5660ba8f7..efd472311 100644
--- a/openttd.vcproj
+++ b/openttd.vcproj
@@ -250,6 +250,21 @@
 				RelativePath=".\heightmap.c">
 			</File>
 			<File
+				RelativePath=".\helpers.cpp">
+				<FileConfiguration
+					Name="Release|Win32">
+					<Tool
+						Name="VCCLCompilerTool"
+						CompileAs="2"/>
+				</FileConfiguration>
+				<FileConfiguration
+					Name="Debug|Win32">
+					<Tool
+						Name="VCCLCompilerTool"
+						CompileAs="2"/>
+				</FileConfiguration>
+			</File>
+			<File
 				RelativePath=".\landscape.c">
 			</File>
 			<File
diff --git a/openttd_vs80.vcproj b/openttd_vs80.vcproj
index 78a5e4614..79f8ec3d0 100644
--- a/openttd_vs80.vcproj
+++ b/openttd_vs80.vcproj
@@ -581,6 +581,26 @@
 				>
 			</File>
 			<File
+				RelativePath=".\helpers.cpp"
+				>
+				<FileConfiguration
+					Name="Release|Win32"
+					>
+					<Tool
+						Name="VCCLCompilerTool"
+						CompileAs="2"
+					/>
+				</FileConfiguration>
+				<FileConfiguration
+					Name="Debug|Win32"
+					>
+					<Tool
+						Name="VCCLCompilerTool"
+						CompileAs="2"
+					/>
+				</FileConfiguration>
+			</File>
+			<File
 				RelativePath=".\landscape.c"
 				>
 			</File>
diff --git a/train_gui.c b/train_gui.c
index 5d208799e..46ab1ce2e 100644
--- a/train_gui.c
+++ b/train_gui.c
@@ -8,6 +8,7 @@
 #include "table/sprites.h"
 #include "table/strings.h"
 #include "map.h"
+#include "engine.h"
 #include "window.h"
 #include "gui.h"
 #include "gfx.h"
@@ -16,7 +17,6 @@
 #include "station.h"
 #include "command.h"
 #include "player.h"
-#include "engine.h"
 #include "vehicle_gui.h"
 #include "depot.h"
 #include "train.h"
@@ -27,15 +27,12 @@
 typedef enum BuildTrainWidgets {
 	BUILD_TRAIN_WIDGET_CLOSEBOX = 0,
 	BUILD_TRAIN_WIDGET_CAPTION,
-	BUILD_TRAIN_WIDGET_SORT_ASSENDING_DESCENDING,
+	BUILD_TRAIN_WIDGET_SORT_ASCENDING_DESCENDING,
 	BUILD_TRAIN_WIDGET_SORT_TEXT,
 	BUILD_TRAIN_WIDGET_SORT_DROPDOWN,
 	BUILD_TRAIN_WIDGET_LIST,
 	BUILD_TRAIN_WIDGET_SCROLLBAR,
 	BUILD_TRAIN_WIDGET_PANEL,
-	BUILD_TRAIN_WIDGET_ENGINES,
-	BUILD_TRAIN_WIDGET_WAGONS,
-	BUILD_TRAIN_WIDGET_BOTH,
 	BUILD_TRAIN_WIDGET_BUILD,
 	BUILD_TRAIN_WIDGET_RENAME,
 	BUILD_TRAIN_WIDGET_RESIZE,
@@ -50,20 +47,25 @@ static const Widget _new_rail_vehicle_widgets[] = {
 	{     WWT_MATRIX, RESIZE_BOTTOM,    14,     0,   215,    26,   137, 0x801,                  STR_8843_TRAIN_VEHICLE_SELECTION},
 	{  WWT_SCROLLBAR, RESIZE_BOTTOM,    14,   216,   227,    26,   137, 0x0,                    STR_0190_SCROLL_BAR_SCROLLS_LIST},
 	{      WWT_PANEL,     RESIZE_TB,    14,     0,   227,   138,   239, 0x0,                    STR_NULL},
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,     0,    76,   240,   251, STR_BLACK_ENGINES,      STR_BUILD_TRAIN_ENGINES_TIP},
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,    77,   151,   240,   251, STR_BLACK_WAGONS,       STR_BUILD_TRAIN_WAGONS_TIP},
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,   152,   227,   240,   251, STR_BLACK_BOTH,         STR_BUILD_TRAIN_BOTH_TIP},
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,     0,   107,   252,   263, STR_881F_BUILD_VEHICLE, STR_8844_BUILD_THE_HIGHLIGHTED_TRAIN},
-	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,   108,   215,   252,   263, STR_8820_RENAME,        STR_8845_RENAME_TRAIN_VEHICLE_TYPE},
-	{  WWT_RESIZEBOX,     RESIZE_TB,    14,   216,   227,   252,   263, 0x0,                    STR_RESIZE_BUTTON},
+	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,     0,   107,   240,   251, STR_881F_BUILD_VEHICLE, STR_8844_BUILD_THE_HIGHLIGHTED_TRAIN},
+	{ WWT_PUSHTXTBTN,     RESIZE_TB,    14,   108,   215,   240,   251, STR_8820_RENAME,        STR_8845_RENAME_TRAIN_VEHICLE_TYPE},
+	{  WWT_RESIZEBOX,     RESIZE_TB,    14,   216,   227,   240,   251, 0x0,                    STR_RESIZE_BUTTON},
 	{   WIDGETS_END},
 };
 
