pango:layout-spacing (layout)

layout -- a pango:layout object
spacing -- an integer for the amount of spacing

The pango:layout-spacing function gets the amount of spacing in Pango units between the lines of the Pango layout. The (setf pango:layout-spacing) function sets the amount of spacing. When placing lines with spacing, Pango arranges things so that

line2.top = line1.bottom + spacing  

Pango defaults to using the line height (as determined by the font) for placing lines. The spacing set with this function is only taken into account when the line-height factor is set to zero with the pango:layout-line-spacing function.