abstract System.Windows.Media.Visual:
FrameworkElement的子类还包括Decorator，Panel，Adorner，AdornerLayer，
Decorator：
https://learn.microsoft.com/en-us/dotnet/api/system.windows.controls.decorator?view=windowsdesktop-8.0
子类包括Border,AdornerDecorator
SystemParameters ： Contains properties that you can use to query system settings.
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