Merge pull request #28528 from bdach/break-autogeneration

osu.Game.Rulesets.Catch.Tests/Mods/TestSceneCatchModNoScope.cs

@@ -74,7 +74,7 @@ namespace osu.Game.Rulesets.Catch.Tests.Mods
                             StartTime = 5000,
                         }
                     },
-                    Breaks = new List<BreakPeriod>
+                    Breaks =
                     {
                         new BreakPeriod(2000, 4000),
                     }

osu.Game.Rulesets.Osu.Tests/Mods/TestSceneOsuModAlternate.cs

@@ -133,7 +133,7 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
             Autoplay = false,
             Beatmap = new Beatmap
             {
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(500, 2000),
                 },

osu.Game.Rulesets.Osu.Tests/Mods/TestSceneOsuModNoScope.cs

@@ -46,7 +46,7 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
                             StartTime = 5000,
                         }
                     },
-                    Breaks = new List<BreakPeriod>
+                    Breaks =
                     {
                         new BreakPeriod(2000, 4000),
                     }

osu.Game.Rulesets.Osu.Tests/Mods/TestSceneOsuModSingleTap.cs

@@ -132,7 +132,7 @@ namespace osu.Game.Rulesets.Osu.Tests.Mods
             Autoplay = false,
             Beatmap = new Beatmap
             {
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(500, 2000),
                 },

osu.Game.Rulesets.Taiko.Tests/Mods/TestSceneTaikoModSingleTap.cs

@@ -177,7 +177,7 @@ namespace osu.Game.Rulesets.Taiko.Tests.Mods
             Autoplay = false,
             Beatmap = new Beatmap
             {
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(100, 1600),
                 },

osu.Game.Tests/Editing/Checks/CheckBreaksTest.cs

@@ -1,7 +1,6 @@
 // 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 System.Collections.Generic;
 using System.Linq;
 using NUnit.Framework;
 using osu.Game.Beatmaps;
@@ -29,7 +28,7 @@ namespace osu.Game.Tests.Editing.Checks
         {
             var beatmap = new Beatmap<HitObject>
             {
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(0, 649)
                 }
@@ -52,7 +51,7 @@ namespace osu.Game.Tests.Editing.Checks
                     new HitCircle { StartTime = 0 },
                     new HitCircle { StartTime = 1_200 }
                 },
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(100, 751)
                 }
@@ -75,7 +74,7 @@ namespace osu.Game.Tests.Editing.Checks
                     new HitCircle { StartTime = 0 },
                     new HitCircle { StartTime = 1_298 }
                 },
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(200, 850)
                 }
@@ -98,7 +97,7 @@ namespace osu.Game.Tests.Editing.Checks
                     new HitCircle { StartTime = 0 },
                     new HitCircle { StartTime = 1200 }
                 },
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(1398, 2300)
                 }
@@ -121,7 +120,7 @@ namespace osu.Game.Tests.Editing.Checks
                     new HitCircle { StartTime = 1100 },
                     new HitCircle { StartTime = 1500 }
                 },
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(0, 652)
                 }
@@ -145,7 +144,7 @@ namespace osu.Game.Tests.Editing.Checks
                     new HitCircle { StartTime = 1_297 },
                     new HitCircle { StartTime = 1_298 }
                 },
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(200, 850)
                 }
@@ -168,7 +167,7 @@ namespace osu.Game.Tests.Editing.Checks
                     new HitCircle { StartTime = 0 },
                     new HitCircle { StartTime = 1_300 }
                 },
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(200, 850)
                 }

osu.Game.Tests/Editing/Checks/CheckDrainLengthTest.cs

@@ -53,7 +53,7 @@ namespace osu.Game.Tests.Editing.Checks
                     new HitCircle { StartTime = 0 },
                     new HitCircle { StartTime = 40_000 }
                 },
-                Breaks = new List<BreakPeriod>
+                Breaks =
                 {
                     new BreakPeriod(10_000, 21_000)
                 }

