styleFromMeta
=============

[![Hackage](https://img.shields.io/hackage/v/pandoc-stylefrommeta)](https://hackage.haskell.org/package/pandoc-stylefrommeta)

Pandoc filter to apply styles found in the metadata of the document to various
objects.

Styling is supported for following types of objects:

- Standalone and inlined images
- Links
- Paragraphs (with restrictions, see below)

Styles are read from the metadata of the document: they may reside inside the
document or in a separate YAML file. For example,

```yaml
    ---
    img_style :
      html : |
        ~~~~~
        <div style="clear: both; text-align: center; margin-bottom: 16px">
        <a href="$SRC$" style="margin-left: 10em;" alt="$ALT$">
        <img border="0" src="$SRC$" /></a></div>
        ~~~~~
      latex : |
        ~~~~~
        \begin{center}
        \includegraphics{$$SRC$$}
        \end{center}
        ~~~~~
      rst: |
        ~~~~~
        .. image:: $$SRC$$
           :height: 100px
           :width: 200 px
           :scale: 50 %
           :alt: $$ALT$$
           :align: right
        ~~~~~
      haddock: |
        ~~~~~
        <<$$SRC$$ An image $ALT$>>
        ~~~~~
    link_style :
      html : |
        ~~~~~
        <a href="$SRC$" style="margin-left: 1em; margin-right: 1em;">$ALT$</a>
        ~~~~~
      latex : |
        ~~~~~
        \href{$SRC$}{\colorbox{green}{$ALT$}}
        ~~~~~
    para_style :
      html : |
        <span style="display: block; margin-bottom: 16px;"></span>
    ...
```

declares styles `img_style`, `link_style` and `para_style`. Their names (except
for the last) are arbitrarily chosen and may be referred from the document, for
example

```markdown
    ![$img_style$](../images/an_image.png)
    [$link_style$ *here*](http://example.com/)
```

Placeholders `$ALT$`, `$SRC$` and `$TITLE$` from style declarations are to be
replaced by corresponding data found in the object declaration. In this example
`*here*` corresponds to `$ALT$`, and `http://example.com/` corresponds to
`$SRC$`. Placeholders `$$SRC$$` and `$$TITLE$$` are replaced verbatim, in
`$$ALT$$` all formatting gets removed. In the example `$$SRC$$` is used to keep
underscores unescaped as they may reside in image names.

Notice that all metablocks contents, with the exclusion of `para_style`, are
wrapped inside code blocks. This let the contents be substituted verbatim for
any output format. However, raw HTML and TeX blocks are well supported by
Pandoc, so we could rewrite parts of the example like this:

```yaml
    ---
    img_style :
      html : |
        <div style="clear: both; text-align: center; margin-bottom: 16px">
        <a href="$SRC$" style="margin-left: 10em;" alt="$ALT$">
        <img border="0" src="$SRC$" /></a></div>
      latex : |
        \begin{center}
        \includegraphics{$$SRC$$}
        \end{center}

    # ...

    ...
```

The filter has support for raw HTML and TeX blocks, but this support is not
complete, and in some cases substitutions may fail. In addition, Pandoc may
re-format substitutions. That's why this method is not recommended to use.

As soon as paragraphs do not have place where to put extra data, style
`para_style` is applied to all paragraphs in the document. Currently, only
transformation to a span block is supported (which is probably useful only in
HTML). Any contents found between opening and closing span tags are ignored:
actual paragraph contents will be inserted inside them. Notice that wrapping
inside code blocks is not allowed in `para_style` block.