-static bool _internal_sort_order; // descending/ascending
+static bool _internal_sort_order; // false = ascending, true = descending
 static byte _last_sort_criteria = 0;
 static bool _last_sort_order = false;
 
-typedef int CDECL VehicleSortListingTypeFunction(const void*, const void*);
+static int CDECL TrainEnginesThenWagonsSorter(const void *a, const void *b)
+{
+	EngineID va = *(const EngineID*)a;
+	EngineID vb = *(const EngineID*)b;
+	int val_a = ((RailVehInfo(va)->flags & RVI_WAGON) != 0) ? 1 : 0;
+	int val_b = ((RailVehInfo(vb)->flags & RVI_WAGON) != 0) ? 1 : 0;
+	int r = val_a - val_b;
+	return _internal_sort_order ? -r : r;
+}
 
 static int CDECL TrainEngineNumberSorter(const void *a, const void *b)
 {
@@ -205,7 +207,7 @@ static int CDECL TrainEngineReliabilitySorter(const void *a, const void *b)
 	return _internal_sort_order ? -r : r;
 }
 
-static VehicleSortListingTypeFunction* const _engine_sorter[] = {
+static EngList_SortTypeFunction * const _engine_sorter[] = {
 	&TrainEngineNumberSorter,
 	&TrainEngineCostSorter,
 	&TrainEngineSpeedSorter,
@@ -385,138 +387,82 @@ void CcCloneTrain(bool success, TileIndex tile, uint32 p1, uint32 p2)
 {
 	if (success) ShowTrainViewWindow(GetVehicle(_new_vehicle_id));
 }
-static void engine_drawing_loop(const EngineID *engines, const uint16 engine_count,
-								const int x, int *y, const EngineID sel, EngineID *position, const int16 show_max)
-{
-	for (; (*position) < min(engine_count, show_max); (*position)++) {
-		EngineID i = engines[*position];
 
-		DrawString(x + 59, *y + 2, GetCustomEngineName(i), sel == i ? 0xC : 0x10);
-		DrawTrainEngine(x + 29, *y + 6, i, GetEnginePalette(i, _local_player));
-		*y += 14;
-	}
-}
-
-static inline void ExtendEngineListSize(const EngineID **engine_list, uint16 *engine_list_length, uint16 step_size)
+static void engine_drawing_loop(const EngineList *engines, int x, int *y, EngineID sel, EngineID position, int16 show_max)
 {
-	*engine_list_length = min(*engine_list_length + step_size, NUM_TRAIN_ENGINES);
-	*engine_list = realloc((void*)*engine_list, (*engine_list_length) * sizeof((*engine_list)[0]));
+	int count = min(EngList_Count(engines), show_max);
+	for (; position < count; *y += 14, position++) {
+		EngineID id = (*engines)[position];
+		DrawString(x + 59, *y + 2, GetCustomEngineName(id), sel == id ? 0xC : 0x10);
+		DrawTrainEngine(x + 29, *y + 6, id, GetEnginePalette(id, _local_player));
+	}
 }
 
