use maxNativeZoom to (over-) scale tiles to common max zoom

(avoids gray screen when switching)

js/index.js

@@ -13,20 +13,23 @@
         L.Icon.Default.imagePath = 'dist/images';
         
         var osmAttribution = '&copy; <a target="_blank" href="http://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors';
+        var maxZoom = 19;
 
         var osm = L.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
-            maxZoom: 19,
+            maxZoom: maxZoom,
             attribution: 'tiles ' + osmAttribution
         });
 
         var osmde = L.tileLayer('http://{s}.tile.openstreetmap.de/tiles/osmde/{z}/{x}/{y}.png', {
-            maxZoom: 18,
+            maxNativeZoom: 18,
+            maxZoom: maxZoom,
             attribution: 'tiles by <a target="_blank" href="http://openstreetmap.de/karte.html">openstreetmap.de</a> ' + osmAttribution
         });
 
         var topo = L.tileLayer('http://{s}.tile.opentopomap.org/{z}/{x}/{y}.png', {
             minZoom: 5,
-            maxZoom: 15,
+            maxNativeZoom: 15,
+            maxZoom: maxZoom,
             attribution: 'tiles &copy; <a target="_blank" href="https://opentopomap.org">OpenTopoMap</a>, <a target="_blank" href="https://creativecommons.org/licenses/by-sa/3.0/">CC-BY-SA</a>'
                 + ', <a target="_blank" href="http://viewfinderpanoramas.org">SRTM</a>'
         });
@@ -34,22 +37,26 @@
         var thunderforestAttribution = 'tiles &copy; <a target="_blank" href="http://www.thunderforest.com">Thunderforest</a> '
             + '(<a target="_blank" href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA 2.0</a>)';
         var cycle = L.tileLayer('http://{s}.tile.thunderforest.com/cycle/{z}/{x}/{y}.png', {
-            maxZoom: 18,
+            maxNativeZoom: 18,
+            maxZoom: maxZoom,
             attribution: thunderforestAttribution
         });
         var outdoors = L.tileLayer('http://{s}.tile.thunderforest.com/outdoors/{z}/{x}/{y}.png', {
-            maxZoom: 18,
+            maxNativeZoom: 18,
+            maxZoom: maxZoom,
             attribution: thunderforestAttribution
         });
 
         var cycling = L.tileLayer('http://tile.waymarkedtrails.org/cycling/{z}/{x}/{y}.png', {
-          maxZoom: 18,
+          maxNativeZoom: 18,
+          maxZoom: maxZoom,
           opacity: 0.7,
           attribution: 'Cycling &copy; <a target="_blank" href="http://cycling.waymarkedtrails.org">Waymarked Trails</a> '
                   + '(<a target="_blank" href="http://creativecommons.org/licenses/by-sa/3.0/de/deed.en">CC-BY-SA 3.0 DE</a>)'
         });
         var hiking = L.tileLayer('http://tile.waymarkedtrails.org/hiking/{z}/{x}/{y}.png', {
-          maxZoom: 18,
+          maxNativeZoom: 18,
+          maxZoom: maxZoom,
           opacity: 0.7,
           attribution: 'Hiking &copy; <a target="_blank" href="http://hiking.waymarkedtrails.org">Waymarked Trails</a> '
                   + '(<a target="_blank" href="http://creativecommons.org/licenses/by-sa/3.0/de/deed.en">CC-BY-SA 3.0 DE</a>)'