From dcae86e39a0d9b4058d6f77a2cdc9c05bb3c922e Mon Sep 17 00:00:00 2001
From: David Zhao <nyquill@ppy.sh>
Date: Fri, 22 Mar 2019 14:10:38 +0900
Subject: [PATCH] Add a new test for OsuScreenStack, fix parallax

---
 .../Visual/TestCaseOsuScreenStack.cs          | 45 +++++++++++++++++++
 osu.Game/OsuGame.cs                           |  2 +
 osu.Game/Screens/OsuScreenStack.cs            |  8 +++-
 osu.Game/Tests/Visual/AllPlayersTestCase.cs   | 10 ++---
 osu.Game/Tests/Visual/PlayerTestCase.cs       |  7 +--
 5 files changed, 59 insertions(+), 13 deletions(-)
 create mode 100644 osu.Game.Tests/Visual/TestCaseOsuScreenStack.cs

diff --git a/osu.Game.Tests/Visual/TestCaseOsuScreenStack.cs b/osu.Game.Tests/Visual/TestCaseOsuScreenStack.cs
new file mode 100644
index 0000000000..c3a9e94448
--- /dev/null
+++ b/osu.Game.Tests/Visual/TestCaseOsuScreenStack.cs
@@ -0,0 +1,45 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using NUnit.Framework;
+using osu.Framework.Graphics;
+using osu.Framework.Screens;
+using osu.Framework.Testing;
+using osu.Game.Graphics.Containers;
+using osu.Game.Screens;
+using osu.Game.Screens.Play;
+
+namespace osu.Game.Tests.Visual
+{
+    [TestFixture]
+    public class TestCaseOsuScreenStack : OsuTestCase
+    {
+        private TestScreen baseScreen;
+        private TestOsuScreenStack stack;
+
+        [SetUpSteps]
+        public void Setup()
+        {
+            AddStep("Create new screen stack", () => { Child = stack = new TestOsuScreenStack { RelativeSizeAxes = Axes.Both }; });
+            AddStep("Push new base screen", () => stack.Push(baseScreen = new TestScreen()));
+        }
+
+        [Test]
+        public void ParallaxAssignmentTest()
+        {
+            AddStep("Push new screen to base screen", () => baseScreen.Push(new TestScreen()));
+            AddAssert("Parallax is correct", () => stack.IsParallaxSet);
+            AddStep("Exit from new screen", () => { baseScreen.MakeCurrent(); });
+            AddAssert("Parallax is correct", () => stack.IsParallaxSet);
+        }
+
+        private class TestScreen : ScreenWithBeatmapBackground
+        {
+        }
+
+        private class TestOsuScreenStack : OsuScreenStack
+        {
+            public bool IsParallaxSet => ParallaxAmount == ((TestScreen)CurrentScreen).BackgroundParallaxAmount * ParallaxContainer.DEFAULT_PARALLAX_AMOUNT;
+        }
+    }
+}
diff --git a/osu.Game/OsuGame.cs b/osu.Game/OsuGame.cs
index ad2980d818..079a0d5bb6 100644
--- a/osu.Game/OsuGame.cs
+++ b/osu.Game/OsuGame.cs
@@ -406,6 +406,8 @@ namespace osu.Game
             loadComponentSingleFile(osuLogo, logo =>
             {
                 logoContainer.Add(logo);
+
+                // Loader has to be created synchronously in order for DI to be successful for its background screen stack.
                 screenStack.Push(new Loader
                 {
                     RelativeSizeAxes = Axes.Both
diff --git a/osu.Game/Screens/OsuScreenStack.cs b/osu.Game/Screens/OsuScreenStack.cs
index 2eea7bebbb..1c929470d1 100644
--- a/osu.Game/Screens/OsuScreenStack.cs
+++ b/osu.Game/Screens/OsuScreenStack.cs
@@ -15,6 +15,8 @@ namespace osu.Game.Screens
 
         private ParallaxContainer parallaxContainer;
 
+        protected float ParallaxAmount => parallaxContainer.ParallaxAmount;
+
         public OsuScreenStack()
         {
             initializeStack();
@@ -35,11 +37,15 @@ namespace osu.Game.Screens
             };
 
             ScreenPushed += setParallax;
+            ScreenExited += setParallax;
         }
 
         private void setParallax(IScreen prev, IScreen next)
         {
-            parallaxContainer.ParallaxAmount = ParallaxContainer.DEFAULT_PARALLAX_AMOUNT * ((IOsuScreen)next).BackgroundParallaxAmount;
+            if (next != null)
+            {
+                parallaxContainer.ParallaxAmount = ParallaxContainer.DEFAULT_PARALLAX_AMOUNT * ((IOsuScreen)next).BackgroundParallaxAmount;
+            }
         }
     }
 }
diff --git a/osu.Game/Tests/Visual/AllPlayersTestCase.cs b/osu.Game/Tests/Visual/AllPlayersTestCase.cs
index 507848730f..03bd7b218a 100644
--- a/osu.Game/Tests/Visual/AllPlayersTestCase.cs
+++ b/osu.Game/Tests/Visual/AllPlayersTestCase.cs
@@ -73,15 +73,11 @@ namespace osu.Game.Tests.Visual
             Player?.Exit();
             Player = null;
 
-            var player = CreatePlayer(r);
+            Player = CreatePlayer(r);
 
-            LoadComponentAsync(player, p =>
-            {
-                Player = p;
-                LoadScreen(p);
-            });
+            LoadScreen(Player);
 
-            return player;
+            return Player;
         }
 
         protected virtual Player CreatePlayer(Ruleset ruleset) => new Player
diff --git a/osu.Game/Tests/Visual/PlayerTestCase.cs b/osu.Game/Tests/Visual/PlayerTestCase.cs
index ad01d82281..50cb839ed9 100644
--- a/osu.Game/Tests/Visual/PlayerTestCase.cs
+++ b/osu.Game/Tests/Visual/PlayerTestCase.cs
@@ -52,11 +52,8 @@ namespace osu.Game.Tests.Visual
             if (!AllowFail)
                 Beatmap.Value.Mods.Value = new[] { ruleset.GetAllMods().First(m => m is ModNoFail) };
 
-            LoadComponentAsync(Player = CreatePlayer(ruleset), p =>
-            {
-                Player = p;
-                LoadScreen(p);
-            });
+            Player = CreatePlayer(ruleset);
+            LoadScreen(Player);
         }
 
         protected virtual Player CreatePlayer(Ruleset ruleset) => new Player