#+title:                 standard-themes: Like the default theme but more consistent
#+author:                Protesilaos Stavrou
#+email:                 info@protesilaos.com
#+language:              en
#+options:               ':t toc:nil author:t email:t num:t
#+startup:               content
#+macro:                 stable-version 1.0.0
#+macro:                 release-date 2022-11-30
#+macro:                 development-version 1.1.0-dev
#+export_file_name:      standard-themes.texi
#+texinfo_filename:      standard-themes.info
#+texinfo_dir_category:  Emacs misc features
#+texinfo_dir_title:     Standard-Themes: (standard-themes)
#+texinfo_dir_desc:      Like the default theme but more consistent
#+texinfo_header:        @set MAINTAINERSITE @uref{https://protesilaos.com,maintainer webpage}
#+texinfo_header:        @set MAINTAINER Protesilaos Stavrou
#+texinfo_header:        @set MAINTAINEREMAIL @email{info@protesilaos.com}
#+texinfo_header:        @set MAINTAINERCONTACT @uref{mailto:info@protesilaos.com,contact the maintainer}

#+texinfo: @insertcopying

This manual, written by Protesilaos Stavrou, describes the Emacs package
called =standard-themes=, and provides every other piece of information
pertinent to it.

The documentation furnished herein corresponds to stable version
{{{stable-version}}}, released on {{{release-date}}}.  Any reference to
a newer feature which does not yet form part of the latest tagged
commit, is explicitly marked as such.

Current development target is {{{development-version}}}.

+ Package name (GNU ELPA): =standard-themes=
+ Official manual: <https://protesilaos.com/emacs/standard-themes>
+ Git repo on SourceHut: <https://git.sr.ht/~protesilaos/standard-themes>
  - Mirrors:
    + GitHub: <https://github.com/protesilaos/standard-themes>
    + GitLab: <https://gitlab.com/protesilaos/standard-themes>
+ Mailing list: <https://lists.sr.ht/~protesilaos/standard-themes>
+ Backronym: Standard Themes Are Not Derivatives but the
  Affectionately Reimagined Default ... themes.

If you are viewing the README.org version of this file, please note that
the GNU ELPA machinery automatically generates an Info manual out of it.

#+toc: headlines 8 insert TOC here, with eight headline levels

* COPYING
:PROPERTIES:
:COPYING: t
:CUSTOM_ID: h:1164c8e7-6b52-433c-a2a1-1bf181ca2752
:END:

Copyright (C) 2022  Free Software Foundation, Inc.

#+begin_quote
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, with the Front-Cover Texts being “A GNU Manual,” and
with the Back-Cover Texts as in (a) below.  A copy of the license is
included in the section entitled “GNU Free Documentation License.”

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and
modify this GNU manual.”
#+end_quote

* About the Standard themes
:PROPERTIES:
:CUSTOM_ID: h:fd5bf657-937d-4e42-b936-b423ef4f45ee
:END:

The ~standard-themes~ are a pair of light and dark themes for GNU
Emacs.  They emulate the out-of-the-box looks of Emacs (which
technically do NOT constitute a theme) while bringing to them thematic
consistency, customizability, and extensibility.

* Installation
:PROPERTIES:
:CUSTOM_ID: h:3306414a-e56a-4fda-b70a-73a4140cfa0a
:END:
#+cindex: Installation instructions

** GNU ELPA package
:PROPERTIES:
:CUSTOM_ID: h:cb6ae4d6-76a1-4bc3-90af-aafcaa05dc35
:END:

The package is available as =standard-themes=.  Simply do:

: M-x package-refresh-contents
: M-x package-install

And search for it.

GNU ELPA provides the latest stable release.  Those who prefer to follow
the development process in order to report bugs or suggest changes, can
use the version of the package from the GNU-devel ELPA archive.  Read:
https://protesilaos.com/codelog/2022-05-13-emacs-elpa-devel/.

** Manual installation
:PROPERTIES:
:CUSTOM_ID: h:49a5e35d-834e-434f-a8f2-d3a69b688d63
:END:

Assuming your Emacs files are found in =~/.emacs.d/=, execute the
following commands in a shell prompt:

#+begin_src sh
cd ~/.emacs.d

# Create a directory for manually-installed packages
mkdir manual-packages

# Go to the new directory
cd manual-packages

# Clone this repo, naming it "standard-themes"
git clone https://git.sr.ht/~protesilaos/standard-themes standard-themes
#+end_src

Finally, in your =init.el= (or equivalent) evaluate this:

#+begin_src emacs-lisp
;; Make Elisp files in that directory available to the user.
(add-to-list 'load-path "~/.emacs.d/manual-packages/standard-themes")
#+end_src

Everything is in place to set up the package.

