Add message box in bracket editor explaining how to get started

osu.Game.Tournament/Screens/Editors/LadderEditorScreen.cs

@@ -26,6 +26,8 @@ public class LadderEditorScreen : LadderScreen, IHasContextMenu
         [Cached]
         private LadderEditorInfo editorInfo = new LadderEditorInfo();
 
+        private WarningBox rightClickMessage;
+
         protected override bool DrawLoserPaths => true;
 
         [BackgroundDependencyLoader]
@@ -37,6 +39,16 @@ private void load()
                 Origin = Anchor.TopRight,
                 Margin = new MarginPadding(5)
             });
+
+            AddInternal(rightClickMessage = new WarningBox("Right click to place and link matches"));
+
+            LadderInfo.Matches.CollectionChanged += (_, __) => updateMessage();
+            updateMessage();
+        }
+
+        private void updateMessage()
+        {
+            rightClickMessage.Alpha = LadderInfo.Matches.Count > 0 ? 0 : 1;
         }
 
         public void BeginJoin(TournamentMatch match, bool losers)

osu.Game.Tournament/TournamentGame.cs

@@ -87,30 +87,7 @@ private void load(FrameworkConfigManager frameworkConfig)
                         },
                     }
                 },
-                heightWarning = new Container
+                heightWarning = new WarningBox("Please make the window wider"),
-                {
-                    Masking = true,
-                    CornerRadius = 5,
-                    Depth = float.MinValue,
-                    Anchor = Anchor.Centre,
-                    Origin = Anchor.Centre,
-                    AutoSizeAxes = Axes.Both,
-                    Children = new Drawable[]
-                    {
-                        new Box
-                        {
-                            Colour = Color4.Red,
-                            RelativeSizeAxes = Axes.Both,
-                        },
-                        new TournamentSpriteText
-                        {
-                            Text = "Please make the window wider",
-                            Font = OsuFont.Torus.With(weight: FontWeight.Bold),
-                            Colour = Color4.White,
-                            Padding = new MarginPadding(20)
-                        }
-                    }
-                },
                 new OsuContextMenuContainer
                 {
                     RelativeSizeAxes = Axes.Both,

osu.Game.Tournament/WarningBox.cs

@@ -0,0 +1,40 @@
+// 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 osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Shapes;
+using osu.Game.Graphics;
+using osuTK.Graphics;
+
+namespace osu.Game.Tournament
+{
+    internal class WarningBox : Container
+    {
+        public WarningBox(string text)
+        {
+            Masking = true;
+            CornerRadius = 5;
+            Depth = float.MinValue;
+            Anchor = Anchor.Centre;
+            Origin = Anchor.Centre;
+            AutoSizeAxes = Axes.Both;
+
+            Children = new Drawable[]
+            {
+                new Box
+                {
+                    Colour = Color4.Red,
+                    RelativeSizeAxes = Axes.Both,
+                },
+                new TournamentSpriteText
+                {
+                    Text = text,
+                    Font = OsuFont.Torus.With(weight: FontWeight.Bold),
+                    Colour = Color4.White,
+                    Padding = new MarginPadding(20)
+                }
+            };
+        }
+    }
+}