osu.Game.Tests/Editing/TestSceneEditorBeatmapProcessor.cs

@@ -0,0 +1,300 @@
+// 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.Game.Beatmaps;
+using osu.Game.Beatmaps.ControlPoints;
+using osu.Game.Beatmaps.Timing;
+using osu.Game.Rulesets.Osu;
+using osu.Game.Rulesets.Osu.Objects;
+using osu.Game.Screens.Edit;
+
+namespace osu.Game.Tests.Editing
+{
+    [TestFixture]
+    public class TestSceneEditorBeatmapProcessor
+    {
+        [Test]
+        public void TestEmptyBeatmap()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.That(beatmap.Breaks, Is.Empty);
+        }
+
+        [Test]
+        public void TestSingleObjectBeatmap()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1000 },
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.That(beatmap.Breaks, Is.Empty);
+        }
+
+        [Test]
+        public void TestTwoObjectsCloseTogether()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1000 },
+                    new HitCircle { StartTime = 2000 },
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.That(beatmap.Breaks, Is.Empty);
+        }
+
+        [Test]
+        public void TestTwoObjectsFarApart()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1000 },
+                    new HitCircle { StartTime = 5000 },
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(beatmap.Breaks, Has.Count.EqualTo(1));
+                Assert.That(beatmap.Breaks[0].StartTime, Is.EqualTo(1200));
+                Assert.That(beatmap.Breaks[0].EndTime, Is.EqualTo(4000));
+            });
+        }
+
+        [Test]
+        public void TestBreaksAreFused()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1000 },
+                    new HitCircle { StartTime = 9000 },
+                },
+                Breaks =
+                {
+                    new BreakPeriod(1200, 4000),
+                    new BreakPeriod(5200, 8000),
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(beatmap.Breaks, Has.Count.EqualTo(1));
+                Assert.That(beatmap.Breaks[0].StartTime, Is.EqualTo(1200));
+                Assert.That(beatmap.Breaks[0].EndTime, Is.EqualTo(8000));
+            });
+        }
+
+        [Test]
+        public void TestBreaksAreSplit()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1000 },
+                    new HitCircle { StartTime = 5000 },
+                    new HitCircle { StartTime = 9000 },
+                },
+                Breaks =
+                {
+                    new BreakPeriod(1200, 8000),
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(beatmap.Breaks, Has.Count.EqualTo(2));
+                Assert.That(beatmap.Breaks[0].StartTime, Is.EqualTo(1200));
+                Assert.That(beatmap.Breaks[0].EndTime, Is.EqualTo(4000));
+                Assert.That(beatmap.Breaks[1].StartTime, Is.EqualTo(5200));
+                Assert.That(beatmap.Breaks[1].EndTime, Is.EqualTo(8000));
+            });
+        }
+
+        [Test]
+        public void TestBreaksAreNudged()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1100 },
+                    new HitCircle { StartTime = 9000 },
+                },
+                Breaks =
+                {
+                    new BreakPeriod(1200, 8000),
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(beatmap.Breaks, Has.Count.EqualTo(1));
+                Assert.That(beatmap.Breaks[0].StartTime, Is.EqualTo(1300));
+                Assert.That(beatmap.Breaks[0].EndTime, Is.EqualTo(8000));
+            });
+        }
+
+        [Test]
+        public void TestManualBreaksAreNotFused()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1000 },
+                    new HitCircle { StartTime = 9000 },
+                },
+                Breaks =
+                {
+                    new ManualBreakPeriod(1200, 4000),
+                    new ManualBreakPeriod(5200, 8000),
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(beatmap.Breaks, Has.Count.EqualTo(2));
+                Assert.That(beatmap.Breaks[0].StartTime, Is.EqualTo(1200));
+                Assert.That(beatmap.Breaks[0].EndTime, Is.EqualTo(4000));
+                Assert.That(beatmap.Breaks[1].StartTime, Is.EqualTo(5200));
+                Assert.That(beatmap.Breaks[1].EndTime, Is.EqualTo(8000));
+            });
+        }
+
+        [Test]
+        public void TestManualBreaksAreSplit()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1000 },
+                    new HitCircle { StartTime = 5000 },
+                    new HitCircle { StartTime = 9000 },
+                },
+                Breaks =
+                {
+                    new ManualBreakPeriod(1200, 8000),
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(beatmap.Breaks, Has.Count.EqualTo(2));
+                Assert.That(beatmap.Breaks[0].StartTime, Is.EqualTo(1200));
+                Assert.That(beatmap.Breaks[0].EndTime, Is.EqualTo(4000));
+                Assert.That(beatmap.Breaks[1].StartTime, Is.EqualTo(5200));
+                Assert.That(beatmap.Breaks[1].EndTime, Is.EqualTo(8000));
+            });
+        }
+
+        [Test]
+        public void TestManualBreaksAreNotNudged()
+        {
+            var controlPoints = new ControlPointInfo();
+            controlPoints.Add(0, new TimingControlPoint { BeatLength = 500 });
+            var beatmap = new Beatmap
+            {
+                ControlPointInfo = controlPoints,
+                HitObjects =
+                {
+                    new HitCircle { StartTime = 1000 },
+                    new HitCircle { StartTime = 9000 },
+                },
+                Breaks =
+                {
+                    new ManualBreakPeriod(1200, 8800),
+                }
+            };
+
+            var beatmapProcessor = new EditorBeatmapProcessor(beatmap, new OsuRuleset());
+            beatmapProcessor.PreProcess();
+            beatmapProcessor.PostProcess();
+
+            Assert.Multiple(() =>
+            {
+                Assert.That(beatmap.Breaks, Has.Count.EqualTo(1));
+                Assert.That(beatmap.Breaks[0].StartTime, Is.EqualTo(1200));
+                Assert.That(beatmap.Breaks[0].EndTime, Is.EqualTo(8800));
+            });
+        }
+    }
+}