-static void GenerateBuildList(EngineID **engines, uint16 *num_engines, EngineID **wagons, uint16 *num_wagons, RailType railtype)
+static void GenerateBuildList(Window *w)
 {
-	uint16 engine_length = *num_engines;
-	uint16 wagon_length  = *num_wagons;
 	EngineID j;
+	int num_engines = 0;
+	buildvehicle_d *bv = &WP(w, buildvehicle_d);
 
-	(*num_engines) = 0;
-	(*num_wagons)  = 0;
-
-	if (*engines == NULL) ExtendEngineListSize((const EngineID**)engines, &engine_length, 25);
-	if (*wagons  == NULL) ExtendEngineListSize((const EngineID**)wagons,  &wagon_length,  25);
+	if (w->window_number != 0)
+		bv->filter.railtype = GetRailType(w->window_number);
+	else
+		bv->filter.railtype = RAILTYPE_END;
 
+	EngList_RemoveAll(&bv->eng_list);
+	// make list of all available cars
 	for (j = 0; j < NUM_TRAIN_ENGINES; j++) {
-		EngineID i = GetRailVehAtPosition(j); // XXX Can be removed when the wagon list is also sorted.
-		const Engine *e = GetEngine(i);
-		const RailVehicleInfo *rvi = RailVehInfo(i);
+		EngineID id = GetRailVehAtPosition(j); // XXX Can be removed when the wagon list is also sorted.
+		const Engine *e = GetEngine(id);
+		const RailVehicleInfo *rvi = RailVehInfo(id);
 
-		if (!HasPowerOnRail(e->railtype, railtype)) continue;
-		if (!IsEngineBuildable(i, VEH_Train)) continue;
+		if (bv->filter.railtype != RAILTYPE_END && !HasPowerOnRail(e->railtype, bv->filter.railtype)) continue;
+		if (!IsEngineBuildable(id, VEH_Train)) continue;
 
-		if (rvi->flags & RVI_WAGON) {
-			if (*num_wagons == wagon_length) ExtendEngineListSize((const EngineID**)wagons, &wagon_length, 5);
-			(*wagons)[(*num_wagons)++] = i;
-		} else {
-			if (*num_engines == engine_length) ExtendEngineListSize((const EngineID**)engines, &engine_length, 5);
-			(*engines)[(*num_engines)++] = i;
-		}
+		EngList_Add(&bv->eng_list, id);
+		if ((rvi->flags & RVI_WAGON) == 0) num_engines++;
 	}
-
-	/* Reduce array sizes if they are too big */
-	if (*num_engines != engine_length) *engines = realloc((void*)*engines, (*num_engines) * sizeof((*engines)[0]));
-	if (*num_wagons  != wagon_length)  *wagons  = realloc((void*)*wagons,  (*num_wagons)  * sizeof((*wagons)[0]));
-}
-
-static void SortTrainBuildList(Window *w)
-{
-	_internal_sort_order = WP(w,buildvehicle_d).decenting_sort_order;
-	qsort((void*)WP(w, buildvehicle_d).list_a, WP(w, buildvehicle_d).list_a_length, sizeof(WP(w, buildvehicle_d).list_a[0]),
-		  _engine_sorter[WP(w,buildvehicle_d).sort_criteria]);
+	// make engines first, and then wagons
+	_internal_sort_order = false;
+	EngList_Sort(&bv->eng_list, TrainEnginesThenWagonsSorter);
+	// and then sort engines
+	_internal_sort_order = WP(w,buildvehicle_d).descending_sort_order;
+	EngList_SortPartial(&bv->eng_list, _engine_sorter[bv->sort_criteria], 0, num_engines);
 }
 
 static void DrawTrainBuildWindow(Window *w)
 {
+	buildvehicle_d *bv = &WP(w,buildvehicle_d);
+	int num_engines = EngList_Count(&bv->eng_list);
 	int x = 1;
 	int y = 27;
-	EngineID position = w->vscroll.pos;
-	EngineID selected_id = WP(w,buildvehicle_d).sel_engine;
+	EngineID selected_id = bv->sel_engine;
 	int max = w->vscroll.pos + w->vscroll.cap;
 	uint16 scrollcount = 0;
 
