= Asciidoctor PDF Theming Guide
Dan Allen <https://github.com/mojavelinux[@mojavelinux]>
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////
Topics remaining to document:
* document which attributes can be set in document (pdf-page-size, front-cover-image, back-cover-image, etc) (issue #428)
* line height and line height length (and what that all means)
* title page layout / title page images (logo & background)
* document that unicode escape sequences can be used inside double-quoted strings
////

[.lead]
The theming system in Asciidoctor PDF is used to control the layout and styling of the PDF file Asciidoctor PDF generates from AsciiDoc.
This document describes how the theming system works, how to define a custom theme in YAML and how to activate the theme when running Asciidoctor PDF.

IMPORTANT: If you're using a custom theme, you're expected to override some of keys described in the sections below, in particular fonts.
If you don't define your own fonts, the built-in PDF fonts will be used.

toc::[]

== Language Overview

The theme language in Asciidoctor PDF is based on the http://en.wikipedia.org/wiki/YAML[YAML] data format and incorporates many concepts from CSS and SASS.
Therefore, if you have a background in web design, the theme language should be immediately familiar to you.

Like CSS, themes have both selectors and properties.
Selectors are the component you want to style.
The properties are the style elements of that component that can be styled.
All selector names are implicit (e.g., `heading`), so you customize the theme primarily by manipulating pre-defined property values (e.g., `font_size`).

[NOTE]
====
The theme language in Asciidoctor PDF supports a limited subset of the properties from CSS.
Some of these properties have different names from those found in CSS.

* Underscores (`_`) can be used in place of hyphens (`-`) for all property names in the theme language.
* Instead of separate properties for font weight and font style, the theme language combines these settings in the `font_style` property (allowed values: `normal`, `bold`, `italic` and `bold_italic`).
* The `text_align` property from CSS is the `align` property in the theme language.
* The `color` property from CSS is the `font_color` property in the theme language.
====

A theme (or style) is described in a YAML-based data format and stored in a dedicated theme file.
YAML is a human-friendly data format that resembles CSS and helps to describe the theme.
The theme language adds some extra features to YAML, such as variables, basic math, measurements and color values.
These enhancements will be explained in detail in later sections.

The theme file must be named _<name>-theme.yml_, where `<name>` is the name of the theme.

Here's an example of a basic theme file:

.basic-theme.yml
[source,yaml]
----
page:
  layout: portrait
  margin: [0.75in, 1in, 0.75in, 1in]
  size: Letter
base:
  font_color: #333333
  font_family: Times-Roman
  font_size: 12
  line_height_length: 17
  line_height: $base_line_height_length / $base_font_size
vertical_spacing: $base_line_height_length
heading:
  font_color: #262626
  font_size: 17
  font_style: bold
  line_height: 1.2
  margin_bottom: $vertical_spacing
link:
  font_color: #002FA7
outline_list:
  indent: $base_font_size * 1.5
----

When creating a new theme, you only have to define the keys you want to override from the base theme, which is loaded prior to loading your custom theme.
The converter uses the information from the theme map to help construct the PDF.
All the available keys are documented in <<keys>>.

Keys may be nested to an arbitrary depth to eliminate redundant prefixes (an approach inspired by SASS).
Once the theme is loaded, all keys are flattened into a single map of qualified keys.
Nesting is simply a shorthand way of organizing the keys.
In the end, a theme is just a map of key/value pairs.

Nested keys are adjoined to their parent key with an underscore (`_`).
This means the selector part (e.g., `link`) is combined with the property name (e.g., `font_color`) into a single, qualified key (e.g., `link_font_color`).

For example, let's assume we want to set the base (i.e., global) font size and color.
These keys may be written longhand:

[source,yaml]
----
base_font_color: #333333
base_font_family: Times-Roman
base_font_size: 12
----

Or, to avoid having to type the prefix `base_` multiple times, the keys may be written hierarchically:

[source,yaml]
----
base:
  font_color: #333333
  font_family: Times-Roman
  font_size: 12
----

Or even:

[source,yaml]
----
base:
  font:
    color: #333333
    family: Times-Roman
    size: 12
----

Each level of nesting must be indented by twice the amount of indentation of the parent level.
Also note the placement of the colon after each key name.

== Values

The value of a key may be one of the following types:

* String
  - Font family name (e.g., Roboto)
  - Font style (normal, bold, italic, bold_italic)
  - Alignment (left, center, right, justify)
  - Color as hex string (e.g., #ffffff)
  - Image path
* Null (clears any previously assigned value)
  - _empty_ (i.e., no value specified)
  - null
  - ~
* Number (integer or float) with optional units (default unit is points)
* Array
  - Color as RGB array (e.g., [51, 51, 51])
  - Color CMYK array (e.g., [50, 100, 0, 0])
  - Margin (e.g., [1in, 1in, 1in, 1in])
  - Padding (e.g., [1in, 1in, 1in, 1in])
* Variable reference (e.g., $base_font_color)
* Math expression

Note that keys almost always require a value of a specific type, as documented in <<keys>>.

=== Inheritance

Like CSS, inheritance is a key feature in the Asciidoctor PDF theme language.
For many of the properties, if a key is not specified, the key inherits the value applied to the parent content in the content hierarchy.
This behavior saves you from having to specify properties unless you want to override the inherited value.

The following keys are inherited:

* font_family
* font_color
* font_size
* font_style
* line_height (currently some exceptions)
* text_transform (only for headings)
* margin_bottom (falls back to $vertical_spacing)

.Heading Inheritance
****
Headings inherit starting from a specific heading level (e.g., `heading_h2_font_size`), then to the heading category (e.g., `heading_font_size`), then directly to the base value (e.g., `base_font_size`).
Any setting from an enclosing context, such as a sidebar, is skipped.
****

=== Variables

To save you from having to type the same value in your theme over and over, or to allow you to base one value on another, the theme language supports variables.
Variables consist of the key name preceded by a dollar (`$`) (e.g., `$base_font_size`).
Any qualified key that has already been defined can be referenced in the value of another key.
(In order words, as soon as the key is assigned, it's available to be used as a variable).

For example, once the following line is processed,

[source,yaml]
----
base:
  font_color: #333333
----

the variable `$base_font_color` will be available for use in subsequent lines and will resolve to `#333333`.

Let's say you want to make the font color of the sidebar title the same as the heading font color.
Just assign the value `$heading_font_color` to the `$sidebar_title_font_color`.

[source,yaml]
----
heading:
  font_color: #191919
sidebar:
  title:
    font_color: $heading_font_color
----

You can also use variables in math expressions to use one value to build another.
This is commonly done to set font sizes proportionally.
It also makes it easy to test different values very quickly.

[source,yaml]
----
base:
  font_size: 12
  font_size_large: $base_font_size * 1.25
  font_size_small: $base_font_size * 0.85
----

We'll cover more about math expressions later.

