make sure the map refreshes at least every 2nd data read even when

panning or zooming
also instantly update aircraft positions if the visible aircraft count is
less than 500

html/script.js

@@ -99,7 +99,7 @@ let firstFetchDone = false;
 let overrideMapType = null;
 let halloween = false;
 let noRegOnly = false;
-let triggerMapRefresh = false;
+let triggerMapRefresh = 0;
 let firstDraw = true;
 
 let shareLink = '';
@@ -367,7 +367,9 @@ function fetchData() {
             }
 
             if (PendingFetches <= 1) {
-                triggerMapRefresh = true;
+                triggerMapRefresh++;
+                if (TrackedAircraftPositions < 500)
+                    checkRefresh(); // immediately trigger refresh if aircraft count is low enough
             }
             PendingFetches--;
 
@@ -3807,7 +3809,7 @@ function checkMovement() {
         //console.timeEnd("fire!");
     }
 
-    if (noMovement >= 3)
+    if (noMovement >= 3 || triggerMapRefresh > 1)
         checkRefresh();
 
     noMovement++;
@@ -3829,7 +3831,7 @@ function checkRefresh() {
         mapRefresh();
         //console.timeEnd("refreshTable");
 
-        triggerMapRefresh = false;
+        triggerMapRefresh = 0;
     }
 }
 function mapRefresh() {
@@ -3914,9 +3916,6 @@ function changeZoom(init) {
     else
         scaleFactor = markerSmall;
 
-    if (scaleFactor != oldScaleFactor)
-        triggerMapRefresh = true;
-
     // scale markers according to global scaling
     scaleFactor *= Math.pow(1.3, globalScale) * globalScale * iconScale;;