 	SetWindowWidgetDisabledState(w, BUILD_TRAIN_WIDGET_BUILD, w->window_number == 0); // Disable unless we got a depot to build in
-
-	/* Draw the clicked engine/wagon/both button pressed and unpress the other two */
-	SetWindowWidgetLoweredState(w, BUILD_TRAIN_WIDGET_ENGINES, WP(w,buildvehicle_d).show_engine_button == 1);
-	SetWindowWidgetLoweredState(w, BUILD_TRAIN_WIDGET_WAGONS,  WP(w,buildvehicle_d).show_engine_button == 2);
-	SetWindowWidgetLoweredState(w, BUILD_TRAIN_WIDGET_BOTH,    WP(w,buildvehicle_d).show_engine_button == 3);
-
-	if (WP(w,buildvehicle_d).data_invalidated) {
-		GenerateBuildList(&WP(w, buildvehicle_d).list_a, &WP(w, buildvehicle_d).list_a_length, &WP(w, buildvehicle_d).list_b, &WP(w, buildvehicle_d).list_b_length, WP(w,buildvehicle_d).railtype);
-		WP(w,buildvehicle_d).data_invalidated = false;
-		SortTrainBuildList(w);
-
-		/* Make sure that the selected engine is still in the list*/
-		if (WP(w,buildvehicle_d).sel_engine != INVALID_ENGINE) {
-			int i;
-			bool found = false;
-			if (HASBIT(WP(w,buildvehicle_d).show_engine_button, 0)) {
-				for (i = 0; i < WP(w, buildvehicle_d).list_a_length; i++) {
-					if (WP(w,buildvehicle_d).sel_engine != WP(w, buildvehicle_d).list_a[i]) continue;
-					found = true;
-					break;
-				}
-			}
-			if (!found && HASBIT(WP(w,buildvehicle_d).show_engine_button, 1)) {
-				for (i = 0; i < WP(w, buildvehicle_d).list_b_length; i++) {
-					if (WP(w,buildvehicle_d).sel_engine != WP(w, buildvehicle_d).list_b[i]) continue;
-					found = true;
-					break;
-				}
-			}
-			if (!found) WP(w,buildvehicle_d).sel_engine = INVALID_ENGINE;
+	GenerateBuildList(w);
+
+	/* Make sure that the selected engine is still in the list*/
+	if (bv->sel_engine != INVALID_ENGINE) {
+		int i;
+		bool found = false;
+		for (i = 0; i < num_engines; i++) {
+			if (bv->sel_engine != bv->eng_list[i]) continue;
+			found = true;
+			break;
 		}
+		if (!found) bv->sel_engine = INVALID_ENGINE;
 	}
 
-	if (HASBIT(WP(w,buildvehicle_d).show_engine_button, 0)) scrollcount += WP(w, buildvehicle_d).list_a_length;
-	if (HASBIT(WP(w,buildvehicle_d).show_engine_button, 1)) scrollcount += WP(w, buildvehicle_d).list_b_length;
+	scrollcount = EngList_Count(&bv->eng_list);
 
 	SetVScrollCount(w, scrollcount);
-	SetDParam(0, WP(w,buildvehicle_d).railtype + STR_881C_NEW_RAIL_VEHICLES);
+	SetDParam(0, bv->filter.railtype + STR_881C_NEW_RAIL_VEHICLES);
 	DrawWindowWidgets(w);
 
-	if (selected_id == INVALID_ENGINE && scrollcount != 0) {
-		if (HASBIT(WP(w,buildvehicle_d).show_engine_button, 0) && WP(w, buildvehicle_d).list_a_length != 0) {
-			selected_id = WP(w, buildvehicle_d).list_a[0];
-		} else {
-			selected_id = WP(w, buildvehicle_d).list_b[0];
-		}
-		WP(w,buildvehicle_d).sel_engine = selected_id;
-	}
-
 	/* Draw the engines */
-	if (HASBIT(WP(w,buildvehicle_d).show_engine_button, 0)) {
-		engine_drawing_loop(WP(w, buildvehicle_d).list_a, WP(w, buildvehicle_d).list_a_length, x, &y, selected_id, &position, max);
-
-		/* Magically set the number 0 line to the one right after the last engine
-		* This way the line numbers fit the indexes in the wagon array */
-		position -= WP(w, buildvehicle_d).list_a_length;
-		max      -= WP(w, buildvehicle_d).list_a_length;
-	}
-
-	/* Draw the wagons */
-	if (HASBIT(WP(w,buildvehicle_d).show_engine_button, 1)) {
-		engine_drawing_loop(WP(w, buildvehicle_d).list_b,  WP(w, buildvehicle_d).list_b_length,  x, &y, selected_id, &position, max);
-	}
+	engine_drawing_loop(&bv->eng_list, x, &y, selected_id, w->vscroll.pos, max);
 
