Photo.Unload() is now async

Program.cs

@@ -187,9 +187,10 @@ public class Photo {
     image = tmp;
   }
 
-  public void Unload() {
+  public async void UnloadAsync() {
+    Loaded = false;
     if (texture != placeholder) {
-      texture.Dispose();
+      await Task.Run( () => { texture.Dispose(); });
       texture = placeholder;
     }
   }
@@ -703,19 +704,15 @@ public class Game : GameWindow {
     int maxLoadedImage = Math.Min(photoIndex + 20, photos.Count - 1);
     // First, unload images that are far outside our window.
     // FIXME: also cancel any in-progress loading tasks that have moved outside our window.
-    Stopwatch stopwatch = new Stopwatch();
-    stopwatch.Start();
+    // FIXME: maybe use an LRU cache for evicting images?
+    // FIXME: keep around thumbnail-sized textures?
     foreach (int i in loadedImages) {
       if (i < minUnloadedImage || i > maxUnloadedImage) {
-        loadedImages.Remove(i);
-        photos[i].Unload();
         // Console.WriteLine("unloading " + i);
+        loadedImages.Remove(i);
+        photos[i].UnloadAsync();
       }
     }
-    stopwatch.Stop();
-    if (stopwatch.Elapsed.TotalMilliseconds > 1) {
-      Console.WriteLine(stopwatch.Elapsed.TotalMilliseconds);
-    }
 
     // Then, start loading any images that aren't in our window.
     for (int i = minLoadedImage; i <= maxLoadedImage; i++) {