(svn r13352) [0.6] -Backport from trunk (r13348, r13222, r13221, r13217):

- Fix: Industry tiles would sometimes tell they need a 'level' slope when they do not want the slope (r13348)
- Fix: Attempts to make the old AI perform better (r13217, r13221, r13222)

src/ai/default/default.cpp

@@ -3377,7 +3377,8 @@ static void AiStateAirportStuff(Player *p)
 
 			AirportFTAClass::Flags flags = st->Airport()->flags;
 
-			if (!(flags & (_players_ai[p->index].build_kind == 1 && i == 0 ? AirportFTAClass::HELICOPTERS : AirportFTAClass::AIRPLANES))) {
+			/* if airport doesn't accept our kind of plane, dismiss it */
+			if (!(flags & (_players_ai[p->index].build_kind == 1 ? AirportFTAClass::HELICOPTERS : AirportFTAClass::AIRPLANES))) {
 				continue;
 			}
 
@@ -3463,12 +3464,29 @@ static bool AiCheckAirportResources(TileIndex tile, const AiDefaultBlockData *p,
 static int AiFindBestDefaultAirportBlock(TileIndex tile, byte cargo, byte heli, CommandCost *cost)
 {
 	const AiDefaultBlockData *p;
-	uint i;
 
-	for (i = 0; (p = _airport_default_block_data[i]) != NULL; i++) {
-		// If we are doing a helicopter service, avoid building
-		// airports where they can't land.
-		if (heli && !(GetAirport(p->attr)->flags & AirportFTAClass::HELICOPTERS)) continue;
+	bool no_small = false;
+
+	if (!heli) {
+		/* do not build small airport if we have large available and we are not building heli route */
+		uint valid = GetValidAirports();
+		for (uint i = 0; (p = _airport_default_block_data[i]) != NULL; i++) {
+			uint flags = GetAirport(p->attr)->flags;
+			if (HasBit(valid, p->attr) && (flags & AirportFTAClass::AIRPLANES) && !(flags & AirportFTAClass::SHORT_STRIP)) {
+				no_small = true;
+				break;
+			}
+		}
+	}
+
+	for (uint i = 0; (p = _airport_default_block_data[i]) != NULL; i++) {
+		uint flags = GetAirport(p->attr)->flags;
+		/* If we are doing a helicopter service, avoid building airports where they can't land */
+		if (heli && !(flags & AirportFTAClass::HELICOPTERS)) continue;
+		/* Similiar with aircraft ... */
+		if (!heli && !(flags & AirportFTAClass::AIRPLANES)) continue;
+		/* Do not build small airport if we prefer large */
+		if (no_small && (flags & AirportFTAClass::SHORT_STRIP)) continue;
 
 		*cost = AiDoBuildDefaultAirportBlock(tile, p, 0);
 		if (CmdSucceeded(*cost) && AiCheckAirportResources(tile, p, cargo))

src/industry_cmd.cpp

@@ -330,6 +330,20 @@ static uint GetSlopeZ_Industry(TileIndex tile, uint x, uint y)
 
 static Foundation GetFoundation_Industry(TileIndex tile, Slope tileh)
 {
+	IndustryGfx gfx = GetIndustryGfx(tile);
+
+	/* For NewGRF industry tiles we might not be drawing a foundation. We need to
+	 * account for this, otherwise we might be applying a FOUNDATION_LEVELED
+	 * on a steep slope which is not allowed. Furthermore other structures should
+	 * draw the wall of the foundation in this case.
+	 */
+	if (gfx >= NEW_INDUSTRYTILEOFFSET) {
+		const IndustryTileSpec *indts = GetIndustryTileSpec(gfx);
+		if (indts->grf_prop.spritegroup != NULL && HasBit(indts->callback_flags, CBM_INDT_DRAW_FOUNDATIONS)) {
+			uint32 callback_res = GetIndustryTileCallback(CBID_INDUSTRY_DRAW_FOUNDATIONS, 0, 0, gfx, GetIndustryByTile(tile), tile);
+			if (callback_res == 0) return FOUNDATION_NONE;
+		}
+	}
 	return FlatteningFoundation(tileh);
 }
 

src/table/ai_rail.h

@@ -591,15 +591,27 @@ static const AiDefaultBlockData _airportdata_ai_5[] = {
 	MKEND(),
 };
 
+static const AiDefaultBlockData _airportdata_ai_6[] = {
+	MKAIR(6, 0, 0),
+	MKEND(),
+};
+
 static const AiDefaultBlockData _airportdata_ai_7[] = {
 	MKAIR(7, 0, 0),
 	MKEND(),
 };
 
+static const AiDefaultBlockData _airportdata_ai_8[] = {
+	MKAIR(8, 0, 0),
+	MKEND(),
+};
+
 #undef MKAIR
 #undef MDEND
 
 static const AiDefaultBlockData * const _airport_default_block_data[] = {
+	_airportdata_ai_8, // helistation
+	_airportdata_ai_6, // helidepot
 	_airportdata_ai_7, // intercontinental airport
 	_airportdata_ai_4, // international airport
 	_airportdata_ai_3, // metropolitan airport