==== Custom Variables

You can define arbitrary key names to make custom variables.
This is one way to group reusable values at the top of your theme file.
If you are going to do this, it's recommended that you organize the keys under a custom namespace, such as `brand`.

For instance, here's how you can define your brand colors:

[source,yaml,subs=attributes+]
----
brand:
  primary: #E0162B {conum-guard-yaml} <1>
  secondary: '#FFFFFF' {conum-guard-yaml} <2>
  alert: '0052A5' {conum-guard-yaml} <3>
----
<1> To align with CSS, you may add a `+#+` in front of the hex color value.
A YAML preprocessor is used to ensure the value is not treated as a comment as it would normally be the case in YAML.
<2> You may put quotes around the CSS-style hex value to make it friendly to a YAML editor or validation tool.
<3> The leading `+#+` on a hex value is entirely optional.
However, we recommend that you always use either a leading `+#+` or surrounding quotes (or both) to prevent YAML from mangling the value.

You can now use these custom variables later in the theme file:

[source,yaml]
----
base:
  font_color: $brand_primary
----

=== Math Expressions & Functions

The theme language supports basic math operations to support calculated values.
Like programming languages, multiple and divide take precedence over add and subtract.

The following table lists the supported operations and the corresponding operator for each.

[%header%autowidth]
|===
|Operation |Operator

|multiply
|*

|divide
|/

|add
|+

|subtract
|-
|===

IMPORTANT: The operator must always be surrounded by a space on either side (e.g., 2 + 2 and not 2+2).

Here's an example of a math expression with fixed values.

[source,yaml]
----
conum:
  line_height: 4 / 3
----

Variables may be used in place of numbers anywhere in the expression:

[source,yaml]
----
base:
  font_size: 12
  font_size_large: $base_font_size * 1.25
----

Values used in a math expression are automatically coerced to a float value before the operation.
If the result of the expression is an integer, the value is coerced to an integer afterwards.

IMPORTANT: Numeric values less than 1 must have a 0 before the decimal point (e.g., 0.85).

The theme language also supports several functions for rounding the result of a math expression.
The following functions may be used if they surround the whole value or expression for a key.

round(...):: Rounds the number to the nearest half integer.
floor(...):: Rounds the number up to the next integer.
ceil(...):: Rounds the number down the previous integer.

You might use these functions in font size calculations so that you get more exact values.

[source,yaml]
----
base:
  font_size: 12.5
  font_size_large: ceil($base_font_size * 1.25)
----

=== Measurement Units

Several of the keys require a value in points (pt), the unit of measure for the PDF canvas.
A point is defined as 1/72 of an inch.
However, us humans like to think in real world units like inches (in), centimeters (cm) or millimeters (mm).
You can let the theme do this conversion for you automatically by adding a unit notation next to any number.

The following units are supported:

[%header%autowidth]
|===
|Unit |Suffix

|Inches
|in

|Centimeter
|cm

|Millimeter
|mm

|Points
|pt
|===

Here's an example of how you can use inches to define the page margins:

[source,yaml]
----
page:
  margin: [0.75in, 1in, 0.75in, 1in]
----

The order of elements in a measurement array is the same as it is in CSS:

. top
. right
. bottom
. left

=== Colors

The theme language supports color values in three formats:

Hex:: A string of 3 or 6 characters with an optional leading `#`, optional surrounding quotes or both.
RGB:: An array of numeric values ranging from 0 to 255.
CMYK:: An array of numeric values ranging from 0 to 1 or from 0% to 100%.
Transparent:: The special value `transparent` indicates that a color should not be used.

==== Hex

The hex color value is likely most familiar to web developers.
The value must be either 3 or 6 characters (case insensitive) with an optional leading hash (`#`), optional surrounding quotes or both.

To align with CSS, you may add a `+#+` in front of the hex color value.
A YAML preprocessor is used to ensure the value is not treated as a comment as it would normally be the case in YAML.

You also may put quotes around the CSS-style hex value to make it friendly to a YAML editor or validation tool.
In this case, the leading `+#+` on a hex value is entirely optional.

Regardless, we recommend that you always use either a leading `+#+` or surrounding quotes (or both) to prevent YAML from mangling the value.

The following are all equivalent values for the color red:

[%autowidth,cols=4]
|===
|#f00
|'f00'
|#ff0000
|'ff0000'

|#F00
|'F00'
|#FF0000
|'FF0000'
|===

Here's how a hex color value appears in the theme file:

[source,yaml]
----
base:
  font_color: #ff0000
----

==== RGB

An RGB array value must be three numbers ranging from 0 to 255.
The values must be separated by commas and be surrounded by square brackets.

NOTE: An RGB array is automatically converted to a hex string internally, so there's no difference between ff0000 and [255, 0, 0].

Here's how to specify the color red in RGB:

* [255, 0, 0]

Here's how a RGB color value appears in the theme file:

[source,yaml]
----
base:
  font_color: [255, 0, 0]
----

==== CMYK

A CMYK array value must be four numbers ranging from 0 and 1 or from 0% to 100%.
The values must be separated by commas and be surrounded by square brackets.

Unlike the RGB array, the CMYK array _is not_ converted to a hex string internally.
PDF has native support for CMYK colors, so you can preserve the original color values in the final PDF.

Here's how to specify the color red in CMYK:

* [0, 0.99, 1, 0]
* [0, 99%, 100%, 0]

Here's how a CMYK color value appears in the theme file:

[source,yaml]
----
base:
  font_color: [0, 0.99, 1, 0]
----

==== Transparent

It's possible to specify no color by assigning the special value `transparent`, as shown here:

[source,yaml]
----
base:
  background_color: transparent
----

=== Images

An image is specified either as a bare image path or as an inline image macro as found in the AsciiDoc syntax.
Images are currently resolved relative to the value of the `pdf-stylesdir` attribute.

The following image types (and corresponding file extensions) are supported:

* PNG (.png)
* JPEG (.jpg)
* SVG (.svg)

CAUTION: The GIF format (.gif) is not supported.

Here's how an image is specified in the theme file as a bare image path:

[source,yaml]
----
title_page:
  background_image: title-cover.png
----

Here's how the image is specified using the inline image macro:

[source,yaml]
----
title_page:
  background_image: image:title-cover.png[]
----

Like in the AsciiDoc syntax, the inline image macro allows you to supply set the width of the image and the alignment:

[source,yaml]
----
title_page:
  logo_image: image:logo.png[width=250,align=center] 
----

== Fonts

You can select from <<built-in-afm-fonts,built-in PDF fonts>>, <<bundled-fonts,fonts bundled with Asciidoctor PDF>> or <<custom-fonts,custom fonts>> loaded from TrueType font (TTF) files.
If you want to use custom fonts, you must first declare them in your theme file.

IMPORTANT: Asciidoctor has no challenge working with Unicode.
In fact, it prefers Unicode and considers the whole range.
However, once you convert to PDF, you have to meet the font requirements of PDF in order to preserve Unicode characters.
There's nothing Asciidoctor can do to convince PDF to work without the right fonts in play.