* Sample configuration
:PROPERTIES:
:CUSTOM_ID: h:7141f66d-f1b3-4c9a-b07a-f8e78068dcdc
:END:

#+begin_src emacs-lisp
;; Make customisations that affect Emacs faces BEFORE loading a theme
;; (any change needs a theme re-load to take effect).
(require 'standard-themes)

;; Read the doc string of each of those user options.  These are some
;; sample values.
(setq standard-themes-bold-constructs t
      standard-themes-italic-constructs t
      standard-themes-mixed-fonts t
      standard-themes-variable-pitch-ui t
      standard-themes-mode-line-accented t

      ;; Accepts a symbol value:
      standard-themes-fringes 'subtle

      ;; The following accept lists of properties
      standard-themes-links '(neutral-underline)
      standard-themes-region '(no-extend neutral intense)
      standard-themes-prompts '(bold italic)

      ;; more complex alist to set weight, height, and optional
      ;; `variable-pitch' per heading level (t is for any level not
      ;; specified):
      standard-themes-headings
      '((0 . (variable-pitch light 1.9))
        (1 . (variable-pitch light 1.8))
        (2 . (variable-pitch light 1.7))
        (3 . (variable-pitch semilight 1.6))
        (4 . (variable-pitch semilight 1.5))
        (5 . (variable-pitch 1.4))
        (6 . (variable-pitch 1.3))
        (7 . (variable-pitch 1.2))
        (t . (variable-pitch 1.1))))

;; Disable all other themes to avoid awkward blending:
(mapc #'disable-theme custom-enabled-themes)

(load-theme 'standard-light :no-confirm)

(define-key global-map (kbd "<f5>") #'standard-themes-toggle)
#+end_src

* Customization options
:PROPERTIES:
:CUSTOM_ID: h:c3975e07-8bbb-42b2-a160-27e3afeb3258
:END:

The =standard-themes= provide user options which tweak secondary
aspects of the theme.  All customizations need to be evaluated before
loading a theme.  Any change after the theme has been loaded require a
re-load ([[#h:59c399d6-5dca-4686-b793-255be8bffc31][Loading a theme]]).

** Enable mixed fonts
:PROPERTIES:
:CUSTOM_ID: h:a939ee30-f705-4d70-aa00-cca5528ef172
:END:

#+vindex: standard-themes-mixed-fonts
The user option ~standard-themes-mixed-fonts~ controls whether strictly
spacing-sensitive constructs inherit from ~fixed-pitch~ (a monospaced
font family).

By default (a ~nil~ value for this user option) no face inherits from
~fixed-pitch~: they all use the default font family, regardless of
whether it is monospaced or not.

When ~standard-themes-mixed-fonts~ is set to a non-~nil~ value, faces
such as for Org tables, inline code, code blocks, and the like, are
rendered in a monospaced font at all times.  The user can thus set
their default font family to a proportionately spaced font without
worrying about breaking the alignment of relevant elements, or if they
simply prefer the aesthetics of mixed mono and proportionately spaced
font families.

A temporary switch to a proportionately spaced font (known in Emacs as
~variable-pitch~) can be enabled in the current buffer with the
activation of the built-in ~variable-pitch-mode~.

To get consistent typography, the user may need to edit the font
family of the ~fixed-pitch~ and ~variable-pitch~ faces.  The
=fontaine= package on GNU ELPA (by Protesilaos) can be helpful in this
regard.

** Accented mode line
:PROPERTIES:
:CUSTOM_ID: h:7ccb3fce-4980-4bd6-9281-bdf5fc750902
:END:

#+vindex: standard-themes-mode-line-accented
The user option ~standard-themes-mode-line-accented~ handles the
background color of the active mode line.  When the value is ~nil~,
the color is gray, while non-~nil~ uses an accent value.

** UI typeface
:PROPERTIES:
:CUSTOM_ID: h:fbe4de97-f582-4a53-93cb-6ed4747cdc42
:END:

#+vindex: standard-themes-variable-pitch-ui
The user option ~standard-themes-variable-pitch-ui~ controls whether
the elements of the User Interface (UI) use a proportionately spaced
font.  By default (a ~nil~ value), all UI elements use the default
font family.  When this user option is set to a non-~nil~ value, all
UI elements will inherit the face ~variable-pitch~, thus rendering
them in a proportionately spaced font.

In this context, the UI elements are:

- ~header-line~
- ~mode-line~ (active and inactive)
- ~tab-bar-mode~
- ~tab-line-mode~

To get consistent typography, the user may need to edit the font
family of the ~fixed-pitch~ and ~variable-pitch~ faces.  The
=fontaine= package on GNU ELPA (by Protesilaos) can be helpful in this
regard.

** Bold constructs
:PROPERTIES:
:CUSTOM_ID: h:9bd84648-681b-4369-9868-4f89f2d6abf5
:END:

#+vindex: standard-themes-bold-constructs
The user option ~standard-themes-bold-constructs~ determines whether
select faces will inherit the ~bold~ face.  When the value is
non-~nil~, a bold weight is applied to code constructs.  This affects
keywords, builtins, and a few other elements.

[[#h:2c92df8a-02c5-4124-82f8-e3ccdef1a4f8][Configure bold and italic faces]].

** Italic constructs
:PROPERTIES:
:CUSTOM_ID: h:a49f7515-04cb-4932-a75c-e45080f12c28
:END:

#+vindex: standard-themes-italic-constructs
The user option ~standard-themes-italic-constructs~ determines whether
select faces will inherit the ~italic~ face.  When the value is
non-~nil~, an italic style is applied to code constructs.  This
affects comments, doc strings, and a few other minor elements.

[[#h:2c92df8a-02c5-4124-82f8-e3ccdef1a4f8][Configure bold and italic faces]].

