GNU libtextstyle, version 0.22
Output of styled text
updated 15 December 2020
Bruno Haible
Copyright (C) 2018-2020 Free Software Foundation, Inc.
This manual is free documentation. It is dually licensed under the GNU FDL and the GNU
GPL. This means that you can redistribute this manual under either of these two licenses,
at your choice.
This manual is covered by the GNU FDL. Permission is granted to copy, distribute and/or
modify this document under the terms of the GNU Free Documentation License (FDL),
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html.
This manual is covered by the GNU GPL. You can redistribute it and/or modify it under
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i
Table of Contents
1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Style definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Built-in versus separate styling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 The end user’s perspective . . . . . . . . . . . . . . . . . . . . . 3
2.1 The environment variable TERM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.1 Terminal emulator programs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1.2 Consoles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 The environment variable NO_COLOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 The environment variable NO_TERM_HYPERLINKS . . . . . . . . . . . . . . . . 4
2.4 Emacs as a terminal emulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.5 The --color option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.6 The --style option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.6.1 Creating your own style files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.6.2 Debugging style files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 The programmer’s perspective . . . . . . . . . . . . . . . . 8
3.1 Basic use of libtextstyle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1.1 Hyperlinks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 Include files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3 Link options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4 Command-line options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.5 The output stream hierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.5.1 The abstract ostream class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.5.2 The abstract styled_ostream class. . . . . . . . . . . . . . . . . . . . . . . 12
3.5.3 Concrete ostream subclasses without styling . . . . . . . . . . . . . . 13
3.5.3.1 The file_ostream class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.5.3.2 The fd_ostream class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.5.3.3 The term_ostream class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.5.3.4 The html_ostream class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.5.3.5 The memory_ostream class . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.5.3.6 The iconv_ostream class. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.5.4 Concrete styled_ostream subclasses . . . . . . . . . . . . . . . . . . . . . 16
3.5.4.1 The term_styled_ostream class. . . . . . . . . . . . . . . . . . . . . 17
3.5.4.2 The html_styled_ostream class. . . . . . . . . . . . . . . . . . . . . 17
3.5.4.3 The noop_styled_ostream class. . . . . . . . . . . . . . . . . . . . . 17
3.5.5 Accessor functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.6 Debugging the text styling support . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.7 Documenting the text styling support . . . . . . . . . . . . . . . . . . . . . . . . . 19
ii
Appendix A Licenses . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
A.1 GNU GENERAL PUBLIC LICENSE . . . . . . . . . . . . . . . . . . . . . . . . . 21
A.2 GNU Free Documentation License . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Function Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Variable Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
General Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Chapter 1: Introduction 1
1 Introduction
Text is easier to read when it is accompanied with styling information, such as color, font
attributes (weight, posture), or underlining, and this styling is customized appropriately for
the output device.
GNU libtextstyle provides an easy way to add styling to programs that produce output
to a console or terminal emulator window. It does this in a way that allows the end user to
customize the styling using the industry standard, namely Cascading Style Sheets (CSS).
1.1 Style definitions
Let’s look at the traditional way styling is done for specific programs.
Browsers, when they render HTML, use CSS styling.
The older approach to user-customizable text styling is that the user associates patterns
with escape sequences in an environment variable or a command-line argument. This is the
approach used, for example, by the GNU ‘ls’ program in combination with the ‘dircolors’
program. The processing is distributed across several steps:
1. There is default style definition that is hard-coded in the ‘dircolors’ program. The
user can also define their own definitions in a file such as ~/.dir_colors. This style
definition contains explicit terminal escape sequences; thus, it can only be used with
consoles and terminal emulators, and each style definition applies only to a certain class
of mostly-compatible terminal emulators.
2. The dircolors program, when invoked, translates such a style definition to a sequence
of shell statements that sets an environment variable LS_COLORS.
3. The shell executes these statements, and thus sets the environment variable LS_COLORS.
4. The program looks at the environment variable and emits the listed escape sequences.
In contrast, this library implements styling as follows:
1. There is a default style definition in a CSS file that is part of the same package as the
stylable program. The user can also define their own definitions in a CSS file, and set
an environment environment variable to point to it.
2. The program looks at the environment variable, parses the CSS file, translates the
styling specifications to the form that is appropriate for the output device (escape
sequences for terminal emulators, inline CSS and <span> elements for HTML output),
and emits it.
Thus, with GNU libtextstyle, the styling has the following properties:
• It is easier for the user to define their own styling, because the file format is standardized
and supported by numerous syntax aware editors.
• A styling file does not depend on the particular output device. An HTML output and
a black-on-white terminal emulator can use the same styling file. A white-on-black (or
even green-on-black) terminal emulator will need different styling, though.
• It is simpler: There is no need for a program that converts the style specification from
one format to another.
Chapter 1: Introduction 2
1.2 Built-in versus separate styling
There are generally two approaches for adding styling to text:
• The program that generates the text adds the styling. It does so through interleaved
statements that turn on or off specific attributes.
• The styling gets added by a separate program, that postprocesses the output. This
separate program usually uses regular expressions to determine which text regions to
style with a certain set of text attributes.
The first approach produces a styling that is 100% correct, regardless of the complexity
of the text that is being output. This is the preferred approach for example for JSON,
XML, or programming language text.
The second approach works well if the output has a simple, easy-to-parse format. It may
produce wrong styling in some cases when the text format is more complex. This approach
is often used for viewing log files.
GNU libtextstyle supports both approaches; it includes an example program for each of
the two approaches.
Chapter 2: The end user’s perspective 3
2 The end user’s perspective
Styled output can viewed fine in a console or terminal emulator window.
The stylable program will typically have the following options:
--color Use colors and other text attributes always.
--color=when
Use colors and other text attributes if when. when may be always, never,
auto, or html.
--style=style-file
Specify the CSS style rule file for --color.
For more details, see the sections Section 2.5 [The –color option], page 5 and Section 2.6
[The –style option], page 5 below.
If the output does not fit on a screen, you can use ‘less -R’ to scroll around in the styled
output. For example:
program --color arguments | less -R
2.1 The environment variable TERM
The environment variable TERM contains a identifier for the text window’s capabilities.
You can get a detailed list of these cababilities by using the ‘infocmp’ command (for ex-
ample: infocmp -L1 xterm), using ‘man 5 terminfo’ as a reference.
When producing text with embedded color directives, a libtextstyle-enabled program
looks at the TERM variable. Text windows today typically support at least 8 colors. Often,
however, the text window supports 16 or more colors, even though the TERM variable is set
to a identifier denoting only 8 supported colors. It can be worth setting the TERM variable
to a different value in these cases.
After setting TERM, you can verify how well it works by invoking ‘program
--color=test’, where program is any libtextstyle-enabled program, and seeing whether
the output looks like a reasonable color map.
2.1.1 Terminal emulator programs
The following terminal emulator programs support 256 colors and set
TERM=xterm-256color accordingly:
• In GNOME: gnome-terminal, tilda.
• rxvt-unicode (sets TERM=rxvt-unicode-256color).
• st (sets TERM=st-256color).
• QTerminal.
• On macOS: Terminal, iTerm2.
The following terminal emulator programs support 256 colors. You only need to set
TERM=xterm-256color or similar; the programs by default set TERM to a value that supports
only 8 colors.
• xterm is in many cases built with support for 256 colors. But it sets TERM=xterm. You
need to set TERM=xterm-256color.
Chapter 2: The end user’s perspective 4
• In GNOME: guake (sets TERM=xterm). You need to set TERM=xterm-256color.
• In KDE: konsole (sets TERM=xterm). You need to set TERM=xterm-256color or
TERM=konsole-256color.
• In KDE: yakuake (sets TERM=xterm). You need to set TERM=xterm-256color.
• In Enlightenment: Eterm (sets TERM=Eterm). You need to set TERM=Eterm-256color.
• mlterm (sets TERM=mlterm). You need to set TERM=mlterm-256color.
• On Windows: PuTTY (sets TERM=xterm). You need to set TERM=xterm-256color or
TERM=putty-256color.
• On Windows: TeraTerm (sets TERM=xterm). You need to set TERM=xterm-256color.
A couple of terminal emulator programs support even the entire RGB color space (16
million colors). To get this to work, at this date (2019), you need three things:
• The ncurses library version 6.1 or newer must be installed.
• You need a recent version of the respective terminal emulator program. See https://
gist.github.com/XVilka/8346728 for the most recent developments in this area.
• You need to set the TERM environment variable to the corresponding value:
TERM=xterm-direct instead of TERM=xterm or TERM=xterm-256color,
TERM=konsole-direct in konsole, TERM=st-direct in st, TERM=mlterm-direct in
mlterm, or TERM=iterm2-direct in iTerm2 on macOS.
2.1.2 Consoles
On OpenBSD 6 consoles, TERM=xterm produces better results than the default
TERM=vt220.
On NetBSD 8 consoles, TERM=netbsd6 produces better results than the default
TERM=vt100.
On Windows consoles, no TERM setting is needed.
2.2 The environment variable NO_COLOR
The environment variable NO_COLOR can be used to suppress styling in the textual output.
When this environment variable is set (to any value), libtextstyle-enabled programs will
not emit colors and other text styling.
This environment variable can be overridden by passing the command-line option
‘--color=always’ (see Section 2.5 [The –color option], page 5).
2.3 The environment variable NO_TERM_HYPERLINKS
The environment variable NO_TERM_HYPERLINKS can be used to suppress hyperlinks in
the textual output. When this environment variable is set (to any value), libtextstyle-
enabled programs will not emit hyperlinks. This may be useful for terminal emulators which
produce garbage output when they receive the escape sequence for a hyperlink. Currently
(as of 2019), this affects some versions of konsole, emacs, lxterminal, guake, yakuake,
rxvt.
Chapter 2: The end user’s perspective 5
2.4 Emacs as a terminal emulator
Emacs has several terminal emulators: M-x shell and M-x term. M-x term has good
support for styling, whereas in M-x shell most of the styling gets lost.
