Refactor ScreenFooter to prepare for global usage and add transitions

osu.Game/Screens/Footer/ScreenFooter.cs

@@ -2,54 +2,33 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Shapes;
-using osu.Game.Graphics;
 using osu.Game.Overlays;
 using osuTK;
 
 namespace osu.Game.Screens.Footer
 {
-    public partial class ScreenFooter : InputBlockingContainer
+    public partial class ScreenFooter : OverlayContainer
     {
-        private const int height = 60;
         private const int padding = 60;
+        private const float delay_per_button = 30;
+
+        public const int HEIGHT = 60;
 
         private readonly List<OverlayContainer> overlays = new List<OverlayContainer>();
 
-        /// <param name="button">The button to be added.</param>
+        private FillFlowContainer<ScreenFooterButton> buttonsFlow = null!;
-        /// <param name="overlay">The <see cref="OverlayContainer"/> to be toggled by this button.</param>
+        private Container<ScreenFooterButton> removedButtonsContainer = null!;
-        public void AddButton(ScreenFooterButton button, OverlayContainer? overlay = null)
-        {
-            if (overlay != null)
-            {
-                overlays.Add(overlay);
-                button.Action = () => showOverlay(overlay);
-                button.OverlayState.BindTo(overlay.State);
-            }
-
-            buttons.Add(button);
-        }
-
-        private void showOverlay(OverlayContainer overlay)
-        {
-            foreach (var o in overlays)
-            {
-                if (o == overlay)
-                    o.ToggleVisibility();
-                else
-                    o.Hide();
-            }
-        }
-
-        private FillFlowContainer<ScreenFooterButton> buttons = null!;
 
         public ScreenFooter()
         {
             RelativeSizeAxes = Axes.X;
-            Height = height;
+            Height = HEIGHT;
             Anchor = Anchor.BottomLeft;
             Origin = Anchor.BottomLeft;
         }
@@ -64,9 +43,10 @@ namespace osu.Game.Screens.Footer
                     RelativeSizeAxes = Axes.Both,
                     Colour = colourProvider.Background5
                 },
-                buttons = new FillFlowContainer<ScreenFooterButton>
+                buttonsFlow = new FillFlowContainer<ScreenFooterButton>
                 {
-                    Position = new Vector2(ScreenBackButton.BUTTON_WIDTH + padding, 10),
+                    Margin = new MarginPadding { Left = 12f + ScreenBackButton.BUTTON_WIDTH + padding },
+                    Y = 10f,
                     Anchor = Anchor.BottomLeft,
                     Origin = Anchor.BottomLeft,
                     Direction = FillDirection.Horizontal,
@@ -80,7 +60,125 @@ namespace osu.Game.Screens.Footer
                     Origin = Anchor.BottomLeft,
                     Action = () => { },
                 },
+                removedButtonsContainer = new Container<ScreenFooterButton>
+                {
+                    Margin = new MarginPadding { Left = 12f + ScreenBackButton.BUTTON_WIDTH + padding },
+                    Y = 10f,
+                    Anchor = Anchor.BottomLeft,
+                    Origin = Anchor.BottomLeft,
+                    AutoSizeAxes = Axes.Both,
+                },
             };
         }
+
+        protected override void PopIn()
+        {
+            this.MoveToY(0, 400, Easing.OutQuint)
+                .FadeIn(400, Easing.OutQuint);
+        }
+
+        protected override void PopOut()
+        {
+            this.MoveToY(HEIGHT, 400, Easing.OutQuint)
+                .FadeOut(400, Easing.OutQuint);
+        }
+
+        public void SetButtons(IReadOnlyList<ScreenFooterButton> buttons)
+        {
+            overlays.Clear();
+
+            var oldButtons = buttonsFlow.ToArray();
+
+            for (int i = 0; i < oldButtons.Length; i++)
+            {
+                var oldButton = oldButtons[i];
+
+                buttonsFlow.Remove(oldButton, false);
+                removedButtonsContainer.Add(oldButton);
+
+                if (buttons.Count > 0)
+                    fadeButtonToLeft(oldButton, i, oldButtons.Length);
+                else
+                    fadeButtonToBottom(oldButton, i, oldButtons.Length);
+
+                Scheduler.AddDelayed(() => oldButton.Expire(), oldButton.TopLevelContent.LatestTransformEndTime - Time.Current);
+            }
+
+            for (int i = 0; i < buttons.Count; i++)
+            {
+                var newButton = buttons[i];
+
+                if (newButton.Overlay != null)
+                {
+                    newButton.Action = () => showOverlay(newButton.Overlay);
+                    overlays.Add(newButton.Overlay);
+                }
+
+                Debug.Assert(!newButton.IsLoaded);
+                buttonsFlow.Add(newButton);
+
+                int index = i;
+
+                // ensure transforms are added after LoadComplete to not be aborted by the FinishTransforms call.
+                newButton.OnLoadComplete += _ =>
+                {
+                    if (oldButtons.Length > 0)
+                        fadeButtonFromRight(newButton, index, buttons.Count, 240);
+                    else
+                        fadeButtonFromBottom(newButton, index);
+                };
+            }
+        }
+
+        private void fadeButtonFromRight(ScreenFooterButton button, int index, int count, float startDelay)
+        {
+            button.TopLevelContent
+                  .MoveToX(-300f)
+                  .FadeOut();
+
+            button.TopLevelContent
+                  .Delay(startDelay + (count - index) * delay_per_button)
+                  .MoveToX(0f, 240, Easing.OutCubic)
+                  .FadeIn(240, Easing.OutCubic);
+        }
+
+        private void fadeButtonFromBottom(ScreenFooterButton button, int index)
+        {
+            button.TopLevelContent
+                  .MoveToY(100f)
+                  .FadeOut();
+
+            button.TopLevelContent
+                  .Delay(index * delay_per_button)
+                  .MoveToY(0f, 240, Easing.OutCubic)
+                  .FadeIn(240, Easing.OutCubic);
+        }
+
+        private void fadeButtonToLeft(ScreenFooterButton button, int index, int count)
+        {
+            button.TopLevelContent
+                  .Delay((count - index) * delay_per_button)
+                  .FadeOut(240, Easing.InOutCubic)
+                  .MoveToX(300f, 360, Easing.InOutCubic);
+        }
+
+        private void fadeButtonToBottom(ScreenFooterButton button, int index, int count)
+        {
+            button.TopLevelContent
+                  .Delay((count - index) * delay_per_button)
+                  .FadeOut(240, Easing.InOutCubic)
+                  .MoveToY(100f, 240, Easing.InOutCubic);
+        }
+
+        private void showOverlay(OverlayContainer overlay)
+        {
+            foreach (var o in overlays)
+            {
+                if (o == overlay)
+                    o.ToggleVisibility();
+                else
+                    o.Hide();
+            }
+        }
     }
 }