allow diagonal crossing over a border (fixes #58)

Author: brean

pathfinding/core/grid.py

@@ -117,44 +117,48 @@ def neighbors(
         x = node.x
         y = node.y
         neighbors = []
-        s0 = d0 = s1 = d1 = s2 = d2 = s3 = d3 = False
+        north = nw = east = ne = south = se = west = sw = False
+
+        lr = self.passable_left_right_border
+        ud = self.passable_up_down_border
 
         # ↑
         if y == 0 and self.passable_up_down_border:
-            if self.walkable(x, self.height - 1):
-                neighbors.append(self.nodes[self.height - 1][x])
-                s0 = True
+            north_y = self.height - 1
         else:
-            if self.walkable(x, y - 1):
-                neighbors.append(self.nodes[y - 1][x])
-                s0 = True
+            north_y = y - 1
+
+        if self.walkable(x, north_y):
+            neighbors.append(self.nodes[north_y][x])
+            north = True
+
         # →
         if x == self.width - 1 and self.passable_left_right_border:
-            if self.walkable(0, y):
-                neighbors.append(self.nodes[y][0])
-                s1 = True
+            east_x = 0
         else:
-            if self.walkable(x + 1, y):
-                neighbors.append(self.nodes[y][x + 1])
-                s1 = True
+            east_x = x + 1
+
+        if self.walkable(east_x, y):
+            neighbors.append(self.nodes[y][east_x])
+            east = True
+        
         # ↓
         if y == self.height - 1 and self.passable_up_down_border:
-            if self.walkable(x, 0):
-                neighbors.append(self.nodes[0][x])
-                s2 = True
+            south_y = 0
         else:
-            if self.walkable(x, y + 1):
-                neighbors.append(self.nodes[y + 1][x])
-                s2 = True
+            south_y = y + 1
+        if self.walkable(x, south_y):
+            neighbors.append(self.nodes[south_y][x])
+            south = True
+
         # ←
         if x == 0 and self.passable_left_right_border:
-            if self.walkable(self.width - 1, y):
-                neighbors.append(self.nodes[y][self.width - 1])
-                s3 = True
+            west_x = self.width - 1
         else:
-            if self.walkable(x - 1, y):
-                neighbors.append(self.nodes[y][x - 1])
-                s3 = True
+            west_x = x - 1
+        if self.walkable(west_x, y):
+            neighbors.append(self.nodes[y][west_x])
+            west = True
 
         # check for connections to other grids
         if node.connections:
@@ -164,33 +168,69 @@ def neighbors(
             return neighbors
 
         if diagonal_movement == DiagonalMovement.only_when_no_obstacle:
-            d0 = s3 and s0
-            d1 = s0 and s1
-            d2 = s1 and s2
-            d3 = s2 and s3
+            nw = north and west
+            ne = north and east
+            se = south and east
+            sw = south and west
         elif diagonal_movement == DiagonalMovement.if_at_most_one_obstacle:
-            d0 = s3 or s0
-            d1 = s0 or s1
-            d2 = s1 or s2
-            d3 = s2 or s3
+            nw = north or west
+            ne = north or east
+            se = south or east
+            sw = south or west
         elif diagonal_movement == DiagonalMovement.always:
-            d0 = d1 = d2 = d3 = True
+            nw = ne = se = sw = True
 
         # ↖
-        if d0 and self.walkable(x - 1, y - 1):
-            neighbors.append(self.nodes[y - 1][x - 1])
+        if nw:
+            if x == 0 and self.passable_left_right_border:
+                nw_x = self.width - 1
+            else:
+                nw_x = x - 1
+            if y == 0 and self.passable_up_down_border:
+                nw_y = self.height - 1
+            else:
+                nw_y = y - 1
+            if self.walkable(nw_x, nw_y):
+                neighbors.append(self.nodes[nw_y][nw_x])
 
         # ↗
-        if d1 and self.walkable(x + 1, y - 1):
-            neighbors.append(self.nodes[y - 1][x + 1])
-
+        if ne:
+            if x == self.width - 1 and self.passable_left_right_border:
+                ne_x = 0
+            else:
+                ne_x = x + 1
+            if y == 0 and self.passable_up_down_border:
+                ne_y = self.height - 1
+            else:
+                ne_y = y - 1
+            if self.walkable(ne_x, ne_y):
+                neighbors.append(self.nodes[ne_y][ne_x])
+        
         # ↘
-        if d2 and self.walkable(x + 1, y + 1):
-            neighbors.append(self.nodes[y + 1][x + 1])
+        if se:
+            if x == self.width - 1 and self.passable_left_right_border:
+                se_x = 0
+            else:
+                se_x = x + 1
+            if y == self.height - 1 and self.passable_up_down_border:
+                se_y = 0
+            else:
+                se_y = y + 1
+            if self.walkable(se_x, se_y):
+                neighbors.append(self.nodes[se_y][se_x])
 
         # ↙
-        if d3 and self.walkable(x - 1, y + 1):
-            neighbors.append(self.nodes[y + 1][x - 1])
+        if sw:
+            if x == 0 and self.passable_left_right_border:
+                sw_x = self.width - 1
+            else:
+                sw_x = x - 1
+            if y == self.height - 1 and self.passable_up_down_border:
+                sw_y = 0
+            else:
+                sw_y = y + 1
+            if self.walkable(sw_x, sw_y):
+                neighbors.append(self.nodes[sw_y][sw_x])
 
         return neighbors
 

test/test_diagonal_crossing_border.py

@@ -0,0 +1,12 @@
+from pathfinding.core.grid import Grid, DiagonalMovement
+
+
+def test_diagonal_crossing():
+    grid = Grid(5, 5)
+    grid.set_passable_left_right_border()
+    nb = grid.neighbors(grid.node(4, 2), DiagonalMovement.always)
+    neighbors = [(n.x, n.y) for n in nb]
+    print(grid.grid_str(path=nb))
+    assert set(neighbors) == set([
+        (4, 1), (0, 2), (4, 3), (3, 2), 
+        (3, 1), (3, 3), (0, 1), (0, 3)])