2.5 The --color option
The ‘--color=when’ option specifies under which conditions styled (colorized) output
should be generated. The when part can be one of the following:
always
yes The output will be colorized.
never
no The output will not be colorized.
auto
tty The output will be colorized if the output device is a tty, i.e. when the output
goes directly to a text screen or terminal emulator window.
html The output will be colorized and be in HTML format. This value is only
supported by some programs.
test This is a special value, understood only by some programs. It is explained in
the section (Section 2.1 [The TERM variable], page 3) above.
‘--color’ is equivalent to ‘--color=yes’. The default is ‘--color=auto’.
Thus, a command that invokes a libtextstyle-enabled program will produce colorized
output when called by itself in a command window. Whereas in a pipe, such as ‘program
arguments | less -R’, it will not produce colorized output. To get colorized output in this
situation nevertheless, use the command ‘program --color arguments | less -R’.
The ‘--color=html’ option will produce output that can be viewed in a browser. This
can be useful, for example, for Indic languages, because the renderic of Indic scripts in
browsers is usually better than in terminal emulators.
Note that the output produced with the --color option is not consumable by programs
that expect the raw text. It contains additional terminal-specific escape sequences or HTML
tags. For example, an XML parser will give a syntax error when confronted with a colored
XML output. Except for the ‘--color=html’ case, you therefore normally don’t need to
save output produced with the --color option in a file.
2.6 The --style option
The ‘--style=style_file’ option specifies the style file to use when colorizing. It has
an effect only when the --color option is effective.
If the --style option is not specified, the program may consider the value of an envi-
ronment variable. It is meant to point to the user’s preferred style for such output. The
name of such an environment variable, if supported, is documented in the documentation
of the libtextstyle-enabled program.
You can also design your own styles. This is described in the next section.
Chapter 2: The end user’s perspective 6
2.6.1 Creating your own style files
The same style file can be used for styling a certain type of output, for terminal output
and for HTML output. It is written in CSS (Cascading Style Sheet) syntax. See https://
www.w3. org/TR/css2/cover.html for a formal definition of CSS. Many HTML authoring
tutorials also contain explanations of CSS.
In the case of HTML output, the style file is embedded in the HTML output. In the
case of text output, the style file is interpreted by the libtextstyle-enabled program.
You should avoid @import statements, because
− In the case of HTML output, the files referenced by the @import statements would not
be embedded in the HTML output. In fact, relative file names would be interpreted
relative to the resulting HTML file.
− In the case of text output, @imports are not supported, due to a limitation in libcroco.
CSS rules are built up from selectors and declarations. The declarations specify graphical
properties; the selectors specify when they apply.
GNU libtextstyle supports simple selectors based on "CSS classes", see the CSS2 spec,
section 5.8.3. The set of CSS classes that are supported by a libtextstyle-enabled program
are documented in the documentation of that program.
These selectors can be combined to hierarchical selectors. For example, assume a pro-
gram supports the CSS classes string (that matches a string) and non-ascii (that matches
a word with non-ASCII characters), you could write
.string .non-ascii { color: red; }
to highlight only the non-ASCII words inside strings.
In text mode, pseudo-classes (CSS2 spec, section 5.11) and pseudo-elements (CSS2 spec,
section 5.12) are not supported.
The declarations in HTML mode are not limited; any graphical attribute supported by
the browsers can be used.
The declarations in text mode are limited to the following properties. Other properties
will be silently ignored.
color (CSS2 spec, section 14.1)
background-color (CSS2 spec, section 14.2.1)
These properties are supported. Colors will be adjusted to match the terminal’s
capabilities. Note that many terminals support only 8 colors.
font-weight (CSS2 spec, section 15.2.3)
This property is supported, but most terminals can only render two different
weights: normal and bold. Values >= 600 are rendered as bold.
font-style (CSS2 spec, section 15.2.3)
This property is supported. The values italic and oblique are rendered the
same way.
text-decoration (CSS2 spec, section 16.3.1)
This property is supported, limited to the values none and underline.
Chapter 2: The end user’s perspective 7
2.6.2 Debugging style files
If you want to understand why the style rules in a style file produce the output that you
see, you can do so in three steps:
1. Run the program with the command-line option --color=html, redirecting the output
to a file.
2. Open the resulting HTML file in a browser.
3. Use the browser’s built-in CSS debugging tool.
• In Firefox: From the pop-up menu, select "Inspect Element". Click somewhere in
the DOM tree ("Inspector" tab) and look at the CSS declarations in the "Rules"
tab.
• In Chromium: From the pop-up menu, select "Inspect". Click somewhere in the
DOM tree ("Elements" tab) and look at the CSS declarations in the "Styles" tab.
This technique allows you, in particular, to see which CSS declarations override which
other CSS declarations from other CSS rules.
Chapter 3: The programmer’s perspective 8
3 The programmer’s perspective
As a programmer, enabling styling consists of the following tasks:
1. Define the command-line options and environment variable that the user can use to
control the styling.
2. Define the CSS classes that the user can use in the CSS file. Each CSS class corresponds
to a text role; each CSS class can be given a different styling by the user.
3. Change the output routines so that they take an ‘ostream_t’ object as argument
instead of a ‘FILE *’.
4. Insert paired invocations to styled_ostream_begin_css_class, styled_ostream_
end_css_class around each run of text with a specific text role.
5. Link with libtextstyle. If your package is using GNU autoconf, you can use the
libtextstyle.m4 macro from Gnulib.
6. Prepare a default style file.
7. Update the documentation of your package.
The following sections go into more detail.
3.1 Basic use of libtextstyle
Source code that makes use of GNU libtextstyle needs an include statement:
#include <textstyle.h>
Basic use of GNU libtextstyle consists of statements like these:
styled_ostream_t stream =
styled_ostream_create (STDOUT_FILENO, "(stdout)", TTYCTL_AUTO,
style_file_name);
...
styled_ostream_begin_use_class (stream, css_class);
...
ostream_write_str (stream, string);
...
styled_ostream_end_use_class (stream, css_class);
...
styled_ostream_free (stream);
Before this snippet, your code needs to determine the name of the style file to use
(style_file_name). If no styling is desired – the precise condition depends on the value of
color_mode but also on your application logic –, you should set style_file_name to NULL.
An object of type styled_ostream_t is allocated. The function styled_ostream_
create allocates it; the function styled_ostream_free deallocates it.
Such styled_ostream_t supports output operations (ostream_write_str), interleaved
with adding and removing CSS classes. The CSS class in effect when an output operation is
performed determines, through the style file, the text attributes associated with that piece
of text.
3.1.1 Hyperlinks
Text output may contain hyperlinks. These hyperlinks are encoded through an escape
sequence, specified at Hyperlinks in terminal emulators (https: / / gist . github .com /
Chapter 3: The programmer’s perspective 9
egmontkob/eb114294efbcd5adb1944c9f3cb5feda). Currently (as of 2019), they are dis-
played only in gnome-terminal version 3.26 or above. More terminal emulators will support
hyperlinks in the future. Terminal emulators which don’t support hyperlinks ignore it, ex-
cept for a few terminal emulators, for which users may need to disable the hyperlinks (see
Section 2.3 [The NO TERM HYPERLINKS variable], page 4) if the heuristic built into
libtextstyle does not already disable them.
To emit a hyperlink, use code like this:
styled_ostream_t stream = ...
...
/* Start a hyperlink. */
styled_ostream_set_hyperlink (stream, url, NULL);
...
/* Emit the anchor text. This can be styled text. */
ostream_write_str (stream, "Click here!");
...
/* End the current hyperlink. */
styled_ostream_set_hyperlink (stream, NULL, NULL);
The anchor text can be styled. But the hyperlinks themselves cannot be styled; they
behave as implemented by the terminal emulator.
3.2 Include files
The include file <textstyle.h> declares all facilities defined by the library.
3.3 Link options
The library to link with is called libtextstyle, with a system-dependent suffix. You
link with it though link options of the form -ltextstyle for a library installed in sys-
tem locations, or -Llibdir -ltextstyle for a static library installed in other locations,
or -Llibdir -ltextstyle -Wl,-rpath,libdir for a shared library installed in other lo-
cations (assuming a GCC compatible compiler and linker and no libtool), or -Llibdir
-ltextstyle -Rlibdir for a shared library installed in other locations (with libtool).
Additionally, the link options may need to include the dependencies: -lm, and -lncurses
or (on NetBSD) -ltermcap or (on AIX) -lxcurses or (on HP-UX) -lcurses, and on some
systems also -liconv.
It is a bit complicated to determine the right link options in a portable way. Therefore
an Autoconf macro is provided in the file libtextstyle.m4 in Gnulib, that makes this task
easier. Assuming the build system of your package is based on GNU Autoconf, you invoke
it through gl_LIBTEXTSTYLE. It searches for an installed libtextstyle. If found, it sets
and AC SUBSTs HAVE_LIBTEXTSTYLE=yes and the LIBTEXTSTYLE and LTLIBTEXTSTYLE
variables, and augments the CPPFLAGS variable, and #defines HAVE_LIBTEXTSTYLE to
1. Otherwise, it sets and AC SUBSTs HAVE_LIBTEXTSTYLE=no and LIBTEXTSTYLE and
LTLIBTEXTSTYLE to empty. In link commands that use libtool, use LTLIBTEXTSTYLE; in
link commands that don’t use libtool, use LIBTEXTSTYLE.
If you use GNU Automake, the proper place to use the link options is program_LDADD
for programs and library_LIBADD for libraries.
Chapter 3: The programmer’s perspective 10
3.4 Command-line options
While you are free to provide any command-line option to enable the styling of the
output, it is good if different GNU programs use the same command-line options for this
purpose. These options are described in the sections Section 2.5 [The –color option], page 5
and Section 2.6 [The –style option], page 5. To achieve this, use the following API (declared
in <textstyle.h>):
[Variable]bool color_test_mode
True if a --color option with value test has been seen.