 	if (selected_id != INVALID_ENGINE) {
 		const RailVehicleInfo *rvi = RailVehInfo(selected_id);
@@ -528,115 +474,83 @@ static void DrawTrainBuildWindow(Window *w)
 			DrawTrainEnginePurchaseInfo(2, wi->top + 1, wi->right - wi->left - 2, selected_id);
 		}
 	}
-	DrawString(85, 15, _engine_sort_listing[WP(w,buildvehicle_d).sort_criteria], 0x10);
-	DoDrawString(WP(w,buildvehicle_d).decenting_sort_order ? DOWNARROW : UPARROW, 69, 15, 0x10);
+	DrawString(85, 15, _engine_sort_listing[bv->sort_criteria], 0x10);
+	DoDrawString(bv->descending_sort_order ? DOWNARROW : UPARROW, 69, 15, 0x10);
 }
 
 static void NewRailVehicleWndProc(Window *w, WindowEvent *e)
 {
+	buildvehicle_d *bv = &WP(w,buildvehicle_d);
 	switch (e->event) {
 		case WE_CREATE:
-			WP(w, buildvehicle_d).list_a_length = 0;
-			WP(w, buildvehicle_d).list_b_length = 0;
-			WP(w, buildvehicle_d).list_a        = NULL;
-			WP(w, buildvehicle_d).list_b        = NULL;
-			WP(w, buildvehicle_d).show_engine_button   = 3;
-			WP(w, buildvehicle_d).data_invalidated     = true;
-			WP(w, buildvehicle_d).sel_engine           = INVALID_ENGINE;
-			WP(w, buildvehicle_d).sort_criteria        = _last_sort_criteria;
-			WP(w, buildvehicle_d).decenting_sort_order = _last_sort_order;
+			EngList_Create(&bv->eng_list);
+			bv->sel_engine            = INVALID_ENGINE;
+			bv->sort_criteria         = _last_sort_criteria;
+			bv->descending_sort_order = _last_sort_order;
 			break;
 
 		case WE_INVALIDATE_DATA:
-			if (w->window_number != 0) WP(w,buildvehicle_d).railtype = GetRailType(w->window_number);
-			WP(w,buildvehicle_d).data_invalidated = true;
 			SetWindowDirty(w);
 			break;
 
 		case WE_DESTROY:
-			free((void*)WP(w, buildvehicle_d).list_a);
-			free((void*)WP(w, buildvehicle_d).list_b);
+			EngList_Destroy(&bv->eng_list);
 			break;
 
 		case WE_PAINT:
 			DrawTrainBuildWindow(w);
 			break;
 
-
 		case WE_CLICK: {
 			switch (e->we.click.widget) {
-				case BUILD_TRAIN_WIDGET_SORT_ASSENDING_DESCENDING:
-					WP(w,buildvehicle_d).decenting_sort_order = !WP(w,buildvehicle_d).decenting_sort_order;
-					_last_sort_order = WP(w,buildvehicle_d).decenting_sort_order;
-					SortTrainBuildList(w);
+				case BUILD_TRAIN_WIDGET_SORT_ASCENDING_DESCENDING:
+					_last_sort_order = bv->descending_sort_order = !bv->descending_sort_order;
 					SetWindowDirty(w);
 					break;
 
