An exception occurs in the listener of ScreenRetriever When the system screen scaling ratio is changed on the Windows platform.

[iamsongdeng]

在Windows平台下，运行示例程序(packages/screen_retriever/example)。
当改变Windows系统的屏幕设置，修改缩放比例时，产生了异常，onScreenEvent没有触发。

[copywith9]

See #24

https://github.com/copywith99/screen_retriever