osu.Game.Tests/Visual/Editing/TestSceneEditorChangeStates.cs

@@ -4,10 +4,12 @@
 #nullable disable
 
 using NUnit.Framework;
+using osu.Game.Beatmaps;
 using osu.Game.Rulesets;
 using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.Osu;
 using osu.Game.Rulesets.Osu.Objects;
+using osu.Game.Tests.Beatmaps;
 
 namespace osu.Game.Tests.Visual.Editing
 {
@@ -15,6 +17,8 @@ namespace osu.Game.Tests.Visual.Editing
     {
         protected override Ruleset CreateEditorRuleset() => new OsuRuleset();
 
+        protected override IBeatmap CreateBeatmap(RulesetInfo ruleset) => new TestBeatmap(ruleset, false);
+
         [Test]
         public void TestSelectedObjects()
         {

osu.Game/Beatmaps/Beatmap.cs

@@ -8,6 +8,7 @@ using System.Collections.Generic;
 using System.Linq;
 using osu.Game.Beatmaps.ControlPoints;
 using Newtonsoft.Json;
+using osu.Framework.Bindables;
 using osu.Game.IO.Serialization.Converters;
 
 namespace osu.Game.Beatmaps
@@ -61,7 +62,7 @@ namespace osu.Game.Beatmaps
 
         public ControlPointInfo ControlPointInfo { get; set; } = new ControlPointInfo();
 
-        public List<BreakPeriod> Breaks { get; set; } = new List<BreakPeriod>();
+        public BindableList<BreakPeriod> Breaks { get; set; } = new BindableList<BreakPeriod>();
 
         public List<string> UnhandledEventLines { get; set; } = new List<string>();
 

osu.Game/Beatmaps/IBeatmap.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using osu.Framework.Bindables;
 using osu.Game.Beatmaps.ControlPoints;
 using osu.Game.Beatmaps.Timing;
 using osu.Game.Rulesets.Objects;
@@ -40,7 +41,7 @@ namespace osu.Game.Beatmaps
         /// <summary>
         /// The breaks in this beatmap.
         /// </summary>
-        List<BreakPeriod> Breaks { get; }
+        BindableList<BreakPeriod> Breaks { get; }
 
         /// <summary>
         /// All lines from the [Events] section which aren't handled in the encoding process yet.

osu.Game/Beatmaps/Timing/BreakPeriod.cs

@@ -1,26 +1,44 @@
 // 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 System;
 using osu.Game.Screens.Play;
 
 namespace osu.Game.Beatmaps.Timing
 {
-    public class BreakPeriod
+    public class BreakPeriod : IEquatable<BreakPeriod>
     {
+        /// <summary>
+        /// The minimum gap between the start of the break and the previous object.
+        /// </summary>
+        public const double GAP_BEFORE_BREAK = 200;
+
+        /// <summary>
+        /// The minimum gap between the end of the break and the next object.
+        /// Based on osu! preempt time at AR=10.
+        /// See also: https://github.com/ppy/osu/issues/14330#issuecomment-1002158551
+        /// </summary>
+        public const double GAP_AFTER_BREAK = 450;
+
         /// <summary>
         /// The minimum duration required for a break to have any effect.
         /// </summary>
         public const double MIN_BREAK_DURATION = 650;
 
