From 681da9b6258b8e75b5ebe2735632ae11a600c9d1 Mon Sep 17 00:00:00 2001
From: Clemens <fischer.clemens@gmail.com>
Date: Wed, 10 Nov 2021 22:31:39 +0100
Subject: [PATCH] Add LoadBackgroundTiles property

---
 MapControl/Shared/MapTileLayer.cs     | 11 ++++-------
 MapControl/Shared/MapTileLayerBase.cs |  6 +++++-
 MapControl/Shared/WmtsTileLayer.cs    |  2 +-
 3 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/MapControl/Shared/MapTileLayer.cs b/MapControl/Shared/MapTileLayer.cs
index fd8bff44..4b77e5ad 100644
--- a/MapControl/Shared/MapTileLayer.cs
+++ b/MapControl/Shared/MapTileLayer.cs
@@ -211,15 +211,12 @@ namespace MapControl
             }
             else
             {
-                var newTiles = new List<Tile>();
-                var minZoomLevel = maxZoomLevel;
-
-                if (this == ParentMap.MapLayer) // load background tiles
-                {
-                    minZoomLevel = Math.Max(TileMatrix.ZoomLevel - MaxBackgroundLevels, MinZoomLevel);
-                }
+                var minZoomLevel = LoadBackgroundTiles
+                    ? Math.Max(TileMatrix.ZoomLevel - MaxBackgroundLevels, MinZoomLevel)
+                    : maxZoomLevel;
 
                 var oldTiles = Tiles.Where(t => t.ZoomLevel >= minZoomLevel && t.ZoomLevel <= maxZoomLevel).ToList();
+                var newTiles = new List<Tile>();
 
                 Tiles.Clear();
 
diff --git a/MapControl/Shared/MapTileLayerBase.cs b/MapControl/Shared/MapTileLayerBase.cs
index 51d2ab97..cf3f96a1 100644
--- a/MapControl/Shared/MapTileLayerBase.cs
+++ b/MapControl/Shared/MapTileLayerBase.cs
@@ -69,7 +69,6 @@ namespace MapControl
         {
             RenderTransform = new MatrixTransform();
             TileImageLoader = tileImageLoader;
-
 #if WINUI
             updateTimer = DispatcherQueue.CreateTimer();
 #endif
@@ -177,6 +176,11 @@ namespace MapControl
             }
         }
 
+        protected bool LoadBackgroundTiles
+        {
+            get { return this == parentMap?.MapLayer; }
+        }
+
         private async void OnViewportChanged(object sender, ViewportChangedEventArgs e)
         {
             if (Children.Count == 0 || e.ProjectionChanged || Math.Abs(e.LongitudeOffset) > 180d)
diff --git a/MapControl/Shared/WmtsTileLayer.cs b/MapControl/Shared/WmtsTileLayer.cs
index 1160dc2e..b5718fad 100644
--- a/MapControl/Shared/WmtsTileLayer.cs
+++ b/MapControl/Shared/WmtsTileLayer.cs
@@ -126,7 +126,7 @@ namespace MapControl
                 .Where((matrix, i) => i == 0 || matrix.Scale <= maxScale)
                 .ToList();
 
-            if (this != ParentMap.MapLayer) // do not load background tiles
+            if (!LoadBackgroundTiles)
             {
                 currentMatrixes = currentMatrixes.Skip(currentMatrixes.Count - 1).ToList(); // last element only
             }