From cc25edf9f1ff64e57d04c26b1cef2c72b979b3f3 Mon Sep 17 00:00:00 2001
From: cirdan <cirdansw@gmail.com>
Date: Sat, 22 Feb 2014 14:37:45 +0100
Subject: [PATCH] Rework handling of ignored pylons

Rework handling of ignored pylons by keeping IgnoredPCP in a
much more compact way that does not store redundant information.
---
 src/elrail.cpp          |  14 ++++++-
 src/table/elrail_data.h | 104 ++++++++++++------------------------------------
 2 files changed, 37 insertions(+), 81 deletions(-)

diff --git a/src/elrail.cpp b/src/elrail.cpp
index 1739761fa..24f3fd636 100644
--- a/src/elrail.cpp
+++ b/src/elrail.cpp
@@ -312,7 +312,10 @@ static void DrawCatenaryRailway(const TileInfo *ti)
 	/* Note that ti->tileh has already been adjusted for Foundations */
 	home.tileh = ti->tileh;
 
-	TLG tlg = (TLG)((IsOddX(ti->tile) << 1) + IsOddY(ti->tile));
+	bool odd[AXIS_END];
+	odd[AXIS_X] = IsOddX(ti->tile);
+	odd[AXIS_Y] = IsOddY(ti->tile);
+	TLG tlg = (TLG)((odd[AXIS_X] << 1) + odd[AXIS_Y]);
 	byte PCPstatus = 0;
 	DiagDirection overridePCP = INVALID_DIAGDIR;
 
@@ -468,8 +471,15 @@ static void DrawCatenaryRailway(const TileInfo *ti)
 		 * Delete the PCP if this is the case.
 		 * Level means that the slope is the same, or the track is flat */
 		if (home.tileh == nbconfig.tileh || (home.isflat && nbconfig.isflat)) {
+			Axis axis = DiagDirToAxis(i);
 			for (uint k = 0; k < NUM_IGNORE_GROUPS; k++) {
-				if (PPPpreferred == IgnoredPCP[tlg][i][k]) ClrBit(PCPstatus, i);
+				if (PPPpreferred == IgnoredPCPconfigs[axis][k] ) {
+					/* This configuration may be subject to pylon elision. */
+					bool ignore = HasBit (IgnoredPCP[axis][odd[OtherAxis(axis)]], k);
+					/* Toggle ignore if we are in an odd row, or heading the other way. */
+					if (ignore ^ odd[axis] ^ HasBit(i, 1)) ClrBit(PCPstatus, i);
+					break;
+				}
 			}
 			if (!HasBit(PCPstatus, i)) continue;
 		}
diff --git a/src/table/elrail_data.h b/src/table/elrail_data.h
index 190051103..0df584f37 100644
--- a/src/table/elrail_data.h
+++ b/src/table/elrail_data.h
@@ -111,92 +111,38 @@ static const byte PreferredPPPofTrackAtPCP[TRACK_END][DIAGDIR_END] = {
 