[Variable]enum color_option color_mode
Stores the value of the --color option.
[Variable]const char * style_file_name
Stores the value of the --style option.
Note: These variables, like any variables exported from shared libraries, can only be
used in executable code. You cannot portably use their address in initializers of global or
static variables. This is a restriction that is imposed by the Windows, Cygwin, and Android
platforms.
[Function]bool handle_color_option (const char *option)
You invoke this function when, during argument parsing, you have encountered a
--color or --color=... option. The return value is an error indicator: true means
an invalid option.
[Function]void handle_style_option (const char *option)
You invoke this function when, during argument parsing, you have encountered a
--style or --style=... option.
[Function]void print_color_test (void)
Prints a color test page. You invoke this function after argument parsing, when the
color_test_mode variable is true.
[Function]void style_file_prepare (const char *style_file_envvar,
const char *stylesdir_envvar, const char *stylesdir_after_install,
const char *default_style_file)
Assigns a default value to style_file_name if necessary. You invoke this function
after argument parsing, when color_test_mode is false.
style_file_envvar is an environment variable that, when set to a non-empty value,
specifies the style file to use. This environment variable is meant to be set by the
user.
stylesdir_envvar is an environment variable that, when set to a non-empty value,
specifies the directory with the style files, or NULL. This is necessary for running the
testsuite before ‘make install’.
stylesdir_after_install is the directory with the style files after ‘make install’.
default_style_file is the file name of the default style file, relative to stylesdir.
Chapter 3: The programmer’s perspective 11
3.5 The output stream hierarchy
There are various classes of output streams, some of them with styling support. These
“classes” are defined in an object-oriented programming style that resembles C++ or Java,
but are actually implemented in C with a little bit of object orientation syntax. These
definitions are preprocessed down to C. As a consequence, GNU libtextstyle is a C library
and does not need to link with the C++ standard library.
All these classes are declared in <textstyle.h>.
The base output stream type is ‘ostream_t’. It is a pointer type to a (hidden) imple-
mentation type. Similarly for the subclasses.
When we say that ‘some_ostream_t’ is a subclass of ‘ostream_t’, what we mean is:
• Every ‘some_ostream_t’ object can be converted to an ‘ostream_t’, by virtue of a
simple assignment. No cast is needed.
• The opposite conversion, from ‘ostream_t’ to ‘some_ostream_t’, can also be per-
formed, provided that the object is actually an instance of ‘some_ostream_t’. You
can test whether an object is an instance of ‘some_ostream_t’ by invoking the method
‘bool is_instance_of_some_ostream (ostream_t stream)’.
• Every method ‘ostream_foobar’ exists also as a method ‘some_ostream_foobar’ with
compatible argument types and a compatible return type.
3.5.1 The abstract ostream class
The base output stream type is ‘ostream_t’.
It has the following methods:
[Function]void ostream_write_mem (ostream t stream, const void *data,
size t len)
Writes a sequence of bytes to a stream.
[Function]void ostream_write_str (ostream t stream, const char *string)
Writes a string’s contents to a stream.
[Function]ptrdiff_t ostream_printf (ostream t stream, const char *format,
...)
[Function]ptrdiff_t ostream_vprintf (ostream t stream, const char *format,
va list args)
Writes formatted output to a stream.
These functions return the size of formatted output, or a negative value in case of an
error.
[Function]void ostream_flush (ostream t stream, ostream flush scope t scope)
Brings buffered data to its destination.
[Function]void ostream_free (ostream t stream)
Closes and frees a stream.
Chapter 3: The programmer’s perspective 12
3.5.2 The abstract styled_ostream class
The type for a styled output stream is ‘styled_ostream_t’. It is a subclass of
‘ostream_t’ that adds the following methods:
[Function]void styled_ostream_begin_use_class (styled ostream t stream,
const char *classname)
Starts a run of text belonging to classname. The classname is the name of a CSS
class. It can be chosen arbitrarily and customized through the CSS file.
[Function]void styled_ostream_end_use_class (styled ostream t stream,
const char *classname)
Ends a run of text belonging to classname. The styled_ostream_begin_use_class
/ styled_ostream_end_use_class calls must match properly.
[Function]const char * styled_ostream_get_hyperlink_ref
(styled ostream t stream)
Returns the referred URL of the currently set hyperlink, or NULL if no hyperlink
attribute is currently set.
Note: The returned string is only valid up to the next invocation of styled_ostream_
set_hyperlink.
[Function]const char * styled_ostream_get_hyperlink_id
(styled ostream t stream)
Returns the id of the currently set hyperlink, or NULL if no hyperlink attribute is
currently set.
Note: The returned string is only valid up to the next invocation of styled_ostream_
set_hyperlink.
[Function]void styled_ostream_set_hyperlink (styled ostream t stream,
const char *ref, const char *id)
Sets or removes a hyperlink attribute.
To set a hyperlink attribute, pass a non-NULL ref. ref is an URL; it should be at
most 2083 bytes long. Non-ASCII characters should be URI-escaped (using the %nn
syntax). id is an optional identifier. On terminal output, multiple hyperlinks with
the same id will be highlighted together. If specified, id should be at most 250 bytes
long.
To remove a hyperlink attribute, pass NULL for ref and id.
Hyperlinks don’t nest. That is, a hyperlink attribute is enabled only up to the next
invocation of styled_ostream_set_hyperlink.
[Function]void styled_ostream_flush_to_current_style
(styled ostream t stream)
This function acts like ostream_flush (stream, FLUSH_THIS_STREAM), except that
it leaves the destination with the current text style enabled, instead of with the default
text style.
After calling this function, you can output strings without newlines(!) to the under-
lying stream, and they will be rendered like strings passed to ostream_write_mem,
ostream_write_str, or ostream_printf.
Chapter 3: The programmer’s perspective 13
3.5.3 Concrete ostream subclasses without styling
3.5.3.1 The file_ostream class
The file_ostream class supports output to an <stdio.h> FILE stream. Its type is
‘file_ostream_t’. It is a subclass of ‘ostream_t’ that adds no methods.
It can be instantiated through this function:
[Function]file_ostream_t file_ostream_create (FILE *fp)
Creates an output stream referring to fp.
Note: The resulting stream must be closed before fp can be closed.
3.5.3.2 The fd_ostream class
The file_ostream class supports output to a file descriptor. Its type is ‘fd_ostream_t’.
It is a subclass of ‘ostream_t’ that adds no methods.
It can be instantiated through this function:
[Function]fd_ostream_t fd_ostream_create (int fd, const char *filename,
bool buffered)
Creates an output stream referring to the file descriptor fd.
filename is used only for error messages.
Note: The resulting stream must be closed before fd can be closed.
3.5.3.3 The term_ostream class
The term_ostream class supports output to a file descriptor that is connected to a
terminal emulator or console. Its type is ‘term_ostream_t’. It is a subclass of ‘ostream_t’.
It can be instantiated through this function:
[Function]term_ostream_t term_ostream_create (int fd,
const char *filename, ttyctl t tty_control)
Creates an output stream referring to the file descriptor fd.
filename is used only for error messages.
tty_control specifies the amount of control to take over the underlying tty.
The resulting stream will be line-buffered.
Note: The resulting stream must be closed before fd can be closed.
The class adds the following methods:
[Function]term_color_t term_ostream_rgb_to_color
(term ostream t stream, int red, int green, int blue)
Converts an RGB value (red, green, blue in [0..255]) to a color, valid for this stream
only.
[Function]term_color_t term_ostream_get_color (term ostream t stream)
[Function]void term_ostream_set_color (term ostream t stream,
term color t color)
Gets/sets the text color.
Chapter 3: The programmer’s perspective 14
[Function]term_color_t term_ostream_get_bgcolor (term ostream t stream)
[Function]void term_ostream_set_bgcolor (term ostream t stream,
term color t color)
Gets/sets the background color.
[Function]term_weight_t term_ostream_get_weight (term ostream t stream)
[Function]void term_ostream_set_weight (term ostream t stream,
term weight t weight)
Gets/sets the font weight.
[Function]term_posture_t term_ostream_get_posture
(term ostream t stream)
[Function]void term_ostream_set_posture (term ostream t stream,
term posture t posture)
Gets/sets the font posture.
[Function]term_underline_t term_ostream_get_underline
(term ostream t stream)
[Function]void term_ostream_set_underline (term ostream t stream,
term underline t underline)
Gets/sets the text underline decoration.
[Function]const char * term_ostream_get_hyperlink_ref
(term ostream t stream)
Returns the referred URL of the currently set hyperlink, or NULL if no hyperlink
attribute is currently set.
Note: The returned string is only valid up to the next invocation of term_ostream_
set_hyperlink.
[Function]const char * term_ostream_get_hyperlink_id
(term ostream t stream)
Returns the id of the currently set hyperlink, or NULL if no hyperlink attribute is
currently set.
Note: The returned string is only valid up to the next invocation of term_ostream_
set_hyperlink.
[Function]void term_ostream_set_hyperlink (term ostream t stream,
const char *ref, const char *id)
Sets or removes a hyperlink attribute.
To set a hyperlink attribute, pass a non-NULL ref. ref is an URL; it should be at
most 2083 bytes long. Non-ASCII characters should be URI-escaped (using the %nn
syntax). id is an optional identifier. Multiple hyperlinks with the same id will be
highlighted together. If specified, id should be at most 250 bytes long.
To remove a hyperlink attribute, pass NULL for ref and id.
Hyperlinks don’t nest. That is, a hyperlink attribute is enabled only up to the next
invocation of styled_ostream_set_hyperlink.
Chapter 3: The programmer’s perspective 15
[Function]void term_ostream_flush_to_current_style
(term ostream t stream)
This function acts like ostream_flush (stream, FLUSH_THIS_STREAM), except that
it leaves the terminal with the current text attributes enabled, instead of with the
default text attributes.
