= Upgrade to Asciidoctor PDF 2

This guide is written for anyone making the switch from an Asciidoctor PDF 1.x release to an Asciidoctor PDF 2.x release.
Although Asciidoctor PDF 2 was carefully designed to make this transition a smooth one, it is still a major release, so there are changes that may impact you.
You'll also want to begin taking advantage of the new and improved functionality.

This page doesn't call attention to all the changes in the Asciidoctor PDF 2 release line.
Rather, it focuses on the changes at the transition from Asciidoctor PDF 1 to Asciidoctor PDF 2.
To find a complete list of changes to Asciidoctor PDF, refer to the {url-project-repo}/blob/main/CHANGELOG.adoc[CHANGELOG^].

== Breaking changes and removals

The Asciidoctor PDF 2 major release gave us the opportunity to clean up and refine some of the behavior of this converter.
As a result, breaking changes and removals are customary.
This section summarizes that changes that may impact your content and configuration in order to help you make the transition.

=== Runtimes and dependencies

* Support for Ruby < 2.7 and JRuby < 9.2 has been removed.
* The converter now relies on Ruby's built-in multibyte support for the uppercase, lowercase, and capitalize text transforms; no additional gems are required.
* It's no longer necessary to use an unreleased version of the *prawn-table* gem with Asciidoctor PDF.
If you are, please remove that dependency from your [.path]_Gemfile_ and allow Asciidoctor PDF to handle the dependency on the prawn-table gem.
* `safe_yaml gem` has been removed; `YAML.safe_load` from the Ruby stdlib is used instead.

=== Theming system and built-in fonts

* Support for the `pdf-style` and `pdf-stylesdir` attributes has been removed (deprecated since 1.5.0.beta.1).
Use the `pdf-theme` and `pdf-themesdir` attributes instead to specify the location of a custom theme.
* A custom theme no longer inherits from the base theme when the `extends` key is not specified.
Instead, it starts with no keys set (plus `base-font-size` starting in 2.3.2) and relies on fallback values when needed by the converter.
If you're getting errors after upgrading, this could be the culprit.
To make your theme portable across versions of Asciidoctor PDF, explicitly declare the theme you want your theme to extend using the `extends` key.
* The basic running footer is now enabled when you use the base theme or extend the base theme.
(Previously, the basic running footer was only enabled if you used or extended the default theme.)
* The `top-margin` key on block and prose categories in theme has been removed; space between delimited blocks and lists is now controlled using bottom margins only.
* The previously undocumented `vertical-spacing` key has been removed from the built-in themes.
* The `lead` category keys in theme have been replaced with the built-in role named `lead`.
* Support for the `<color>` tag in passthrough and theme content has been removed; use `<font color="...">` instead; may affect themes that use pseudo-HTML in the value of the `content` key.
* The previously deprecated "`ascii`" fonts have been removed; only the more complete "`subset`" fonts are now bundled with the gem.

=== Document attributes and options

* The deprecated `chapter-label` document attribute has been renamed to the `chapter-signifier` attribute.
* The `untitled` section option has been renamed to the `notitle` option
* Most blocks are now breakable by default.
You can apply the `unbreakable` option on a block to revert to the old behavior.

=== Require paths and APIs

* The [.path]_asciidoctor-pdf/converter_ and [.path]_asciidoctor-pdf/version_ shim scripts have been removed; use [.path]_asciidoctor/pdf/converter_ and [.path]_asciidoctor/pdf/version_ instead.
* The `Pdf` module alias in the API has been removed in favor of `PDF`.

== Deprecations

The following features are deprecated with the release of Asciidoctor PDF 2 and will be removed in the next major release.

* The `blockquote` category prefix is deprecated in the theme; use the `quote` prefix instead.
See xref:theme:quote.adoc[].
* The `key` category prefix is deprecated in the theme; use the `kbd` prefix instead.
See xref:theme:keyboard.adoc[].
* The `literal` category prefix is deprecated in the theme; use the `codespan` prefix instead.
See xref:theme:codespan.adoc[].
* The `outline-list` category prefix is deprecated in the theme; use the `list` prefix instead.
See xref:theme:list.adoc[].
* The `Optimizer#generate_file` method is deprecated; use `Optimizer#optimize_file` instead.
* The built-in `default-with-fallback-fonts` and `default-for-print-with-fallback-fonts` theme names are deprecated in favor of `default-with-font-fallbacks` and `default-for-print-with-font-fallbacks`, respectively.

