Add IsRewinding tool/Lua API (#4497)

* Add IsRewinding tool/Lua API

* Remove unused member

Author: kalimag

src/BizHawk.Client.Common/Api/Classes/EmuClientApi.cs

@@ -143,6 +143,8 @@ public int GetWindowSize()
 
 		public bool IsTurbo() => _mainForm.IsTurboing;
 
+		public bool IsRewinding() => _mainForm.IsRewinding;
+
 		public bool LoadState(string name)
 			=> _mainForm.LoadState(
 				path: Path.Combine(_config.PathEntries.SaveStateAbsolutePath(Game.System), $"{name}.State"),

src/BizHawk.Client.Common/Api/Interfaces/IEmuClientApi.cs

@@ -83,6 +83,8 @@ public interface IEmuClientApi : IDisposable, IExternalApi
 
 		bool IsTurbo();
 
+		bool IsRewinding();
+
 		/// <summary>
 		/// Load a savestate specified by its name
 		/// </summary>

src/BizHawk.Client.Common/IMainFormForApi.cs

@@ -27,6 +27,9 @@ public interface IMainFormForApi
 		/// <remarks>only referenced from <c>EmuClientApi</c></remarks>
 		bool IsTurboing { get; }
 
+		/// <remarks>only referenced from <c>EmuClientApi</c></remarks>
+		bool IsRewinding { get; }
+
 		/// <remarks>only referenced from <see cref="CommApi"/></remarks>
 		(HttpCommunication HTTP, MemoryMappedFiles MMF, SocketServer Sockets) NetworkingHelpers { get; }
 

src/BizHawk.Client.Common/lua/CommonLibs/ClientLuaLibrary.cs

@@ -156,6 +156,11 @@ public bool IsTurbo()
 		public bool IsSeeking()
 			=> APIs.EmuClient.IsSeeking();
 
+		[LuaMethodExample("if ( client.isrewinding( ) ) then\r\n\tconsole.log( \"Returns true if emulator is rewinding, otherwise, false\" );\r\nend;")]
+		[LuaMethod("isrewinding", "Returns true if emulator is rewinding, otherwise, false")]
+		public bool IsRewinding()
+			=> APIs.EmuClient.IsRewinding();
+
 		[LuaMethodExample("client.opencheats( );")]
 		[LuaMethod("opencheats", "opens the Cheats dialog")]
 		public void OpenCheats()

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -1130,6 +1130,7 @@ private set
 		private bool IsTurboSeeking => PauseOnFrame.HasValue && Config.TurboSeek;
 		public bool IsTurboing => InputManager.ClientControls["Turbo"] || IsTurboSeeking;
 		public bool IsFastForwarding => InputManager.ClientControls["Fast Forward"] || IsTurboing || InvisibleEmulation;
+		public bool IsRewinding { get; private set; }
 
 		/// <summary>
 		/// Used to disable secondary throttling (e.g. vsync, audio) for unthrottled modes or when the primary (clock) throttle is taking over (e.g. during fast forward/rewind).
@@ -2934,6 +2935,7 @@ private void StepRunLoop_Core(bool force = false)
 			}
 
 			bool isRewinding = Rewind(ref runFrame, currentTimestamp, out var returnToRecording);
+			IsRewinding = isRewinding;
 			_runloopFrameProgress |= isRewinding;
 
 			float atten = 0;