anchor.diff:  * conum not aligned vertically with callout text (perhaps too small?)
   * conum should never wrap (push it into the text if necessary)
   * decouple theme settings for section titles and discrete headings
  -* table should expand to 100% if "spread" role is set
  +* decouple listing/literal/source theme settings; currently all under code
   * replace explicit char ranges with classes in regexp (e.g., [[:word:]] or \w)
  -* test Rouge upgrade (should address workaround we have in encoder)
   * devise a way to specify a value as a string literal (variable replacement only) in theme
  -* document pdfwidth in themeing guide (currently no mention of it)
  -* convert "-" in variable name in theme to underscore (e.g., $base-font-size)
   * apply calculated theme values after loading?
   * allow "content" in place of recto_content & verso_content for running header/footer
  +  - still relevant after restructuring?
  +* be more specific in theming guide as to where prose_margin_top and prose_margin_bottom apply
   * allow image to span width of page (role=canvas, role=canvas-x or role=canvas-y); if role is canvas or canvas-y, then it does not consume height
     - partially addressed by vw units
   * allow valign value to be a number (requires change to Prawn)
   * layout SVG without using keep_together (since we know all the dimensions)
     - fix SVG to a single page (check height + caption height)
  -* allow background color to be set for heading
  +* allow background color to be set for chapter / heading
   * allow border to be set around block image
  -* switch wolpertinger to howling wolf mouse
  +* switch wolpertinger to howling grasshopper mouse
   * file issue in prawn to dispatch to image handler for images it doesn't know about
  -* support arbitrary numeric entities (convert to unicode)
   * add brief mention in theming guide that deeper customizations can be achieved by extending the converter
  +  - reference infoq-minibook repo & blog post
  +  - document how to extend the converter, use Prawn
   * allow alignment of list to be set separately from base align (and perhaps a hint in document)
  -* due to order of loading, getting warnings when redefining methods in Asciidoctor core
  -* prawn-pdfimage https://github.com/packetmonkey/prawn-pdfimage
  +* is https://github.com/packetmonkey/prawn-pdfimage a safer way than prawn-templates to import PDF as image?
   * rename ThemeLoader to ThemeReader (or ThemeManager)?
  -* document autofit option on verbatim blocks
  -* document how to extend the converter, use Prawn
  -* using tabs instead of spaces for source code indentation allows leading whitespace to be preserved when copying
  -  - is this always the case?
  +* SIMPLE: document autofit option on verbatim blocks (in README?)
   * normalize step leaves space after endline (i.e., `\n `) at a hard line break (doesn't seem to affect flow)
   
  -* *margin per heading level* (see https://github.com/asciidoctor/asciidoctor-pdf/issues/176)
  +* *margin per heading level* (#176)
  +* can't put margin top on chapter (chapter_top?) (#576)
   * document how to override the Ruby code to get custom styling in the theming guide
   * convenience method to check if there's enough room for another line on page
   * allow font size in theme to be specified in em or %
   * allow dynamic background image with page number in path
   * running header/footer covers content (perhaps just a limitation that needs to be documented)
   * document that palette-based transparent in PNGs is not supported
  -* add broader character range to monospace font so we can drop fallback font by default (#282)
  -  - consider having a fallback for prose and fallback for literal
   * file issue for prawn to preserve space (even w/ guards, spaces don't preserve over wrapped lines)
     - if this is fixed, we can remove all the guard indent code
   * file issue for prawn to support spacer fragments with fixed width / height and no text (or text is ignored in calculations)
  
positive.code: 
  == TODO
  
  * use <a id=""></a> instead of <a name=""></a> for anchor point in formatted text
    - benchmark to see if it's faster to use empty or non-empty element in parser
  * rename "convert_context_for_" since it can collide with existing blocks
  * rework resolve_image_path API so it's more logical; override based on type of first argument; document as option
  * implicit width of inline image calculated incorrectly (see sandbox/issue-494)
  * QUESTION should we report full image path of gif in warning message?
  * QUESTION should we add destination to top of imported PDF page?
    - import page should accept id as section, optional argument
  * leading (line height) isn't applied when content is split across pages
  * generate fonts without PS Glyph Names to reduce file size (waiting PR #550 to be marged)
    - create script that can generate fonts entirely from original font source
  * if start_new_page is called at end of layout_chapter_title, and media=prepress, ghostscript reports an error
    - problem is no color space is set; can fix by calling update_colors before advancing to recto page in start_new_chapter
    - maybe introduce a skip_page helper to combine these operations?
  * SIMPLE: document vw/vh measurement units in theming guide (make it clear it only applies in certain cases)
  * SIMPLE: in theming guide, emphasize not using the fallback font when working with very large documents; explain that default theme uses a fallback font
  * document how to test / use a PR
    - see https://github.com/asciidoctor/asciidoctor-pdf/issues/462#issuecomment-246200953
  * FILE ISSUE break printed URIs at each forward slash (and perhaps at ? and & too)
  * add empty? method to Page (instead of page_empty? on document)
  * SIMPLE: add warning that AsciiDoc table cell content is not supported; print as raw source
  * FILE ISSUE in prawn-svg not to move cursor (maybe an option?)
  * FILE ISSUE: prevent import_page from adding an extra page; leaves blank page when placing two inserts in a row
    - have import_page first delete current page if page is empty
  * FILE ISSUE in prawn: go_to_page should accept second argument that is cursor position
  * autowidth causes cells in header row to break word (wraps by char to fit; does not expand table)
  * UNRESOLVED: dry_run should start at cursor of main document (or as option); total height calculation would need to be revised
    - box_height isn't currently accurate when it spans more than one page
    - this should fix height calculation when content is split over a page break (leaving small amount of excess)
    - however, if cursor is advanced to fit content on page, then that excess will cause box_height to be too large
    - life would be simpler if Prawn allowed us to draw graphics at bottom layer
  * allow height of inline image to be set to line height (perhaps 1em?)
  * space around inline anchors/index entries doesn't get collapsed by text formatter
  * add support for format attribute on image macro to image-related attributes such as title-page-background-image
    - support explicit image format for cover page image and page background image
  * need some sort of post_construct method for converter that receives document
    - monkeypatch?
  * backport resize method from prawn-svg and use it in converter
  * create document that explains how built-in fonts are generated and what subsets are selected
  
negative.code:   - chapter and section number (easily solved by previous)
    - separate running content for chapter page (by default uses normal content)
  * should we rename base_ to body_ to make it more familiar to CSS developers?
  * support !include in theme file (#571)
  * add cover page example to chronicles so people see how to use it
  * don't orphan a single line of paragraph (send it with a buddy line)
    - implement orphan sentences for paragraph
  * implement stem support
    - see asciidoctor-mathematical and asciidoctor-mathoid
  * fail gracefully if theme file cannot be found
  * expose theme variable on document (attr_reader?)
  * dedicated style for top/bottom margin of outline list
    - allow margin top and bottom to be set for lists (applies to outer-most list)
    - allow spacing between nested lists levels be configured in theme
  * need dedicated theme styles for paragraph spacings, etc
  * recto/verso indentation (on body?)
  * don't indent and draw line next to quote block unless width > 0 or color != transparent
  * subtitles for chapters
  