=== Built-In (AFM) Fonts

The names of the built-in fonts (for general-purpose text) are as follows:

[%header%autowidth]
|===
|Font Name |Font Family

|Helvetica
|sans-serif

|Times-Roman
|serif

|Courier
|monospace
|===

Using a built-in font requires no additional files.
You can use the key anywhere a `font_family` property is accepted in the theme file.
For example:

[source,yaml]
----
base:
  font_family: Times-Roman
----

However, when you use a built-in font, the characters that you use in your document are limited to the characters in the WINANSI (http://en.wikipedia.org/wiki/Windows-1252[Windows-1252]) code set.
WINANSI includes most of the characters needed for writing in Western languages (English, French, Spanish, etc).
For anything outside of that, PDF is BYOF (Bring Your Own Font).

Even though the built-in fonts require the content to be encoded in WINANSI, _you still type your AsciiDoc document in UTF-8_.
Asciidoctor PDF encodes the content into WINANSI when building the PDF.

.WINANSI Encoding Behavior
****
If you're using Prawn 1.3.0 with one of the built-in fonts, any characters in your AsciiDoc document that cannot be encoded to WINANSI will be replaced with an underscore glyph (`_`).
If you're using Prawn 2.0.0 or above with one of the built-in fonts, if your AsciiDoc document contains a character that cannot be encoded to WINANSI, a warning will be issued and conversion will halt.

For more information about how Prawn handles character encodings for built-in fonts, see https://github.com/prawnpdf/prawn/blob/master/CHANGELOG.md#vastly-improved-handling-of-encodings-for-pdf-built-in-afm-fonts[this note in the Prawn CHANGELOG].
****

=== Bundled Fonts

Asciidoctor PDF bundles several fonts that are used in the default theme.
You can also use these fonts in your custom theme.
These fonts provide more characters than the built-in PDF fonts, but still only a subset of UTF-8.

The family name of the fonts bundled with Asciidoctor PDF are as follows:

http://www.google.com/get/noto/#/family/noto-serif[Noto Serif]::
A serif font that can be styled as normal, italic, bold or bold_italic.

http://mplus-fonts.osdn.jp/mplus-outline-fonts/design/index-en.html#mplus_1mn[M+ 1mn]::
A monospaced font that maps different thicknesses to the styles normal, italic, bold and bold_italic.
Also provides the circuled numbers used in callouts.

http://mplus-fonts.osdn.jp/mplus-outline-fonts/design/index-en.html#mplus_1p[M+ 1p Fallback]::
A sans-serif font that provides a very complete set of Unicode glyphs.
Cannot be styled as italic, bold or bold_italic.
Useful as a fallback font.

CAUTION: At the time of this writing, you cannot use the bundled fonts if you define your own custom fonts.
This limitation may be lifted in the future.

=== Custom Fonts

The limited character set of WINANSI, or the bland look of the built-in fonts, may motivate you to load your own font.
Custom fonts can enhance the look of your PDF theme substantially.

To start, you need to find a collection of TTF file of the font you want to use.
A collection typically consists of all four styles of a font:

* normal
* italic
* bold
* bold_italic

You'll need all four styles to support AsciiDoc content properly.
_Asciidoctor PDF cannot italicize a font that is not italic like a browser can._

Once you've obtained the TTF files, put them into a directory in your project where you want to store the fonts.
It's recommended that you name them consistently so it's easier to type the names in the theme file.

Let's assume the name of the font is https://github.com/google/roboto/tree/master/out/RobotoTTF[Roboto].
Name the files as follows:

* roboto-normal.ttf (_originally Roboto-Regular.ttf_)
* roboto-italic.ttf (_originally Roboto-Italic.ttf_)
* roboto-bold.ttf (_originally Roboto-Bold.ttf_)
* roboto-bold_italic.ttf (_originally Roboto-BoldItalic.ttf_)

Next, declare the font under the `font_catalog` key at the top of your theme file, giving it a unique key (e.g., `Roboto`).

[source,yaml]
----
font:
  catalog:
    Roboto:
      normal: roboto-normal.ttf
      italic: roboto-italic.ttf
      bold: roboto-bold.ttf
      bold_italic: roboto-bold_italic.ttf
----

You can use the key you gave to the font in the font catalog anywhere a `font_family` property is accepted in the theme file.
For instance, to use the Roboto font for all headings, you'd use:

[source,yaml]
----
heading:
  font_family: Roboto
----

When you execute Asciidoctor PDF, you need to specify the directory where the fonts reside using the `pdf-fontsdir` attribute:

 $ asciidoctor-pdf -a pdf-style=basic-theme.yml -a pdf-fontsdir=path/to/fonts document.adoc

WARNING: Currently, all fonts referenced by the theme need to be present in the directory specified by the `pdf-fontsdir` attribute.

You can add any number of fonts to the catalog.
Each font must be assigned a unique key, as shown here:

[source,yaml]
----
font:
  catalog:
    Roboto:
      normal: roboto-normal.ttf
      italic: roboto-italic.ttf
      bold: roboto-bold.ttf
      bold_italic: roboto-bold_italic.ttf
    Roboto Light:
      normal: roboto-light-normal.ttf
      italic: roboto-light-italic.ttf
      bold: roboto-light-bold.ttf
      bold_italic: roboto-light-bold_italic.ttf
----

TIP: Text in SVGs will use the font catalog from your theme.
We recommend that you match the font key to the name of the font seen by the operating system.
This will allow you to use the same font names (aka families) in both your graphics program and Asciidoctor PDF.

=== Fallback Fonts

If one of your fonts is missing a character that is used in a document, such as special symbols, you can tell Asciidoctor PDF to retrieve the character from a fallback font.
You only need to specify one fallback font...typically one that has a full set of symbols.

Like with other custom fonts, you first need to declare the fallback font.
Let's choose https://android.googlesource.com/platform/frameworks/base/+/master/data/fonts/[Droid Sans Fallback].
You can map all the styles to a single font file (since bold and italic don't usually make sense for symbols).

[source,yaml]
----
font:
  catalog:
    Roboto:
      normal: roboto-normal.ttf
      italic: roboto-italic.ttf
      bold: roboto-bold.ttf
      bold_italic: roboto-bold_italic.ttf
    DroidSansFallback:
      normal: droid-sans-fallback.ttf
      italic: droid-sans-fallback.ttf
      bold: droid-sans-fallback.ttf
      bold_italic: droid-sans-fallback.ttf
----

Next, assign the key to the `fallbacks` key under the `font_catalog` key.
Be sure to surround the key name in square brackets as shown below.

[source,yaml]
----
font:
  catalog:
    Roboto:
      normal: roboto-normal.ttf
      italic: roboto-italic.ttf
      bold: roboto-bold.ttf
      bold_italic: roboto-bold_italic.ttf
    DroidSansFallback:
      normal: droid-sans-fallback.ttf
      italic: droid-sans-fallback.ttf
      bold: droid-sans-fallback.ttf
      bold_italic: droid-sans-fallback.ttf
  fallbacks: [DroidSansFallback]
----

TIP: If you are using more than one fallback font, separate each key name by a comma.