+        /// <summary>
+        /// The minimum required duration of a gap between two objects such that a break can be placed between them.
+        /// </summary>
+        public const double MIN_GAP_DURATION = GAP_BEFORE_BREAK + MIN_BREAK_DURATION + GAP_AFTER_BREAK;
+
         /// <summary>
         /// The break start time.
         /// </summary>
-        public double StartTime;
+        public double StartTime { get; }
 
         /// <summary>
         /// The break end time.
         /// </summary>
-        public double EndTime;
+        public double EndTime { get; }
 
         /// <summary>
         /// The break duration.
@@ -49,5 +67,14 @@ namespace osu.Game.Beatmaps.Timing
         /// <param name="time">The time to check in milliseconds.</param>
         /// <returns>Whether the time falls within this <see cref="BreakPeriod"/>.</returns>
         public bool Contains(double time) => time >= StartTime && time <= EndTime - BreakOverlay.BREAK_FADE_DURATION;
+
+        public bool Intersects(BreakPeriod other) => StartTime <= other.EndTime && EndTime >= other.StartTime;
+
+        public virtual bool Equals(BreakPeriod? other) =>
+            other != null
+            && StartTime == other.StartTime
+            && EndTime == other.EndTime;
+
+        public override int GetHashCode() => HashCode.Combine(StartTime, EndTime);
     }
 }

osu.Game/Rulesets/Difficulty/DifficultyCalculator.cs

@@ -9,6 +9,7 @@ using System.Linq;
 using System.Threading;
 using JetBrains.Annotations;
 using osu.Framework.Audio.Track;
+using osu.Framework.Bindables;
 using osu.Framework.Extensions.IEnumerableExtensions;
 using osu.Game.Beatmaps;
 using osu.Game.Beatmaps.ControlPoints;
@@ -329,7 +330,7 @@ namespace osu.Game.Rulesets.Difficulty
                 set => baseBeatmap.Difficulty = value;
             }
 
-            public List<BreakPeriod> Breaks => baseBeatmap.Breaks;
+            public BindableList<BreakPeriod> Breaks => baseBeatmap.Breaks;
             public List<string> UnhandledEventLines => baseBeatmap.UnhandledEventLines;
 
             public double TotalBreakTime => baseBeatmap.TotalBreakTime;

osu.Game/Rulesets/Edit/Checks/CheckBreaks.cs

@@ -13,13 +13,7 @@ namespace osu.Game.Rulesets.Edit.Checks
     {
         // Breaks may be off by 1 ms.
         private const int leniency_threshold = 1;
-        private const double minimum_gap_before_break = 200;
 
-        // Break end time depends on the upcoming object's pre-empt time.
-        // As things stand, "pre-empt time" is only defined for osu! standard
-        // This is a generic value representing AR=10
-        // Relevant: https://github.com/ppy/osu/issues/14330#issuecomment-1002158551
-        private const double min_end_threshold = 450;
         public CheckMetadata Metadata => new CheckMetadata(CheckCategory.Events, "Breaks not achievable using the editor");
 
         public IEnumerable<IssueTemplate> PossibleTemplates => new IssueTemplate[]
@@ -45,8 +39,8 @@ namespace osu.Game.Rulesets.Edit.Checks
                 if (previousObjectEndTimeIndex >= 0)
                 {
                     double gapBeforeBreak = breakPeriod.StartTime - endTimes[previousObjectEndTimeIndex];
-                    if (gapBeforeBreak < minimum_gap_before_break - leniency_threshold)
+                    if (gapBeforeBreak < BreakPeriod.GAP_BEFORE_BREAK - leniency_threshold)
-                        yield return new IssueTemplateEarlyStart(this).Create(breakPeriod.StartTime, minimum_gap_before_break - gapBeforeBreak);
+                        yield return new IssueTemplateEarlyStart(this).Create(breakPeriod.StartTime, BreakPeriod.GAP_BEFORE_BREAK - gapBeforeBreak);
                 }
 
