Since: nightly builds only

If specified, overrides the base thickness of underlines. The underline thickness is also used for rendering split pane dividers and a number of other lines in custom glyphs.

The default is to use the underline thickness metric specified by the designer of the primary font.

This config option accepts different units that have slightly different interpretations:

  • 2, 2.0 or "2px" all specify a thickness of 2 pixels
  • "2pt" specifies a thickness of 2 points, which scales according to the DPI of the window
  • "200%" takes the font-specified underline_thickness and multiplies it by 2 to arrive at a thickness double the normal size
  • "0.1cell" takes the cell height, scales it by 0.1 and uses that as the thickness