== New and noteworthy

=== Paragraph roles and indent

You can define custom roles in your theme and apply them to specific paragraphs in your document.
See xref:theme:custom-role.adoc[] to learn how to create a custom role and xref:roles.adoc#custom[Use a custom role] for how to assign a custom role to a paragraph.
Applying custom roles to other blocks is not yet supported.
However, you can learn how to enable this feature using an extended converter on the xref:extend:use-cases.adoc[extended converter use cases page].

With the advent of roles being supported on paragraphs, the `lead` category in the theme has been dropped and replaced by a built-in role named `lead`.
See xref:theme:role.adoc#built-in[Built-in roles] for details.

To control the indent of inner paragraphs (instead of all paragraphs), you can set the new `prose-text-indent-inner` key in your theme.
See xref:theme:prose.adoc[] for details.

=== Breakable and unbreakable blocks

The following blocks are now breakable by default, which includes automatic anchor and caption orphan prevention:

* Admonitions
* Block images
* Code blocks (literal, listing, and source)
* Examples
* Open blocks
* Quote blocks
* Sidebars
* Verses

Tables and sections are breakable by default, but do not provide automatic anchor and caption orphan prevention.
For tables, that means the anchor and caption can be left on the current page if the table is advanced to the next page.
For sections, that means the section's title may be left on the current page if the first content block doesn't fit.
However, you can turn on orphan prevention for tables and sections by adding the (seemingly redundant) xref:breakable-and-unbreakable.adoc#breakable[breakable option] as a hint.

The `unbreakable` option can be applied to all delimited blocks (including admonitions and tables), but not sections.
When the xref:breakable-and-unbreakable.adoc#unbreakable[unbreakable option] is applied to a block, the converter will advance the block and its caption and anchor to the next page if it detects that the block would break across pages and it can fit on a single page.

=== Notitle section option

The `untitled` option on sections has been renamed to `notitle`.
With the name change, it's also gained new capabilities.
The `notitle` option hides a section title in the body of a document, but displays the title in the TOC and allows the anchor resulting from that title to still be referencable.
It can also be used to add an entry to the TOC for a preamble, anonymous preface, and imported PDF pages.
See xref:notitle.adoc[] for examples and more details.

=== Blocks and block captions

Blocks and block captions gained a lot of new theming capabilities in Asciidoctor PDF 2.
Here are a few of the highlights:

Padding::
The theme can now control the padding on a block using a 2-value array for ends and sides or 3-value array with implied left side value.
Border width::
The border width of delimited blocks, admonitions, and block images can be customized per edge with the xref:theme:blocks.adoc#border-width[border-width key].
Border style::
The border style of delimited blocks, admonitions, and block images can be changed with the xref:theme:blocks.adoc#border-style[border-style key].
Border styles include dashed, dotted, double, and solid.
Line height::
Wherever font properties are accepted in the theme, you can now control the line height of blocks using the `line-height` key.
Anchor positioning::
The anchor location for blocks can be positioned relative to the content using the `block-anchor-top` theme key.
Caption text alignment::
The text alignment of captions can now be controlled independent of the block alignment using the global xref:theme:caption.adoc[caption-text-align theme key] or per block category with `<category>-caption-text-align`.
The xref:theme:block-images.adoc#caption-text-align[image-caption-text-align] and xref:theme:tables.adoc#caption-text-align[table-caption-text-align] theme keys accept the value `inherit` in addition to the standard text alignment values.
The value `inherit` resolves to the alignment of the block image or table.
Global caption text decoration::
The text decoration style, color, and width can be applied to captions globally with the `caption-text-decoration-style`, `caption-text-decoration-color`, and `caption-text-decoration-width` theme keys.
See xref:theme:caption.adoc[] for more information.
Caption background color::
You can now specify a background color for captions globally using the `caption-background-color` theme key or per block category (`<category>-caption-background-color`).
See xref:theme:caption.adoc[] for more information.
Caption max-width::
A caption's `max-width` value can be set to a percentage of the content by passing the percentage as an argument to `fit-content` function.
First line of abstract::
The theme can control the font color of first line of abstract using `abstract-first-line-font-color` key.

.Notable fixes for blocks
* Asciidoctor PDF now uses smarter bottom margin logic that prevents extra space from being added below blocks, particularly when blocks are nested or used inside an AsciiDoc table cell.
* Syntax highlighting isn't applied to a source block if the `specialchars` substitution is disabled.
* Borders, shading, and padding aren't applied to collapsible blocks.
* The `callouts` substitution can be removed on code blocks.

=== Tables

Border widths and styles::
The table border width can be customized per edge with the xref:theme:blocks.adoc#border-width[border-width key].
The border style can be xref:theme:tables.adoc#border-style[specified per edge by assigning an array of styles] to the `border-style` key.
Border styles include dashed, dotted, and solid.

