[WPF] Don't include the margin when calculating the size of a widget
[WPF] Don't include the margin when calculating the size of a widget

mminns/xwt,mono/xwt,TheBrainTech/xwt,sevoku/xwt,directhex/xwt,residuum/xwt,cra0zy/xwt,mminns/xwt,steffenWi/xwt,hamekoz/xwt,akrisiun/xwt,iainx/xwt,hwthomas/xwt,lytico/xwt,antmicro/xwt