That's it!
Now you're covered.
You don't need to reference the fallback font anywhere else in your theme file to use it.

CAUTION: Using a fallback font does slow down PDF generation slightly.
It's best to select fonts that have all the characters you need.

== Keys

This section lists all the keys that are available when creating a custom theme.
The converter uses the values of these keys to control how most elements are arranged and styled in the PDF.

NOTE: When creating a theme, all keys are optional.
You only have to assign values to keys you want to customize.
Any required keys are assigned by the base theme.

The keys in this section are organized by category.
Each category represents a common prefix under which the keys are typically nested.
The default values are those assigned by the base theme (not the default theme).

TIP: Keys can be partioned and nested wherever an underscore (`_`) appears in the name.
This nested structure is flatted when the theme is loaded.

=== Page

The keys in this category control the size, margins and background of each page (i.e., canvas).

NOTE: The background of the title page can be styled independently.
See <<Title Page>> for details.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* page

|background_color^[1]^
|<<colors,Color>> +
(default: #ffffff)
|page:
  background_color: #fefefe

|background_image^[1]^
|Inline image macro^[2]^ +
(default: none)
|page:
  background_image: +image:page-bg.png[]+

|layout
|portrait {vbar} landscape +
(default: portrait)
|page:
  layout: landscape

|margin
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>> +
(default: 36)
|page:
  margin: [0.5in, 0.67in, 1in, 0.67in]

|size
|https://github.com/prawnpdf/pdf-core/blob/0.6.0/lib/pdf/core/page_geometry.rb#L16-L68[Named size^] {vbar} <<measurement-units,Measurement[width,height]>> +
(default: A4)
|page:
  size: Letter
|===

. Page backgrounds do not currently work when using AsciidoctorJ PDF.
This limitation is due to a bug in Prawn 1.3.1.
The limitation will remain until AsciidoctorJ PDF upgrades to Prawn 2.x (an upgrade that is waiting on AsciidoctorJ to migrate to JRuby 9000).
For more details, see http://discuss.asciidoctor.org/Asciidoctor-YAML-style-file-for-PDF-and-maven-td3849.html[this thread].
. Target may be an absolute path or a path relative to the value of the `pdf-stylesdir` attribute.

=== Base

The keys in this category provide generic theme settings and are often referenced throughout the theme file as variables.
It's common to define additional keys in this category (e.g., `base_border_radius`) that serve as custom variables to help keep your theme DRY.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* base

|align
|left {vbar} center {vbar} right {vbar} justify +
(default: left)
|base:
  align: justify

|font_color
|<<colors,Color>> +
(default: #000000)
|base:
  font_color: #333333

|font_family
|<<fonts,Font family name>> +
(default: Helvetica)
|base:
  font_family: Noto Serif

|font_size
|<<values,Number>> +
(default: 12)
|base:
  font_size: 10.5

// font_size_large and font_size_small aren't official keys
//|font_size_large
//|<<values,Number>>
//|base:
//  font_size_large: 13
//
//|font_size_small
//|<<values,Number>>
//|base:
//  font_size_small: 9

|font_size_min
|<<values,Number>> +
(default: 9)
|base:
  font_size_min: 6

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic +
(default: normal)
|base:
  font_style: normal

|line_height_length^[1]^
|<<values,Number>> +
(default: 13.8)
|base:
  line_height_length: 12

|line_height^[1]^
|<<values,Number>> +
(default: 1.15)
|base:
  line_height: >
    $base_line_height_length /
    $base_font_size

// border_radius is not an official key
//|border_radius
//|<<values,Number>>
//|base:
//  border_radius: 4

|border_width
|<<values,Number>> +
(default: 0.5)
|base:
  border_width: 0.5

|border_color
|<<colors,Color>> +
(default: #eeeeee)
|base:
  border_color: #eeeeee
|===

. You should set one of `line_height` or `line_height_length`, then derive the value of the other using a calculation as these are correlated values.
For instance, if you set `line_height_length`, then use `$base_line_height_length / $base_font_size` as the value of `line_height`.

=== Vertical Spacing

The keys in this category control the general spacing between elements where a more specific setting is not designated.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

|vertical_spacing
|<<values,Number>> +
(default: 12)
|vertical_spacing: 10
|===

=== Link

The keys in this category are used to style hyperlink text.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* link

|font_color
|<<colors,Color>> +
(default: #0000ee)
|link:
  font_color: #428bca

// font_family, font_size and font_style not yet implemented
//|font_family
//|<<fonts,Font family name>>
//|link:
//  font_family: Roboto
//
//|font_size
//|<<values,Number>>
//|link:
//  font_size: 9
//
//|font_style
//|normal {vbar} italic {vbar} bold {vbar} bold_italic
//|link:
//  font_style: normal
|===

=== Literal (Inline)

The keys in this category are used for inline monospaced text in prose and table cells.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* literal

|font_color
|<<colors,Color>>
|literal:
  font_color: #b12146

|font_family
|<<fonts,Font family name>> +
(default: Courier)
|literal:
  font_family: M+ 1mn

|font_size
|<<values,Number>>
|literal:
  font_size: 12

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|literal:
  font_style: bold
|===

=== Heading

The keys in this category control the style of most headings, including part titles, chapter titles, sections titles, the table of contents title and discrete headings.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* heading

|align
|left {vbar} center {vbar} right {vbar} justify +
(default: left)
|heading:
  align: center

|font_color
|<<colors,Color>> +
(default: $base_font_color)
|heading:
  font_color: #222222

|font_family
|<<fonts,Font family name>> +
(default: $base_font_family)
|heading:
  font_family: Noto Serif

|font_size
|<<values,Number>> +
(default: $base_font_size)
|heading:
  font_size: 18

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic +
(default: bold)
|heading:
  font_style: bold

|line_height
|<<values,Number>> +
(default: 1.15)
|heading:
  line_height: 1.2

|margin_top
|<<measurement-units,Measurement>> +
(default: 4)
|heading:
  margin_top: $vertical_spacing * 0.2

|margin_bottom
|<<measurement-units,Measurement>> +
(default: 12)
|heading:
  margin_bottom: 9.6

|text_transform
|none {vbar} uppercase {vbar} lowercase +
(default: none)
|heading:
  text_transform: uppercase

3+|*Key Prefix:* heading_h<n>^[1]^

|align
|left {vbar} center {vbar} right {vbar} justify +
(default: $heading_align)
|heading:
  h2_align: center

|font_color
|<<colors,Color>> +
(default: $heading_font_color)
|heading:
  h2_font_color: [0, 99%, 100%, 0]

|font_family
|<<fonts,Font family name>> +
(default: $heading_font_family)
|heading:
  h4_font_family: Roboto

|font_size^[1]^
|<<values,Number>> +
(default: h1=24; h2=18; h3=16; h4=14; h5=12; h6=10)
|heading:
  h6_font_size: $base_font_size * 1.7

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic +
(default: $heading_font_style)
|heading:
  h3_font_style: bold_italic

|text_transform
|none {vbar} uppercase {vbar} lowercase +
(default: $heading_text_transform)
|heading:
  text_transform: lowercase
|===

. `<n>` is a number ranging from 1 to 6, representing each of the six heading levels.
. A font size is assigned to each heading level by the base theme.
If you want the font size of a specific level to be inherited, you must assign the value `null` (or `~` for short).

