Add an option to RewindConfig to specify if the rewinder should allow out-of-order states. Currently, the default rewinder should but TAStudio rewinders should not.

Previously, TAStudio's ZwinderStateManager had to handle this, which made the code somewhat confusing. (Especially when I was looking at ZwinderBuffer and forgetting about the default rewinder.)

src/BizHawk.Client.Common/config/RewindConfig.cs

@@ -34,6 +34,11 @@
 		/// </summary>
 		int TargetRewindInterval { get; }
 
+		/// <summary>
+		/// Specifies if the rewinder should accept states that are given out of order.
+		/// </summary>
+		bool AllowOutOfOrderStates { get; }
+
 		public enum BackingStoreType
 		{
 			Memory,
@@ -52,6 +57,8 @@
 		public bool UseFixedRewindInterval { get; set; } = false;
 		public int TargetFrameLength { get; set; } = 600;
 		public int TargetRewindInterval { get; set; } = 5;
+		public bool AllowOutOfOrderStates { get; set; } = true;
+
 		public IRewindSettings.BackingStoreType BackingStore { get; set; } = IRewindSettings.BackingStoreType.Memory;
 	}
 }

src/BizHawk.Client.Common/movie/tasproj/ZwinderStateManager.cs

@@ -320,23 +320,12 @@ namespace BizHawk.Client.Common
 			}
 
 			// We use the gap buffer for forced capture to avoid crowding the "current" buffer and thus reducing it's actual span of covered frames.
-			if (force)
+			if (NeedsGap(frame) || force)
 			{
 				CaptureGap(frame, source);
 				return;
 			}
 
-			// We do not want to consider reserved states for a notion of Last
-			// reserved states can include future states in the case of branch states
-			if (frame <= LastRing)
-			{
-				if (NeedsGap(frame))
-				{
-					CaptureGap(frame, source);
-				}
-				return;
-			}
-
 			_current.Capture(frame,
 				s =>
 				{
@@ -404,6 +393,12 @@ namespace BizHawk.Client.Common
 
 		private bool NeedsGap(int frame)
 		{
+			// We don't want to "fill gaps" if we are past the latest state in the current/recent buffers.
+			if (frame >= LastRing)
+			{
+				return false;
+			}
+
 			// When starting to fill gaps we won't actually know the true frequency, so fall back to current
 			// Current may very well not be the same as gap, but it's a reasonable behavior to have a current sized gap before seeing filler sized gaps
 			var frequency = _gapFiller.Count == 0 ? _current.RewindFrequency : _gapFiller.RewindFrequency;

src/BizHawk.Client.Common/movie/tasproj/ZwinderStateManagerSettings.cs

@@ -109,6 +109,7 @@ namespace BizHawk.Client.Common
 				BufferSize = CurrentBufferSize,
 				UseFixedRewindInterval = false,
 				TargetFrameLength = CurrentTargetFrameLength,
+				AllowOutOfOrderStates = false,
 				BackingStore = CurrentStoreType
 			};
 		}
@@ -120,6 +121,7 @@ namespace BizHawk.Client.Common
 				BufferSize = RecentBufferSize,
 				UseFixedRewindInterval = false,
 				TargetFrameLength = RecentTargetFrameLength,
+				AllowOutOfOrderStates = false,
 				BackingStore = RecentStoreType
 			};
 		}
@@ -131,6 +133,7 @@ namespace BizHawk.Client.Common
 				BufferSize = GapsBufferSize,
 				UseFixedRewindInterval = false,
 				TargetFrameLength = GapsTargetFrameLength,
+				AllowOutOfOrderStates = false,
 				BackingStore = GapsStoreType
 			};
 		}

src/BizHawk.Client.Common/rewind/ZwinderBuffer.cs

@@ -65,6 +65,7 @@ namespace BizHawk.Client.Common
 				_fixedRewindInterval = false;
 				_targetFrameLength = settings.TargetFrameLength;
 			}
+			_allowOutOfOrderStates = settings.AllowOutOfOrderStates;
 			_states = new StateInfo[STATEMASK + 1];
 			_useCompression = settings.UseCompression;
 		}
@@ -111,6 +112,8 @@ namespace BizHawk.Client.Common
 		private readonly int _targetFrameLength;
 		private readonly int _targetRewindInterval;
 
+		private readonly bool _allowOutOfOrderStates;
+
 		private struct StateInfo
 		{
 			public long Start;
@@ -162,6 +165,7 @@ namespace BizHawk.Client.Common
 				_useCompression == settings.UseCompression &&
 				_fixedRewindInterval == settings.UseFixedRewindInterval &&
 				(_fixedRewindInterval ? _targetRewindInterval == settings.TargetRewindInterval : _targetFrameLength == settings.TargetFrameLength) &&
+				_allowOutOfOrderStates == settings.AllowOutOfOrderStates &&
 				_backingStoreType == settings.BackingStore;
 		}
 
@@ -173,9 +177,8 @@ namespace BizHawk.Client.Common
 			}
 			if (frameDiff < 1)
 			{
-				// non-linear time is from a combination of other state changing mechanisms and the rewinder
-				// not much we can say here, so just take a state
-				return true;
+				// Manually loading a savestate can cause this. The default rewinder should capture in this situation.
+				return _allowOutOfOrderStates;
 			}
 			return frameDiff >= ComputeIdealRewindInterval();
 		}
@@ -369,6 +372,7 @@ namespace BizHawk.Client.Common
 					UseFixedRewindInterval = false,
 					TargetFrameLength = targetFrameLength,
 					TargetRewindInterval = 5,
+					AllowOutOfOrderStates = false,
 					UseCompression = useCompression
 				});
 				if (ret.Size != size || ret._sizeMask != sizeMask)