After calling this function, you can output strings without newlines(!) to the under-
lying file descriptor, and they will be rendered like strings passed to ostream_write_
mem, ostream_write_str, or ostream_printf.
3.5.3.4 The html_ostream class
The html_ostream class supports output to any destination, in HTML syntax. Its type
is ‘html_ostream_t’. It is a subclass of ‘ostream_t’.
It can be instantiated through this function:
[Function]html_ostream_t html_ostream_create (ostream t destination)
Creates an output stream that takes input in the UTF-8 encoding and writes it in
HTML form on destination.
This stream produces a sequence of lines. The caller is responsible for opening the
<body><html> elements before and for closing them after the use of this stream.
Note: The resulting stream must be closed before destination can be closed.
The class adds the following methods:
[Function]void html_ostream_begin_span (html ostream t stream,
const char *classname)
Starts a <span class="classname"> element. The classname is the name of a CSS
class. It can be chosen arbitrarily and customized through the CSS file.
[Function]void html_ostream_end_span (html ostream t stream,
const char *classname)
Ends a <span class="classname"> element.
The html_ostream_begin_span / html_ostream_end_span calls must match prop-
erly.
[Function]const char * html_ostream_get_hyperlink_ref
(html ostream t stream)
Returns the referred URL of the currently set hyperlink, or NULL if no hyperlink
attribute is currently set.
Note: The returned string is only valid up to the next invocation of html_ostream_
set_hyperlink_ref.
[Function]void html_ostream_set_hyperlink_ref (html ostream t stream,
const char *ref)
Sets or removes a hyperlink attribute.
To set a hyperlink attribute, pass a non-NULL ref. ref is an URL; it should be at
most 2083 bytes long. Non-ASCII characters should be URI-escaped (using the %nn
syntax).
Chapter 3: The programmer’s perspective 16
To remove a hyperlink attribute, pass NULL for ref.
Hyperlinks don’t nest. That is, a hyperlink attribute is enabled only up to the next
invocation of html_ostream_set_hyperlink_ref.
[Function]void html_ostream_flush_to_current_style
(html ostream t stream)
This function acts like ostream_flush (stream, FLUSH_THIS_STREAM), except that
it leaves the destination with the current text style enabled, instead of with the default
text style.
After calling this function, you can output strings without newlines(!) to the under-
lying stream, and they will be rendered like strings passed to ostream_write_mem,
ostream_write_str, or ostream_printf.
3.5.3.5 The memory_ostream class
The memory_ostream class supports output to an in-memory buffer. Its type is
‘memory_ostream_t’. It is a subclass of ‘ostream_t’.
It can be instantiated through this function:
[Function]memory_ostream_t memory_ostream_create (void)
Creates an output stream that accumulates the output in a memory buffer.
The class adds the following method:
[Function]void memory_ostream_contents (memory ostream t stream,
const void **bufp, size t *buflenp)
Returns a pointer to the output accumulated so far and its size. It stores them in
*bufp and *buflenp, respectively.
Note: These two return values become invalid when more output is done to the stream
or when the stream is freed.
3.5.3.6 The iconv_ostream class
The iconv_ostream class supports output to any destination. Its type is
‘iconv_ostream_t’. It is a subclass of ‘ostream_t’ that adds no methods.
It can be instantiated through this function:
[Function]iconv_ostream_t iconv_ostream_create
(const char *from_encoding, const char *to_encoding,
ostream t destination)
Creates an output stream that converts from from_encoding to to_encoding, writing
the result to destination.
Note: The resulting stream must be closed before destination can be closed.
3.5.4 Concrete styled_ostream subclasses
Chapter 3: The programmer’s perspective 17
3.5.4.1 The term_styled_ostream class
The term_styled_ostream class supports styled output to a file descriptor that is con-
nected to a terminal emulator or console. Its type is ‘term_styled_ostream_t’. It is a
subclass of ‘styled_ostream_t’.
It can be instantiated through this function:
[Function]term_styled_ostream_t term_styled_ostream_create (int fd,
const char *filename, ttyctl t tty_control, const char *css_filename)
Creates an output stream referring to the file descriptor fd, styled with the file css_
filename.
filename is used only for error messages.
tty_control specifies the amount of control to take over the underlying tty.
Note: The resulting stream must be closed before fd can be closed.
Returns NULL upon failure.
The following is a variant of this function. Upon failure, it does not return NULL; instead,
it returns a styled fd_stream on which the styling operations exist but are no-ops.
[Function]styled_ostream_t styled_ostream_create (int fd,
const char *filename, ttyctl t tty_control, const char *css_filename)
Creates an output stream referring to the file descriptor fd, styled with the file css_
filename if possible.
filename is used only for error messages.
tty_control specifies the amount of control to take over the underlying tty.
Note: The resulting stream must be closed before fd can be closed.
3.5.4.2 The html_styled_ostream class
The html_styled_ostream class supports styled output to any destination, in HTML
syntax. Its type is ‘html_styled_ostream_t’. It is a subclass of ‘styled_ostream_t’.
It can be instantiated through this function:
[Function]html_styled_ostream_t html_styled_ostream_create
(ostream t destination, const char *css_filename)
Creates an output stream that takes input in the UTF-8 encoding and writes it in
HTML form on destination, styled with the file css_filename.
Note: The resulting stream must be closed before destination can be closed.
3.5.4.3 The noop_styled_ostream class
The noop_styled_ostream class supports the styled output operations to any desti-
nation. The text is output to the given destination; the styling operations, however, do
nothing. Its type is ‘noop_styled_ostream_t’. It is a subclass of ‘styled_ostream_t’.
It can be instantiated through this function:
Chapter 3: The programmer’s perspective 18
[Function]noop_styled_ostream_t noop_styled_ostream_create
(ostream t destination, bool pass_ownership)
Creates an output stream that delegates to destination and that supports the styling
operations as no-ops.
If pass_ownership is true, closing the resulting stream will automatically close the
destination.
Note: If pass_ownership is false, the resulting stream must be closed before
destination can be closed.
3.5.5 Accessor functions
The various concrete stream classes have methods that allow you to retrieve the argu-
ments passed to the respective constructor function.
Note: While these methods allow you to retrieve the underlying destination stream
of various kinds of stream, it is not recommended to operate on both the stream and its
underlying destination stream at the same time. Doing so can lead to undesired interactions
between the two streams.
The file_ostream class has this accessor method:
[Function]FILE * file_ostream_get_stdio_stream (file ostream t stream)
The fd_ostream class has these accessor methods:
[Function]int fd_ostream_get_descriptor (fd ostream t stream)
[Function]const char * fd_ostream_get_filename (fd ostream t stream)
[Function]bool fd_ostream_is_buffered (fd ostream t stream)
The term_ostream class has these accessor methods:
[Function]int term_ostream_get_descriptor (term ostream t stream)
[Function]const char * term_ostream_get_filename
(term ostream t stream)
[Function]ttyctl_t term_ostream_get_tty_control (term ostream t stream)
[Function]ttyctl_t term_ostream_get_effective_tty_control
(term ostream t stream)
Returns the effective tty control of the stream (not TTYCTL_AUTO).
The iconv_ostream class has these accessor methods:
[Function]const char * iconv_ostream_get_from_encoding
(iconv ostream t stream)
[Function]const char * iconv_ostream_get_to_encoding
(iconv ostream t stream)
[Function]ostream_t iconv_ostream_get_destination
(iconv ostream t stream)
The html_ostream class has this accessor method:
Chapter 3: The programmer’s perspective 19
[Function]ostream_t html_ostream_get_destination
(html ostream t stream)
The term_styled_ostream class has these accessor methods:
[Function]term_ostream_t term_styled_ostream_get_destination
(term styled ostream t stream)
[Function]const char * term_styled_ostream_get_css_filename
(term styled ostream t stream)
The html_styled_ostream class has these accessor methods:
[Function]ostream_t html_styled_ostream_get_destination
(html styled ostream t stream)
[Function]html_ostream_t html_styled_ostream_get_html_destination
(html styled ostream t stream)
[Function]const char * html_styled_ostream_get_css_filename
(html styled ostream t stream)
The noop_styled_ostream class has these accessor methods:
[Function]ostream_t noop_styled_ostream_get_destination
(noop styled ostream t stream)
[Function]bool noop_styled_ostream_is_owning_destination
(noop styled ostream t stream)
3.6 Debugging the text styling support
If you want to understand which output of your program is associated with which CSS
classes, the simplest way is as follows:
1. Run the program with the command-line option --color=html, redirecting the output
to a file.
2. Then inspect this output. Text regions associated with a CSS class are surrounded by
<span class="css-class">...</span>.
3.7 Documenting the text styling support
To make the text styling support available to the end user of your package, the following
need to be documented:
• The command-line options. This typically needs to be done in several places: in the
‘--help’ output, in the man pages (if present), and in the documentation.
• Which programs support ‘--color=test’?
• The list of CSS classes and their meaning. This is necessary, so that the user can create
their own style file; the CSS classes are part of the selectors in the CSS rules.
• The location of the default style file. This is a convenience, so that the user, when
creating their own style file, can start from the default one.
• The environment variable, called style_file_envvar above, that, when set to a non-
empty value, specifies the style file to use.
Appendix A: Licenses 20
Appendix A Licenses
The files of this package are covered by the licenses indicated in each particular file or
directory. Here is a summary:
• The libtextstyle library and the example programs are covered by the GNU General
Public License (GPL). A copy of the license is included in Section A.1 [GNU GPL],
page 21.
• This manual is free documentation. It is dually licensed under the GNU FDL and the
GNU GPL. This means that you can redistribute this manual under either of these two
licenses, at your choice.
This manual is covered by the GNU FDL. Permission is granted to copy, distribute
and/or modify this document under the terms of the GNU Free Documentation Li-
cense (FDL), either version 1.2 of the License, or (at your option) any later version
published by the Free Software Foundation (FSF); with no Invariant Sections, with no
Front-Cover Text, and with no Back-Cover Texts. A copy of the license is included in
Section A.2 [GNU FDL], page 32.
