InputRoll - only invalidate the necessary rectangle size

BizHawk.Client.EmuHawk/CustomControls/InputRoll/InputRoll.cs

@@ -271,7 +271,24 @@ namespace BizHawk.Client.EmuHawk
 				// Similarly to ListView in virtual mode, we want to always refresh
 				// when setting row count, that gives the calling code assurance that
 				// redraw will happen
-				Refresh();
+				
+				// TODO: horizontal orientation
+				if (HorizontalOrientation)
+				{
+					Refresh();
+				}
+				else
+				{
+					int x = _hBar.Value;
+					int y = ColumnHeight;
+
+					int w = VisibleColumns.Any()
+						? Math.Min(VisibleColumns.Max(c => c.Right) - _hBar.Value, Width)
+						: 0;
+
+					int h = Height - y;
+					Invalidate(new Rectangle(x, y, w, h));
+				}
 			}
 		}