From ce30b159f93ba023dd3392be44c7111a97e1cafd Mon Sep 17 00:00:00 2001
From: pietervdvn <pietervdvn@posteo.net>
Date: Tue, 5 Jan 2021 10:56:25 +0100
Subject: [PATCH] Performance improvement

---
 Logic/FeatureSource/FilteringFeatureSource.ts | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/Logic/FeatureSource/FilteringFeatureSource.ts b/Logic/FeatureSource/FilteringFeatureSource.ts
index 9ab1097..57f6e34 100644
--- a/Logic/FeatureSource/FilteringFeatureSource.ts
+++ b/Logic/FeatureSource/FilteringFeatureSource.ts
@@ -44,7 +44,17 @@ export default class FilteringFeatureSource implements FeatureSource {
         }
         upstream.features.addCallback(() => {
             update()});
-        location.map(l => l.zoom).addCallback(() => {
+        location.map(l => {
+            // We want something that is stable for the shown layers
+            const displayedLayerIndexes = [];
+            for (let i = 0; i < layers.length; i++) {
+                if(l.zoom <= layers[i].layerDef.minzoom){
+                    displayedLayerIndexes.push(i);
+                }
+            }
+            return displayedLayerIndexes.join(",")
+        })
+            .addCallback(() => {
             update();});