 
 #define NUM_IGNORE_GROUPS 3
-#define IGNORE_NONE 0xFF
+
 /**
  * In case we have a straight line, we place pylon only every two tiles,
  * so there are certain tiles which we ignore. A straight line is found if
  * we have exactly two PPPs.
  */
-static const byte IgnoredPCP[TLG_END][DIAGDIR_END][NUM_IGNORE_GROUPS] = {
-	{   // X even, Y even
-		{    // DIAGDIR_NE
-			IGNORE_NONE,              // Ignore group 1, X and Y tracks
-			1 << DIR_E  | 1 << DIR_W, // Ignore group 2, LEFT and RIGHT tracks
-			1 << DIR_N  | 1 << DIR_S, // Ignore group 3, UPPER and LOWER tracks
-		}, { // DIAGDIR_SE
-			1 << DIR_NE | 1 << DIR_SW,
-			IGNORE_NONE,
-			1 << DIR_N  | 1 << DIR_S,
-		}, { // DIAGDIR_SW
-			1 << DIR_NW | 1 << DIR_SE,
-			IGNORE_NONE,
-			IGNORE_NONE,
-		}, { // DIAGDIR_NW
-			IGNORE_NONE,
-			1 << DIR_E  | 1 << DIR_W,
-			IGNORE_NONE,
-		}
-	},
-	{   // X even, Y odd
-		{    // DIAGDIR_NE
-			IGNORE_NONE,
-			IGNORE_NONE,
-			IGNORE_NONE,
-		}, { // DIAGDIR_SE
-			IGNORE_NONE,
-			1 << DIR_E  | 1 << DIR_W,
-			IGNORE_NONE,
-		}, { // DIAGDIR_SW
-			1 << DIR_NW | 1 << DIR_SE,
-			1 << DIR_E  | 1 << DIR_W,
-			1 << DIR_N  | 1 << DIR_S,
-		}, { // DIAGDIR_NW
-			1 << DIR_NE | 1 << DIR_SW,
-			IGNORE_NONE,
-			1 << DIR_N  | 1 << DIR_S,
-		}
-	},
-	{   // X odd, Y even
-		{    // DIAGDIR_NE
-			1 << DIR_NW | 1 << DIR_SE,
-			IGNORE_NONE,
-			IGNORE_NONE,
-		}, { // DIAGDIR_SE
-			1 << DIR_NE | 1 << DIR_SW,
-			1 << DIR_E  | 1 << DIR_W,
-			IGNORE_NONE,
-		}, { // DIAGDIR_SW
-			IGNORE_NONE,
-			1 << DIR_E  | 1 << DIR_W,
-			1 << DIR_N  | 1 << DIR_S,
-		}, { // DIAGDIR_NW
-			IGNORE_NONE,
-			IGNORE_NONE,
-			1 << DIR_N  | 1 << DIR_S,
-		}
-	},
-	{   // X odd, Y odd
-		{    // DIAGDIR_NE
-			1 << DIR_NW | 1 << DIR_SE,
-			1 << DIR_E  | 1 << DIR_W,
-			1 << DIR_N  | 1 << DIR_S,
-		}, { // DIAGDIR_SE
-			IGNORE_NONE,
-			IGNORE_NONE,
-			1 << DIR_N  | 1 << DIR_S,
-		}, { // DIAGDIR_SW
-			IGNORE_NONE,
-			IGNORE_NONE,
-			IGNORE_NONE,
-		}, { // DIAGDIR_NW
-			1 << DIR_NE | 1 << DIR_SW,
-			1 << DIR_E  | 1 << DIR_W,
-			IGNORE_NONE,
-		}
-	},
+static const byte IgnoredPCPconfigs[AXIS_END][NUM_IGNORE_GROUPS] = {
+	{    // X axis
+		1 << DIR_NW | 1 << DIR_SE,
+		1 << DIR_E  | 1 << DIR_W,
+		1 << DIR_N  | 1 << DIR_S,
+	}, { // Y axis
+		1 << DIR_NE | 1 << DIR_SW,
+		1 << DIR_E  | 1 << DIR_W,
+		1 << DIR_N  | 1 << DIR_S,
+	}
 };
 
-#undef NO_IGNORE
+/**
+ * In case we have a straight line, we place pylon only every two tiles,
+ * so there are certain tiles which we ignore. This struct encodes on
+ * which tile sides pylons are omitted.
+ */
+static const byte IgnoredPCP[AXIS_END][2] = {
+	{    // X axis
+		0x6, // configurations to ignore on even X and even Y tile sides
+		  0, // configurations to ignore on even X and odd Y tile sides
+	}, { // Y axis
+		0x5, // configurations to ignore on odd Y and even X tile sides
+		0x3, // configurations to ignore on odd Y and odd X tile sides
+	}
+};
 
 /** Which pylons can definitely NOT be built */
 static const byte AllowedPPPofTrackAtPCP[TRACK_END] = {
-- 
2.11.4.GIT