Problem:
Headings in :help do not stand out visually.
Solution:
Define a non-standard `@markup.heading.1.delimiter` group and
special-case it in `highlight_group.c`.
FUTURE:
This is a cheap workaround until we have #25718 which will enable:
- fully driven by `vimdoc/highlights.scm` instead of using highlight
tricks (`guibg=bg guifg=bg guisp=fg`)
- better support of "cterm" ('notermguicolors')
Tree-sitter queries can add URLs to a capture using the `#set!`
directive, e.g.
(inline_link
(link_text) @text.reference
(link_destination) @text.uri
(#set! @text.reference "url" @text.uri))
The pattern above is included by default in the `markdown_inline`
highlight query so that users with supporting terminals will see
hyperlinks. For now, this creates a hyperlink for *all* Markdown URLs of
the pattern [link text](link url), even if `link url` does not contain
a valid protocol (e.g. if `link url` is a path to a file). We may wish to
change this in the future to only linkify when the URL has a valid
protocol scheme, but for now we delegate handling this to the terminal
emulator.
In order to support directives which reference other nodes, the
highlighter must be updated to use `iter_matches` rather than
`iter_captures`. The former provides the `match` table which maps
capture IDs to nodes. However, this has its own challenges:
- `iter_matches` does not guarantee the order in which patterns are
iterated matches the order in the query file. So we must enforce
ordering manually using "subpriorities" (#27131). The pattern index of
each match dictates the extmark's subpriority.
- When injections are used, the highlighter contains multiple trees. The
pattern indices of each tree must be offset relative to the maximum
pattern index from all previous trees to ensure that extmarks appear
in the correct order.
- The `iter_captures` implementation currently has a bug where the
"match" table is only returned for the first capture within a pattern
(see #27274). This bug means that `#set!` directives in a query
apply only to the first capture within a pattern. Unfortunately, many
queries in the wild have come to depend on this behavior.
`iter_matches` does not share this flaw, so switching to
`iter_matches` exposed bugs in existing highlight queries. These
queries have been updated in this repo, but may still need to be
updated by users. The `#set!` directive applies to the _entire_ query
pattern when used without a capture argument. To make `#set!`
apply only to a single capture, the capture must be given as an
argument.
Problem: Sharing queries with upstream and Helix is difficult due to
different capture names.
Solution: Define and document a new set of standard captures that
matches tree-sitter "standard captures" (where defined) and is closer to
Helix' Atom-style nested groups.
This is a breaking change for colorschemes that defined highlights based
on the old captures. On the other hand, the default colorscheme now
defines links for all standard captures (not just those used in bundled
queries), improving the out-of-the-box experience.
