fix #2369

move tasview context menu to the other side of the cursor if it's not fitting into the screen fully. of course if there's not enough space there EITHER, the user must do something about it, meanwhile best we can do is clamp location to 0. not using MouseEventArgs because we need absolute on-screen coords

other tastudio menus are small so probably fine?

src/BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.ListView.cs

@@ -819,7 +819,24 @@ private void TasView_MouseUp(object sender, MouseEventArgs e)
 				}
 				else
 				{
-					RightClickMenu.Show(TasView, e.X, e.Y);
+					var offset = new Point(0);
+					var topLeft = Cursor.Position;
+					var bottomRight = new Point(
+						topLeft.X + RightClickMenu.Width,
+						topLeft.Y + RightClickMenu.Height);
+					var screen = Screen.AllScreens
+						.Where(s => s.WorkingArea.Contains(topLeft))
+						.FirstOrDefault();
+					// if we don't fully fit, move to the other side of the pointer
+					if (bottomRight.X > screen.WorkingArea.Right)
+						offset.X -= RightClickMenu.Width;
+					if (bottomRight.Y > screen.WorkingArea.Bottom)
+						offset.Y -= RightClickMenu.Height;
+					topLeft.Offset(offset);
+					// if the screen is insultingly tiny, best we can do is avoid negative pos
+					RightClickMenu.Show(
+						Math.Max(0, topLeft.X),
+						Math.Max(0, topLeft.Y));
 				}
 			}
 			else if (e.Button == MouseButtons.Left)