                 int nextObjectStartTimeIndex = startTimes.BinarySearch(breakPeriod.EndTime);
@@ -55,8 +49,8 @@ namespace osu.Game.Rulesets.Edit.Checks
                 if (nextObjectStartTimeIndex < startTimes.Count)
                 {
                     double gapAfterBreak = startTimes[nextObjectStartTimeIndex] - breakPeriod.EndTime;
-                    if (gapAfterBreak < min_end_threshold - leniency_threshold)
+                    if (gapAfterBreak < BreakPeriod.GAP_AFTER_BREAK - leniency_threshold)
-                        yield return new IssueTemplateLateEnd(this).Create(breakPeriod.StartTime, min_end_threshold - gapAfterBreak);
+                        yield return new IssueTemplateLateEnd(this).Create(breakPeriod.StartTime, BreakPeriod.GAP_AFTER_BREAK - gapAfterBreak);
                 }
             }
         }

osu.Game/Screens/Edit/Components/Timelines/Summary/Parts/BreakPart.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using osu.Framework.Allocation;
+using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Shapes;
 using osu.Game.Beatmaps.Timing;
@@ -14,35 +15,33 @@ namespace osu.Game.Screens.Edit.Components.Timelines.Summary.Parts
     /// </summary>
     public partial class BreakPart : TimelinePart
     {
+        private readonly BindableList<BreakPeriod> breaks = new BindableList<BreakPeriod>();
+
         protected override void LoadBeatmap(EditorBeatmap beatmap)
         {
             base.LoadBeatmap(beatmap);
+
+            breaks.UnbindAll();
+            breaks.BindTo(beatmap.Breaks);
+            breaks.BindCollectionChanged((_, _) =>
+            {
                 foreach (var breakPeriod in beatmap.Breaks)
                     Add(new BreakVisualisation(breakPeriod));
+            }, true);
         }
 
         private partial class BreakVisualisation : Circle
         {
-            private readonly BreakPeriod breakPeriod;
-
             public BreakVisualisation(BreakPeriod breakPeriod)
             {
-                this.breakPeriod = breakPeriod;
-
                 RelativePositionAxes = Axes.X;
                 RelativeSizeAxes = Axes.Both;
-            }
-
-            protected override void Update()
-            {
-                base.Update();
-
                 X = (float)breakPeriod.StartTime;
                 Width = (float)breakPeriod.Duration;
             }
 
             [BackgroundDependencyLoader]
-            private void load(OsuColour colours) => Colour = colours.GreyCarmineLight;
+            private void load(OsuColour colours) => Colour = colours.Gray7;
         }
     }
 }

osu.Game/Screens/Edit/Compose/Components/Timeline/TimelineBreak.cs

@@ -5,6 +5,7 @@ using System;
 using System.Diagnostics;
 using System.Linq;
 using osu.Framework.Allocation;
+using osu.Framework.Bindables;
 using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
@@ -20,11 +21,11 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
 {
     public partial class TimelineBreak : CompositeDrawable
     {
-        public BreakPeriod Break { get; }
+        public Bindable<BreakPeriod> Break { get; } = new Bindable<BreakPeriod>();
 
         public TimelineBreak(BreakPeriod b)
         {
-            Break = b;
+            Break.Value = b;
         }
 
         [BackgroundDependencyLoader]
@@ -44,44 +45,50 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
                     Child = new Box
                     {
                         RelativeSizeAxes = Axes.Both,
-                        Colour = colours.PurpleLight,
+                        Colour = colours.Gray5,
-                        Alpha = 0.4f,
+                        Alpha = 0.7f,
                     },
                 },
-                new DragHandle(Break, isStartHandle: true)
+                new DragHandle(isStartHandle: true)
                 {
+                    Break = { BindTarget = Break },
                     Anchor = Anchor.TopLeft,
                     Origin = Anchor.TopLeft,
-                    Action = (time, breakPeriod) => breakPeriod.StartTime = time,
+                    Action = (time, breakPeriod) => new ManualBreakPeriod(time, breakPeriod.EndTime),
                 },
-                new DragHandle(Break, isStartHandle: false)
+                new DragHandle(isStartHandle: false)
                 {
+                    Break = { BindTarget = Break },
                     Anchor = Anchor.TopRight,
                     Origin = Anchor.TopRight,
-                    Action = (time, breakPeriod) => breakPeriod.EndTime = time,
+                    Action = (time, breakPeriod) => new ManualBreakPeriod(breakPeriod.StartTime, time),
                 },
             };
         }
 
