Move threading into the preview generation.

OpenRA.Game/Widgets/MapPreviewWidget.cs

@@ -12,6 +12,7 @@ using System;
 using System.Collections.Generic;
 using System.Drawing;
 using System.Linq;
+using System.Threading;
 using OpenRA.FileFormats;
 using OpenRA.Graphics;
 
@@ -26,8 +27,6 @@ namespace OpenRA.Widgets
 		public bool IgnoreMouseInput = false;
 		public bool ShowSpawnPoints = true;
 
-		static readonly Cache<Map,Bitmap> PreviewCache = new Cache<Map, Bitmap>(stub => Minimap.RenderMapPreview( new Map( stub.Path )));
-
 		public MapPreviewWidget() : base() { }
 
 		protected MapPreviewWidget(MapPreviewWidget other)
@@ -68,19 +67,30 @@ namespace OpenRA.Widgets
 		public override void Draw()
 		{
 			var map = Map();
-			if( map == null ) return;
+			if (map == null)
+				return;
+
+			// Preview unavailable
+			if (!Loaded)
+			{
+				GeneratePreview();
+				return;
+			}
 
 			if (lastMap != map)
 			{
 				lastMap = map;
 
 				// Update image data
-				var preview = PreviewCache[map];
+				Bitmap preview;
-				if( mapChooserSheet == null || mapChooserSheet.Size.Width != preview.Width || mapChooserSheet.Size.Height != preview.Height )
+				lock (syncRoot)
-					mapChooserSheet = new Sheet(new Size( preview.Width, preview.Height ) );
+					preview = Previews[map.Uid];
 
-				mapChooserSheet.Texture.SetData( preview );
+				if (mapChooserSheet == null || mapChooserSheet.Size.Width != preview.Width || mapChooserSheet.Size.Height != preview.Height)
-				mapChooserSprite = new Sprite( mapChooserSheet, new Rectangle( 0, 0, map.Bounds.Width, map.Bounds.Height ), TextureChannel.Alpha );
+					mapChooserSheet = new Sheet(new Size(preview.Width, preview.Height));
+
+				mapChooserSheet.Texture.SetData(preview);
+				mapChooserSprite = new Sprite(mapChooserSheet, new Rectangle(0, 0, map.Bounds.Width, map.Bounds.Height), TextureChannel.Alpha);
 			}
 
 			// Update map rect
@@ -90,9 +100,9 @@ namespace OpenRA.Widgets
 			var dh = (int)(PreviewScale * (size - map.Bounds.Height)) / 2;
 			MapRect = new Rectangle(RenderBounds.X + dw, RenderBounds.Y + dh, (int)(map.Bounds.Width * PreviewScale), (int)(map.Bounds.Height * PreviewScale));
 
-			Game.Renderer.RgbaSpriteRenderer.DrawSprite( mapChooserSprite,
+			Game.Renderer.RgbaSpriteRenderer.DrawSprite(mapChooserSprite,
 				new float2(MapRect.Location),
-				new float2( MapRect.Size ) );
+				new float2(MapRect.Size));
 
 			if (ShowSpawnPoints)
 			{
@@ -119,15 +129,70 @@ namespace OpenRA.Widgets
 			}
 		}
 
-		/// <summary>
+		// Async map preview generation bits
-		/// Forces loading the preview into the map cache.
+		enum PreviewStatus { Invalid, Uncached, Generating, Cached }
-		/// </summary>
+		static Thread previewLoaderThread;
-		public Bitmap LoadMapPreview()
+		static object syncRoot = new object();
-		{
+		static Queue<string> cacheUids = new Queue<string>();
-			var map = Map();
+		static readonly Dictionary<string, Bitmap> Previews = new Dictionary<string, Bitmap>();
-			if( map == null ) return null;
 
-			return PreviewCache[map];
+		void LoadAsyncInternal()
+		{
+			for (;;)
+			{
+				string uid;
+				lock (syncRoot)
+				{
+					if (cacheUids.Count == 0)
+						break;
+					uid = cacheUids.Peek();
+				}
+
+				var bitmap = Minimap.RenderMapPreview(Game.modData.AvailableMaps[uid]);
+				lock (syncRoot)
+				{
+					// TODO: We should add previews to a sheet here (with multiple previews per sheet)
+					Previews.Add(uid, bitmap);
+					cacheUids.Dequeue();
+				}
+			}
 		}
+
+		void GeneratePreview()
+		{
+			var m = Map();
+			if (m == null)
+				return;
+
+			var status = Status(m);
+			if (status == PreviewStatus.Uncached)
+				lock (syncRoot)
+					cacheUids.Enqueue(m.Uid);
+
+			if (previewLoaderThread == null || !previewLoaderThread.IsAlive)
+			{
+				previewLoaderThread = new Thread(LoadAsyncInternal);
+				previewLoaderThread.Priority = ThreadPriority.Lowest;
+				previewLoaderThread.Start();
+			}
+		}
+
+		static PreviewStatus Status(Map m)
+		{
+			if (m == null)
+				return PreviewStatus.Invalid;
+
+			lock (syncRoot)
+			{
+				if (Previews.ContainsKey(m.Uid))
+					return PreviewStatus.Cached;
+
+				if (cacheUids.Contains(m.Uid))
+					return PreviewStatus.Generating;
+			}
+			return PreviewStatus.Uncached;
+		}
+
+		public bool Loaded { get { return Status(Map()) == PreviewStatus.Cached; } }
 	}
 }

