From 491ddd57c35fa1276eb9c86d53fb88ae0dbb4881 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 2 Mar 2019 14:41:31 +0000
Subject: [PATCH] use edge centroid

---
 generate-board | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/generate-board b/generate-board
index 8525735..7c79f96 100755
--- a/generate-board
+++ b/generate-board
@@ -136,11 +136,15 @@ sub calculate_centres () {
   #  $region{NAME}{Centre}
   foreach my $rr (values %region) {
     next if $rr->{Special};
-    my $poly = $rr->{Polygon};
     my $sum = Math::GSL::Vector->new(2);
-    $sum += $_->{Pos} foreach @$poly;
-    $rr->{Centre} = $sum * (1.0 / @$poly);
-    # xxx use mean edge location (ie weight by edge length)
+    my $wsum = 0;
+    foreach my $adj (@{ $rr->{Adj} }) {
+      my @ends = map { $_->{Pos} } @{ $adj->{Ends} };
+      my $w = ($ends[1] - $ends[0])->norm();
+      $sum += $w * $_ foreach @ends;
+      $wsum += $w;
+    }
+    $rr->{Centre} = $sum * (0.5 / $wsum);
   }
 }
 
-- 
2.30.2