This manual is covered by the GNU GPL. You can redistribute it and/or modify it
under the terms of the GNU General Public License (GPL), either version 3 of the Li-
cense, or (at your option) any later version published by the Free Software Foundation
(FSF). A copy of the license is included in Section A.1 [GNU GPL], page 21.
Appendix A: Licenses 21
A.1 GNU GENERAL PUBLIC LICENSE
Version 3, 29 June 2007
Copyright
c
2007 Free Software Foundation, Inc. https://fsf.org/
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
Preamble
The GNU General Public License is a free, copyleft license for software and other kinds
of works.
The licenses for most software and other practical works are designed to take away your
freedom to share and change the works. By contrast, the GNU General Public License is
intended to guarantee your freedom to share and change all versions of a program—to make
sure it remains free software for all its users. We, the Free Software Foundation, use the
GNU General Public License for most of our software; it applies also to any other work
released this way by its authors. You can apply it to your programs, too.
When we speak of free software, we are referring to freedom, not price. Our General
Public Licenses are designed to make sure that you have the freedom to distribute copies
of free software (and charge for them if you wish), that you receive source code or can get
it if you want it, that you can change the software or use pieces of it in new free programs,
and that you know you can do these things.
To protect your rights, we need to prevent others from denying you these rights or asking
you to surrender the rights. Therefore, you have certain responsibilities if you distribute
copies of the software, or if you modify it: responsibilities to respect the freedom of others.
For example, if you distribute copies of such a program, whether gratis or for a fee, you
must pass on to the recipients the same freedoms that you received. You must make sure
that they, too, receive or can get the source code. And you must show them these terms so
they know their rights.
Developers that use the GNU GPL protect your rights with two steps: (1) assert copy-
right on the software, and (2) offer you this License giving you legal permission to copy,
distribute and/or modify it.
For the developers’ and authors’ protection, the GPL clearly explains that there is no
warranty for this free software. For both users’ and authors’ sake, the GPL requires that
modified versions be marked as changed, so that their problems will not be attributed
erroneously to authors of previous versions.
Some devices are designed to deny users access to install or run modified versions of the
software inside them, although the manufacturer can do so. This is fundamentally incom-
patible with the aim of protecting users’ freedom to change the software. The systematic
pattern of such abuse occurs in the area of products for individuals to use, which is pre-
cisely where it is most unacceptable. Therefore, we have designed this version of the GPL
to prohibit the practice for those products. If such problems arise substantially in other
domains, we stand ready to extend this provision to those domains in future versions of the
GPL, as needed to protect the freedom of users.
Appendix A: Licenses 22
Finally, every program is threatened constantly by software patents. States should not
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be used to render the program non-free.
The precise terms and conditions for copying, distribution and modification follow.
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Appendix A: Licenses 23
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Appendix A: Licenses 24
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b. The work must carry prominent notices stating that it is released under this Li-
cense and any conditions added under section 7. This requirement modifies the
requirement in section 4 to “keep intact all notices”.
c. You must license the entire work, as a whole, under this License to anyone who
comes into possession of a copy. This License will therefore apply, along with any
applicable section 7 additional terms, to the whole of the work, and all its parts,
regardless of how they are packaged. This License gives no permission to license
the work in any other way, but it does not invalidate such permission if you have
separately received it.
d. If the work has interactive user interfaces, each must display Appropriate Legal
Notices; however, if the Program has interactive interfaces that do not display
Appropriate Legal Notices, your work need not make them do so.
A compilation of a covered work with other separate and independent works, which
are not by their nature extensions of the covered work, and which are not combined
with it such as to form a larger program, in or on a volume of a storage or distribution
medium, is called an “aggregate” if the compilation and its resulting copyright are
not used to limit the access or legal rights of the compilation’s users beyond what the
individual works permit. Inclusion of a covered work in an aggregate does not cause
this License to apply to the other parts of the aggregate.
6. Conveying Non-Source Forms.
You may convey a covered work in object code form under the terms of sections 4 and
5, provided that you also convey the machine-readable Corresponding Source under
the terms of this License, in one of these ways:
Appendix A: Licenses 25
a. Convey the object code in, or embodied in, a physical product (including a phys-
ical distribution medium), accompanied by the Corresponding Source fixed on a
durable physical medium customarily used for software interchange.
b. Convey the object code in, or embodied in, a physical product (including a physi-
cal distribution medium), accompanied by a written offer, valid for at least three
years and valid for as long as you offer spare parts or customer support for that
product model, to give anyone who possesses the object code either (1) a copy of
the Corresponding Source for all the software in the product that is covered by this
License, on a durable physical medium customarily used for software interchange,
for a price no more than your reasonable cost of physically performing this con-
veying of source, or (2) access to copy the Corresponding Source from a network
server at no charge.
c. Convey individual copies of the object code with a copy of the written offer to
provide the Corresponding Source. This alternative is allowed only occasionally
and noncommercially, and only if you received the object code with such an offer,
in accord with subsection 6b.
d. Convey the object code by offering access from a designated place (gratis or for
a charge), and offer equivalent access to the Corresponding Source in the same
way through the same place at no further charge. You need not require recipients
to copy the Corresponding Source along with the object code. If the place to
copy the object code is a network server, the Corresponding Source may be on
a different server (operated by you or a third party) that supports equivalent
copying facilities, provided you maintain clear directions next to the object code
saying where to find the Corresponding Source. Regardless of what server hosts
the Corresponding Source, you remain obligated to ensure that it is available for
as long as needed to satisfy these requirements.
e. Convey the object code using peer-to-peer transmission, provided you inform other
peers where the object code and Corresponding Source of the work are being offered
to the general public at no charge under subsection 6d.
A separable portion of the object code, whose source code is excluded from the Cor-
responding Source as a System Library, need not be included in conveying the object
code work.
A “User Product” is either (1) a “consumer product”, which means any tangible per-
sonal property which is normally used for personal, family, or household purposes, or
(2) anything designed or sold for incorporation into a dwelling. In determining whether
a product is a consumer product, doubtful cases shall be resolved in favor of coverage.
For a particular product received by a particular user, “normally used” refers to a
typical or common use of that class of product, regardless of the status of the par-
ticular user or of the way in which the particular user actually uses, or expects or is
expected to use, the product. A product is a consumer product regardless of whether
the product has substantial commercial, industrial or non-consumer uses, unless such
uses represent the only significant mode of use of the product.
“Installation Information” for a User Product means any methods, procedures, autho-
rization keys, or other information required to install and execute modified versions of a
covered work in that User Product from a modified version of its Corresponding Source.
Appendix A: Licenses 26
The information must suffice to ensure that the continued functioning of the modified
object code is in no case prevented or interfered with solely because modification has
been made.
If you convey an object code work under this section in, or with, or specifically for
use in, a User Product, and the conveying occurs as part of a transaction in which
the right of possession and use of the User Product is transferred to the recipient in
perpetuity or for a fixed term (regardless of how the transaction is characterized),
the Corresponding Source conveyed under this section must be accompanied by the
Installation Information. But this requirement does not apply if neither you nor any
third party retains the ability to install modified object code on the User Product (for
example, the work has been installed in ROM).
The requirement to provide Installation Information does not include a requirement
to continue to provide support service, warranty, or updates for a work that has been
modified or installed by the recipient, or for the User Product in which it has been
modified or installed. Access to a network may be denied when the modification itself
materially and adversely affects the operation of the network or violates the rules and
protocols for communication across the network.
Corresponding Source conveyed, and Installation Information provided, in accord with
this section must be in a format that is publicly documented (and with an implementa-
tion available to the public in source code form), and must require no special password
or key for unpacking, reading or copying.
7. Additional Terms.
“Additional permissions” are terms that supplement the terms of this License by mak-
ing exceptions from one or more of its conditions. Additional permissions that are
applicable to the entire Program shall be treated as though they were included in this
License, to the extent that they are valid under applicable law. If additional permis-
sions apply only to part of the Program, that part may be used separately under those
permissions, but the entire Program remains governed by this License without regard
to the additional permissions.
When you convey a copy of a covered work, you may at your option remove any
additional permissions from that copy, or from any part of it. (Additional permissions
may be written to require their own removal in certain cases when you modify the
work.) You may place additional permissions on material, added by you to a covered
work, for which you have or can give appropriate copyright permission.
Notwithstanding any other provision of this License, for material you add to a covered
work, you may (if authorized by the copyright holders of that material) supplement
the terms of this License with terms:
a. Disclaiming warranty or limiting liability differently from the terms of sections 15
and 16 of this License; or
b. Requiring preservation of specified reasonable legal notices or author attributions
in that material or in the Appropriate Legal Notices displayed by works containing
it; or
c. Prohibiting misrepresentation of the origin of that material, or requiring that mod-
ified versions of such material be marked in reasonable ways as different from the
original version; or
Appendix A: Licenses 27
d. Limiting the use for publicity purposes of names of licensors or authors of the
material; or
e. Declining to grant rights under trademark law for use of some trade names, trade-
marks, or service marks; or
f. Requiring indemnification of licensors and authors of that material by anyone who
conveys the material (or modified versions of it) with contractual assumptions
of liability to the recipient, for any liability that these contractual assumptions
directly impose on those licensors and authors.
All other non-permissive additional terms are considered “further restrictions” within
the meaning of section 10. If the Program as you received it, or any part of it, con-
tains a notice stating that it is governed by this License along with a term that is a
further restriction, you may remove that term. If a license document contains a further
restriction but permits relicensing or conveying under this License, you may add to a
covered work material governed by the terms of that license document, provided that
the further restriction does not survive such relicensing or conveying.
If you add terms to a covered work in accord with this section, you must place, in the
relevant source files, a statement of the additional terms that apply to those files, or a
notice indicating where to find the applicable terms.
Additional terms, permissive or non-permissive, may be stated in the form of a sep-
arately written license, or stated as exceptions; the above requirements apply either
way.
