From 08d357d5cefa8142acfe42b8bd34de2092b34371 Mon Sep 17 00:00:00 2001
From: Maxim <maxim@smspower.org>
Date: Tue, 24 May 2022 17:39:08 +0100
Subject: [PATCH] Fix for map screens crashing the game if they are
 "background-only"

---
 editor/Cartridge.cs           |  2 +-
 editor/GameObjects/TileMap.cs | 16 ++++++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/editor/Cartridge.cs b/editor/Cartridge.cs
index ca7ae33..54780e5 100644
--- a/editor/Cartridge.cs
+++ b/editor/Cartridge.cs
@@ -1701,7 +1701,7 @@ private void ReadAssets()
                         {
                             // We assume these are set second so we have to check if it's a set or overlay
                             var tileMap = new TileMap(Memory, offset, asset.GetLength(Memory));
-                            if (tileMap.IsOverlay() && item.TileMap != null)
+                            if (item.TileMap != null && item.TileMap.HasForeground)
                             {
                                 item.TileMap.OverlayWith(tileMap);
                                 _assetsLookup[asset] = item.TileMap; // Point at the same object for both
diff --git a/editor/GameObjects/TileMap.cs b/editor/GameObjects/TileMap.cs
index 97a009b..e8e5906 100644
--- a/editor/GameObjects/TileMap.cs
+++ b/editor/GameObjects/TileMap.cs
@@ -25,10 +25,16 @@ public void SetAllForeground()
             {
                 _data[i] |= 0x1000;
             }
+            HasForeground = true;
         }
 
         public void OverlayWith(TileMap other)
         {
+            // Extend data if smaller (should not happen)
+            if (other._data.Count > _data.Count)
+            {
+                _data.AddRange(Enumerable.Repeat((ushort)0, other._data.Count - _data.Count));
+            }
             for (var i = 0; i < _data.Count; i++)
             {
                 if (other._data[i] != 0xff)
@@ -40,9 +46,10 @@ public void OverlayWith(TileMap other)
 
         public Bitmap GetImage(TileSet tileSet, Palette palette)
         {
-            var image = new Bitmap(256, 192, PixelFormat.Format8bppIndexed);
-            // We work in 8bpp again...
-            image.Palette = palette.ImagePalette;
+            var image = new Bitmap(256, 192, PixelFormat.Format8bppIndexed)
+            {
+                Palette = palette.ImagePalette
+            };
             var data = image.LockBits(new Rectangle(0, 0, image.Width, image.Height), ImageLockMode.WriteOnly, PixelFormat.Format8bppIndexed);
             try
             {
@@ -79,10 +86,11 @@ public Bitmap GetImage(TileSet tileSet, Palette palette)
         public int Offset { get; set; }
         public int ForegroundTileMapSize { get; private set; }
         public int BackgroundTileMapSize { get; private set; }
+        public bool HasForeground { get; private set; }
 
         public IList<byte> GetData()
         {
-            if (!_data.Any(x => x > 0xff))
+            if (!HasForeground)
             {
                 // Single tilemap mode
                 var tileMap = Compression.CompressRle(_data.Select(x => (byte)x).ToArray());