 				case BUILD_TRAIN_WIDGET_SORT_TEXT: case BUILD_TRAIN_WIDGET_SORT_DROPDOWN:/* Select sorting criteria dropdown menu */
-					ShowDropDownMenu(w, _engine_sort_listing, WP(w,buildvehicle_d).sort_criteria, BUILD_TRAIN_WIDGET_SORT_DROPDOWN, 0, 0);
+					ShowDropDownMenu(w, _engine_sort_listing, bv->sort_criteria, BUILD_TRAIN_WIDGET_SORT_DROPDOWN, 0, 0);
 					return;
 
 				case BUILD_TRAIN_WIDGET_LIST: {
 					uint i = ((e->we.click.pt.y - 26) / 14) + w->vscroll.pos;
-					uint num_items = (HASBIT(WP(w,buildvehicle_d).show_engine_button, 0) ? WP(w, buildvehicle_d).list_a_length : 0)
-					               + (HASBIT(WP(w,buildvehicle_d).show_engine_button, 1) ? WP(w, buildvehicle_d).list_b_length : 0);
-					if (i < num_items) {
-						if (i < WP(w, buildvehicle_d).list_a_length && HASBIT(WP(w,buildvehicle_d).show_engine_button, 0)) {
-							WP(w,buildvehicle_d).sel_engine = WP(w, buildvehicle_d).list_a[i];
-						} else {
-							WP(w,buildvehicle_d).sel_engine = WP(w, buildvehicle_d).list_b[i - (HASBIT(WP(w,buildvehicle_d).show_engine_button, 0) ? WP(w, buildvehicle_d).list_a_length : 0)];
-						}
-						SetWindowDirty(w);
-					}
-				} break;
-
-				case BUILD_TRAIN_WIDGET_ENGINES:
-				case BUILD_TRAIN_WIDGET_WAGONS:
-				case BUILD_TRAIN_WIDGET_BOTH: {
-					/* First we need to figure out the new show_engine_wagon setting
-					 * Because the button widgets are ordered as they are (in a row), we can calculate as following:
-					 * engines = bit 0 (1 for set), wagons bit 1 (2 for set), both (2 | 1 = 3)
-					 * Those numbers are the same as the clicked button - BUILD_TRAIN_WIDGET_ENGINES + 1 */
-
-					byte click_state = e->we.click.widget - BUILD_TRAIN_WIDGET_ENGINES + 1;
-					if (WP(w,buildvehicle_d).show_engine_button == click_state) break; // We clicked the pressed button
-					WP(w,buildvehicle_d).sel_engine = INVALID_ENGINE;
-					WP(w,buildvehicle_d).show_engine_button = click_state;
-					w->vscroll.pos = 0;
+					uint num_items = EngList_Count(&bv->eng_list);
+					bv->sel_engine = (i < num_items) ? bv->eng_list[i] : INVALID_ENGINE;
 					SetWindowDirty(w);
-					}
 					break;
+				}
 
 				case BUILD_TRAIN_WIDGET_BUILD: {
-					EngineID sel_eng = WP(w,buildvehicle_d).sel_engine;
+					EngineID sel_eng = bv->sel_engine;
 					if (sel_eng != INVALID_ENGINE)
 						DoCommandP(w->window_number, sel_eng, 0, (RailVehInfo(sel_eng)->flags & RVI_WAGON) ? CcBuildWagon : CcBuildLoco, CMD_BUILD_RAIL_VEHICLE | CMD_MSG(STR_882B_CAN_T_BUILD_RAILROAD_VEHICLE));
-				}	break;
+					break;
+				}
 
 				case BUILD_TRAIN_WIDGET_RENAME: {
-					EngineID sel_eng = WP(w,buildvehicle_d).sel_engine;
+					EngineID sel_eng = bv->sel_engine;
 					if (sel_eng != INVALID_ENGINE) {
-						WP(w,buildvehicle_d).rename_engine = sel_eng;
-						ShowQueryString(GetCustomEngineName(sel_eng),
-										STR_886A_RENAME_TRAIN_VEHICLE_TYPE, 31, 160, w->window_class, w->window_number, CS_ALPHANUMERAL);
+						bv->rename_engine = sel_eng;
+						ShowQueryString(GetCustomEngineName(sel_eng), STR_886A_RENAME_TRAIN_VEHICLE_TYPE, 31, 160, w->window_class, w->window_number, CS_ALPHANUMERAL);
 					}
-				} break;
+					break;
+				}
 			}
-		} break;
+		}
+		break;
 
