From d2fdfcba9e56af96a0ea689f0399a292775e284c Mon Sep 17 00:00:00 2001
From: cchandon <cedric.chandon_github@polytechnique.org>
Date: Mon, 24 Jun 2019 21:59:52 +0200
Subject: [PATCH] Fix usort

---
 src/Nurbs/Voronoi.php | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/Nurbs/Voronoi.php b/src/Nurbs/Voronoi.php
index e67b028..aa37e9a 100644
--- a/src/Nurbs/Voronoi.php
+++ b/src/Nurbs/Voronoi.php
@@ -73,11 +73,15 @@ public function compute ($sites, $bbox)
 		
 		// Initialize site event queue
 		$siteEvents = array_slice($sites, 0);
-		usort($siteEvents, function($a,$b){
-			$r = $b->y - $a->y;
-			if ($r) {return $r;}
-			return $b->x - $a->x;
-		});
+        usort($siteEvents, function($a,$b){
+            $r = $b->y - $a->y;
+            if ($r>0) {return 1;}
+            elseif ($r<0) { return -1;}
+            $s=$b->x - $a->x;
+            if ($s>0) { return 1; } 
+            elseif ($s<0) { return -1; }
+            return 0;
+        });
 	
 		// process queue
 		$site = array_pop($siteEvents);