overline-margin

overline-margin is a variable defined in `C source code'.
Its value is

2

Documentation:
Space between overline and text, in pixels.
The default value is 2: the height of the overline (1 pixel) plus 1 pixel
margin to the character height.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.