Support for 16 million colors

[Anton Kochkov]

Here's a test case

printf "\x1b[38;2;255;100;0mTRUECOLOR\x1b[0m\n"

According to Wikipedia[1], this is only supported by xterm and konsole.

It's a common confusion about terminal colors... Actually we have this:

* plain ascii
* ansi escape codes (16 color codes with bold/italic and background)
* 256 color palette (216 colors+16gray + ansi) (colors are 24bit)
* 24bit true color (8*8*8 colors (aka 16 milion)

The 256 color palete is configured at start, and it's a 6*6*6 cube of
colors, each of them defined as a 24bit (8*8*8 rgb) color.

This means that current support can only display 256 *different* colors
in the terminal, while truecolor means that you can display 16 milion
different colors at the same time.

Truecolor escape codes doesnt uses a color palete. It just specifies the
color itself.

[1] https://en.wikipedia.org/wiki/ANSI_color

Here is another terminals discussions:

st (from suckless) - http://lists.suckless.org/dev/1307/16688.html
urxvt - http://lists.schmorp.de/pipermail/rxvt-unicode/2013q3/001826.html
konsole (already fixed) https://bugs.kde.org/show_bug.cgi?id=138740
mlterm - https://bitbucket.org/arakiken/mlterm/issue/1/support-for-16-million-colors

[Egmont Koblinger (egmont-gmail)]

Implemented in vte git, will be released in vte-0.35.1