Isso é letterSpace , que pode ser consultado e definido por meio da interface perl.
A documentação lista vários recursos que podem ser tratados desta maneira:
$value = $term->resource ($name[, $newval])
Returns the current resource value associated with a given name and
optionally sets a new value. Setting values is most useful in the
"init" hook. Unset resources are returned and accepted as "undef".
The new value must be properly encoded to a suitable character
encoding before passing it to this method. Similarly, the returned
value may need to be converted from the used encoding to text.
Resource names are as defined in src/rsinc.h. Colours can be
specified as resource names of the form "color+", e.g.
"color+5". (will likely change).
Please note that resource strings will currently only be freed when
the terminal is destroyed, so changing options frequently will eat
memory.
Here is a likely non-exhaustive list of resource names, not all of
which are supported in every build, please see the source file
/src/rsinc.h to see the actual list:
answerbackstring backgroundPixmap backspace_key blurradius
boldFont boldItalicFont borderLess buffered chdir color cursorBlink
cursorUnderline cutchars delete_key depth display_name embed ext_bwidth
fade font geometry hold iconName iconfile imFont imLocale inputMethod
insecure int_bwidth intensityStyles iso14755 iso14755_52 italicFont
jumpScroll letterSpace lineSpace loginShell mapAlert meta8 modifier
mouseWheelScrollPage name override_redirect pastableTabs path perl_eval
perl_ext_1 perl_ext_2 perl_lib pointerBlank pointerBlankDelay
preeditType print_pipe pty_fd reverseVideo saveLines scrollBar
scrollBar_align scrollBar_floating scrollBar_right scrollBar_thickness
scrollTtyKeypress scrollTtyOutput scrollWithBuffer scrollstyle
secondaryScreen secondaryScroll shade skipBuiltinGlyphs skipScroll
term_name title transient_for transparent tripleclickwords urgentOnBell
utmpInhibit visualBell
Leitura adicional:
- Extensões Perl do URxvt (Jérôme Belleman)
- rxvt-unicode (Gentoo)