 		case WE_ON_EDIT_TEXT: {
 			if (e->we.edittext.str[0] != '\0') {
 				_cmd_text = e->we.edittext.str;
-				DoCommandP(0, WP(w,buildvehicle_d).rename_engine, 0, NULL,
-					CMD_RENAME_ENGINE | CMD_MSG(STR_886B_CAN_T_RENAME_TRAIN_VEHICLE));
+				DoCommandP(0, bv->rename_engine, 0, NULL, CMD_RENAME_ENGINE | CMD_MSG(STR_886B_CAN_T_RENAME_TRAIN_VEHICLE));
 			}
-		} break;
+			break;
+		}
 
 		case WE_DROPDOWN_SELECT: /* we have selected a dropdown item in the list */
-			if (WP(w,buildvehicle_d).sort_criteria != e->we.dropdown.index) {
-				WP(w,buildvehicle_d).sort_criteria = e->we.dropdown.index;
+			if (bv->sort_criteria != e->we.dropdown.index) {
+				bv->sort_criteria = e->we.dropdown.index;
 				_last_sort_criteria = e->we.dropdown.index;
-				SortTrainBuildList(w);
 			}
 			SetWindowDirty(w);
 			break;
@@ -646,12 +560,13 @@ static void NewRailVehicleWndProc(Window *w, WindowEvent *e)
 
 			w->vscroll.cap += e->we.sizing.diff.y / 14;
 			w->widget[BUILD_TRAIN_WIDGET_LIST].data = (w->vscroll.cap << 8) + 1;
-		} break;
+			break;
+		}
 	}
 }
 
 static const WindowDesc _new_rail_vehicle_desc = {
-	WDP_AUTO, WDP_AUTO, 228, 264,
+	WDP_AUTO, WDP_AUTO, 228, 252,
 	WC_BUILD_VEHICLE,0,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS | WDF_RESIZABLE,
 	_new_rail_vehicle_widgets,
@@ -673,10 +588,10 @@ void ShowBuildTrainWindow(TileIndex tile)
 
 	if (tile != 0) {
 		w->caption_color = GetTileOwner(tile);
-		WP(w,buildvehicle_d).railtype = GetRailType(tile);
+		WP(w,buildvehicle_d).filter.railtype = GetRailType(tile);
 	} else {
 		w->caption_color = _local_player;
-		WP(w,buildvehicle_d).railtype = GetBestRailtype(GetPlayer(_local_player));
+		WP(w,buildvehicle_d).filter.railtype = RAILTYPE_END;
 	}
 }
 
@@ -986,8 +901,8 @@ static void TrainDetailsCapacityTab(const Vehicle *v, int x, int y)
 static void DrawTrainDetailsWindow(Window *w)
 {
 	byte det_tab = WP(w, traindetails_d).tab;
-	const Vehicle* v;
-	const Vehicle* u;
+	const Vehicle *v;
+	const Vehicle *u;
 	AcceptedCargo act_cargo;
 	AcceptedCargo max_cargo;
 	uint i;
diff --git a/window.h b/window.h
index 1c1aed22c..39a5f8837 100644
--- a/window.h
+++ b/window.h
@@ -396,20 +396,16 @@ assert_compile(WINDOW_CUSTOM_SIZE >= sizeof(tooltips_d));
 
 typedef struct {
 	byte vehicle_type;
-	byte railtype;
+	union {
+		byte railtype;
+		byte acc_planes; // AIRCRAFT_ONLY, ALL, HELICOPTERS_ONLY
+	} filter;
 	byte sel_index;
-	byte show_engine_button;
-	bool data_invalidated;
-	bool decenting_sort_order;
+	bool descending_sort_order;
 	byte sort_criteria;
 	EngineID sel_engine;
 	EngineID rename_engine;
-	EngineID *list_a;
-	EngineID *list_b;
-	EngineID *list_c;
-	uint16 list_a_length;
-	uint16 list_b_length;
-	uint16 list_c_length;
+	EngineList eng_list;
 } buildvehicle_d;
 assert_compile(WINDOW_CUSTOM_SIZE >= sizeof(buildvehicle_d));