How to make JavaFX Separator be 1px wide?

Question

User interface

The subject was discussed here .
Discussion abandoned, issue not resolved.
If we prescribe

.separator *.line {
-fx-border-style: solid;
-fx-border-width: 1px;
-fx-border-color: red;
}

The separator is still 2px wide! 2 pixels is its default width. What is it? Java bug?

You can see in the picture that the square has a 1 pixel wide stroke, while the red divider is clearly 2 px thick.
How to be?

Answer 1

It seems to me that there is no error here - the element has a zero height. A border is added on each side. That is, the upper border is plused with the lower one - here you have two pixels.
Not 100% sure, but maybe this will help you: -fx-border-style: hidden hidden solid hidden;