** Fringe visibility
:PROPERTIES:
:CUSTOM_ID: h:a04db578-dacc-422e-a3a9-e4b41afd9b0b
:END:

#+vindex: standard-themes-fringes
The user option ~standard-themes-fringes~ controls the visibility and
intensity of the fringes.  With regular Emacs settings "Fringe" is a
small surface area to either side of the Emacs window: it is where
certain indicators are displayed, such as continuation lines.

When the value is ~nil~, do not apply a distinct background color.

With a value of ~subtle~, use a gray background color that is visible
yet close to the main background color.  This is the default style.

With ~intense~, use a more pronounced gray background color.

** Link style
:PROPERTIES:
:CUSTOM_ID: h:b92555bf-1542-40f6-945b-f59849e6446c
:END:

#+vindex: standard-themes-links
The user option ~standard-themes-links~ controls the style of links.
The value is a list of properties, each designated by a symbol.  The
default (a ~nil~ value or an empty list) is a prominent text color,
typically blue, with an underline of the same color.

For the style of the underline, a ~neutral-underline~ property
turns the color of the line into a subtle gray, while the
~no-underline~ property removes the line altogether.  If both of
those are set, the latter takes precedence.

For text coloration, a ~faint~ property desaturates the color of
the text and the underline, unless the underline is affected by
the aforementioned properties.

A ~bold~ property applies a heavy typographic weight to the text
of the link.

An ~italic~ property adds a slant to the link's text (italic or
oblique forms, depending on the typeface).

Combinations of any of those properties are expressed as a list,
like in these examples:

#+begin_src emacs-lisp
(faint)
(no-underline faint)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq standard-themes-links '(neutral-underline faint))
#+end_src

The placement of the underline, meaning its proximity to the
text, is controlled by ~x-use-underline-position-properties~,
~x-underline-at-descent-line~, ~underline-minimum-offset~.
Please refer to their documentation strings.

** Option for command prompts
:PROPERTIES:
:CUSTOM_ID: h:eedd0b6b-9f84-48bc-8871-620934506aa6
:END:

#+vindex: standard-themes-prompts
The user option ~standard-themes-prompts~ controls the style of all
prompts, such as those of the minibuffer and REPLs.

The value is a list of properties, each designated by a symbol.  The
default (a ~nil~ value or an empty list) means to only use an accented
foreground color.

The property ~background~ applies a background color to the prompt's
text and adjusts the foreground accordingly.

The property ~bold~ makes the text use a bold typographic weight.
Similarly, ~italic~ adds a slant to the font's forms (italic or
oblique forms, depending on the typeface).

Combinations of any of those properties are expressed as a list, like
in these examples:

#+begin_src emacs-lisp
(background)
(bold italic)
(background bold italic)
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq standard-themes-prompts '(background bold))
#+end_src

** Option for headings
:PROPERTIES:
:CUSTOM_ID: h:8540fd7a-7633-4eb9-af4b-4f160568f79a
:END:

#+vindex: standard-themes-headings
The user option ~standard-themes-headings~ provides support for individual
heading styles for levels 0 through 8.

This is an alist that accepts a =(KEY . LIST-OF-VALUES)= combination.
The =KEY= is either a number, representing the heading's level (0-8)
or ~t~, which pertains to the fallback style.  The fallback applies to
all heading levels that are not customized.

Level 0 is a special heading: it is used for what counts as a document
title or equivalent, such as the =#+TITLE= construct we find in Org
files.  Levels 1-8 are regular headings.

The list of values covers symbols that refer to properties, as
described below.  Here is a complete sample, followed by a
presentation of all available properties:

#+begin_src emacs-lisp
(setq standard-themes-headings
      '((1 . (light variable-pitch 1.5))
        (2 . (regular 1.3))
        (3 . (1.1))
        (t . (variable-pitch))))
#+end_src

By default (a ~nil~ value for this variable), all headings have a normal
typographic weight, a font family that is the same as the ~default~ face
(typically monospaced), and a height that is equal to the ~default~
face's height.

- A ~variable-pitch~ property changes the font family of the heading
  to that of the ~variable-pitch~ face (normally a proportionately
  spaced typeface).  Also check the =fontaine= package (by
  Protesilaos) for tweaking fonts via faces.

- The symbol of a weight attribute adjusts the font of the heading
  accordingly, such as ~light~, ~semibold~, etc.  Valid symbols are
  defined in the variable ~standard-themes-weights~.  The absence of a
  weight means that no distinct weight will be used.

- A number, expressed as a floating point (e.g. 1.5), adjusts the
  height of the heading to that many times the base font size.  The
  default height is the same as 1.0, though it need not be explicitly
  stated.  Instead of a floating point, an acceptable value can be in
  the form of a cons cell like =(height . FLOAT)= or =(height FLOAT)=,
  where =FLOAT= is the given number.