=== Title Page

The keys in this category control the style of the title page as well as the arrangement and style of the elements on it.

TIP: The title page can be disabled from the document by setting the `notitle` attribute in the document header.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* title_page

|align
|left {vbar} center {vbar} right {vbar} justify +
(default: center)
|title_page:
  align: right

|background_color^[1]^
|<<colors,Color>>
|title_page:
  background_color: #eaeaea

|background_image^[1]^
|Inline image macro^[2]^
|title_page:
  +background_image: image:title.png[]+

|font_color
|<<colors,Color>>
|title_page:
  font_color: #333333

|font_family
|<<fonts,Font family name>>
|title_page:
  font_family: Noto Serif

|font_size
|<<values,Number>>
|title_page:
  font_size: $base_font_size_large

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|title_page:
  font_style: bold

|line_height
|<<values,Number>> +
(default: 1.15)
|title_page:
  line_height: 1

3+|*Key Prefix:* title_page_logo

|align
|left {vbar} center {vbar} right
|title_page:
  logo:
    align: right

|image
|Inline image macro^[2]^
|title_page:
  logo:
    +image: image:logo.png[pdfwidth=25%]+

|top
|Percentage +
(default: 10%)
|title_page:
  logo:
    top: 25%

3+|*Key Prefix:* title_page_title

|font_color
|<<colors,Color>>
|title_page:
  title:
    font_color: #999999

|font_family
|<<fonts,Font family name>>
|title_page:
  title:
    font_family: Noto Serif

|font_size
|<<values,Number>> +
(default: 18)
|title_page:
  title:
    font_size: $heading_h1_font_size

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|title_page:
  title:
    font_style: bold

|line_height
|<<values,Number>>
|title_page:
  title:
    line_height: 0.9

|top
|Percentage +
(default: 40%)
|title_page:
  title:
    top: 55%

3+|*Key Prefix:* title_page_subtitle

|font_color
|<<colors,Color>>
|title_page:
  subtitle:
    font_color: #181818

|font_family
|<<fonts,Font family name>>
|title_page:
  subtitle:
    font_family: Noto Serif

|font_size
|<<values,Number>> +
(default: 14)
|title_page:
  subtitle:
    font_size: $heading_h3_font_size

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|title_page:
  subtitle:
    font_style: bold_italic

|line_height
|<<values,Number>>
|title_page:
  subtitle:
    line_height: 1

3+|*Key Prefix:* title_page_authors

|font_color
|<<colors,Color>>
|title_page:
  authors:
    font_color: #181818

|font_family
|<<fonts,Font family name>>
|title_page:
  authors:
    font_family: Noto Serif

|font_size
|<<values,Number>>
|title_page:
  authors:
    font_size: $base_font_size_large

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|title_page:
  authors:
    font_style: bold_italic

|margin_top
|<<measurement-units,Measurement>> +
(default: 12)
|title_page:
  authors:
    margin_top: 13.125

3+|*Key Prefix:* title_page_revision

|font_color
|<<colors,Color>>
|title_page:
  revision:
    font_color: #181818

|font_family
|<<fonts,Font family name>>
|title_page:
  revision:
    font_family: Noto Serif

|font_size
|<<values,Number>>
|title_page:
  revision:
    font_size: $base_font_size_small

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|title_page:
  revision:
    font_style: bold

|margin_top
|<<measurement-units,Measurement>>
|title_page:
  revision:
    margin_top: 13.125
|===

. Page backgrounds do not currently work when using AsciidoctorJ PDF.
This limitation is due to a bug in Prawn 1.3.1.
The limitation will remain until AsciidoctorJ PDF upgrades to Prawn 2.x (an upgrade that is waiting on AsciidoctorJ to migrate to JRuby 9000).
For more details, see http://discuss.asciidoctor.org/Asciidoctor-YAML-style-file-for-PDF-and-maven-td3849.html[this thread].
. Target may be an absolute path or a path relative to the value of the `pdf-stylesdir` attribute.

=== Block

The keys in this category control the spacing around block elements when a more specific setting is not designated.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* block

//|padding
//|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>>
//|block:
//  padding: [12, 15, 12, 15]

|margin_top
|<<measurement-units,Measurement>> +
(default: 0)
|block:
  margin_top: 6

|margin_bottom
|<<measurement-units,Measurement>> +
(default: 12)
|block:
  margin_bottom: 6
|===

Block styles are applied to the following block types:

[cols="1a,1a,1a", grid=none, frame=none]
|===
|
* admonition
* example
* quote
|
* verse
* sidebar
* image
|
* listing
* literal
* table
|===

=== Caption

The keys in this category control the arrangement and style of block captions.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* caption

|align
|left {vbar} center {vbar} right {vbar} justify +
(default: left)
|caption:
  align: left

|font_color
|<<colors,Color>>
|caption:
  font_color: #333333

|font_family
|<<fonts,Font family name>>
|caption:
  font_family: M+ 1mn

|font_size
|<<values,Number>>
|caption:
  font_size: 11

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic +
(default: italic)
|caption:
  font_style: italic

|margin_inside
|<<measurement-units,Measurement>> +
(default: 4)
|caption:
  margin_inside: 3

|margin_outside
|<<measurement-units,Measurement>> +
(default: 0)
|caption:
  margin_outside: 0
|===

=== Code

The keys in this category are used to control the style of literal, listing and source blocks.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* code

|background_color
|<<colors,Color>>
|code:
  background_color: #f5f5f5

|border_color
|<<colors,Color>> +
(default: #eeeeee)
|code:
  border_color: #cccccc

|border_radius
|<<values,Number>> +
(default: 0)
|code:
  border_radius: 4

|border_width
|<<values,Number>> +
(default: 0.5)
|code:
  border_width: 0.75

|font_color
|<<colors,Color>>
|code:
  font_color: #333333

|font_family
|<<fonts,Font family name>> +
(default: Courier)
|code:
  font_family: M+ 1mn

|font_size
|<<values,Number>> +
(default: 10.5)
|code:
  font_size: 11

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|code:
  font_style: italic

|line_height
|<<values,Number>> +
(default: 1.2)
|code:
  line_height: 1.25

|padding
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>> +
(default: 9)
|code:
  padding: 11
|===