8. Termination.
You may not propagate or modify a covered work except as expressly provided un-
der this License. Any attempt otherwise to propagate or modify it is void, and will
automatically terminate your rights under this License (including any patent licenses
granted under the third paragraph of section 11).
However, if you cease all violation of this License, then your license from a particular
copyright holder is reinstated (a) provisionally, unless and until the copyright holder
explicitly and finally terminates your license, and (b) permanently, if the copyright
holder fails to notify you of the violation by some reasonable means prior to 60 days
after the cessation.
Moreover, your license from a particular copyright holder is reinstated permanently if
the copyright holder notifies you of the violation by some reasonable means, this is the
first time you have received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after your receipt of the
notice.
Termination of your rights under this section does not terminate the licenses of parties
who have received copies or rights from you under this License. If your rights have
been terminated and not permanently reinstated, you do not qualify to receive new
licenses for the same material under section 10.
9. Acceptance Not Required for Having Copies.
You are not required to accept this License in order to receive or run a copy of the
Program. Ancillary propagation of a covered work occurring solely as a consequence of
using peer-to-peer transmission to receive a copy likewise does not require acceptance.
Appendix A: Licenses 28
However, nothing other than this License grants you permission to propagate or modify
any covered work. These actions infringe copyright if you do not accept this License.
Therefore, by modifying or propagating a covered work, you indicate your acceptance
of this License to do so.
10. Automatic Licensing of Downstream Recipients.
Each time you convey a covered work, the recipient automatically receives a license
from the original licensors, to run, modify and propagate that work, subject to this
License. You are not responsible for enforcing compliance by third parties with this
License.
An “entity transaction” is a transaction transferring control of an organization, or
substantially all assets of one, or subdividing an organization, or merging organizations.
If propagation of a covered work results from an entity transaction, each party to that
transaction who receives a copy of the work also receives whatever licenses to the work
the party’s predecessor in interest had or could give under the previous paragraph, plus
a right to possession of the Corresponding Source of the work from the predecessor in
interest, if the predecessor has it or can get it with reasonable efforts.
You may not impose any further restrictions on the exercise of the rights granted or
affirmed under this License. For example, you may not impose a license fee, royalty, or
other charge for exercise of rights granted under this License, and you may not initiate
litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent
claim is infringed by making, using, selling, offering for sale, or importing the Program
or any portion of it.
11. Patents.
A “contributor” is a copyright holder who authorizes use under this License of the
Program or a work on which the Program is based. The work thus licensed is called
the contributor’s “contributor version”.
A contributor’s “essential patent claims” are all patent claims owned or controlled by
the contributor, whether already acquired or hereafter acquired, that would be infringed
by some manner, permitted by this License, of making, using, or selling its contributor
version, but do not include claims that would be infringed only as a consequence of
further modification of the contributor version. For purposes of this definition, “con-
trol” includes the right to grant patent sublicenses in a manner consistent with the
requirements of this License.
Each contributor grants you a non-exclusive, worldwide, royalty-free patent license
under the contributor’s essential patent claims, to make, use, sell, offer for sale, import
and otherwise run, modify and propagate the contents of its contributor version.
In the following three paragraphs, a “patent license” is any express agreement or com-
mitment, however denominated, not to enforce a patent (such as an express permission
to practice a patent or covenant not to sue for patent infringement). To “grant” such
a patent license to a party means to make such an agreement or commitment not to
enforce a patent against the party.
If you convey a covered work, knowingly relying on a patent license, and the Corre-
sponding Source of the work is not available for anyone to copy, free of charge and under
the terms of this License, through a publicly available network server or other readily
accessible means, then you must either (1) cause the Corresponding Source to be so
Appendix A: Licenses 29
available, or (2) arrange to deprive yourself of the benefit of the patent license for this
particular work, or (3) arrange, in a manner consistent with the requirements of this
License, to extend the patent license to downstream recipients. “Knowingly relying”
means you have actual knowledge that, but for the patent license, your conveying the
covered work in a country, or your recipient’s use of the covered work in a country,
would infringe one or more identifiable patents in that country that you have reason
to believe are valid.
If, pursuant to or in connection with a single transaction or arrangement, you convey,
or propagate by procuring conveyance of, a covered work, and grant a patent license
to some of the parties receiving the covered work authorizing them to use, propagate,
modify or convey a specific copy of the covered work, then the patent license you grant
is automatically extended to all recipients of the covered work and works based on it.
A patent license is “discriminatory” if it does not include within the scope of its cover-
age, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the
rights that are specifically granted under this License. You may not convey a covered
work if you are a party to an arrangement with a third party that is in the business of
distributing software, under which you make payment to the third party based on the
extent of your activity of conveying the work, and under which the third party grants,
to any of the parties who would receive the covered work from you, a discriminatory
patent license (a) in connection with copies of the covered work conveyed by you (or
copies made from those copies), or (b) primarily for and in connection with specific
products or compilations that contain the covered work, unless you entered into that
arrangement, or that patent license was granted, prior to 28 March 2007.
Nothing in this License shall be construed as excluding or limiting any implied license or
other defenses to infringement that may otherwise be available to you under applicable
patent law.
12. No Surrender of Others’ Freedom.
If conditions are imposed on you (whether by court order, agreement or otherwise) that
contradict the conditions of this License, they do not excuse you from the conditions
of this License. If you cannot convey a covered work so as to satisfy simultaneously
your obligations under this License and any other pertinent obligations, then as a
consequence you may not convey it at all. For example, if you agree to terms that
obligate you to collect a royalty for further conveying from those to whom you convey
the Program, the only way you could satisfy both those terms and this License would
be to refrain entirely from conveying the Program.
13. Use with the GNU Affero General Public License.
Notwithstanding any other provision of this License, you have permission to link or
combine any covered work with a work licensed under version 3 of the GNU Affero
General Public License into a single combined work, and to convey the resulting work.
The terms of this License will continue to apply to the part which is the covered work,
but the special requirements of the GNU Affero General Public License, section 13,
concerning interaction through a network will apply to the combination as such.
14. Revised Versions of this License.
Appendix A: Licenses 30
The Free Software Foundation may publish revised and/or new versions of the GNU
General Public License from time to time. Such new versions will be similar in spirit
to the present version, but may differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Program specifies that
a certain numbered version of the GNU General Public License “or any later version”
applies to it, you have the option of following the terms and conditions either of that
numbered version or of any later version published by the Free Software Foundation.
If the Program does not specify a version number of the GNU General Public License,
you may choose any version ever published by the Free Software Foundation.
If the Program specifies that a proxy can decide which future versions of the GNU
General Public License can be used, that proxy’s public statement of acceptance of a
version permanently authorizes you to choose that version for the Program.
Later license versions may give you additional or different permissions. However, no
additional obligations are imposed on any author or copyright holder as a result of your
choosing to follow a later version.
15. Disclaimer of Warranty.
THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PER-
MITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN
WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE
THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EX-
PRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE
OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFEC-
TIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
CORRECTION.
16. Limitation of Liability.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO
MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE
LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, IN-
CIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR
INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO
LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUS-
TAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM
TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR
OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAM-
AGES.
17. Interpretation of Sections 15 and 16.
If the disclaimer of warranty and limitation of liability provided above cannot be given
local legal effect according to their terms, reviewing courts shall apply local law that
most closely approximates an absolute waiver of all civil liability in connection with
the Program, unless a warranty or assumption of liability accompanies a copy of the
Program in return for a fee.
Appendix A: Licenses 31
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest possible use to
the public, the best way to achieve this is to make it free software which everyone can
redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest to attach them to the
start of each source file to most effectively state the exclusion of warranty; and each file
should have at least the “copyright” line and a pointer to where the full notice is found.
one line to give the program’s name and a brief idea of what it does.
Copyright (C) year name of author
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see https://www.gnu.org/licenses/.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short notice like this when it
starts in an interactive mode:
program Copyright (C) year name of author
This program comes with ABSOLUTELY NO WARRANTY; for details type ‘show w’.
This is free software, and you are welcome to redistribute it
under certain conditions; type ‘show c’ for details.
The hypothetical commands ‘show w’ and ‘show c’ should show the appropriate parts of
the General Public License. Of course, your program’s commands might be different; for a
GUI interface, you would use an “about box”.
You should also get your employer (if you work as a programmer) or school, if any, to
sign a “copyright disclaimer” for the program, if necessary. For more information on this,
and how to apply and follow the GNU GPL, see https://www.gnu.org/licenses/.
The GNU General Public License does not permit incorporating your program into
proprietary programs. If your program is a subroutine library, you may consider it more
useful to permit linking proprietary applications with the library. If this is what you want
to do, use the GNU Lesser General Public License instead of this License. But first, please
read https://www.gnu.org/licenses/why-not-lgpl.html.
Appendix A: Licenses 32
A.2 GNU Free Documentation License
Version 1.3, 3 November 2008
Copyright
c
2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
https://fsf.org/
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
0. PREAMBLE
The purpose of this License is to make a manual, textbook, or other functional and
useful document free in the sense of freedom: to assure everyone the effective freedom
to copy and redistribute it, with or without modifying it, either commercially or non-
commercially. Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible for modifications
made by others.
This License is a kind of “copyleft”, which means that derivative works of the document
must themselves be free in the same sense. It complements the GNU General Public
License, which is a copyleft license designed for free software.
We have designed this License in order to use it for manuals for free software, because
free software needs free documentation: a free program should come with manuals
providing the same freedoms that the software does. But this License is not limited to
software manuals; it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book. We recommend this License principally for
works whose purpose is instruction or reference.
1. APPLICABILITY AND DEFINITIONS
This License applies to any manual or other work, in any medium, that contains a
notice placed by the copyright holder saying it can be distributed under the terms
of this License. Such a notice grants a world-wide, royalty-free license, unlimited in
duration, to use that work under the conditions stated herein. The “Document”,
below, refers to any such manual or work. Any member of the public is a licensee, and
is addressed as “you”. You accept the license if you copy, modify or distribute the work
in a way requiring permission under copyright law.