OpenRA.Mods.RA/Widgets/Logic/MapChooserLogic.cs

@@ -27,7 +27,6 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 		ScrollPanelWidget scrollpanel;
 		ScrollItemWidget itemTemplate;
 		string gameMode;
-		Thread mapLoaderThread;
 
 		[ObjectCreator.UseCtor]
 		internal MapChooserLogic(Widget widget, string initialMap, Action onExit, Action<Map> onSelect)
@@ -61,7 +60,7 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				{
 					var item = ScrollItemWidget.Setup(template,
 						() => gameMode == ii.First,
-						() => { gameMode = ii.First; EnumerateMapsAsync(); });
+						() => { gameMode = ii.First; EnumerateMaps(); });
 					item.Get<LabelWidget>("LABEL").GetText = () => showItem(ii);
 					return item;
 				};
@@ -84,16 +83,7 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				randomMapButton.IsDisabled = () => visibleMaps == null || visibleMaps.Count == 0;
 			}
 
-			EnumerateMapsAsync();
+			EnumerateMaps();
-		}
-
-		void EnumerateMapsAsync()
-		{
-			if (mapLoaderThread != null && mapLoaderThread.IsAlive) 
-				mapLoaderThread.Abort(); // violent, but should be fine since we are not doing anything sensitive in this thread
-
-			mapLoaderThread = new Thread(EnumerateMaps);
-			mapLoaderThread.Start();
 		}
 
 		void EnumerateMaps()
@@ -104,7 +94,7 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				.OrderBy(kv => kv.Value.PlayerCount)
 				.ThenBy(kv => kv.Value.Title);
 
-			var children = new List<ScrollItemWidget>();
+			scrollpanel.RemoveChildren();
 			foreach (var kv in maps)
 			{
 				var m = kv.Value;
@@ -117,17 +107,20 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				previewWidget.IgnoreMouseOver = true;
 				previewWidget.IgnoreMouseInput = true;
 				previewWidget.Map = () => m;
-				previewWidget.LoadMapPreview();
 
-				var detailsWidget = item.Get<LabelWidget>("DETAILS");
+				var previewLoadingWidget = item.GetOrNull<BackgroundWidget>("PREVIEW_PLACEHOLDER");
+				if (previewLoadingWidget != null)
+					previewLoadingWidget.IsVisible = () => !previewWidget.Loaded;
+
+				var detailsWidget = item.GetOrNull<LabelWidget>("DETAILS");
 				if (detailsWidget != null)
 					detailsWidget.GetText = () => "{0} ({1})".F(m.Type, m.PlayerCount);
 
-				var authorWidget = item.Get<LabelWidget>("AUTHOR");
+				var authorWidget = item.GetOrNull<LabelWidget>("AUTHOR");
 				if (authorWidget != null)
 					authorWidget.GetText = () => m.Author;
 
-				var sizeWidget = item.Get<LabelWidget>("SIZE");
+				var sizeWidget = item.GetOrNull<LabelWidget>("SIZE");
 				if (sizeWidget != null)
 				{
 					var size = m.Bounds.Width + "x" + m.Bounds.Height;
@@ -139,20 +132,12 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 					sizeWidget.GetText = () => size;
 				}
 
-				children.Add(item);
+				scrollpanel.AddChild(item);
 			}
 
-			Game.RunAfterTick(() =>
+			visibleMaps = maps.ToDictionary(kv => kv.Key, kv => kv.Value);
-			{
+			if (visibleMaps.ContainsValue(map))
-				scrollpanel.RemoveChildren();
+				scrollpanel.ScrollToItem(visibleMaps.First(m => m.Value == map).Key);
-
-				foreach (var c in children)
-					scrollpanel.AddChild(c);
-
-				visibleMaps = maps.ToDictionary(kv => kv.Key, kv => kv.Value);
-				if (visibleMaps.ContainsValue(map))
-					scrollpanel.ScrollToItem(visibleMaps.First(m => m.Value == map).Key);
-			});
 		}
 	}
 }

mods/cnc/chrome/mapchooser.yaml

@@ -43,6 +43,13 @@ Container@MAPCHOOSER_PANEL:
 							Y:0
 							Visible:false
 							Children:
+								Background@PREVIEW_PLACEHOLDER:
+									X:(PARENT_RIGHT - WIDTH)/2
+									Y:4
+									Width:158
+									Height:158
+									Background:panel-black
+									ClickThrough: false
 								MapPreview@PREVIEW:
 									X:(PARENT_RIGHT - WIDTH)/2
 									Y:4