=== Blockquote

The keys in this category control the arrangement and style of quote blocks.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* blockquote

|border_width
|<<values,Number>> +
(default: 4)
|blockquote:
  border_width: 5

|border_color
|<<colors,Color>> +
(default: #eeeeee)
|blockquote:
  border_color: #eeeeee

|font_color
|<<colors,Color>>
|blockquote:
  font_color: #333333

|font_family
|<<fonts,Font family name>>
|blockquote:
  font_family: Noto Serif

|font_size
|<<values,Number>>
|blockquote:
  font_size: 13

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|blockquote:
  font_style: bold

|padding
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>> +
(default: [6, 12, -6, 14])
|blockquote:
  padding: [5, 10, -5, 12]

3+|*Key Prefix:* blockquote_cite

|font_size
|<<values,Number>>
|blockquote:
  cite:
    font_size: 9

|font_color
|<<colors,Color>>
|blockquote:
  cite:
    font_color: #999999

|font_family
|<<fonts,Font family name>>
|blockquote:
  cite:
    font_family: Noto Serif

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|blockquote:
  cite:
    font_style: bold
|===

=== Sidebar

The keys in this category control the arrangement and style of sidebar blocks.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* sidebar

|background_color
|<<colors,Color>> +
(default: #eeeeee)
|sidebar:
  background_color: #eeeeee

|border_color
|<<colors,Color>>
|sidebar:
  border_color: #ffffff

|border_radius
|<<values,Number>>
|sidebar:
  border_radius: 4

|border_width
|<<values,Number>>
|sidebar:
  border_width: 0.5

|padding
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>> +
(default: [12, 12, 0, 12])
|sidebar:
  padding: [12, 15, 0, 15]

3+|*Key Prefix:* sidebar_title

|align
|left {vbar} center {vbar} right {vbar} justify +
(default: center)
|sidebar:
  title:
    align: center

|font_color
|<<colors,Color>>
|sidebar:
  title:
    font_color: #333333

|font_family
|<<fonts,Font family name>>
|sidebar:
  title:
    font_family: Noto Serif

|font_size
|<<values,Number>>
|sidebar:
  title:
    font_size: 13

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic +
(default: bold)
|sidebar:
  title:
    font_style: bold
|===

=== Example

The keys in this category control the arrangement and style of example blocks.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* example

|background_color
|<<colors,Color>>
|example:
  background_color: #fffef7

|border_color
|<<colors,Color>> +
(default: #eeeeee)
|example:
  border_color: #eeeeee

|border_radius
|<<values,Number>> +
(default: 0)
|example:
  border_radius: 4

|border_width
|<<values,Number>> +
(default: 0.5)
|example:
  border_width: 0.75
|===

=== Admonition

The keys in this category control the arrangement and style of admonition blocks and the icon used for each admonition type.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* admonition

|border_color
|<<colors,Color>> +
(default: #eeeeee)
|admonition:
  border_color: #eeeeee

|border_width
|<<values,Number>> +
(default: 0.5)
|admonition:
  border_width: 0.5

|padding
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>> +
(default: [0, 12, 0, 12])
|admonition:
  padding: [0, 12, 0, 12]

3+|*Key Prefix:* admonition_icon

|<name>_name^[1]^
|String^[2]^
|admonition:
  icon:
    tip:
      name: fa-fire

|<name>_stroke_color^[1]^
|<<colors,Color>>
|admonition:
  icon:
    tip:
      stroke_color: ff0000

|<name>_size^[1]^
|<<values,Number>> +
(default: 24)
|admonition:
  icon:
    tip:size: 24
|===

. `<name>` can be `note`, `tip`, `warning`, `important` or `caution`. +
. See the `.yml` files in the https://github.com/jessedoyle/prawn-icon/tree/master/data/fonts[prawn-icon repository] for a list of valid names.
The prefix (e.g., `fa-`) determines which font set to use.

=== Image

The keys in this category control the arrangement of block images.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* image

|align
|left {vbar} center {vbar} right +
(default: left)
|image:
  align: left
|===

=== Lead

The keys in this category control the styling of lead paragraphs.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* lead

|font_size
|<<values,Number>> +
(default: 13.5)
|lead:
  font_size: 13

|line_height
|<<values,Number>> +
(default: 1.4)
|lead:
  line_height: 1.4
|===

=== Abstract

The keys in this category control the arrangement and style of the abstract.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* abstract

|font_color
|<<colors,Color>>
|abstract:
  font_color: #5c6266

|font_size
|<<values,Number>> +
(default: 13.5)
|abstract:
  font_size: 13

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|abstract:
  font_style: italic

|line_height
|<<values,Number>> +
(default: 1.4)
|abstract:
  line_height: 1.4

|padding
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>> +
(default: 0)
|abstract:
  padding: [0, 12, 0, 12]
|===

=== Thematic Break

The keys in this category control the style of thematic breaks (aka horizontal rules).

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* thematic_break

|border_color
|<<colors,Color>> +
(default: #eeeeee)
|thematic_break:
  border_color: #eeeeee

|border_style
|solid {vbar} double {vbar} dashed {vbar} dotted +
(default: solid)
|thematic_break:
  border_style: dashed

|border_width
|<<measurement-units,Measurement>> +
(default: 0.5)
|thematic_break:
  border_width: 0.5

|margin_top
|<<measurement-units,Measurement>>
|thematic_break:
  margin_top: 6

|margin_bottom
|<<measurement-units,Measurement>>
|thematic_break:
  margin_bottom: 18
|===

=== Description List

The keys in this category control the arrangement and style of definition list items (terms and descriptions).

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* description_list

|term_font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|description_list:
  term_font_style: italic

|term_spacing
|<<measurement-units,Measurement>> +
(default: 4)
|description_list:
  term_spacing: 5

|description_indent
|<<values,Number>> +
(default: 30)
|description_list:
  description_indent: 15
|===

=== Outline List

The keys in this category control the arrangement and style of outline list items.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* outline_list

|indent
|<<measurement-units,Measurement>> +
(default: 30)
|outline_list:
  indent: 40

|item_spacing
|<<measurement-units,Measurement>> +
(default: 6)
|outline_list:
  item_spacing: 4
|===

=== Table

The keys in this category control the arrangement and style of tables and table cells.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* table

|background_color
|<<colors,Color>>
|table:
  background_color: #ffffff

|border_color
|<<colors,Color>> +
(default: #000000)
|table:
  border_color: #dddddd

|border_width
|<<values,Number>> +
(default: 0.5)
|table:
  border_width: 0.5

|font_color
|<<colors,Color>> +
(default: $base_font_color)
|table:
  font_color: #333333

|font_family
|<<fonts,Font family name>>
|table:
  font_family: Helvetica

|font_size
|<<values,Number>>
|table:
  font_size: 9.5

|grid_color
|<<colors,Color>> +
(default: $table_border_color)
|table:
  grid_color: #eeeeee

|grid_width
|<<values,Number>> +
(default: $table_border_width)
|table:
  grid_width: 0.5

