Merge pull request #8103 from RoosterDragon/mapcache-better-threading

Fix graphical glitches & crashes related to map loading

OpenRA.Game/Map/MapCache.cs

@@ -11,7 +11,6 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Drawing.Imaging;
 using System.IO;
 using System.Linq;
 using System.Net;
@@ -176,34 +175,31 @@ namespace OpenRA
 						bitmap = Minimap.RenderMapPreview(modData.DefaultRules.TileSets[p.Map.Tileset], p.Map, modData.DefaultRules, true);
 					}
 
-					// Note: this is not generally thread-safe, but it works here because:
-					//   (a) This worker is the only thread writing to this sheet
-					//   (b) The main thread is the only thread reading this sheet
-					//   (c) The sheet is marked dirty after the write is completed,
-					//       which causes the main thread to copy this to the texture during
-					//       the next render cycle.
-					//   (d) Any partially written bytes from the next minimap is in an
-					//       unallocated area, and will be committed in the next cycle.
-					try
+					Game.RunAfterTick(() =>
 					{
-						p.SetMinimap(sheetBuilder.Add(bitmap));
-					}
-					finally
-					{
-						if (createdPreview)
-							bitmap.Dispose();
-					}
+						try
+						{
+							p.SetMinimap(sheetBuilder.Add(bitmap));
+						}
+						finally
+						{
+							if (createdPreview)
+								bitmap.Dispose();
+						}
+					});
 
 					// Yuck... But this helps the UI Jank when opening the map selector significantly.
 					Thread.Sleep(Environment.ProcessorCount == 1 ? 25 : 5);
 				}
 			}
 
-			sheetBuilder.Current.ReleaseBuffer();
-
 			// The buffer is not fully reclaimed until changes are written out to the texture.
 			// We will access the texture in order to force changes to be written out, allowing the buffer to be freed.
-			Game.RunAfterTick(() => sheetBuilder.Current.GetTexture());
+			Game.RunAfterTick(() =>
+			{
+				sheetBuilder.Current.ReleaseBuffer();
+				sheetBuilder.Current.GetTexture();
+			});
 			Log.Write("debug", "MapCache.LoadAsyncInternal ended");
 		}
 
@@ -224,7 +220,6 @@ namespace OpenRA
 					if (previewLoaderThread != null)
 						previewLoaderThread.Join();
 
-					sheetBuilder.Current.CreateBuffer();
 					previewLoaderThread = new Thread(LoadAsyncInternal)
 					{
 						Name = "Map Preview Loader",