Combinations of any of those properties are expressed as a list, like
in these examples:

#+begin_src emacs-lisp
(semibold)
(variable-pitch semibold)
(variable-pitch semibold 1.3)
(variable-pitch semibold (height 1.3))   ; same as above
(variable-pitch semibold (height . 1.3)) ; same as above
#+end_src

The order in which the properties are set is not significant.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq standard-themes-headings
      '((1 . (light variable-pitch 1.5))
        (2 . (regular 1.3))
        (3 . (1.1))
        (t . (variable-pitch))))
#+end_src

When defining the styles per heading level, it is possible to
pass a non-~nil~ value (t) instead of a list of properties.  This
will retain the original aesthetic for that level.  For example:

#+begin_src emacs-lisp
(setq standard-themes-headings
      '((1 . t)           ; keep the default style
        (2 . (variable-pitch 1.2))
        (t . (variable-pitch)))) ; style for all unspecified headings

(setq standard-themes-headings
      '((1 . (variable-pitch 1.6))
        (2 . (1.3))
        (t . t))) ; default style for all unspecified levels
#+end_src

** Style of region highlight
:PROPERTIES:
:CUSTOM_ID: h:827e4fff-0416-4eba-a364-a6588f80b768
:END:

#+vindex: standard-themes-region
The user option ~standard-themes-region~ controls the appearance of
the ~region~ face (the highlighted selection of an area).

The value it accepts is a list of symbols.

If ~nil~ or an empty list (the default), use a subtle background for
the region and preserve the color of selected text.

The ~no-extend~ symbol limits the highlighted area to the end of the
line, so that it does not reach the edge of the window.

The ~neutral~ symbol makes the highlighted area's background gray (or
more gray, depending on the theme).

The ~intense~ symbol amplifies the intensity of the highlighted area's
background color.  It also overrides any text color to keep it
legible.

Combinations of those symbols are expressed in any order.

In user configuration files the form may look like this:

#+begin_src emacs-lisp
(setq standard-themes-region '(intense no-extend))
#+end_src

Other examples:

#+begin_src emacs-lisp
(setq standard-themes-region '(intense))
(setq standard-themes-region '(intense no-extend neutral))
#+end_src

* Loading a theme
:PROPERTIES:
:CUSTOM_ID: h:59c399d6-5dca-4686-b793-255be8bffc31
:END:

Emacs can load and maintain enabled multiple themes at once.  This
typically leads to awkward styling and weird combinations.  The theme
looks broken and the designer's intent is misunderstood.  Before
loading either of the =standard-themes=, the user is encouraged to
disable all others:

#+begin_src emacs-lisp
(mapc #'disable-theme custom-enabled-themes)
#+end_src

Then load the theme of choice.  For example:

#+begin_src emacs-lisp
(load-theme 'standard-light :no-confirm)
#+end_src

The =:no-confirm= is optional.  It simply skips the step where Emacs
asks the user whether they are sure about loading the theme.

Consider adding code like the above to the user configuration file, such
as =init.el=.

#+findex: standard-themes-load-dark
#+findex: standard-themes-load-light
#+findex: standard-themes-toggle
As the Standard themes are extensible, another way to load the theme
of choice is to use either ~standard-themes-load-dark~ or
~standard-themes-load-light~.  These functions take care of (i)
disabling other themes, (ii) loading the specified Standard theme, and
(iii) running the ~standard-themes-post-load-hook~ which is useful for
do-it-yourself customizations ([[#h:a6d48445-c215-4f2e-b0ff-c83b0c673fa7][The general approach to DIY changes]]).
These two functions are also called by the command
~standard-themes-toggle~.

* Preview theme colors
:PROPERTIES:
:CUSTOM_ID: h:1eebe221-0d0c-43e8-877a-202d2f15ef34
:END:

#+findex: standard-themes-preview-colors
The command ~standard-themes-preview-colors~ uses minibuffer
completion to select an item from the Standard themes and then
produces a buffer with previews of its color palette entries.  The
buffer has a naming scheme which reflects the given choice, like
=standard-light-preview-colors= for the ~standard-light~ theme.

#+findex: standard-themes-preview-colors-current
The command ~standard-themes-preview-colors-current~ skips the
minibuffer selection process and just produces a preview for the
current Standard theme.

* Use colors from the active Standard theme
:PROPERTIES:
:CUSTOM_ID: h:a4d62b3e-0f90-4016-829a-6b6ff8ff7c23
:END:

#+findex: standard-themes-with-colors
Advanced users may want to call color variables from the palette of
the active Standard theme.  The macro ~standard-themes-with-colors~
supplies those to any form called inside of it.  For example:

#+begin_src emacs-lisp
(standard-themes-with-colors
  (list bg-main fg-main bg-mode-line))
;; => ("#ffffff" "#000000" "#b3b3b3")
#+end_src

The above return value is for =standard-light= when that is the active
Standard theme.  Switching to =standard-dark= and evaluating this code
anew will give us the relevant results for that theme:

#+begin_src emacs-lisp
(standard-themes-with-colors
  (list bg-main fg-main bg-mode-line cursor))
;; => ("#000000" "#ffffff" "#505050")
#+end_src

[[#h:a4f7a8fb-11a5-4e32-897b-f930b7d5c043][Do-It-Yourself customizations]].

The palette of each Standard theme is considered stable.  No removals
shall be made.  Though please note that some tweaks to individual hues
or color mapping are still possible.  At any rate, we will not
outright break any code that uses ~standard-themes-with-colors~.

