From fb07e9d06f244a76537f8b769c0bd4e044fa673c Mon Sep 17 00:00:00 2001
From: "nethack.rankin" <nethack.rankin>
Date: Thu, 21 Dec 2006 04:03:33 +0000
Subject: [PATCH] boomerang path (trunk only)

     Thrown boomerangs travelled in a clockwise path, appropriate for
left-handed throwing.  But nethack heroes are treated as right-handed by
the weapon wielding and shield wearing code, so make boomerangs travel
counterclockwise instead.  Switching is straightforward, in case we ever
implement user-specified or random handedness.
---
 doc/fixes35.0 |  1 +
 src/zap.c     | 26 +++++++++++++++++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/doc/fixes35.0 b/doc/fixes35.0
index 405cfe437..1396e8c21 100644
--- a/doc/fixes35.0
+++ b/doc/fixes35.0
@@ -181,6 +181,7 @@ same-race sacrifice can't damage high altars
 allow corpses on floor to be offered at high altars
 allow hero to attempt to offer the Amulet at ordinary altars
 shooting range for crossbow isn't affected by strength; multi-shot volley is
+right-handed boomerang throw travels counterclockwise
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/src/zap.c b/src/zap.c
index adce79186..c025c2891 100644
--- a/src/zap.c
+++ b/src/zap.c
@@ -3082,17 +3082,31 @@ struct obj *obj;
 int dx, dy;
 {
 	register int i, ct;
-	int boom = S_boomleft;	/* showsym[] index  */
+	int boom;	/* showsym[] index  */
 	struct monst *mtmp;
+	boolean counterclockwise = TRUE;	/* right-handed throw */
+
+/* counterclockwise traversal patterns:
+ *  ..........................54.................................
+ *  ..................43.....6..3....765.........................
+ *  ..........32.....5..2...7...2...8...4....87..................
+ *  .........4..1....6..1...8..1....9...3...9..6.....98..........
+ *  ..21@....5...@...7..@....9@......@12....@...5...@..7.....@9..
+ *  .3...9....6..9....89.....................1..4...1..6....1..8.
+ *  .4...8.....78.............................23....2..5...2...7.
+ *  ..567............................................34....3..6..
+ *  ........................................................45...
+ * (invert rows for corresponding clockwise patterns)
+ */
 
 	bhitpos.x = u.ux;
 	bhitpos.y = u.uy;
-
+	boom = counterclockwise ? S_boomleft : S_boomright;
 	for (i = 0; i < 8; i++) if (xdir[i] == dx && ydir[i] == dy) break;
 	tmp_at(DISP_FLASH, cmap_to_glyph(boom));
 	for (ct = 0; ct < 10; ct++) {
-		if(i == 8) i = 0;
-		boom = (boom == S_boomleft) ? S_boomright : S_boomleft;
+		i = (i + 8) % 8;	/* 0..7 (8 -> 0, -1 -> 7) */
+		boom = (S_boomleft + S_boomright - boom);	/* toggle */
 		tmp_at(DISP_CHANGE, cmap_to_glyph(boom));/* change glyph */
 		dx = xdir[i];
 		dy = ydir[i];
@@ -3126,11 +3140,13 @@ int dx, dy;
 		}
 		tmp_at(bhitpos.x, bhitpos.y);
 		delay_output();
-		if(ct % 5 != 0) i++;
 #ifdef SINKS
 		if(IS_SINK(levl[bhitpos.x][bhitpos.y].typ))
 			break;	/* boomerang falls on sink */
 #endif
+		/* ct==0, initial position, we want next delta to be same;
+		   ct==5, opposite position, repeat delta undoes first one */
+		if (ct % 5 != 0) i += (counterclockwise ? -1 : 1);
 	}
 	tmp_at(DISP_END, 0);	/* do not leave last symbol */
 	return (struct monst *)0;