Bind to default property value of another control style definition in xaml - wpf

Question

I have a CustomControl and want to have the default value of TextBox default style definition. I don't know if it that is even possible.
This is what I have tried so far without success. But here you can see what I have in mind.
My default implementation to change the default style of the TextBox (in for example app.xaml to apply it global)
<Style TargetType="TextBox">
<Setter Property="BorderThickness" Value="2"/>
</Style>
Here I want to get the value of '2'.
<Style TargetType="controls:CustomControl">
<Setter Property="BorderThickness" Value="{Binding Source={x:Static TextBox.BorderThicknessProperty}}"/>
</Style>

Answer 1

The default value of the BorderThickness property of a TextBox is defined in the default style of the TextBox which is eventually applied to an instance of a TextBox at runtime.
So you cannot do something like this:
<Style TargetType="controls:CustomControl">
<Setter Property="BorderThickness" Value="{Binding Source={x:Static TextBox.BorderThicknessProperty}}"/>
</Style>
...unless you bind to an actual instance of a TextBox that uses the default style.
You could look at the default template of the TextBox and simply copy its default BorderThickness property value of 1 though:
<Style TargetType="controls:CustomControl">
<Setter Property="BorderThickness" Value="1"/>
</Style>
Obviously you can also bind to a property of a class from more than one Style, e.g.:
<Style TargetType="controls:CustomControl">
<Setter Property="BorderThickness" Value="{Binding Thickness, Source={StaticResource settings}}"/>
</Style>