A “Modified Version” of the Document means any work containing the Document or
a portion of it, either copied verbatim, or with modifications and/or translated into
another language.
A “Secondary Section” is a named appendix or a front-matter section of the Document
that deals exclusively with the relationship of the publishers or authors of the Document
to the Document’s overall subject (or to related matters) and contains nothing that
could fall directly within that overall subject. (Thus, if the Document is in part a
textbook of mathematics, a Secondary Section may not explain any mathematics.) The
relationship could be a matter of historical connection with the subject or with related
matters, or of legal, commercial, philosophical, ethical or political position regarding
them.
The “Invariant Sections” are certain Secondary Sections whose titles are designated, as
being those of Invariant Sections, in the notice that says that the Document is released
Appendix A: Licenses 33
under this License. If a section does not fit the above definition of Secondary then it is
not allowed to be designated as Invariant. The Document may contain zero Invariant
Sections. If the Document does not identify any Invariant Sections then there are none.
The “Cover Texts” are certain short passages of text that are listed, as Front-Cover
Texts or Back-Cover Texts, in the notice that says that the Document is released under
this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may
be at most 25 words.
A “Transparent” copy of the Document means a machine-readable copy, represented
in a format whose specification is available to the general public, that is suitable for
revising the document straightforwardly with generic text editors or (for images com-
posed of pixels) generic paint programs or (for drawings) some widely available drawing
editor, and that is suitable for input to text formatters or for automatic translation to
a variety of formats suitable for input to text formatters. A copy made in an otherwise
Transparent file format whose markup, or absence of markup, has been arranged to
thwart or discourage subsequent modification by readers is not Transparent. An image
format is not Transparent if used for any substantial amount of text. A copy that is
not “Transparent” is called “Opaque”.
Examples of suitable formats for Transparent copies include plain ASCII without
markup, Texinfo input format, LaT
E
X input format, SGML or XML using a publicly
available DTD, and standard-conforming simple HTML, PostScript or PDF designed
for human modification. Examples of transparent image formats include PNG, XCF
and JPG. Opaque formats include proprietary formats that can be read and edited
only by proprietary word processors, SGML or XML for which the DTD and/or pro-
cessing tools are not generally available, and the machine-generated HTML, PostScript
or PDF produced by some word processors for output purposes only.
The “Title Page” means, for a printed book, the title page itself, plus such following
pages as are needed to hold, legibly, the material this License requires to appear in the
title page. For works in formats which do not have any title page as such, “Title Page”
means the text near the most prominent appearance of the work’s title, preceding the
beginning of the body of the text.
The “publisher” means any person or entity that distributes copies of the Document
to the public.
A section “Entitled XYZ” means a named subunit of the Document whose title either
is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in
another language. (Here XYZ stands for a specific section name mentioned below, such
as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve
the Title” of such a section when you modify the Document means that it remains a
section “Entitled XYZ” according to this definition.
The Document may include Warranty Disclaimers next to the notice which states that
this License applies to the Document. These Warranty Disclaimers are considered to
be included by reference in this License, but only as regards disclaiming warranties:
any other implication that these Warranty Disclaimers may have is void and has no
effect on the meaning of this License.
2. VERBATIM COPYING
Appendix A: Licenses 34
You may copy and distribute the Document in any medium, either commercially or
noncommercially, provided that this License, the copyright notices, and the license
notice saying this License applies to the Document are reproduced in all copies, and
that you add no other conditions whatsoever to those of this License. You may not use
technical measures to obstruct or control the reading or further copying of the copies
you make or distribute. However, you may accept compensation in exchange for copies.
If you distribute a large enough number of copies you must also follow the conditions
in section 3.
You may also lend copies, under the same conditions stated above, and you may publicly
display copies.
3. COPYING IN QUANTITY
If you publish printed copies (or copies in media that commonly have printed covers) of
the Document, numbering more than 100, and the Document’s license notice requires
Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all
these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover. Both covers must also clearly and legibly identify you as the publisher
of these copies. The front cover must present the full title with all words of the title
equally prominent and visible. You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve the title of the
Document and satisfy these conditions, can be treated as verbatim copying in other
respects.
If the required texts for either cover are too voluminous to fit legibly, you should put
the first ones listed (as many as fit reasonably) on the actual cover, and continue the
rest onto adjacent pages.
If you publish or distribute Opaque copies of the Document numbering more than 100,
you must either include a machine-readable Transparent copy along with each Opaque
copy, or state in or with each Opaque copy a computer-network location from which
the general network-using public has access to download using public-standard network
protocols a complete Transparent copy of the Document, free of added material. If
you use the latter option, you must take reasonably prudent steps, when you begin
distribution of Opaque copies in quantity, to ensure that this Transparent copy will
remain thus accessible at the stated location until at least one year after the last time
you distribute an Opaque copy (directly or through your agents or retailers) of that
edition to the public.
It is requested, but not required, that you contact the authors of the Document well
before redistributing any large number of copies, to give them a chance to provide you
with an updated version of the Document.
4. MODIFICATIONS
You may copy and distribute a Modified Version of the Document under the conditions
of sections 2 and 3 above, provided that you release the Modified Version under precisely
this License, with the Modified Version filling the role of the Document, thus licensing
distribution and modification of the Modified Version to whoever possesses a copy of
it. In addition, you must do these things in the Modified Version:
A. Use in the Title Page (and on the covers, if any) a title distinct from that of the
Document, and from those of previous versions (which should, if there were any,
Appendix A: Licenses 35
be listed in the History section of the Document). You may use the same title as
a previous version if the original publisher of that version gives permission.
B. List on the Title Page, as authors, one or more persons or entities responsible for
authorship of the modifications in the Modified Version, together with at least five
of the principal authors of the Document (all of its principal authors, if it has fewer
than five), unless they release you from this requirement.
C. State on the Title page the name of the publisher of the Modified Version, as the
publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications adjacent to the other
copyright notices.
F. Include, immediately after the copyright notices, a license notice giving the public
permission to use the Modified Version under the terms of this License, in the form
shown in the Addendum below.
G. Preserve in that license notice the full lists of Invariant Sections and required Cover
Texts given in the Document’s license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled “History”, Preserve its Title, and add to it an item
stating at least the title, year, new authors, and publisher of the Modified Version
as given on the Title Page. If there is no section Entitled “History” in the Docu-
ment, create one stating the title, year, authors, and publisher of the Document
as given on its Title Page, then add an item describing the Modified Version as
stated in the previous sentence.
J. Preserve the network location, if any, given in the Document for public access to
a Transparent copy of the Document, and likewise the network locations given in
the Document for previous versions it was based on. These may be placed in the
“History” section. You may omit a network location for a work that was published
at least four years before the Document itself, or if the original publisher of the
version it refers to gives permission.
K. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title
of the section, and preserve in the section all the substance and tone of each of the
contributor acknowledgements and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document, unaltered in their text and
in their titles. Section numbers or the equivalent are not considered part of the
section titles.
M. Delete any section Entitled “Endorsements”. Such a section may not be included
in the Modified Version.
N. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in
title with any Invariant Section.
O. Preserve any Warranty Disclaimers.
If the Modified Version includes new front-matter sections or appendices that qualify
as Secondary Sections and contain no material copied from the Document, you may at
your option designate some or all of these sections as invariant. To do this, add their
Appendix A: Licenses 36
titles to the list of Invariant Sections in the Modified Version’s license notice. These
titles must be distinct from any other section titles.
You may add a section Entitled “Endorsements”, provided it contains nothing but
endorsements of your Modified Version by various parties—for example, statements of
peer review or that the text has been approved by an organization as the authoritative
definition of a standard.
You may add a passage of up to five words as a Front-Cover Text, and a passage of up
to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified
Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be
added by (or through arrangements made by) any one entity. If the Document already
includes a cover text for the same cover, previously added by you or by arrangement
made by the same entity you are acting on behalf of, you may not add another; but
you may replace the old one, on explicit permission from the previous publisher that
added the old one.
The author(s) and publisher(s) of the Document do not by this License give permission
to use their names for publicity for or to assert or imply endorsement of any Modified
Version.
5. COMBINING DOCUMENTS
You may combine the Document with other documents released under this License,
under the terms defined in section 4 above for modified versions, provided that you
include in the combination all of the Invariant Sections of all of the original documents,
unmodified, and list them all as Invariant Sections of your combined work in its license
notice, and that you preserve all their Warranty Disclaimers.
The combined work need only contain one copy of this License, and multiple identical
Invariant Sections may be replaced with a single copy. If there are multiple Invariant
Sections with the same name but different contents, make the title of each such section
unique by adding at the end of it, in parentheses, the name of the original author or
publisher of that section if known, or else a unique number. Make the same adjustment
to the section titles in the list of Invariant Sections in the license notice of the combined
work.
In the combination, you must combine any sections Entitled “History” in the vari-
ous original documents, forming one section Entitled “History”; likewise combine any
sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You
must delete all sections Entitled “Endorsements.”
6. COLLECTIONS OF DOCUMENTS
You may make a collection consisting of the Document and other documents released
under this License, and replace the individual copies of this License in the various
documents with a single copy that is included in the collection, provided that you
follow the rules of this License for verbatim copying of each of the documents in all
other respects.
You may extract a single document from such a collection, and distribute it individu-
ally under this License, provided you insert a copy of this License into the extracted
document, and follow this License in all other respects regarding verbatim copying of
that document.
Appendix A: Licenses 37
7. AGGREGATION WITH INDEPENDENT WORKS
A compilation of the Document or its derivatives with other separate and independent
documents or works, in or on a volume of a storage or distribution medium, is called
an “aggregate” if the copyright resulting from the compilation is not used to limit the
legal rights of the compilation’s users beyond what the individual works permit. When
the Document is included in an aggregate, this License does not apply to the other
works in the aggregate which are not themselves derivative works of the Document.
