From cd32a5f18c6e3cf60e953f80265c2fe40d3821a6 Mon Sep 17 00:00:00 2001
From: rubidium <rubidium@openttd.org>
Date: Thu, 28 Jun 2007 14:11:00 +0000
Subject: [PATCH] (svn r10373) [0.5] -Backport from trunk (r10306, r10311,
 r10317, r10339, r10344): - Fix: Acceleration for trains on slopes is not
 calculated properly [FS#786] (r10317, r10344) - Fix: Rail could be destroyed
 when building tunnels (r10306)

---
 misc_gui.c         |  4 ++--
 train_cmd.c        | 30 ++++++++++++++++--------------
 tunnelbridge_cmd.c |  9 +++++++++
 3 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/misc_gui.c b/misc_gui.c
index 4df7333fcb..fe0f448965 100644
--- a/misc_gui.c
+++ b/misc_gui.c
@@ -213,16 +213,16 @@ static const char *credits[] = {
 	"  Loïc Guilloux (glx) - In training, not yet specialized",
 	"  Jaroslav Mazanec (KUDr) - YAPG (Yet Another Pathfinder God) ;)",
 	"  Attila Bán (MiHaMiX) - WebTranslator, Nightlies, Wiki and bugtracker host",
+	"  Owen Rudge (orudge) - Forum host, OS/2 port",
 	"  Peter Nelson (peter1138) - Spiritual descendant from newgrf gods",
 	"  Remko Bijker (Rubidium) - THE desync hunter",
 	"  Christoph Mallon (Tron) - Programmer, code correctness police",
-	"  Patric Stout (TrueLight) - Coder, network guru, SVN- and website host",
+	"  Patric Stout (TrueLight) - Coder, network guru, SVN-, MS- and website host",
 	"",
 	"Retired Developers:",
 	"  Ludvig Strigeus (ludde) - OpenTTD author, main coder (0.1 - 0.3.3)",
 	"  Serge Paquet (vurlix) - Assistant project manager, coder (0.1 - 0.3.3)",
 	"  Dominik Scherer (dominik81) - Lead programmer, GUI expert (0.3.0 - 0.3.6)",
-	"  Owen Rudge (orudge) - Forum- and masterserver host, OS/2 port (0.1 - 0.4.8)",
 	"",
 	"Special thanks go out to:",
 	"  Josef Drexler - For his great work on TTDPatch",
diff --git a/train_cmd.c b/train_cmd.c
index 59a610b227..5d18b49af4 100644
--- a/train_cmd.c
+++ b/train_cmd.c
@@ -2748,26 +2748,28 @@ static void TrainEnterStation(Vehicle *v, StationID station)
 
 static byte AfterSetTrainPos(Vehicle *v, bool new_tile)
 {
-	byte new_z, old_z;
-
-	// need this hint so it returns the right z coordinate on bridges.
-	_get_z_hint = v->z_pos;
-	new_z = GetSlopeZ(v->x_pos, v->y_pos);
-	_get_z_hint = 0;
-
-	old_z = v->z_pos;
-	v->z_pos = new_z;
+	byte old_z = v->z_pos;
+	v->z_pos = GetSlopeZ(v->x_pos, v->y_pos);
 
 	if (new_tile) {
 		CLRBIT(v->u.rail.flags, VRF_GOINGUP);
 		CLRBIT(v->u.rail.flags, VRF_GOINGDOWN);
 
-		if (new_z != old_z) {
-			TileIndex tile = TileVirtXY(v->x_pos, v->y_pos);
+		if (v->u.rail.track == TRACK_BIT_X || v->u.rail.track == TRACK_BIT_Y) {
+			/* Any track that isn't TRACK_BIT_X or TRACK_BIT_Y cannot be sloped.
+			 * To check whether the current tile is sloped, and in which
+			 * direction it is sloped, we get the 'z' at the center of
+			 * the tile (middle_z) and the edge of the tile (old_z),
+			 * which we then can compare. */
+			static const int HALF_TILE_SIZE = TILE_SIZE / 2;
+			static const int INV_TILE_SIZE_MASK = ~(TILE_SIZE - 1);
 
-			// XXX workaround, whole UP/DOWN detection needs overhaul
-			if (!IsTunnelTile(tile)) {
-				SETBIT(v->u.rail.flags, (new_z > old_z) ? VRF_GOINGUP : VRF_GOINGDOWN);
+			byte middle_z = GetSlopeZ((v->x_pos & INV_TILE_SIZE_MASK) | HALF_TILE_SIZE, (v->y_pos & INV_TILE_SIZE_MASK) | HALF_TILE_SIZE);
+
+			/* For some reason tunnel tiles are always given as sloped :(
+			 * But they are not sloped... */
+			if (middle_z != v->z_pos && !IsTunnelTile(TileVirtXY(v->x_pos, v->y_pos))) {
+				SETBIT(v->u.rail.flags, (middle_z > old_z) ? VRF_GOINGUP : VRF_GOINGDOWN);
 			}
 		}
 	}
diff --git a/tunnelbridge_cmd.c b/tunnelbridge_cmd.c
index 37c702a640..683aa37892 100644
--- a/tunnelbridge_cmd.c
+++ b/tunnelbridge_cmd.c
@@ -507,6 +507,15 @@ int32 CmdBuildTunnel(TileIndex start_tile, uint32 flags, uint32 p1, uint32 p2)
 
 	// slope of end tile must be complementary to the slope of the start tile
 	if (end_tileh != ComplementSlope(start_tileh)) {
+		/* Some (rail) track bits might be terraformed into the correct direction,
+		 * but that would still leave tracks on foundation. Therefor excavation will
+		 * always fail for rail tiles. On the other hand, for road tiles it might
+		 * succeed when there is only one road bit on the tile, but then that road
+		 * bit is removed leaving a clear tile.
+		 * This therefor preserves the behaviour that half road tiles are always removable.
+		 */
+		if (IsTileType(end_tile, MP_RAILWAY)) return_cmd_error(STR_1008_MUST_REMOVE_RAILROAD_TRACK);
+
 		ret = DoCommand(end_tile, end_tileh & start_tileh, 0, flags, CMD_TERRAFORM_LAND);
 		if (CmdFailed(ret)) return_cmd_error(STR_5005_UNABLE_TO_EXCAVATE_LAND);
 	} else {