-        protected override void Update()
+        protected override void LoadComplete()
         {
-            base.Update();
+            base.LoadComplete();
 
-            X = (float)Break.StartTime;
+            Break.BindValueChanged(_ =>
-            Width = (float)Break.Duration;
+            {
+                X = (float)Break.Value.StartTime;
+                Width = (float)Break.Value.Duration;
+            }, true);
         }
 
         private partial class DragHandle : FillFlowContainer
         {
+            public Bindable<BreakPeriod> Break { get; } = new Bindable<BreakPeriod>();
+
             public new Anchor Anchor
             {
                 get => base.Anchor;
                 init => base.Anchor = value;
             }
 
-            public Action<double, BreakPeriod>? Action { get; init; }
+            public Func<double, BreakPeriod, BreakPeriod>? Action { get; init; }
 
-            private readonly BreakPeriod breakPeriod;
             private readonly bool isStartHandle;
 
             private Container handle = null!;
@@ -99,9 +106,8 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
             [Resolved]
             private OsuColour colours { get; set; } = null!;
 
-            public DragHandle(BreakPeriod breakPeriod, bool isStartHandle)
+            public DragHandle(bool isStartHandle)
             {
-                this.breakPeriod = breakPeriod;
                 this.isStartHandle = isStartHandle;
             }
 
@@ -164,13 +170,13 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
                 changeHandler?.BeginChange();
                 updateState();
 
-                double min = beatmap.HitObjects.Last(ho => ho.GetEndTime() <= breakPeriod.StartTime).GetEndTime();
+                double min = beatmap.HitObjects.Last(ho => ho.GetEndTime() <= Break.Value.StartTime).GetEndTime();
-                double max = beatmap.HitObjects.First(ho => ho.StartTime >= breakPeriod.EndTime).StartTime;
+                double max = beatmap.HitObjects.First(ho => ho.StartTime >= Break.Value.EndTime).StartTime;
 
                 if (isStartHandle)
-                    max = Math.Min(max, breakPeriod.EndTime - BreakPeriod.MIN_BREAK_DURATION);
+                    max = Math.Min(max, Break.Value.EndTime - BreakPeriod.MIN_BREAK_DURATION);
                 else
-                    min = Math.Max(min, breakPeriod.StartTime + BreakPeriod.MIN_BREAK_DURATION);
+                    min = Math.Max(min, Break.Value.StartTime + BreakPeriod.MIN_BREAK_DURATION);
 
                 allowedDragRange = (min, max);
 
@@ -183,11 +189,13 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
 
                 Debug.Assert(allowedDragRange != null);
 
-                if (timeline.FindSnappedPositionAndTime(e.ScreenSpaceMousePosition).Time is double time
+                if (Action != null
+                    && timeline.FindSnappedPositionAndTime(e.ScreenSpaceMousePosition).Time is double time
                     && time > allowedDragRange.Value.min
                     && time < allowedDragRange.Value.max)
                 {
-                    Action?.Invoke(time, breakPeriod);
+                    int index = beatmap.Breaks.IndexOf(Break.Value);
+                    beatmap.Breaks[index] = Break.Value = Action.Invoke(time, Break.Value);
                 }
 
                 updateState();
@@ -204,7 +212,7 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
             {
                 bool active = IsHovered || IsDragged;
 
-                var colour = colours.PurpleLighter;
+                var colour = colours.Gray8;
                 if (active)
                     colour = colour.Lighten(0.3f);
 

osu.Game/Screens/Edit/Compose/Components/Timeline/TimelineBreakDisplay.cs

@@ -1,6 +1,7 @@
 // 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 System.Collections.Specialized;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Caching;
@@ -27,8 +28,13 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
         {
             base.LoadBeatmap(beatmap);
 
