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DOLMEN

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Olivier Mengué

NAME

Term::Chrome - DSL for colors and other terminal chrome

SYNOPSIS

    use Term::Chrome qw<Red Blue Bold Reset Underline Green color>;

    # Base color constant and attribute
    say Red, 'red text', Reset;

    # Composition, using operator overloading
    say Red/Blue+Bold, 'red on blue', Reset;

    # Undo
    say Bold, 'bold', !Bold, 'not bold';

    # Extended xterm-256 colors
    say color(125) + Underline, 'Purple', Reset;

    # Define your own constants
    use constant Pink => color 213;

    # Use ${} around Chrome expression inside strings
    say "normal ${ Red+Bold } RED ${ +Reset } normal";

    # Extract components
    say( (Red/Blue)->bg, "blue text", (Green+Reset)->flags );

Chromizer: get a closure that applies given chrome before, and undo after the argument.

    # Get an efficient chromizer
    my $boldifier = \&{ +Bold };
    # Use the chromizer
    say $boldifier->("bold text");
    # Same as:
    say Bold, "bold text", !Bold;

    # Short lived chromizers using color literals:
    say(&{+Red}('red'));
    say(&{ Red/Blue + Bold }('red on blue'));
    # Same, but requires perl 5.21.4+
    #say(( Red/Blue + Bold )->('red on blue'));

DESCRIPTION

Term::Chrome is a domain-specific language (DSL) for terminal decoration (colors and other attributes).

In the current implementation stringification to ANSI sequences for xterm and xterm-256 is hard-coded (which means it doesn't use the terminfo(5) database), but this gives optimized (short) strings.

Colors and attributes are exposed as objects that have overloading for arithmetic operators.

EXPORTS

Functions

color(0-255)

Build a Term::Chrome object with the given color number. You can use this constructor to create your own set of color constants.

For example, color(0) gives the same result as Black (but not the same object).

Colors

Each of these function return a Chrome object.

  • Black: color 0

  • Red: color 1

  • Green: color 2

  • Yellow: color 3

  • Blue: color 4

  • Magenta: color 5

  • Cyan: color 6

  • White: color 7

Decoration flags

The exact rendering of each flag is dependent on how the terminal implements them. For example Underline and Blink may do nothing.

  • Bold

  • Underline

  • Blink

  • Reverse

Special flags

  • Reset: reset all colors and flags

  • ResetFlags: reset (undo) all chrome flags (Bold, Underline, Blink, Reverse)

  • ResetFg: reset (undo) foreground color

  • ResetBg: reset (undo) background color

METHODS

Here are the methods on Term::Chrome objects:

fg

Extract the Chrome object of just the foreground color. Maybe undef.

bg

Extract the Chrome object of the just background color. Maybe undef.

flags

Extract a Chrome object of just the decoration flags. Maybe undef.

OVERLOADED OPERATORS

/ (mnemonic: "over")

Combine a foreground color (on the left) with a background color.

Example:

    my $red_on_black = Red / Black;
+

Add decoration flags (on the right) to colors (on the left).

Example:

    my $bold_red = Red + Bold;
! (negation)

Returns a chrome which is the reverse of chrome to which negation is applied.

    my $reset_foreground = ! Red;
    my $reset_colors = ! (Red / Black);

The reverse of Reset, ResetFg, ResetBg, ResetFlags is nothing.

"" (stringification)

Transform the object into a string of ANSI sequences. This is particularly useful to directly use a Chrome object in a double quoted string.

${} (scalar dereference)

Same result as "" (stringification). This operator is overloaded because it is convenient to interpolate Chrome expressions in double-quoted strings.

Examples:

    say "normal ${ +Red } red ${ +Reset }";
    say "normal ${ Red + Bold } red ${ +Reset }";

Note that you must force expression parsing context when a Chrome constant is used alone inside ${ }: ${ +Red } or ${ (Red) } or ${ Red() }. use strict 'vars'; will detect those cases, but you may miss them in one-liners.

&{} (code dereference, or codulation)

Wrap some text with the given chrome and Reset.

Example:

    say Red->("red text");
    # Same result as:
    say Red, "red text", Reset;

Unfortunately perl had a bug (perl RT#122607) that makes this feature not much usable in practice when applied to constants. That bug is fixed in perl 5.21.4+. On perl < 5.21.4 you have to wrap the chrome constant in a do {} or use &{}():

    say do{ Red }->("red text");
    say &{ +Red }("red text");

Codulation can also be used to extract a colorizer sub that will be more efficient if you use it multiple times:

    my $redifier = \&{ Red };
    say $redifier->("red text");

BUGS

See the warnings about ${} and &{} above.

REFERENCES

  • ISO 6429 / ECMA 48: https://www.ecma-international.org/publications/files/ECMA-ST/Ecma-048.pdf (reference for SGR is at page 61, numbered 75 in PDF)

  • XTerm Control Sequences: http://invisible-island.net/xterm/ctlseqs/ctlseqs.html#h2-Functions-using-CSI-_-ordered-by-the-final-character_s_

SEE ALSO

Comments on each modules are opinions of the author.

TRIVIA

Did you know that chartreuse is one of the favorite colors of Larry Wall?

AUTHOR

Olivier Mengué <dolmen@cpan.org>

COPYRIGHT & LICENSE

Copyright © 2013-2018 Olivier Mengué.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl 5 itself.