Fix artifacting on firmware status icons under Mono

src/BizHawk.Client.EmuHawk/FormBase.cs

@@ -13,6 +13,16 @@ public class FormBase : Form
 	{
 		private const string PLACEHOLDER_TITLE = "(will take value from WindowTitle/WindowTitleStatic)";
 
+		/// <summary>removes transparency from an image by combining it with a solid background</summary>
+		public static Image FillImageBackground(Image img, Color c)
+		{
+			Bitmap result = new(width: img.Width, height: img.Height);
+			using var g = Graphics.FromImage(result);
+			g.Clear(c);
+			g.DrawImage(img, x: 0, y: 0, width: img.Width, height: img.Height);
+			return result;
+		}
+
 		/// <summary>
 		/// Under Mono, <see cref="SystemColors.Control">SystemColors.Control</see> returns an ugly beige.<br/>
 		/// This method recursively replaces the <see cref="Control.BackColor"/> of the given <paramref name="control"/> (can be a <see cref="Form"/>) with <see cref="Color.WhiteSmoke"/>

src/BizHawk.Client.EmuHawk/config/FirmwareConfig.cs

@@ -145,7 +145,13 @@ public FirmwareConfig(
 				= tbbOpenFolder.Image = Properties.Resources.Placeholder;
 
 			// prep ImageList for ListView
-			foreach (var img in StatusIcons.Values) imageList1.Images.Add(img);
+			var iconList = StatusIcons.Values;
+			if (OSTailoredCode.IsUnixHost) // remove crusty artifacts
+			{
+				var bg = lvFirmware.BackColor;
+				iconList = iconList.Select(img => FormBase.FillImageBackground(img, bg));
+			}
+			foreach (var img in iconList) imageList1.Images.Add(img);
 
 			_listViewSorter = new ListViewSorter(-1);