Grid widths and styles::
The width of table grid lines can be specified for rows and columns with the xref:theme:tables.adoc#grid-width[grid-width key].
The style of the grid lines can be specified for rows and columns with the xref:theme:tables.adoc#grid-style[grid-style key].
Grid styles include dashed, dotted, and solid.

Maximum caption width::
The maximum caption width for tables can be set to a percentage of the content by passing an argument to the `fit-content` function.

Caption end::
The `table-caption-side` theme key has been xref:theme:tables.adoc#end[renamed to table-caption-end].

.Notable fixes for tables
* Vertical center alignment is correctly applied to regular table cells.
* The border bottom is correctly applied to a table row when frame and grid are none.
* The font size of a literal table cells and nested blocks in AsciiDoc table cells is now scaled.
* AsciiDoc table cells inherit the font properties from the table.
* The content of an AsciiDoc table cell is prevented from overrunning the footer or subsequent pages.
* The top and bottom padding is taken into account when computing the height of an AsciiDoc table cell.
* An error message is logged if a table cell is truncated.
* Instead of raising an error, the converter logs an error and skips the table if the content cannot fit within the designated width of a cell.

=== Callout lists and numbers

The theming language now has a xref:theme:callout.adoc[callout-list category].
The new theme keys let you customize the font properties, text alignment, and item spacing of callout lists.
The `callout-list` category includes the `margin-top-after-code` key that can control the top margin of callout lists that immediately follow a code block.

.Notable fixes for callouts
* Callout numbers in a callout list stay with primary text when an item is advanced to the next page.
* A sequence of two or more callouts separated by spaces in a code block are processed correctly.
* The font family assigned to `conums` in the theme is applied to the callout numbers displayed in code blocks.

=== Images and icons

Caption end:: You can now configure whether the caption for a block image is placed above or below the image using the `caption-end` theme key.
See xref:theme:block-image.adoc#caption[Block Image Category Keys] for the list of available `image-caption` theme keys and their value types.
Text alignment roles:: The text alignment roles, such as `text-center`, are now supported on block images.
Roles for inline images:: Roles and inherited roles are now supported on inline images.
Image-based icons:: Asciidoctor PDF 2 now supports image-based icons.
They're resolved from `iconsdir` and should have the `icontype` file extension.
Add a link to an icon:: The `link` attribute can now be set on the icon macro.
Admonition icon image:: An admonition icon image can now be remote, if `allow-uri-read` is set, or a data URI.

.Notable fixes for images and icons
* Warnings from background SVGs are now passed through to the logger.
* SVGs are correctly scaled down when `fit=scale-down` is used.
* The textual label on an admonition is displayed if the icon image fails to embed.

=== Links and inline formatting

Typographical quotation marks:: You can now define single and double quotation marks, such as › and », using the `quotes` key in the theme.
See xref:theme:quotes.adoc[] for details.
Hexadecimal characters:: Character references that contain both uppercase and lowercase hexadecimal characters are now supported.
Background color and border offset on links:: You can now control the background color and border offset (only for background) of links from the theme.

.Notable links and inline formatting fixes
* A closing quote preceded by a trailing ellipsis is kept together with the text enclosed in typographic quotes.
* The font size for superscript and subscript is computed correctly when the parent element uses `em` and `%` units.
* Hyphenation exceptions are respected when a word is adjacent to a non-word character.
* The `pre-wrap` role on honored on a phrase.
* The `id` attribute can now be set on the link macro.

=== Fonts, font styles, and text transforms

Small caps:: The `text-transform` theme key now accepts the `smallcaps` value.
When `smallcaps` is specified, the lowercase ASCII letters (a-z) are replaced with their small capital letter variants.
normal_italic:: The xref:theme:text.adoc#font-style[new normal_italic value] for the `font-style` key resets the font style to normal, then applies the italic variant of a font family.
Noto Sans:: xref:theme:font-support.adoc#bundled[Noto Sans is now bundled] with Asciidoctor PDF.
It is used as a fallback font in the `sans-with-fallback-font` theme and can be declared in a custom theme.
Ceiling and floor characters:: The left and right ceiling and floor characters (⌈, ⌉, ⌊, and ⌋)were added to the M+ fallback font.
Checkmark, numero, and y with diaeresis glyphs:: The heavy checkmark glyph (✔) was added to the fallback font; the checkmark and heavy checkmark (✓ and ✔) were added to the monospaced font; the № and ÿ glyphs were added to the default and fallback fonts.

