don't remove reserved states!

Author: SuuperW

src/BizHawk.Client.Common/tools/TAStudio/PagedStateManager.cs

@@ -363,6 +363,10 @@ private int FreePage(int frame)
 						_midPagesUsed += pages;
 						_midStates.Add(stateToKick);
 					}
+					else if (_reserveCallback(stateToKick.Frame))
+					{
+						// Recategorize as old. Nothing to do here.
+					}
 					else
 					{
 						_states.Remove(stateToKick);
@@ -382,7 +386,7 @@ private int FreePage(int frame)
 					StateInfo stateToKick = oldestNewerState.Frame != 0 ? oldestNewerState : _midStates.Min;
 
 					// Kicking a state means checking if it belongs in old.
-					bool recategorizeAsOld = ShouldKeepForOld(stateToKick.Frame);
+					bool recategorizeAsOld = ShouldKeepForOld(stateToKick.Frame) || _reserveCallback(stateToKick.Frame);
 					int pages = (stateToKick.Size + PAGE_DATA_SIZE - 1) / PAGE_DATA_SIZE;
 					_midPagesUsed -= pages;
 					_midStates.Remove(stateToKick);

src/BizHawk.Tests/Client.Common/Movie/PagedStateManagerTests.cs

@@ -473,6 +473,28 @@ public void CanHandleLargeBuffer()
 			Assert.AreEqual(expectedStates, manager.Count);
 		}
 
+		[TestMethod]
+		public void KeepsReservedFrames()
+		{
+			const int reservedFrame1 = 7;
+			int reservedFrame2 = 0;
+
+			IStatable ss = CreateStateSource();
+			PagedStateManager manager = new(MakeDefaultSettings(), (f) => f == reservedFrame1 || f == reservedFrame2);
+			manager.Engage(ss.CloneSavestate());
+
+			for (int i = 0; i < PAGE_COUNT; i++)
+				manager.Capture(i, ss);
+
+			// Reserve a frame after capture
+			reservedFrame2 = 13;
+			for (int i = PAGE_COUNT; i < PAGE_COUNT * 2; i++)
+				manager.Capture(i, ss);
+
+			Assert.IsTrue(manager.HasState(reservedFrame1));
+			Assert.IsTrue(manager.HasState(reservedFrame2));
+		}
+
 		private class StateSource : IStatable
 		{
 			public int Frame { get; set; }