The default GTK+ drawing engine (or rather, the default draw routine) for
focus indication is not themeable with respect to line thickness or dash
pattern.  This has only a minor cosmetic impact, though it restricts theme
flexibility - but it presents a significant barrier to accessibility for
low-vision users.  Though font size and most widget colors can be themed
via RC files to support large fonts and high-contrast, the focus indication
line width and pattern are hard-wired.  Though this can be worked around
via completely rewritten theme engines, these theme engines would still
desire a property-based means of setting focus line thickness.  One would
like to offer a choice of engines for large-print and high-contrast themes,
rather than making such users rely entirely on alternate engines.

Here is a proposed high-contrast/large-print theme, with implied extensions
for focus-indication theming:

# High-Contrast, Large Print Theme v0.1
# This is the whole basic theme, just this one gtkrc file.
# It uses components of the standard theme engine
# Written by Bill Haneman, based on Standard theme by T. Liebeck, 
# which was in turn based on lots of different gtkrc files but
# primarily the one for the metal theme.
# email: bill.haneman@sun.com

gtk-focus-line-width = 3
gtk-focus-line-pattern = "\10\1"

style "default"
{
  font_name = "sans 18"

  GtkEntry::cursor_color    = { 0.80, 0.00, 0.00 }
  GtkEntry::cursor_line_thickness = 2  
  GtkTextView::cursor_line_thickness = 2

  fg[NORMAL]      = { 0.00, 0.00, 0.00 }
  text[NORMAL]      = { 0.00, 0.00, 0.00 }
  bg[NORMAL]      = { 1.00, 1.00, 1.00 }
  base[NORMAL]    = { 1.00, 1.00, 1.00 }

  fg[INSENSITIVE]      = { 0.6, 0.6, 0.6 }
  bg[INSENSITIVE]      = { 0.75, 0.75, 0.77 }
  base[INSENSITIVE]      = { 0.75, 0.75, 0.77 }

  fg[PRELIGHT]    = { 0.80, 0.80, 1.00 }
  text[PRELIGHT]    = { 0.80, 0.80, 1.00 }
  bg[PRELIGHT]    = { 0.00, 0.00, 0.00 }
  base[PRELIGHT]    = { 0.00, 0.00, 0.00 }

  fg[ACTIVE]      = { 0.00, 0.00, 0.00 }
  text[ACTIVE]      = { 0.00, 0.00, 0.00 }
  bg[ACTIVE]      = { 0.65, 0.65, 0.50 }
  base[ACTIVE]      = { 0.65, 0.65, 0.50 }

  fg[SELECTED]    = { 1.00, 1.00, 1.00 }
  text[SELECTED]    = { 1.00, 1.00, 1.00 }
  bg[SELECTED]    = { 0.00, 0.00, 0.00 }
  base[SELECTED]    = { 0.10, 0.20, 0.20 }

  xthickness = 3
  ythickness = 3
 
}

class "GtkWidget" style "default"

-----

A proposed patch is available that fixes this bug.