drawing guide for win - roundrect looks ugly

In my recent thread I’ve released a custom control written on a Mac OSX machine but assumed it should be cross platform.

However, I was surprised by the result being different and so I wonder what I need to take into consideration
when developing a control for window?
I basically use only Xojo function like FillRoundRect. Nothing special but on window the rounded
rectangles look very ugly and being not equal to the output from Mac OSX.

Thread: https://forum.xojo.com/21738-custom-switch-control-feedback/p1#p181903

Does anyone know what I need to do to produce nice sharp Texts and rectangles ? Could a possible answer be like “scale it down” ?
I have experience at all for window.

Did you enable GDI+ on Windows ?