GameMode -> Screen.

osu.Game/Screens/BackgroundScreen.cs

@@ -0,0 +1,96 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using System.Threading;
+using osu.Framework;
+using osu.Framework.Allocation;
+using osu.Framework.Screens;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Transformations;
+using osu.Framework.Input;
+using OpenTK;
+
+namespace osu.Game.Screens
+{
+    public abstract class BackgroundScreen : Screen, IEquatable<BackgroundScreen>
+    {
+        public virtual bool Equals(BackgroundScreen other)
+        {
+            return other?.GetType() == GetType();
+        }
+
+        const float transition_length = 500;
+        const float x_movement_amount = 50;
+
+        protected override bool OnKeyDown(InputState state, KeyDownEventArgs args)
+        {
+            //we don't want to handle escape key.
+            return false;
+        }
+
+        BaseGame game;
+
+        [BackgroundDependencyLoader]
+        private void load(BaseGame game)
+        {
+            this.game = game;
+        }
+
+        public override bool Push(Screen screen)
+        {
+            // When trying to push a non-loaded GameMode, load it asynchronously and re-invoke Push
+            // once it's done.
+            if (screen.LoadState == LoadState.NotLoaded)
+            {
+                screen.Preload(game, d => Push((BackgroundScreen)d));
+                return true;
+            }
+
+            // Make sure the in-progress loading is complete before pushing the GameMode.
+            while (screen.LoadState < LoadState.Loaded)
+                Thread.Sleep(1);
+
+            base.Push(screen);
+
+            return true;
+        }
+
+        protected override void Update()
+        {
+            base.Update();
+            Content.Scale = new Vector2(1 + (x_movement_amount / DrawSize.X) * 2);
+        }
+
+        protected override void OnEntering(Screen last)
+        {
+            Content.FadeOut();
+            Content.MoveToX(x_movement_amount);
+
+            Content.FadeIn(transition_length, EasingTypes.InOutQuart);
+            Content.MoveToX(0, transition_length, EasingTypes.InOutQuart);
+
+            base.OnEntering(last);
+        }
+
+        protected override void OnSuspending(Screen next)
+        {
+            Content.MoveToX(-x_movement_amount, transition_length, EasingTypes.InOutQuart);
+            base.OnSuspending(next);
+        }
+
+        protected override bool OnExiting(Screen next)
+        {
+            Content.FadeOut(transition_length, EasingTypes.OutExpo);
+            Content.MoveToX(x_movement_amount, transition_length, EasingTypes.OutExpo);
+
+            return base.OnExiting(next);
+        }
+
+        protected override void OnResuming(Screen last)
+        {
+            Content.MoveToX(0, transition_length, EasingTypes.OutExpo);
+            base.OnResuming(last);
+        }
+    }
+}