Add the WM_CLASS property to the BizHawk window

src/BizHawk.Client.Common/ArgParser.cs

@@ -117,6 +117,11 @@ public static class ArgParser
 			Description = "pairs in the format `k1:v1;k2:v2` (mind your shell escape sequences); if the value is `true`/`false` it's interpreted as a boolean, if it's a valid 32-bit signed integer e.g. `-1234` it's interpreted as such, if it's a valid 32-bit float e.g. `12.34` it's interpreted as such, else it's interpreted as a string",
 		};
 
+		private static readonly Option<string?> OptionWMClass = new ("--wmclass")
+		{
+			Description = "set a custom WM_CLASS for this Bizhawk initiation, Linux only.",
+		};
+
 		static ArgParser()
 		{
 			OptionAVDumpFrameList.Description = $"comma-separated list of integers, indices of frames which should be included in the A/V dump (encoding); implies `{OptionAVDumpEndAtFrame.Name}=<end>` where `<end>` is the highest frame listed";
@@ -162,6 +167,7 @@ private static RootCommand GetRootCommand()
 			root.Add(/* --url-post */ OptionHTTPClientURIPOST);
 			root.Add(/* --userdata */ OptionUserdataUnparsedPairs);
 			root.Add(/* --version */ OptionQueryAppVersion);
+			root.Add(/* --wmclass */ OptionWMClass);
 
 			return root;
 		}
@@ -268,7 +274,8 @@ private static void EnsureConsole()
 				openExtToolDll: result.GetValue(OptionOpenExternalTool),
 				socketProtocol: result.GetValue(OptionSocketServerUseUDP) ? ProtocolType.Udp : ProtocolType.Tcp,
 				userdataUnparsedPairs: userdataUnparsedPairs,
-				cmdRom: result.GetValue(ArgumentRomFilePath)
+				cmdRom: result.GetValue(ArgumentRomFilePath),
+				wmClassName: result.GetValue(OptionWMClass)
 			);
 			return null;
 		}

src/BizHawk.Client.Common/ParsedCLIFlags.cs

@@ -51,6 +51,8 @@ public readonly struct ParsedCLIFlags
 
 		public readonly string? cmdRom;
 
+		public readonly string? wmClassName;
+
 		public ParsedCLIFlags(
 			int? cmdLoadSlot,
 			string? cmdLoadState,
@@ -73,7 +75,8 @@ public ParsedCLIFlags(
 			string? openExtToolDll,
 			ProtocolType socketProtocol,
 			IReadOnlyList<(string Key, string Value)>? userdataUnparsedPairs,
-			string? cmdRom)
+			string? cmdRom,
+			string? wmClassName)
 		{
 			this.cmdLoadSlot = cmdLoadSlot;
 			this.cmdLoadState = cmdLoadState;
@@ -97,6 +100,7 @@ public ParsedCLIFlags(
 			SocketProtocol = socketProtocol;
 			UserdataUnparsedPairs = userdataUnparsedPairs;
 			this.cmdRom = cmdRom;
+			this.wmClassName = wmClassName;
 		}
 	}
 }

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -295,6 +295,13 @@ private void MainForm_Load(object sender, EventArgs e)
 				else Console.WriteLine($"requested ext. tool dll {requestedExtToolDll} could not be loaded");
 			}
 
+			//Code to set WM_CLASS
+			if(OSTailoredCode.CurrentOS==OSTailoredCode.DistinctOS.Linux)
+			{
+				string wmclass = _argParser.wmClassName is not null ? _argParser.wmClassName : "BizHawk";
+				XlibImports.SetWMClass(_x11Display, wmclass);
+			}
+
 #if DEBUG
 			AddDebugMenu();
 #endif

src/BizHawk.Common/LSB/XlibImports.cs

@@ -715,5 +715,61 @@ public struct XkbDescRec
 		[DllImport(XLIB)]
 		[return: MarshalAs(UnmanagedType.SysUInt)]
 		public static extern Keysym XkbKeycodeToKeysym(IntPtr display, uint keycode, int group, int level);
+
+		[DllImport(XLIB)]
+		public static extern IntPtr XAllocClassHint();
+
+		[DllImport(XLIB)]
+		public static extern Status XSetClassHint(IntPtr display, IntPtr window, IntPtr classHint);
+
+		[DllImport(XLIB)]
+		public static extern Status XGetClassHint(IntPtr display, IntPtr window, out IntPtr classHint);
+
+		public struct XClassHint
+		{
+			public IntPtr res_name;
+			public IntPtr res_class;
+		}
+
+		[DllImport(XLIB)]
+		public static extern Status XQueryTree(IntPtr display, IntPtr window, out IntPtr rootReturn, out IntPtr parentReturn, out IntPtr[] childrenReturn, out int childCount);
+		[DllImport(XLIB)]
+		public static extern Status XFetchName(IntPtr display, IntPtr window, out string returnedName);
+
+		public static void SetWMClass(IntPtr x11Display, string className)
+		{
+			//Establish reference to xDisplay
+			if(x11Display == IntPtr.Zero)
+			{
+				x11Display = XOpenDisplay(null);
+			}
+			//Setup the ClassHint
+			var wmSet = new XClassHint{res_name = Marshal.StringToCoTaskMemAnsi("BizHawk"), res_class = Marshal.StringToCoTaskMemAnsi(className)};
+			IntPtr point = XAllocClassHint();
+			Marshal.StructureToPtr(wmSet, point, true);
+
+			//To find the window we must query twice, once to get the array length and the second to populate
+			XQueryTree(x11Display, XDefaultRootWindow(x11Display), out _, out _, out _, out int windowCount);
+			IntPtr[] windowList = new IntPtr[windowCount];
+			XQueryTree(x11Display, XDefaultRootWindow(x11Display), out _, out _, out windowList, out windowCount);
+			for(int windowIterator = 0; windowIterator < windowCount; windowIterator++)
+			{
+				XFetchName(x11Display, windowList[windowIterator], out string name);
+				if(name?.Contains("BizHawk") == true)
+				{
+					//Interogate if a WM_CLASS is already set
+					XGetClassHint(x11Display, windowList[windowIterator], out var classHint);
+					if(classHint == IntPtr.Zero)
+					{
+						//Assign+Retrieve - doesn't seem to set properly without retrieving it after)
+						XSetClassHint(x11Display, windowList[windowIterator], point);
+						XGetClassHint(x11Display, windowList[windowIterator],out _);
+					}
+					//Reset classHint after checking, doesn't seem to overwrite otherwise.
+					classHint = IntPtr.Zero;
+				}
+			}
+			_ = XFlush(x11Display);
+		}
 	}
 }