* Do-It-Yourself customizations
:PROPERTIES:
:CUSTOM_ID: h:a4f7a8fb-11a5-4e32-897b-f930b7d5c043
:END:

This section shows how the user can tweak the Standard themes to their
liking, often by employing the ~standard-themes-with-colors~ macro
([[#h:a4d62b3e-0f90-4016-829a-6b6ff8ff7c23][Use colors from the active Standard theme]]).

** The general approach to advanced DIY changes
:PROPERTIES:
:CUSTOM_ID: h:a6d48445-c215-4f2e-b0ff-c83b0c673fa7
:END:

When the user wants to customize Emacs faces there are two
considerations they need to make if they care about robustness:

1. Do not hardcode color values, but instead use the relevant variables
   from the Standard themes.
2. Make the changes persist through theme changes between the Standard
   themes.

#+vindex: standard-themes-post-load-hook
For point 1 we provide the ~standard-themes-with-colors~ macro, while for
point 2 we have the ~standard-themes-post-load-hook~.  The hook runs
at the end of the command ~standard-themes-toggle~.

[[#h:a4d62b3e-0f90-4016-829a-6b6ff8ff7c23][Use colors from the active Standard theme]].

[[#h:4296ba7b-7bad-4dbe-9ce8-da20c957c99a][A theme-agnostic hook for theme loading]].

We need to wrap our code in the ~standard-themes-with-colors~ and
declare it as a function which we then add to the hook.  Here we show
the general approach of putting those pieces together.

To customize faces in a way that mirrors the Standard themes' source
code, we use the built-in ~custom-set-faces~.  The value it accepts
has the same syntax as that found in =standard-themes.el=,
specifically the ~standard-themes-faces~ constant.  It thus is easy to
copy lines from there and tweak them.  Let's pick a couple of
font-lock faces (used in all programming modes, among others):

#+begin_src emacs-lisp
(defun my-standard-themes-custom-faces ()
  "My customizations on top of the Standard themes.
This function is added to the `standard-themes-post-load-hook'."
  (standard-themes-with-colors
    (custom-set-faces
     ;; These are the default specifications
     `(font-lock-comment-face ((,c :inherit standard-themes-italic :foreground ,comment)))
     `(font-lock-variable-name-face ((,c :foreground ,variable))))))

;; Using the hook lets our changes persist when we use the commands
;; `standard-themes-toggle', `standard-themes-load-dark',
;; `standard-themes-load-light'.
(add-hook 'standard-themes-post-load-hook #'my-standard-themes-custom-faces)
#+end_src

Each of the Standard themes has its own color palette and
corresponding mapping of values to constructs.  So the color of the
=comment= variable will differ between the themes.  For the purpose of
our demonstration, we make variables look like comments and comments
like variables:

#+begin_src emacs-lisp
(defun my-standard-themes-custom-faces ()
  "My customizations on top of the Standard themes.
This function is added to the `standard-themes-post-load-hook'."
  (standard-themes-with-colors
    (custom-set-faces
     `(font-lock-comment-face ((,c :foreground ,variable)))
     `(font-lock-variable-name-face ((,c :inherit standard-themes-italic :foreground ,comment))))))

;; Using the hook lets our changes persist when we use the commands
;; `standard-themes-toggle', `standard-themes-load-dark',
;; `standard-themes-load-light'.
(add-hook 'standard-themes-post-load-hook #'my-standard-themes-custom-faces)
#+end_src

All changes take effect when a theme is loaded again.  As such, it is
better to use either ~standard-themes-load-dark~ or
~standard-themes-load-light~ at startup so that the function added to
the hook gets applied properly upon first load.  Like this:

#+begin_src emacs-lisp
(defun my-standard-themes-custom-faces ()
  "My customizations on top of the Standard themes.
This function is added to the `standard-themes-post-load-hook'."
  (standard-themes-with-colors
    (custom-set-faces
     `(font-lock-comment-face ((,c :foreground ,variable)))
     `(font-lock-variable-name-face ((,c :inherit standard-themes-italic :foreground ,comment))))))

;; Using the hook lets our changes persist when we use the commands
;; `standard-themes-toggle', `standard-themes-load-dark',
;; `standard-themes-load-light'.
(add-hook 'standard-themes-post-load-hook #'my-standard-themes-custom-faces)

;; Load the theme and run `standard-themes-post-load-hook'
(standard-themes-load-light) ; OR (standard-themes-load-dark)
#+end_src

Please contact us if you have specific questions about this mechanism.
We are willing to help and shall provide comprehensive documentation
where necessary.

** A theme-agnostic hook for theme loading
:PROPERTIES:
:CUSTOM_ID: h:4296ba7b-7bad-4dbe-9ce8-da20c957c99a
:END:

The themes are designed with the intent to be useful to Emacs users of
varying skill levels, from beginners to experts.  This means that we try
to make things easier by not expecting anyone reading this document to
be proficient in Emacs Lisp or programming in general.

Such a case is with the use of the ~standard-themes-post-load-hook~,
which is called after the evaluation of any of the commands we provide
for loading a theme ([[#h:59c399d6-5dca-4686-b793-255be8bffc31][Loading a theme]]).  We recommend using that hook
for advanced customizations, because (1) we know for sure that it is
available once the themes are loaded, and (2) anyone consulting this
manual, especially the sections on enabling and loading the themes,
will be in a good position to benefit from that hook.