If the Cover Text requirement of section 3 is applicable to these copies of the Document,
then if the Document is less than one half of the entire aggregate, the Document’s Cover
Texts may be placed on covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form. Otherwise they
must appear on printed covers that bracket the whole aggregate.
8. TRANSLATION
Translation is considered a kind of modification, so you may distribute translations
of the Document under the terms of section 4. Replacing Invariant Sections with
translations requires special permission from their copyright holders, but you may
include translations of some or all Invariant Sections in addition to the original versions
of these Invariant Sections. You may include a translation of this License, and all the
license notices in the Document, and any Warranty Disclaimers, provided that you
also include the original English version of this License and the original versions of
those notices and disclaimers. In case of a disagreement between the translation and
the original version of this License or a notice or disclaimer, the original version will
prevail.
If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “His-
tory”, the requirement (section 4) to Preserve its Title (section 1) will typically require
changing the actual title.
9. TERMINATION
You may not copy, modify, sublicense, or distribute the Document except as expressly
provided under this License. Any attempt otherwise to copy, modify, sublicense, or
distribute it is void, and will automatically terminate your rights under this License.
However, if you cease all violation of this License, then your license from a particular
copyright holder is reinstated (a) provisionally, unless and until the copyright holder
explicitly and finally terminates your license, and (b) permanently, if the copyright
holder fails to notify you of the violation by some reasonable means prior to 60 days
after the cessation.
Moreover, your license from a particular copyright holder is reinstated permanently if
the copyright holder notifies you of the violation by some reasonable means, this is the
first time you have received notice of violation of this License (for any work) from that
copyright holder, and you cure the violation prior to 30 days after your receipt of the
notice.
Termination of your rights under this section does not terminate the licenses of parties
who have received copies or rights from you under this License. If your rights have
been terminated and not permanently reinstated, receipt of a copy of some or all of the
same material does not give you any rights to use it.
Appendix A: Licenses 38
10. FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of the GNU Free
Documentation License from time to time. Such new versions will be similar in spirit
to the present version, but may differ in detail to address new problems or concerns.
See https://www.gnu.org/copyleft/.
Each version of the License is given a distinguishing version number. If the Document
specifies that a particular numbered version of this License “or any later version”
applies to it, you have the option of following the terms and conditions either of that
specified version or of any later version that has been published (not as a draft) by
the Free Software Foundation. If the Document does not specify a version number of
this License, you may choose any version ever published (not as a draft) by the Free
Software Foundation. If the Document specifies that a proxy can decide which future
versions of this License can be used, that proxy’s public statement of acceptance of a
version permanently authorizes you to choose that version for the Document.
11. RELICENSING
“Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide
Web server that publishes copyrightable works and also provides prominent facilities
for anybody to edit those works. A public wiki that anybody can edit is an example of
such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the
site means any set of copyrightable works thus published on the MMC site.
“CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license pub-
lished by Creative Commons Corporation, a not-for-profit corporation with a principal
place of business in San Francisco, California, as well as future copyleft versions of that
license published by that same organization.
“Incorporate” means to publish or republish a Document, in whole or in part, as part
of another Document.
An MMC is “eligible for relicensing” if it is licensed under this License, and if all works
that were first published under this License somewhere other than this MMC, and
subsequently incorporated in whole or in part into the MMC, (1) had no cover texts
or invariant sections, and (2) were thus incorporated prior to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the site under
CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is
eligible for relicensing.
Appendix A: Licenses 39
ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of the License in the
document and put the following copyright and license notices just after the title page:
Copyright (C) year your name.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
Texts. A copy of the license is included in the section entitled ‘‘GNU
Free Documentation License’’.
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the
“with. . . Texts.” line with this:
with the Invariant Sections being list their titles, with
the Front-Cover Texts being list, and with the Back-Cover Texts
being list.
If you have Invariant Sections without Cover Texts, or some other combination of the
three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing
these examples in parallel under your choice of free software license, such as the GNU
General Public License, to permit their use in free software.
Function Index 40
Function Index
F
fd_ostream_create. . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
fd_ostream_get_descriptor . . . . . . . . . . . . . . . . . . 18
fd_ostream_get_filename. . . . . . . . . . . . . . . . . . . . . 18
fd_ostream_is_buffered . . . . . . . . . . . . . . . . . . . . . . 18
file_ostream_create . . . . . . . . . . . . . . . . . . . . . . . . . 13
file_ostream_get_stdio_stream . . . . . . . . . . . . . . 18
H
handle_color_option . . . . . . . . . . . . . . . . . . . . . . . . . 10
handle_style_option . . . . . . . . . . . . . . . . . . . . . . . . . 10
html_ostream_begin_span. . . . . . . . . . . . . . . . . . . . . 15
html_ostream_create . . . . . . . . . . . . . . . . . . . . . . . . . 15
html_ostream_end_span . . . . . . . . . . . . . . . . . . . . . . . 15
html_ostream_flush_to_current_style . . . . . . . 16
html_ostream_get_destination . . . . . . . . . . . . . . . 19
html_ostream_get_hyperlink_ref. . . . . . . . . . . . . 15
html_ostream_set_hyperlink_ref. . . . . . . . . . . . . 15
html_styled_ostream_create . . . . . . . . . . . . . . . . . 17
html_styled_ostream_get_css_filename . . . . . . 19
html_styled_ostream_get_destination . . . . . . . 19
html_styled_ostream_get_html_destination
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
I
iconv_ostream_create . . . . . . . . . . . . . . . . . . . . . . . . 16
iconv_ostream_get_destination . . . . . . . . . . . . . . 18
iconv_ostream_get_from_encoding . . . . . . . . . . . 18
iconv_ostream_get_to_encoding . . . . . . . . . . . . . . 18
is_instance_of_fd_ostream . . . . . . . . . . . . . . . . . . 11
is_instance_of_file_ostream . . . . . . . . . . . . . . . . 11
is_instance_of_html_ostream . . . . . . . . . . . . . . . . 11
is_instance_of_html_styled_ostream . . . . . . . . 11
is_instance_of_iconv_ostream . . . . . . . . . . . . . . . 11
is_instance_of_memory_ostream . . . . . . . . . . . . . . 11
is_instance_of_noop_styled_ostream . . . . . . . . 11
is_instance_of_styled_ostream . . . . . . . . . . . . . . 11
is_instance_of_term_ostream . . . . . . . . . . . . . . . . 11
is_instance_of_term_styled_ostream . . . . . . . . 11
M
memory_ostream_contents. . . . . . . . . . . . . . . . . . . . . 16
memory_ostream_create . . . . . . . . . . . . . . . . . . . . . . . 16
N
noop_styled_ostream_create . . . . . . . . . . . . . . . . . 18
noop_styled_ostream_get_destination . . . . . . . 19
noop_styled_ostream_is_owning_destination
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
O
ostream_flush . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ostream_free . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ostream_printf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ostream_vprintf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ostream_write_mem. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ostream_write_str. . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
P
print_color_test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
S
style_file_prepare . . . . . . . . . . . . . . . . . . . . . . . . . . 10
styled_ostream_begin_use_class. . . . . . . . . . . . . 12
styled_ostream_create . . . . . . . . . . . . . . . . . . . . . . . 17
styled_ostream_end_use_class . . . . . . . . . . . . . . . 12
styled_ostream_flush_to_current_style. . . . . 12
styled_ostream_get_hyperlink_id . . . . . . . . . . . 12
styled_ostream_get_hyperlink_ref . . . . . . . . . . 12
styled_ostream_set_hyperlink . . . . . . . . . . . . . . . 12
T
term_ostream_create . . . . . . . . . . . . . . . . . . . . . . . . . 13
term_ostream_flush_to_current_style . . . . . . . 15
term_ostream_get_bgcolor . . . . . . . . . . . . . . . . . . . 14
term_ostream_get_color . . . . . . . . . . . . . . . . . . . . . . 13
term_ostream_get_descriptor . . . . . . . . . . . . . . . . 18
term_ostream_get_effective_tty_control . . . 18
term_ostream_get_filename . . . . . . . . . . . . . . . . . . 18
term_ostream_get_hyperlink_id . . . . . . . . . . . . . . 14
term_ostream_get_hyperlink_ref. . . . . . . . . . . . . 14
term_ostream_get_posture . . . . . . . . . . . . . . . . . . . 14
term_ostream_get_tty_control . . . . . . . . . . . . . . . 18
term_ostream_get_underline . . . . . . . . . . . . . . . . . 14
term_ostream_get_weight. . . . . . . . . . . . . . . . . . . . . 14
term_ostream_rgb_to_color . . . . . . . . . . . . . . . . . . 13
term_ostream_set_bgcolor . . . . . . . . . . . . . . . . . . . 14
term_ostream_set_color . . . . . . . . . . . . . . . . . . . . . . 13
term_ostream_set_hyperlink . . . . . . . . . . . . . . . . . 14
term_ostream_set_posture . . . . . . . . . . . . . . . . . . . 14
term_ostream_set_underline . . . . . . . . . . . . . . . . . 14
term_ostream_set_weight. . . . . . . . . . . . . . . . . . . . . 14
term_styled_ostream_create . . . . . . . . . . . . . . . . . 17
term_styled_ostream_get_css_filename . . . . . . 19
term_styled_ostream_get_destination . . . . . . . 19
Variable Index 41
Variable Index
C
color_mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
color_test_mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
N
NO_COLOR, environment variable . . . . . . . . . . . . . . . . . 4
NO_TERM_HYPERLINKS, environment variable . . . . . 4
S
style_file_name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
T
TERM, environment variable . . . . . . . . . . . . . . . . . . . . . . 3
General Index 42
General Index
-
--color option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
--style option . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
<
<textstyle.h> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
D
Debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7, 19
F
FDL, GNU Free Documentation License . . . . . . . 32
G
GPL, GNU General Public License . . . . . . . . . . . . 21
I
Include file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
L
License, GNU FDL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
License, GNU GPL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Licenses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
