| buttonRect | 用于决定窗口位置的按钮（请参阅说明）。 |
| windowSize | 窗口的初始大小。 |
显示包含下拉菜单和样式的窗口。
The window is styled in the same way as a PopupWindow. The window is automatically closed when it loses focus. Note this function auto-fits the window to screen while trying to place it first below then above the button it was triggered from. This means the windowSize might change when fitting it to screen, so you should make sure you read the 'position' afterwards to check whether the size was cropped.