Advanced users who have a need to switch between the Standard themes
and other items (e.g. the =modus-themes= and =ef-themes=) will find
that such a hook does not meet their requirements: it only works with
the Standard themes and only with the functions they provide.

A theme-agnostic setup can be configured thus:

#+begin_src emacs-lisp
(defvar after-enable-theme-hook nil
   "Normal hook run after enabling a theme.")

(defun run-after-enable-theme-hook (&rest _args)
   "Run `after-enable-theme-hook'."
   (run-hooks 'after-enable-theme-hook))

(advice-add 'enable-theme :after #'run-after-enable-theme-hook)
#+end_src

This creates the ~after-enable-theme-hook~ and makes it run after each
call to ~enable-theme~, which means that it will work for all themes
and also has the benefit that it does not depend on functions such as
~standard-themes-select~ and the others mentioned in this manual.  The
function ~enable-theme~ is called internally by ~load-theme~, so the
hook works everywhere.

The downside of the theme-agnostic hook is that any functions added to
it will likely not be able to benefit from macro calls that read the
active theme, such as ~standard-themes-with-colors~ (the Modus and Ef
themes have an equivalent macro).  Not all Emacs themes have the same
capabilities.

In this document, we always mention ~standard-themes-post-load-hook~
though the user can replace it with ~after-enable-theme-hook~ should
they need to (provided they understand the implications).

** Add support for hl-todo
:PROPERTIES:
:CUSTOM_ID: h:f9017f6b-a59d-4512-8d52-9e8ab5a59f87
:END:

The =hl-todo= package provides the user option ~hl-todo-keyword-faces~:
it specifies an association list of =(KEYWORD . COLOR-VALUE)= pairs.
There are no faces, which the theme could style seamlessly.  As such, it
rests on the user to specify appropriate color values.  This can be done
either by hardcoding colors, which is inefficient, or by using the macro
~standard-themes-with-colors~ ([[#h:a6d48445-c215-4f2e-b0ff-c83b0c673fa7][The general approach to DIY changes]]).
Here we show the latter method.

#+begin_src emacs-lisp
(defun my-standard-themes-hl-todo-faces ()
  "Configure `hl-todo-keyword-faces' with Standard themes colors.
The exact color values are taken from the active Standard theme."
  (standard-themes-with-colors
    (setq hl-todo-keyword-faces
          `(("HOLD" . ,yellow)
            ("TODO" . ,red)
            ("NEXT" . ,blue)
            ("THEM" . ,magenta)
            ("PROG" . ,cyan-warmer)
            ("OKAY" . ,green-warmer)
            ("DONT" . ,yellow-warmer)
            ("FAIL" . ,red-warmer)
            ("BUG" . ,red-warmer)
            ("DONE" . ,green)
            ("NOTE" . ,blue-warmer)
            ("KLUDGE" . ,cyan)
            ("HACK" . ,cyan)
            ("TEMP" . ,red)
            ("FIXME" . ,red-warmer)
            ("XXX+" . ,red-warmer)
            ("REVIEW" . ,red)
            ("DEPRECATED" . ,yellow)))))

(add-hook 'standard-themes-post-load-hook #'my-standard-themes-hl-todo-faces)
#+end_src

To find the names of the color variables, the user can rely on the
commands for previewing the palette ([[#h:1eebe221-0d0c-43e8-877a-202d2f15ef34][Preview theme colors]]).

** Configure bold and italic faces
:PROPERTIES:
:CUSTOM_ID: h:2c92df8a-02c5-4124-82f8-e3ccdef1a4f8
:END:
#+cindex: Bold and italic fonts

The Standard themes do not hardcode a ~:weight~ or ~:slant~ attribute in the
faces they cover.  Instead, they configure the generic faces called
~bold~ and ~italic~ to use the appropriate styles and then instruct all
relevant faces that require emphasis to inherit from them.

This practically means that users can change the particularities of what
it means for a construct to be bold/italic, by tweaking the ~bold~ and
~italic~ faces.  Cases where that can be useful include:

+ The default typeface does not have a variant with slanted glyphs
  (e.g. Fira Mono/Code as of this writing on 2022-11-30), so the user
  wants to add another family for the italics, such as Hack.

+ The typeface of choice provides a multitude of weights and the user
  prefers the light one by default.  To prevent the bold weight from
  being too heavy compared to the light one, they opt to make ~bold~ use a
  semibold weight.

+ The typeface distinguishes between oblique and italic forms by
  providing different font variants (the former are just slanted
  versions of the upright forms, while the latter have distinguishing
  features as well).  In this case, the user wants to specify the font
  that applies to the ~italic~ face.

To achieve those effects, one must first be sure that the fonts they use
have support for those features.

In this example, we set the default font family to Fira Code, while we
choose to render italics in the Hack typeface (obviously one needs to
pick fonts that work in tandem):

#+begin_src emacs-lisp
(set-face-attribute 'default nil :family "Fira Code" :height 110)
(set-face-attribute 'italic nil :family "Hack")
#+end_src

And here we play with different weights, using Source Code Pro:

#+begin_src emacs-lisp
(set-face-attribute 'default nil :family "Source Code Pro" :height 110 :weight 'light)
(set-face-attribute 'bold nil :weight 'semibold)
#+end_src

To reset the font family, one can use this:

#+begin_src emacs-lisp
(set-face-attribute 'italic nil :family 'unspecified)
#+end_src

Consider the =fontaine= package on GNU ELPA (by Protesilaos) which
provides the means to configure font families via faces.

