added async loading of scenes for transitions

MacTester/Scenes.cs

@@ -116,7 +116,7 @@ public static Scene sceneTwo()
 		{
 			var scene = new Scene();
 			scene.clearColor = Color.Coral;
-			var moonTexture = scene.contentManager.Load<Texture2D>( "Images/moon" );
+			var moonTexture = scene.contentManager.Load<Texture2D>( "bin/MacOSX/Images/moon" );
 			var bmFont = scene.contentManager.Load<BitmapFont>( "bin/MacOSX/Fonts/pixelfont" );
 			bmFont.spacing = 2f;
 

Nez-PCL/Graphics/Transitions/CrossFadeTransition.cs

@@ -36,7 +36,7 @@ public override IEnumerator onBeginTransition()
 			yield return null;
 
 			// load up the new Scene
-			Core.scene = sceneLoadAction();
+			yield return Core.startCoroutine( loadNextScene() );
 
 			var elapsed = 0f;
 			while( elapsed < fadeDuration )

Nez-PCL/Graphics/Transitions/FadeTransition.cs

@@ -20,12 +20,12 @@ public class FadeTransition : SceneTransition
 		/// <summary>
 		/// duration to fade to fadeToColor
 		/// </summary>
-		public float fadeOutDuration = 1f;
+		public float fadeOutDuration = 0.8f;
 
 		/// <summary>
 		/// delay to start fading out
 		/// </summary>
-		public float delayBeforeFadeInDuration = 0.4f;
+		public float delayBeforeFadeInDuration = 0.2f;
 
 		/// <summary>
 		/// duration to fade from fadeToColor to the new Scene
@@ -66,7 +66,7 @@ public override IEnumerator onBeginTransition()
 			}
 
 			// load up the new Scene
-			Core.scene = sceneLoadAction();
+			yield return Core.startCoroutine( loadNextScene() );
 
 			// dispose of our previousSceneRender. We dont need it anymore.
 			previousSceneRender.Dispose();
@@ -95,7 +95,7 @@ public override void render( Graphics graphics )
 			graphics.spriteBatch.Begin( SpriteSortMode.Deferred, BlendState.NonPremultiplied, Core.defaultSamplerState );
 
 			// we only render the previousSceneRender while fading to _color. It will be null after that.
-			if( previousSceneRender != null )
+			if( !_isNewSceneLoaded )
 				graphics.spriteBatch.Draw( previousSceneRender, _destinationRect, Color.White );
 
 			graphics.spriteBatch.Draw( _overlayTexture, _destinationRect, _color );

Nez-PCL/Graphics/Transitions/ImageMaskTransition.cs

@@ -59,11 +59,6 @@ public class ImageMaskTransition : SceneTransition
 		float _renderScale;
 		float _renderRotation;
 
-		/// <summary>
-		/// true if we are on the 2nd part of the transition
-		/// </summary>
-		bool _isScalingOut;
-
 		/// <summary>
 		/// the Texture used as a mask. It should be white where the mask shows the underlying Scene and transparent elsewhere
 		/// </summary>
@@ -119,14 +114,13 @@ public override IEnumerator onBeginTransition()
 				yield return null;
 			}
 
+			// load up the new Scene
+			yield return Core.startCoroutine( loadNextScene() );
+
 			// dispose of our previousSceneRender. We dont need it anymore.
 			previousSceneRender.Dispose();
 			previousSceneRender = null;
 
-			// load up the new Scene
-			Core.scene = sceneLoadAction();
-			_isScalingOut = true;
-
 			yield return delayBeforeMaskOut;
 
 			elapsed = 0f;
@@ -158,7 +152,7 @@ public override void render( Graphics graphics )
 			Core.graphicsDevice.SetRenderTarget( null );
 
 			// if we are scaling out we dont need to render the previous scene anymore since we want the new scene to be visible
-			if( !_isScalingOut )
+			if( !_isNewSceneLoaded )
 			{
 				graphics.spriteBatch.Begin( SpriteSortMode.Deferred, BlendState.Opaque, Core.defaultSamplerState );
 				graphics.spriteBatch.Draw( previousSceneRender, Vector2.Zero, Color.White );

Nez-PCL/Graphics/Transitions/SceneTransition.cs

@@ -23,6 +23,12 @@ public abstract class SceneTransition
 		/// </summary>
 		public bool wantsPreviousSceneRender;
 
+		/// <summary>
+		/// if true, the next Scene will be loaded on a background thread. Note that if raw PNG files are used they cannot be loaded
+		/// on a background thread.
+		/// </summary>
+		public bool loadSceneOnBackgroundThread = false;
+
 		/// <summary>
 		/// function that should return the newly loaded scene
 		/// </summary>
@@ -48,6 +54,7 @@ internal bool hasPreviousSceneRender
 		}
 		bool _hasPreviousSceneRender;
 
+		protected bool _isNewSceneLoaded;
 
 
 		public SceneTransition( Func<Scene> sceneLoadAction, bool wantsPreviousSceneRender = true )
@@ -61,6 +68,36 @@ public SceneTransition( Func<Scene> sceneLoadAction, bool wantsPreviousSceneRend
 		}
 
 
+		protected IEnumerator loadNextScene()
+		{
+			if( loadSceneOnBackgroundThread )
+			{
+				// load the Scene on a background thread
+				ThreadPool.QueueUserWorkItem( context =>
+				{
+					var scene = sceneLoadAction();
+
+					// get back to the main thread before setting the new Scene active
+					var syncContext = context as SynchronizationContext;
+					syncContext.Post( d =>
+					{
+						Core.scene = scene;
+						_isNewSceneLoaded = true;
+					}, null );
+				}, SynchronizationContext.Current );
+			}
+			else
+			{
+				Core.scene = sceneLoadAction();
+				_isNewSceneLoaded = true;
+			}
+
+			// wait for the scene to load if it was loaded on a background thread
+			while( !_isNewSceneLoaded )
+				yield return null;
+		}
+
+
 		/// <summary>
 		/// called after the previousSceneRender occurs for the first (and only) time. At this point you can load your new Scene after
 		/// yielding one frame (so the first render call happens before scene loading).

Nez-PCL/Graphics/Transitions/TransformTransition.cs

@@ -84,7 +84,7 @@ public override IEnumerator onBeginTransition()
 			yield return null;
 
 			// load up the new Scene
-			Core.scene = sceneLoadAction();
+			yield return Core.startCoroutine( loadNextScene() );
 
 			var elapsed = 0f;
 			while( elapsed < duration )