Add 24-bit (aka truecolor) support to GNU screen config

screenrc

@@ -4,7 +4,7 @@ attrcolor b ".I"
 termcapinfo xterm 'Co#256:AB=\E[48;5;%dm:AF=\E[38;5;%dm'
 defbce on
 altscreen on
-set term=screen-256color
+truecolor on
 
 # Remap Ctrl+A to Ctrl+B
 escape ^Bb

scripts/256_colors.pl

@@ -0,0 +1,63 @@
+#!/usr/bin/perl
+# Author: Todd Larason <jtl@molehill.org>
+# $XFree86: xc/programs/xterm/vttests/256colors2.pl,v 1.2 2002/03/26 01:46:43 dickey Exp $
+
+# use the resources for colors 0-15 - usually more-or-less a
+# reproduction of the standard ANSI colors, but possibly more
+# pleasing shades
+
+# colors 16-231 are a 6x6x6 color cube
+for ($red = 0; $red < 6; $red++) {
+    for ($green = 0; $green < 6; $green++) {
+ for ($blue = 0; $blue < 6; $blue++) {
+     printf("\x1b]4;%d;rgb:%2.2x/%2.2x/%2.2x\x1b\\",
+     16 + ($red * 36) + ($green * 6) + $blue,
+     ($red ? ($red * 40 + 55) : 0),
+     ($green ? ($green * 40 + 55) : 0),
+     ($blue ? ($blue * 40 + 55) : 0));
+ }
+    }
+}
+
+# colors 232-255 are a grayscale ramp, intentionally leaving out
+# black and white
+for ($gray = 0; $gray < 24; $gray++) {
+    $level = ($gray * 10) + 8;
+    printf("\x1b]4;%d;rgb:%2.2x/%2.2x/%2.2x\x1b\\",
+    232 + $gray, $level, $level, $level);
+}
+
+
+# display the colors
+
+# first the system ones:
+print "System colors:\n";
+for ($color = 0; $color < 8; $color++) {
+    print "\x1b[48;5;${color}m  ";
+}
+print "\x1b[0m\n";
+for ($color = 8; $color < 16; $color++) {
+    print "\x1b[48;5;${color}m  ";
+}
+print "\x1b[0m\n\n";
+
+# now the color cube
+print "Color cube, 6x6x6:\n";
+for ($green = 0; $green < 6; $green++) {
+    for ($red = 0; $red < 6; $red++) {
+ for ($blue = 0; $blue < 6; $blue++) {
+     $color = 16 + ($red * 36) + ($green * 6) + $blue;
+     print "\x1b[48;5;${color}m  ";
+ }
+ print "\x1b[0m ";
+    }
+    print "\n";
+}
+
+
+# now the grayscale ramp
+print "Grayscale ramp:\n";
+for ($color = 232; $color < 256; $color++) {
+    print "\x1b[48;5;${color}m  ";
+}
+print "\x1b[0m\n";

scripts/true_color.sh

@@ -0,0 +1,100 @@
+#!/bin/bash
+# This file was originally taken from iterm2 https://github.com/gnachman/iTerm2/blob/master/tests/24-bit-color.sh
+#
+#   This file echoes a bunch of 24-bit color codes
+#   to the terminal to demonstrate its functionality.
+#   The foreground escape sequence is ^[38;2;<r>;<g>;<b>m
+#   The background escape sequence is ^[48;2;<r>;<g>;<b>m
+#   <r> <g> <b> range from 0 to 255 inclusive.
+#   The escape sequence ^[0m returns output to default
+
+setBackgroundColor()
+{
+    #printf '\x1bPtmux;\x1b\x1b[48;2;%s;%s;%sm' $1 $2 $3
+    printf '\x1b[48;2;%s;%s;%sm' $1 $2 $3
+}
+
+resetOutput()
+{
+    echo -en "\x1b[0m\n"
+}
+
+# Gives a color $1/255 % along HSV
+# Who knows what happens when $1 is outside 0-255
+# Echoes "$red $green $blue" where
+# $red $green and $blue are integers
+# ranging between 0 and 255 inclusive
+rainbowColor()
+{ 
+    let h=$1/43
+    let f=$1-43*$h
+    let t=$f*255/43
+    let q=255-t
+
+    if [ $h -eq 0 ]
+    then
+        echo "255 $t 0"
+    elif [ $h -eq 1 ]
+    then
+        echo "$q 255 0"
+    elif [ $h -eq 2 ]
+    then
+        echo "0 255 $t"
+    elif [ $h -eq 3 ]
+    then
+        echo "0 $q 255"
+    elif [ $h -eq 4 ]
+    then
+        echo "$t 0 255"
+    elif [ $h -eq 5 ]
+    then
+        echo "255 0 $q"
+    else
+        # execution should never reach here
+        echo "0 0 0"
+    fi
+}
+
+for i in `seq 0 127`; do
+    setBackgroundColor $i 0 0
+    echo -en " "
+done
+resetOutput
+for i in `seq 255 -1 128`; do
+    setBackgroundColor $i 0 0
+    echo -en " "
+done
+resetOutput
+
+for i in `seq 0 127`; do
+    setBackgroundColor 0 $i 0
+    echo -n " "
+done
+resetOutput
+for i in `seq 255 -1 128`; do
+    setBackgroundColor 0 $i 0
+    echo -n " "
+done
+resetOutput
+
+for i in `seq 0 127`; do
+    setBackgroundColor 0 0 $i
+    echo -n " "
+done
+resetOutput
+for i in `seq 255 -1 128`; do
+    setBackgroundColor 0 0 $i
+    echo -n " "
+done
+resetOutput
+
+for i in `seq 0 127`; do
+    setBackgroundColor `rainbowColor $i`
+    echo -n " "
+done
+resetOutput
+for i in `seq 255 -1 128`; do
+    setBackgroundColor `rainbowColor $i`
+    echo -n " "
+done
+resetOutput

vimrc

@@ -1,9 +1,11 @@
+" There's 8-color, 256-color, and 24-bit AKA TrueColor support
+" possible in different terminals. This enables 24-bit colors.
+" Makes VIM black-and-white in unsupported terminals.
+set termguicolors
+
 " Set desired colorscheme.
 colorscheme desert
 
-" Optional: set 256 color mode
-"set termguicolors
-
 " Turn on code syntax highlighting.
 syntax on
 syntax enable