** Tweak =org-modern= timestamps
:PROPERTIES:
:CUSTOM_ID: h:8c88f697-a14e-468d-935c-7576934e7092
:END:

The =org-modern= package uses faces and text properties to make Org
buffers more aesthetically pleasing.  It affects tables, timestamps,
lists, headings, and more.

In previous versions of the Standard themes, we mistakenly affected one of its
faces: the ~org-modern-label~.  It changed the intended looks and
prevented the user option ~org-modern-label-border~ from having its
desired effect.  As such, we no longer override that face.

Users who were used to the previous design and who generally do not
configure the user options of =org-modern= may thus notice a change in
how clocktables (or generally tables with timestamps) are aligned.  The
simplest solution is to instruct the mode to not prettify timestamps, by
setting the user option ~org-modern-timestamp~ to ~nil~.  For example, by
adding this to the init file:

#+begin_src emacs-lisp
(setq org-modern-timestamp nil)
#+end_src

Alignment in tables will also depend on the use of proportionately
spaced fonts.  Enable the relevant option to work with those without any
further trouble ([[#h:a939ee30-f705-4d70-aa00-cca5528ef172][Enable mixed fonts]]).

For any further issues, you are welcome to ask for help.

** Tweak goto-address-mode faces
:PROPERTIES:
:CUSTOM_ID: h:7d0b7091-63d1-49b3-992d-cd24d3103782
:END:

The built-in ~goto-address-mode~ uses heuristics to identify URLs and
email addresses in the current buffer.  It then applies a face to them
to change their style.  Some packages, such as =notmuch=, use this
minor-mode automatically.

The faces are not declared with ~defface~, meaning that it is better
that the theme does not modify them.  The user is thus encouraged to
consider including this in their setup:

#+begin_src emacs-lisp
(setq goto-address-url-face 'link
      goto-address-url-mouse-face 'highlight
      goto-address-mail-face 'link
      goto-address-mail-mouse-face 'highlight)
#+end_src

My personal preference is to set ~goto-address-mail-face~ to ~nil~,
because it otherwise adds too much visual noise to the buffer (email
addresses stand out more, due to the use of the uncommon =@= caharacter
but also because they are often enclosed in angled brackets).

* Faces defined by the Standard themes
:PROPERTIES:
:CUSTOM_ID: h:2553eaca-d9f7-4cb0-9b0b-63e1a22a40e7
:END:

The themes define some faces to make it possible to achieve
consistency between various groups of faces.  For example, all "marks
for selection" use the ~standard-themes-mark-select~ face.  If, say, the
user wants to edit this face to include an underline, the change will
apply to lots of packages, like Dired, Trashed, Ibuffer.

[[#h:a4f7a8fb-11a5-4e32-897b-f930b7d5c043][Do-It-Yourself customizations]].

All the faces defined by the themes:

+ ~standard-themes-bold~
+ ~standard-themes-fixed-pitch~
+ ~standard-themes-fringe-error~
+ ~standard-themes-fringe-info~
+ ~standard-themes-fringe-warning~
+ ~standard-themes-heading-0~
+ ~standard-themes-heading-1~
+ ~standard-themes-heading-2~
+ ~standard-themes-heading-3~
+ ~standard-themes-heading-4~
+ ~standard-themes-heading-5~
+ ~standard-themes-heading-6~
+ ~standard-themes-heading-7~
+ ~standard-themes-heading-8~
+ ~standard-themes-italic~
+ ~standard-themes-key-binding~
+ ~standard-themes-mark-delete~
+ ~standard-themes-mark-other~
+ ~standard-themes-mark-select~
+ ~standard-themes-ui-variable-pitch~
+ ~standard-themes-underline-error~
+ ~standard-themes-underline-info~
+ ~standard-themes-underline-warning~

* Supported packages or face groups
:PROPERTIES:
:CUSTOM_ID: h:f954364c-bc23-4230-b8ac-d8804bdbabd9
:END:

The =standard-themes= will only ever support a curated list of packages based
on my judgement ([[#h:52524f5a-633e-4e07-917d-06c6e663ec3f][Packages that are hard to support]]).  Nevertheless, the
list of explicitly or implicitly supported packages already covers
everything most users need.