-            // TODO: this will have to be mutable soon enough
+            breaks.UnbindAll();
-            breaks.AddRange(beatmap.Breaks);
+            breaks.BindTo(beatmap.Breaks);
+            breaks.BindCollectionChanged((_, e) =>
+            {
+                if (e.Action != NotifyCollectionChangedAction.Replace)
+                    breakCache.Invalidate();
+            });
         }
 
         protected override void Update()
@@ -56,14 +62,8 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
 
         private void recreateBreaks()
         {
-            // Remove groups outside the visible range
+            Clear();
-            foreach (TimelineBreak drawableBreak in this)
-            {
-                if (!shouldBeVisible(drawableBreak.Break))
-                    drawableBreak.Expire();
-            }
 
-            // Add remaining ones
             for (int i = 0; i < breaks.Count; i++)
             {
                 var breakPeriod = breaks[i];
@@ -71,20 +71,6 @@ namespace osu.Game.Screens.Edit.Compose.Components.Timeline
                 if (!shouldBeVisible(breakPeriod))
                     continue;
 
-                bool alreadyVisible = false;
-
-                foreach (var b in this)
-                {
-                    if (ReferenceEquals(b.Break, breakPeriod))
-                    {
-                        alreadyVisible = true;
-                        break;
-                    }
-                }
-
-                if (alreadyVisible)
-                    continue;
-
                 Add(new TimelineBreak(breakPeriod));
             }
         }

osu.Game/Screens/Edit/EditorBeatmap.cs

@@ -105,7 +105,7 @@ namespace osu.Game.Screens.Edit
                 BeatmapSkin.BeatmapSkinChanged += SaveState;
             }
 
-            beatmapProcessor = playableBeatmap.BeatmapInfo.Ruleset.CreateInstance().CreateBeatmapProcessor(this);
+            beatmapProcessor = new EditorBeatmapProcessor(this, playableBeatmap.BeatmapInfo.Ruleset.CreateInstance());
 
             foreach (var obj in HitObjects)
                 trackStartTime(obj);
@@ -172,7 +172,7 @@ namespace osu.Game.Screens.Edit
             set => PlayableBeatmap.ControlPointInfo = value;
         }
 
-        public List<BreakPeriod> Breaks => PlayableBeatmap.Breaks;
+        public BindableList<BreakPeriod> Breaks => PlayableBeatmap.Breaks;
 
         public List<string> UnhandledEventLines => PlayableBeatmap.UnhandledEventLines;
 
@@ -349,13 +349,13 @@ namespace osu.Game.Screens.Edit
             if (batchPendingUpdates.Count == 0 && batchPendingDeletes.Count == 0 && batchPendingInserts.Count == 0)
                 return;
 
-            beatmapProcessor?.PreProcess();
+            beatmapProcessor.PreProcess();
 
             foreach (var h in batchPendingDeletes) processHitObject(h);
             foreach (var h in batchPendingInserts) processHitObject(h);
             foreach (var h in batchPendingUpdates) processHitObject(h);
 
-            beatmapProcessor?.PostProcess();
+            beatmapProcessor.PostProcess();
 
             BeatmapReprocessed?.Invoke();
 

