From 6913e5a127850e4a14828d8dacb857180c6051bb Mon Sep 17 00:00:00 2001
From: Mark Johnson <mjohnson@threerings.net>
Date: Fri, 21 Jul 2006 08:23:42 +0000
Subject: [PATCH] Created an ExtendedTraversalPred that can check if the
 movement from one tile to another is traversable instead of just the
 destination being a traversable tile

git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@18 ed5b42cb-e716-0410-a449-f6a68f950b19
---
 .../threerings/media/util/AStarPathUtil.java  | 26 +++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/java/com/threerings/media/util/AStarPathUtil.java b/src/java/com/threerings/media/util/AStarPathUtil.java
index 4583fda0..9232f507 100644
--- a/src/java/com/threerings/media/util/AStarPathUtil.java
+++ b/src/java/com/threerings/media/util/AStarPathUtil.java
@@ -52,6 +52,21 @@ public class AStarPathUtil
         public boolean canTraverse (Object traverser, int x, int y);
     }
 
+    /**
+     * Provides extended traversibility information when computing paths.
+     */
+    public static interface ExtendedTraversalPred extends TraversalPred
+    {
+        /**
+         * Requests to know if the specific traverser (which was provided
+         * in the call to {@link #getPath}) can traverse from the specified
+         * source tile coordinate to the specified destination tile
+         * coodinate.
+         */
+        public boolean canTraverse (
+                Object traverser, int sx, int sy, int dx, int dy);
+    }
+
     /**
      * Considers all the possible steps the piece in question can take.
      */
@@ -338,8 +353,15 @@ public class AStarPathUtil
         protected boolean isStepValid (int sx, int sy, int dx, int dy)
         {
             // not traversable if the destination itself fails test
-            if (!isTraversable(dx, dy)) {
-                return false;
+            if (tpred instanceof ExtendedTraversalPred) {
+                if (!((ExtendedTraversalPred)tpred).canTraverse(
+                        trav, sx, sy, dx, dy)) {
+                    return false;
+                }
+            } else {
+                if (!isTraversable(dx, dy)) {
+                    return false;
+                }
             }
 
             // if the step is diagonal, make sure the corners don't impede