From 22fbaed88c94bc670ef8f1158e1bbd6d00b6b937 Mon Sep 17 00:00:00 2001
From: Eryn Wells <eryn@erynwells.me>
Date: Fri, 4 Aug 2017 21:10:52 -0700
Subject: [PATCH] [MetaballsKit] Fix up didSet responder for Field.size

---
 MetaballsKit/Metaballs.swift | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/MetaballsKit/Metaballs.swift b/MetaballsKit/Metaballs.swift
index 247844a..9f900c8 100644
--- a/MetaballsKit/Metaballs.swift
+++ b/MetaballsKit/Metaballs.swift
@@ -36,9 +36,19 @@ public struct Ball {
 public class Field {
     public var size: CGSize {
         didSet {
-            // Remove balls that fall outside the new bounds.
-            balls = balls.filter { bounds.contains($0.bounds) }
-            updateThreadgroupSizes(withFieldSize: size)
+            if size != oldValue {
+                let numberOfBallsBeforeFilter = balls.count
+
+                // Remove balls that fall outside the new bounds.
+                balls = balls.filter { bounds.contains($0.bounds) }
+
+                // Update Metal state as needed.
+                updateThreadgroupSizes(withFieldSize: size)
+                sampleTexture = nil
+                if numberOfBallsBeforeFilter != balls.count {
+                    ballBuffer = nil
+                }
+            }
         }
     }