From Xojo Documentation

Property (As Boolean )
aContainerControl.UseFocusRing = newBooleanValue
BooleanValue = aContainerControl.UseFocusRing

Supported for all project types and targets.

If True, the ContainerControl indicates that it has the focus with a ring around its border; if False, the appearance of the object does not change when it has the focus.

Setting this property to True has no effect on Windows or Linux. The default is True.