
NAME
Terminal::Capabilities - Container for terminal capabilities, with useful defaults
SYNOPSIS
use Terminal::Capabilities;
use Terminal::Capabilities::Autodetect;
# Autodetect terminal and its capabilities via examination of terminal-related
# environment variables. This does not touch the process table or run any
# subprocesses, so it should be quick and safe.
my ($autocaps, $terminal, $version) = terminal-env-detect;
# Create a terminal capabilities object with DEFAULT settings based on the most
# commonly well-supported capabilities, as determined by submissions to the
# Terminal::Tests project. This method does NO AUTODECTION.
my Terminal::Capabilities $caps .= new;
# Examine individual capabilities
say $caps.symbol-set; # ASCII by default, as it is the most compatible
say $caps.vt100-boxes; # False by default, because ASCII does not require it
say $caps.color8bit; # True by default, since most terminals support it
# Override default symbol set
my $symbol-set = Terminal::Capabilities::SymbolSet::Uni1;
my $caps = Terminal::Capabilities.new(:$symbol-set);
# Symbol set affects default for other features
say $caps.vt100-boxes; # True, because WGL4R and all larger sets require it
# Determine best available symbol set supported by terminal out of a list
say $caps.best-symbol-set(< ASCII WGL4 MES2 Uni7 >); # MES2, best <= Uni1
# Select from a list of options keyed by required symbol set
my %arrows = ASCII => « < > »,
Latin1 => < « » >,
WGL4 => < ◄ ► >,
Uni1 => < ◀ ▶ >,
Uni7 => < ⯇ ⯈ >;
say $caps.best-symbol-choice(%arrows); # ◀ ▶ , the Uni1 option
# Map a possibly mis-cased string to a SymbolSet enumerant (for processing
# user symbol set config requests)
my $symbol-set = symbol-set('cp1252'); # Terminal::Capabilities::SymbolSet::CP1252
DESCRIPTION
Terminal::Capabilities is a relatively simple module that collects information about the capabilities of modern terminals (it assumes at least the ASCII character set, and ANSI/DEC VT style control sequence emulation).
The Terminal::Capabilities::Autodetect
child module provides routines for autodetecting the user's terminal and its capabilities. The first such routine only examines environment variables, thus avoiding creating subprocesses, performing asynchronous queries to the terminal emulator, or mucking about in the user's process table. Simply call the terminal-env-detect
routine to obtain a pre-populated Terminal::Capabilities
object with the autodetection's best guesses, along with the terminal type detected and terminal program version if available:
use Terminal::Capabilities::Autodetect;
my ($caps, $type, $version) = terminal-env-detect;
Conversely, the core Terminal::Capabilities
module does not do any autodetection, merely serving as a standard for collecting capabilities detected or configured through other means. That said, there are reasonable defaults for each of the capability flags based on the collected submissions to the Terminal::Tests
project. The default values represent the capabilities that are universally supported (or nearly so -- there are a few truly deeply broken terminals for which nearly nothing works properly which are considered out of scope for the defaults).
One quirk of this method of determining defaults is that 8-bit color is more uniformly supported by modern terminals than various color and style attributes that were "standardized" decades earlier. Thus color8bit
is by default True
, while colorbright
and italic
are by default False
.
Known Symbol Sets
In superset order, from smallest to largest:
Symbol Set | Contents |
---|
ASCII | 7-bit ASCII printables only (most compatible) |
Latin1 | Latin-1 / ISO-8859-1 |
CP1252 | CP1252 / Windows-1252 |
W1G | W1G-compatible subset of WGL4R |
WGL4R | Required (non-optional) WGL4 glyphs |
WGL4 | Full WGL4 / Windows Glyph List 4 |
MES2 | MES-2 / Multilingual European Subset No. 2 |
Uni1 | Unicode 1.1 |
Uni7 | Unicode 7.0 and Emoji 0.7 |
Full | Full modern Unicode support (most features) |
The difference between WGL4R
and full WGL4
is that the latter includes 18 additional symbol and drawing glyphs needed for full compatibility with CP437, the code page (glyph set) used in IBM PC-compatible video ROMs and thus all DOS programs. As these 18 are considered optional in the WGL4 spec, WGL4R
allows specifying only the symbols required by WGL4, and thus guaranteed to work in any terminal font with at least minimal WGL4 compatibility.
Known Feature Flags
Several sets of flag (Bool) attributes indicate support for various features. There are sets for classic ANSI attributes, color support, and emoji handling:
Attribute | Supported Feature |
---|
.bold | ANSI/VT100 bold attribute |
.italic | ANSI/VT100 italic attribute |
.inverse | ANSI/VT100 inverse attribute |
.underline | ANSI/VT100 underline attribute |
.color3bit | Original paletted 3-bit color |
.colorbright | Bright variants of 3-bit palette |
.color8bit | 6x6x6 color cube and 24-value grayscale |
.color24bit | 24-bit RGB color |
.emoji-text | Text outline emoji (VS15) |
.emoji-color | Color emoji (VS16) |
.emoji-skin | Skin tones for faces and people |
.emoji-iso | Emoji flags for ISO country codes |
.emoji-reg | Emoji flags for region codes |
.emoji-zwj | Emoji combinations via joining (ZWJ) |
class Terminal::Capabilities
A container for the available capabilities of a particular terminal
sub symbol-set
sub symbol-set(
Str:D $set = "Full"
) returns SymbolSet:D
Determine the correct SymbolSet enumerant for a possibly mis-cased string
has SymbolSet:D $.symbol-set
Largest supported symbol repertoire
has Bool $.vt100-boxes
Supports VT100 box drawing glyphs (nearly universal, but only required by WGL4R)
method best-symbol-set
method best-symbol-set(
@sets
) returns SymbolSet:D
Find best symbol set supported by this terminal from a list of choices
method best-symbol-choice
method best-symbol-choice(
%options
) returns Mu
Choose the best choice out of options keyed by required symbol set
AUTHOR
Geoffrey Broadwell gjb@sonic.net
COPYRIGHT AND LICENSE
Copyright 2023,2025 Geoffrey Broadwell
This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.