3+|*Key Prefix:* table_head

|background_color
|<<colors,Color>> +
(default: $table_background_color)
|table:
  head:
    background_color: #f0f0f0

|font_color
|<<colors,Color>> +
(default: $table_font_color)
|table:
  head:
    font_color: #333333

|font_family
|<<fonts,Font family name>> +
(default: $table_font_family)
|table:
  head:
    font_family: Noto Serif

|font_size
|<<values,Number>> +
(default: $table_font_size)
|table:
  head:
    font_size: 10

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic +
(default: bold)
|table:
  head:
    font_style: normal

|text_transform
|none {vbar} uppercase {vbar} lowercase +
(default: none)
|table:
  head:
    text_transform: uppercase

3+|*Key Prefix:* table_foot

|background_color
|<<colors,Color>> +
(default: $table_background_color)
|table:
  foot:
    background_color: #f0f0f0

|font_color
|<<colors,Color>> +
(default: $table_font_color)
|table:
  foot:
    font_color: #333333

|font_family
|<<fonts,Font family name>> +
(default: $table_font_family)
|table:
  foot:
    font_family: Noto Serif

|font_size
|<<values,Number>> +
(default: $table_font_size)
|table:
  foot:
    font_size: 10

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic +
(default: normal)
|table:
  foot:
    font_style: italic

3+|*Key Prefix:* table_<parity>_row^[1]^

|background_color
|<<colors,Color>>
|table:
  even_row:
    background_color: #f9f9f9

3+|*Key Prefix:* table_cell

|padding
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>> +
(default: 2)
|table:
  cell:
    padding: [3, 3, 6, 3]

3+|*Key Prefix:* table_header_cell

|align
|left {vbar} center {vbar} right
|table:
  header_cell:
    align: center

|background_color
|<<colors,Color>>
|table:
  header_cell:
    background_color: #f0f0f0

|font_color
|<<colors,Color>>
|table:
  header_cell:
    font_color: #1a1a1a

|font_family
|<<fonts,Font family name>>
|table:
  header_cell: 
    font_family: Noto Sans

|font_size
|<<values,Number>>
|table:
  header_cell:
    font_size: 12

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|table:
  header_cell:
    font_style: italic
|===

. `<parity>` can be `odd` (odd rows) or `even` (even rows).

[[key-toc]]
=== Table of Contents

The keys in this category control the arrangement and style of the table of contents.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* toc

|font_color
|<<colors,Color>>
|toc:
  font_color: #333333

|font_family
|<<fonts,Font family name>>
|toc:
  font_family: Noto Serif

|font_size
|<<values,Number>>
|toc:
  font_size: 9

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|toc:
  font_style: bold

|line_height
|<<values,Number>> +
(default: 1.4)
|toc:
  line_height: 1.5

|indent
|<<measurement-units,Measurement>> +
(default: 15)
|toc:
  indent: 20

|margin_top
|<<measurement-units,Measurement>>
|toc:
  margin_top: 0

3+|*Key Prefix:* toc_h<n>^[1]^

|font_color
|<<colors,Color>>
|toc:
  h3_font_color: #999999

3+|*Key Prefix:* toc_title^[2]^

|align
|left {vbar} center {vbar} right {vbar} justify +
(default: left)
|toc:
  title:
    align: center

3+|*Key Prefix:* toc_dot_leader

|content
|Quoted string
|toc:
  dot_leader:
    content: ". "

|color
|<<colors,Color>>
|toc:
  dot_leader:
    color: #999999
|===

. `<n>` is a number ranging from 1 to 6, representing each of the six heading levels.
. The `toc_title` keys inherit from level-2 heading styles, except where noted.

[#running-content]
=== Running Header & Footer

The keys in this category control the arrangement and style of running header and footer content.

TIP: If you defined running header and footer content in your theme, you can still disable this content per document by setting the `noheader` and `nofooter` document attributes, respectively.

[cols="3,4,5l"]
|===
|Key |Value Type |Example

3+|*Key Prefix:* header

|background_color
|<<colors,Color>>
|header:
  background_color: #eeeeee

|border_color
|<<colors,Color>>
|header:
  border_color: #dddddd

|border_style
|solid {vbar} double {vbar} dashed {vbar} dotted +
(default: solid)
|header:
  border_style: dashed

|border_width
|<<measurement-units,Measurement>>
|header:
  border_width: 0.25

|font_color
|<<colors,Color>>
|header:
  font_color: #333333

|font_family
|<<fonts,Font family name>>
|header:
  font_family: Noto Serif

|font_size
|<<values,Number>>
|header:
  font_size: 9

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|header:
  font_style: italic

|height
|<<measurement-units,Measurement>>
|header:
  height: 0.75in

|line_height
|<<values,Number>> +
(default: $base_line_height)
|header:
  line_height: 1.2

|padding
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>>
|header:
  padding: [0, 3, 0, 3]

|image_vertical_align
|top {vbar} middle {vbar} bottom {vbar} <<measurement-units,Measurement>>
|header:
  image_vertical_align: 4

|vertical_align
|top {vbar} middle {vbar} bottom
|header:
  vertical_align: center

|<face>_content_<position>^[1]^
|Quoted string
|header:
  recto_content:
    left: '\{page-number}'

3+|*Key Prefix:* footer

|background_color
|<<colors,Color>>
|footer:
  background_color: #eeeeee

|border_color
|<<colors,Color>>
|footer:
  border_color: #dddddd

|border_style
|solid {vbar} double {vbar} dashed {vbar} dotted +
(default: solid)
|footer:
  border_style: dashed

|border_width
|<<measurement-units,Measurement>>
|footer:
  border_width: 0.25

|font_color
|<<colors,Color>>
|footer:
  font_color: #333333

|font_family
|<<fonts,Font family name>>
|footer:
  font_family: Noto Serif

|font_size
|<<values,Number>>
|footer:
  font_size: 9

|font_style
|normal {vbar} italic {vbar} bold {vbar} bold_italic
|footer:
  font_style: italic

|height
|<<measurement-units,Measurement>>
|footer:
  height: 0.75in

|line_height
|<<values,Number>> +
(default: $base_line_height)
|footer:
  line_height: 1.2

|padding
|<<measurement-units,Measurement>> {vbar} <<measurement-units,Measurement[top,right,bottom,left]>>
|footer:
  padding: [0, 3, 0, 3]

|image_vertical_align
|top {vbar} middle {vbar} bottom {vbar} <<measurement-units,Measurement>>
|footer:
  image_vertical_align: 4

|vertical_align
|top {vbar} middle {vbar} bottom
|footer:
  vertical_align: top

|<face>_content_<position>^[1]^
|Quoted string
|footer:
  verso_content:
    center: '\{page-number}'
|===

. `<face>` can be `recto` (odd pages) or `verso` (even pages).
`<position>` can be `left`, `center` or `right`.