=== Covers and title page

Front and back cover images::
The front and back cover images can now be xref:theme:covers.adoc[defined in the theme] and the target can be a data URI.
Deactivate title page::
The xref:theme:title-pages.adoc#deactivate[title page can now be deactivated from the theme] by assigning `false` to the `title-page` category key.

=== TOC and PDF outline

PDF outline title and levels:: You can now deactivate the PDF outline by unsetting the `outline` document attribute (`:!outline:`) as well as customize its title with `outline-title` and the section level depth and expansion with `outlinelevels`.
See xref:pdf-outline.adoc[] for details.
Deactivate running content on TOC pages:: The header or footer can be deactivated on TOC pages by assigning the `noheader` or `nofooter` options on the toc macro.
TOC dot leader:: The theme can control the font size of the dot leader in the TOC.
TOC location:: The TOC can now be placed following the preamble by assigning the `preamble` value to the `:toc:` document attribute.
Also, the TOC is only displayed at the first location of a toc macro.
Extended converter:: An extended converter can now override the `get_entries_for_toc` method to insert or filter TOC entries.

.Notable fixes for the TOC
* An image now renders at the end of a section title in the corresponding TOC entry.

[#_footnotes]
=== Footnotes

Reset numbering:: Footnote numbering is now reset in each chapter.
Footnote reference label:: The xreftext of a chapter is now added to the label of a footnote reference that refers to a previous chapter.
Unresolved footnote color:: The theme can configure the font color of an unresolved footnote using the `unresolved` role.

.Notable fixes for footnotes
* A missing footnote reference is shown in superscript.
* Footnotes defined in an AsciiDoc table cell are now rendered with the footnotes at the end of an article or chapter.

=== Index

Index columns:: The theme can now configure the number of index columns using the `index-columns` key.
Style of page numbers:: The new `index-pagenum-sequence-style` document attribute controls the style of sequential page numbers in the index when `media=screen`.

.Notable fixes for the index
* The index section isn't rendered if there are no index entries.
* A blank line is no longer inserted in the index when a term is forced to break.
* Prepress page margins  are honored on subsequent pages in the index.
* Space in front of a hidden index term is now collapsed.

=== Running content and page numbering

Select the page where running content starts:: Specify the page on which the running content starts being displayed by xref:theme:add-running-content.adoc#start-at[assigning an integer to the start-at theme key] on the `running-content` category.
Running content can also start after the TOC, wherever the TOC is placed, by assigning the keyword `after-toc` to the `start-at` key.

Configure where integer page numbering starts:: Specify the page on which the integer (1-based) page numbering begins using the xref:theme:page-numbers.adoc#start-at[start-at key on the page-numbering category].
Integer page numbering can start at the front cover by assigning the keyword `cover` to the `start-at` key.
Or, you can have the page numbering start after the TOC, wherever the TOC is placed, by assigning `after-toc` to the `start-at` key.
Alternatively, the theme can specify an offset from the first body page where the page numbering should begin when an integer is assigned to `start-at`.

Margin and content margin:: The margin and content margin of the running content per periphery (header or footer) and per side (recto or verso) can now be configured from the theme.
The margins in running content can be specified using a 2-value array for ends and sides or 3-value array with implied left side value.

Part and chapter numbers:: If the `partnums` attribute is set, the `part-numeral` attribute is automatically set in the running content.
If the `sectnums` attribute is set, the `chapter-numeral` attribute is automatically set in the running content.

Select a background per layout:: The `page-layout` attribute is now set in the running content.
You can use this attribute to select a background per layout.

.Notable fixes for running content and page numbering
* The `pdf-folio-placement` setting is honored even when `media=prepress`.
* Prepress page margins honor the value of `pdf-folio-placement`.

=== Theming system

Print-optimised themes:: Asciidoctor PDF 2 introduces two new print-optimized themes, named `default-for-print` and `default-for-print-with-fallback-font`.
Extends hierarchy:: Asciidoctor PDF only extends a theme in the `extends` hierarchy once unless the theme is modified with `!important`.
Power operator:: The theming language now supports the power operator.
It has the same precedence as multiply and divide.
Base theme changes:: The top and bottom padding on quote and verse blocks has been reduced in the base theme.
The `base-border-color` is now set and used as the default border color.
The border colors have been removed in the base theme so all border colors can be controlled using the `base-border-color` key when extending the theme.
Default theme changes:: The top and bottom padding on quote blocks is now uniform in the default theme.
Rouge theme:: A Rouge theme can now be specified as a theme class or instance (API only).