** Explicitly supported packages or face groups
:PROPERTIES:
:CUSTOM_ID: h:9b2458f1-6f70-4f45-849d-f10782c9f18f
:END:

- all basic faces
- all-the-icons
- all-the-icons-dired
- all-the-icons-ibuffer
- ansi-color
- auctex
- auto-dim-other-buffers
- bongo
- bookmark
- calendar and diary
- cider
- change-log and log-view (part of VC)
- chart
- clojure-mode
- company
- compilation
- completions
- consult
- corfu
- custom (=M-x customize=)
- denote
- dictionary
- diff-hl
- diff-mode
- dired
- dired-subtree
- diredfl
- dirvish
- display-fill-column-indicator-mode
- doom-modeline
- ediff
- eglot
- eldoc
- elfeed
- embark
- epa
- eshell
- eww
- flycheck
- flymake
- flyspell
- font-lock
- git-commit
- git-rebase
- gnus
- hi-lock (=M-x highlight-regexp=)
- ibuffer
- image-dired
- info
- isearch, occur, query-replace
- keycast
- lin
- line numbers (~display-line-numbers-mode~ and global variant)
- magit
- man
- marginalia
- markdown-mode
- messages
- mode-line
- mu4e
- neotree
- notmuch
- olivetti
- orderless
- org
- org-habit
- org-modern
- outline-mode
- outline-minor-faces
- package (=M-x list-packages=)
- perspective
- pulsar
- pulse
- rainbow-delimiters
- rcirc
- recursion-indicator
- regexp-builder (re-builder)
- ruler-mode
- shell-script-mode (sh-mode)
- show-paren-mode
- shr
- smerge
- tab-bar-mode
- tab-line-mode
- tempel
- term
- textsec
- transient
- trashed
- tree-sitter
- tty-menu
- vc (=vc-dir.el=, =vc-hooks.el=)
- vertico
- wgrep
- which-function-mode
- whitespace-mode
- widget
- writegood-mode
- woman

** Implicitly supported packages or face groups
:PROPERTIES:
:CUSTOM_ID: h:d98d4a5a-6bf0-43e7-b129-875fa05654e7
:END:

Those are known to work with the Standard themes either because their colors
are appropriate or because they inherit from basic faces which the
themes already cover:

- apropos
- dim-autoload
- hl-todo
- icomplete
- ido
- multiple-cursors
- paren-face
- which-key
- xref

Note that "implicitly supported" does not mean that they always fit in
perfectly.  If there are refinements we need to made, then we need to
intervene ([[#h:9b2458f1-6f70-4f45-849d-f10782c9f18f][Explicitly supported packages or face groups]]).

** Packages that are hard to support
:PROPERTIES:
:CUSTOM_ID: h:52524f5a-633e-4e07-917d-06c6e663ec3f
:END:

These are difficult to support due to their (i) incompatibility with the
design of the =standard-themes=, (ii) complexity or multiple points of entry,
(iii) external dependencies, (iv) existence of better alternatives in my
opinion, or (v) inconsiderate use of color out-of-the-box and implicit
unwillingness to be good Emacs citizens:

- avy :: its UI is prone to visual breakage and is hard to style
  correctly.

- calibredb :: has an external dependency that I don't use.

- ctrlf :: use the built-in isearch or the ~consult-line~ command of
  =consult=.

- dired+ :: it is complex and makes inconsiderate use of color.

- ein (Emacs IPython Notebook) :: external dependency that I don't use.

- elfeed-goodies :: depends on =powerline=...

- ement.el :: has an external dependency that I don't use.

- helm :: it is complex and makes inconsiderate use of color.  Prefer
  the =vertico=, =consult=, and =embark= packages.

- info+ :: it is complex and makes inconsiderate use of color.

- ivy/counsel/swiper :: use the =vertico=, =consult=, and =embark=
  packages which are designed to be compatible with standard Emacs
  mechanisms and are modular.

- lsp-mode :: has external dependencies that I don't use.

- powerline :: requires too many shades of background and generally
  violates our expectation of how the mode-line is supposed to look by
  placing the designated default background in unexpected places.

- solaire :: in principle, it is incompatible with practically every
  theme that is not designed around it.  Emacs does not distinguish
  between "UI" and "syntax" buffers.

- spaceline :: same as =powerline=.

- sx :: has an external dependency that I don't use.

- telega :: has an external dependency that I don't use (I don't even
  have a smartphone).

- telephone-line :: same as =powerline=.

- treemacs :: it has too many dependencies and does too many things.

- web-mode :: I don't use all those Web technologies and cannot test
  this properly without support from an expert.  It also defines lots of
  faces that hardcode color values for no good reason.

The above list is non-exhaustive though you get the idea.

* GNU Free Documentation License
:PROPERTIES:
:CUSTOM_ID: h:255fa624-6e3c-4118-9618-17cc25a801bd
:END:

#+texinfo: @include doclicense.texi

#+begin_export html
<pre>

                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 noncommercially.
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 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 composed 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, LaTeX 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
processing 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

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, 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 Document, 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 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 various 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 individually 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.


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 "History", 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.


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/licenses/.

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 published 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.


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.
</pre>
#+end_export

#+html: <!--

* Indices
:PROPERTIES:
:CUSTOM_ID: h:3e760365-f83c-4631-b9ee-13b22de8a6d7
:END:

** Function index
:PROPERTIES:
:INDEX: fn
:CUSTOM_ID: h:c137a71c-b29d-4fd5-a48b-d81c7abc1e86
:END:

** Variable index
:PROPERTIES:
:INDEX: vr
:CUSTOM_ID: h:b31c615f-6c2e-4778-af97-22ac02db2170
:END:

** Concept index
:PROPERTIES:
:INDEX: cp
:CUSTOM_ID: h:4bec8826-9a86-47cb-ae99-d6b4743edac3
:END:

#+html: -->