IMPORTANT: You must define a height for the running header or footer, respectively, or it will not be shown.

TIP: The running header and footer can be disabled from the document by setting the `noheader` and the `nofooter` attributes, respectively, in the document header.

NOTE: If content is not specified for the running footer, the page number (i.e., `\{page-number}`) will be shown on the left side on verso pages and the right side on recto pages.

NOTE: The background color spans the width of the page.
When a background color is specified, the border also spans the width of the page.

==== Attribute References

You can use _any_ attribute defined in your AsciiDoc document in the content of the running header and footer.
In addition, the following attributes are also available when defining the content keys in the footer:

* page-count
* page-number
* document-title
* document-subtitle
* chapter-title
* section-title
* section-or-chapter-title

You can also built-in AsciiDoc text replacements like `+(C)+`, numeric character references like `+&#169;+` and inline formatting (e.g., bold, italic, monospace).

Here's an example that shows how attributes and replacements can be used in the running footer:

[source,yaml]
----
header:
  height: 0.75in
  line_height: 1
  recto_content:
    center: '(C) ACME -- v{revnumber}, {docdate}'
  verso_content:
    center: $header_recto_content_center
footer:
  height: 0.75in
  line_height: 1
  recto_content:
    right: '{section-or-chapter-title} | *{page-number}*'
  verso_content:
    left: '*{page-number}* | {chapter-title}'
----

You can split the content value across multiple lines using YAML's multiline string syntax.
In this case, the single quotes around the string are not necessary.
To force a hard line break in the output, add `{sp}+` to the end of the line in normal AsciiDoc fashion.

[source,yaml]
----
footer:
  height: 0.75in
  line_height: 1.2
  recto_content:
    right: |
      Section Title - Page Number +
      {section-or-chapter-title} - {page-number}
  verso_content:
    left: |
      Page Number - Chapter Title +
      {page-number} - {chapter-title}
----

TIP: You can use most AsciiDoc inline formatting in the values of these keys.
For instance, to make the text bold, surround it in asterisks (as shown above).
One exception to this rule are inline images, which are described in the next section.

==== Images

You can add an image to the running header or footer using the AsciiDoc inline image syntax.
Note that the image must be the whole value for a given position (left, center or right).
It cannot be combined with text.

Here's an example of how to use an image in the running header (which also applies for the footer).

[source,yaml,subs=attributes+]
----
header:
  height: 0.75in
  image_vertical_align: 2 {conum-guard-yaml} <1>
  recto_content:
    center: image:footer-logo.png[width=80]
  verso_content:
    center: $header_recto_content_center
----
<1> You can use the `footer_vertical_align` attribute to slighly nudge the image up or down.

CAUTION: The image must fit in the allotted space for the running header or footer.
Otherwise, you will run into layout issues.
Adjust the width attribute accordingly.

== Applying Your Theme

After creating a theme, you'll need to tell Asciidoctor PDF where to find it.
This is done using AsciiDoc attributes.

There are three AsciiDoc attributes that tell Asciidoctor PDF how to locate and apply your theme.

pdf-stylesdir:: The directory where the theme file is located.
_Specifying an absolute path is recommended._
+
If you use images in your theme, image paths are resolved relative to this directory.

pdf-style:: The name of the YAML theme file to load.
If the name ends with `.yml`, it's assumed to be the complete name of a file.
Otherwise, `-theme.yml` is appended to the name to make the file name (i.e., `<name>-theme.yml`).

pdf-fontsdir:: The directory where the fonts used by your theme, if any, are located.
_Specifying an absolute path is recommended._

Let's assume that you've put your theme files inside a directory named `resources` with the following layout:

....
document.adoc
resources/
  themes/
    basic-theme.yml
  fonts/
    roboto-normal.ttf
    roboto-italic.ttf
    roboto-bold.ttf
    roboto-bold_italic.ttf
....

Here's how you'd load your theme when calling Asciidoctor PDF:

 $ asciidoctor-pdf -a pdf-stylesdir=resources/themes -a pdf-style=basic -a pdf-fontsdir=resources/fonts

If all goes well, Asciidoctor PDF should run without an error or warning.

NOTE: You only need to specify the `pdf-fontsdir` if you are using custom fonts in your theme.

You can skip setting the `pdf-stylesdir` attribute and just pass the absolute path of your theme file to the `pdf-style` attribute.

 $ asciidoctor-pdf -a pdf-style=resources/themes/basic-theme.yml -a pdf-fontsdir=resources/fonts

However, in this case, image paths in your theme won't be resolved properly.

Paths are resolved relative to the current directory.
However, in the future, this may change so that paths are resolved relative to the base directory (typically the document's directory).
Therefore, it's recommend that you specify absolute paths for now to future-proof your configuration.

  $ asciidoctor-pdf -a pdf-stylesdir=/path/to/resources/themes -a pdf-style=basic -a pdf-fontsdir=/path/to/resources/fonts

As usual, you can also use build tools like Maven and Gradle to build a themed PDF.
The only thing you need to add to an existing build is the attributes mentioned above.

* https://github.com/asciidoctor/asciidoctor-maven-examples/tree/master/asciidoctor-pdf-with-theme-example[Maven Example]
* https://github.com/asciidoctor/asciidoctor-gradle-examples/tree/master/asciidoc-to-pdf-with-theme-example[Gradle Example]

== Theme-Related Document Attributes

There are various settings in the theme you control using document attributes.
These settings override equivalent keys defined in the theme file, where applicable.

[cols="2,3,6m"]
|===
|Attribute |Value Type |Example

|autofit-option
|flag (default: _not set_)
|:autofit-option:

|chapter-label
|string (default: Chapter)
|:chapter-label: Chapter

|<face>-cover-image
|inline image macro (target is relative to `imagesdir`; can be image or PDF file)
|+:front-cover-image: image:front-cover.pdf[]+

|pagenums^[2]^
|flag (default: _set_)
|:pagenums:

//|pdf-page-layout
//|portrait, landscape
//|:pdf-page-layout: landscape

|pdf-page-size
|https://github.com/prawnpdf/pdf-core/blob/0.6.0/lib/pdf/core/page_geometry.rb#L16-L68[named size^], <<measurement-units,measurement dimensions>> (width x height)
|:pdf-page-size: 6in x 9in

|title-logo-image
|inline image macro (path is relative to `imagesdir`; can be image or PDF file)
|+:title-logo-image: image:logo.png[top=25%, align=center, pdfwidth=0.5in]+
|===

. `<face>` can be `front` or `back`.
. Controls whether the `page-number` attribute is accessible to the running header and footer content specified in the theme file.
Use the `noheader` and `nofooter` attributes to disable the running header and footer, respectively, from the document.

////
== Resources for Extending Asciidoctor PDF

* http://www.sitepoint.com/hackable-pdf-typesetting-in-ruby-with-prawn[Hackable PDF typesetting in Ruby with Prawn]
////