osu.Game/Screens/Edit/EditorBeatmapProcessor.cs

@@ -0,0 +1,70 @@
+// 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 System;
+using System.Linq;
+using osu.Game.Beatmaps;
+using osu.Game.Beatmaps.Timing;
+using osu.Game.Rulesets;
+using osu.Game.Rulesets.Objects;
+
+namespace osu.Game.Screens.Edit
+{
+    public class EditorBeatmapProcessor : IBeatmapProcessor
+    {
+        public IBeatmap Beatmap { get; }
+
+        private readonly IBeatmapProcessor? rulesetBeatmapProcessor;
+
+        public EditorBeatmapProcessor(IBeatmap beatmap, Ruleset ruleset)
+        {
+            Beatmap = beatmap;
+            rulesetBeatmapProcessor = ruleset.CreateBeatmapProcessor(beatmap);
+        }
+
+        public void PreProcess()
+        {
+            rulesetBeatmapProcessor?.PreProcess();
+        }
+
+        public void PostProcess()
+        {
+            rulesetBeatmapProcessor?.PostProcess();
+
+            autoGenerateBreaks();
+        }
+
+        private void autoGenerateBreaks()
+        {
+            Beatmap.Breaks.RemoveAll(b => b is not ManualBreakPeriod);
+
+            foreach (var manualBreak in Beatmap.Breaks.ToList())
+            {
+                if (Beatmap.HitObjects.Any(ho => ho.StartTime <= manualBreak.EndTime && ho.GetEndTime() >= manualBreak.StartTime))
+                    Beatmap.Breaks.Remove(manualBreak);
+            }
+
+            for (int i = 1; i < Beatmap.HitObjects.Count; ++i)
+            {
+                double previousObjectEndTime = Beatmap.HitObjects[i - 1].GetEndTime();
+                double nextObjectStartTime = Beatmap.HitObjects[i].StartTime;
+
+                if (nextObjectStartTime - previousObjectEndTime < BreakPeriod.MIN_GAP_DURATION)
+                    continue;
+
+                double breakStartTime = previousObjectEndTime + BreakPeriod.GAP_BEFORE_BREAK;
+                double breakEndTime = nextObjectStartTime - Math.Max(BreakPeriod.GAP_AFTER_BREAK, Beatmap.ControlPointInfo.TimingPointAt(nextObjectStartTime).BeatLength * 2);
+
+                if (breakEndTime - breakStartTime < BreakPeriod.MIN_BREAK_DURATION)
+                    continue;
+
+                var breakPeriod = new BreakPeriod(breakStartTime, breakEndTime);
+
+                if (Beatmap.Breaks.Any(b => b.Intersects(breakPeriod)))
+                    continue;
+
+                Beatmap.Breaks.Add(breakPeriod);
+            }
+        }
+    }
+}

osu.Game/Screens/Edit/LegacyEditorBeatmapPatcher.cs

@@ -45,6 +45,7 @@ namespace osu.Game.Screens.Edit
             editorBeatmap.BeginChange();
             processHitObjects(result, () => newBeatmap ??= readBeatmap(newState));
             processTimingPoints(() => newBeatmap ??= readBeatmap(newState));
+            processBreaks(() => newBeatmap ??= readBeatmap(newState));
             processHitObjectLocalData(() => newBeatmap ??= readBeatmap(newState));
             editorBeatmap.EndChange();
         }
@@ -75,6 +76,27 @@ namespace osu.Game.Screens.Edit
             }
         }
 
+        private void processBreaks(Func<IBeatmap> getNewBeatmap)
+        {
+            var newBreaks = getNewBeatmap().Breaks.ToArray();
+
+            foreach (var oldBreak in editorBeatmap.Breaks.ToArray())
+            {
+                if (newBreaks.Any(b => b.Equals(oldBreak)))
+                    continue;
+
+                editorBeatmap.Breaks.Remove(oldBreak);
+            }
+
+            foreach (var newBreak in newBreaks)
+            {
+                if (editorBeatmap.Breaks.Any(b => b.Equals(newBreak)))
+                    continue;
+
+                editorBeatmap.Breaks.Add(newBreak);
+            }
+        }
+
         private void processHitObjects(DiffResult result, Func<IBeatmap> getNewBeatmap)
         {
             findChangedIndices(result, LegacyDecoder<Beatmap>.Section.HitObjects, out var removedIndices, out var addedIndices);

osu.Game/Screens/Edit/ManualBreakPeriod.cs

@@ -0,0 +1,15 @@
+// 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.Game.Beatmaps.Timing;
+
+namespace osu.Game.Screens.Edit
+{
+    public class ManualBreakPeriod : BreakPeriod
+    {
+        public ManualBreakPeriod(double startTime, double endTime)
+            : base(startTime, endTime)
+        {
+        }
+    }
+}

osu.Game/Tests/Beatmaps/TestBeatmap.cs

@@ -26,11 +26,13 @@ namespace osu.Game.Tests.Beatmaps
 
             BeatmapInfo = baseBeatmap.BeatmapInfo;
             ControlPointInfo = baseBeatmap.ControlPointInfo;
-            Breaks = baseBeatmap.Breaks;
             UnhandledEventLines = baseBeatmap.UnhandledEventLines;
 
             if (withHitObjects)
+            {
                 HitObjects = baseBeatmap.HitObjects;
+                Breaks = baseBeatmap.Breaks;
+            }
 
             BeatmapInfo.Ruleset = ruleset;
             BeatmapInfo.Length = 75000;