Instead rely on the markdown writer with appropriate extensions.
Export writeCommonMark variant from Markdown writer.
This changes a few small things in rendering markdown,
e.g. w/r/t requiring backslashes before spaces inside
super/subscripts.
Previously it included all of the following, which make
sense for the legacy markdown_github but not for gfm,
since they are part of base commonmark and thus
can't be turned off in gfm:
- `Ext_all_symbols_escapable`
- `Ext_backtick_code_blocks`
- `Ext_fenced_code_blocks`
- `Ext_space_in_atx_header`
- `Ext_intraword_underscores`
- `Ext_lists_without_preceding_blankline`
- `Ext_shortcut_reference_links`
`
These have been removed from `githubMarkdownExtensions`, though
they're still turned on for legacy `markdown_github`.
This allows attributes to be added to any block or inline
element, in principle. (Though in many cases this will be
done by adding a Div or Span container, since pandoc's
AST doesn't have a slot for attributes for most elements.)
Currently this is only possible with the commonmark and gfm
readers.
Add `Ext_attributes` constructor for `Extension` [API change].
...instead of cmark-gfm (a wrapper around a C library).
We can now support many more pandoc extensions for
commonmark and gfm.
Add fenced_code_attributes to gfm/commonmark extensions.
Screen readers read an image's `alt` attribute and the figure caption,
both of which come from the same source in pandoc. The figure caption is
hidden from screen readers with the `aria-hidden` attribute. This
improves accessibility.
For HTML4, where `aria-hidden` is not allowed, pandoc still uses an
empty `alt` attribute to avoid duplicate contents.
Closes: #6491
The reader now parses the contents of the markdown cell to a Pandoc
structure, but *also* stores the raw markdown in a `source`
attribute on the cell Div. When we convert back to markdown,
this attribute is stripped off and the original source is used.
When we convert to other formats, the attribute is usually
ignored (though it will come through in HTML as a `data-source`
attribute, not unhelpfully).
I'll note some potential drawbacks of this approach:
- It makes it impossible to use pandoc to clean up or
change the contents of markdown cells, e.g.
going from `+smart` to `-smart`.
- There may be formats where the addition of the `source`
attribute is problematic. I can't think of any, though.
Closes#5408.
