vis: add slides lexer for my pandoc beamer presentations

2 files changed, 103 insertions, 0 deletions

diff --git a/config/vis/lexers/slides.lua b/config/vis/lexers/slides.lua
new file mode 100644
index 0000000..98769cc
--- /dev/null
+++ b/config/vis/lexers/slides.lua
@@ -0,0 +1,101 @@
+-- Copyright 2006-2024 Mitchell. See LICENSE.
+-- Markdown LPeg lexer.
+
+local lexer = lexer
+local P, S, B = lpeg.P, lpeg.S, lpeg.B
+
+local lex = lexer.new(..., {no_user_word_lists = true})
+
+-- Distinguish between horizontal and vertical space so html start rule has a chance to match.
+lex:modify_rule('whitespace', lex:tag(lexer.WHITESPACE, S(' \t')^1 + S('\r\n')^1))
+
+-- Block elements.
+local function h(n)
+  return lex:tag(string.format('%s.h%s', lexer.HEADING, n),
+    lexer.to_eol(lexer.starts_line(string.rep('#', n))))
+end
+lex:add_rule('header', h(6) + h(5) + h(4) + h(3) + h(2) + h(1))
+
+lex:add_rule('hr',
+  lex:tag('hr', lpeg.Cmt(lexer.starts_line(lpeg.C(S('*-_')), true), function(input, index, c)
+    local line = input:match('[^\r\n]*', index):gsub('[ \t]', '')
+    if line:find('[^' .. c .. ']') or #line < 2 then return nil end
+    return (select(2, input:find('\r?\n', index)) or #input) + 1 -- include \n for eolfilled styles
+  end)))
+
+lex:add_rule('list', lex:tag(lexer.LIST,
+  lexer.starts_line(lexer.digit^1 * '.' + S('*+-'), true) * S(' \t')))
+
+local hspace = lexer.space - '\n'
+local blank_line = '\n' * hspace^0 * ('\n' + P(-1))
+
+local code_line = lexer.starts_line((B('    ') + B('\t')) * lexer.to_eol(), true)
+local code_block =
+  lexer.range(lexer.starts_line('```', true), '\n```' * hspace^0 * ('\n' + P(-1))) +
+    lexer.range(lexer.starts_line('~~~', true), '\n~~~' * hspace^0 * ('\n' + P(-1)))
+local code_inline = lpeg.Cmt(lpeg.C(P('`')^1), function(input, index, bt)
+  -- `foo`, ``foo``, ``foo`bar``, `foo``bar` are all allowed.
+  local _, e = input:find('[^`]' .. bt .. '%f[^`]', index)
+  return (e or #input) + 1
+end)
+lex:add_rule('block_code', lex:tag(lexer.CODE, code_line + code_block + code_inline))
+
+lex:add_rule('blockquote',
+  lex:tag(lexer.STRING, lpeg.Cmt(lexer.starts_line('>', true), function(input, index)
+    local _, e = input:find('\n[ \t]*\r?\n', index) -- the next blank line (possibly with indentation)
+    return (e or #input) + 1
+  end)))
+
+-- Span elements.
+lex:add_rule('escape', lex:tag(lexer.DEFAULT, P('\\') * 1))
+
+local link_text = lexer.range('[', ']', true)
+local link_target =
+  '(' * (lexer.any - S(') \t'))^0 * (S(' \t')^1 * lexer.range('"', false, false))^-1 * ')'
+local link_url = 'http' * P('s')^-1 * '://' * (lexer.any - lexer.space)^1 +
+  ('<' * lexer.alpha^2 * ':' * (lexer.any - lexer.space - '>')^1 * '>')
+lex:add_rule('link', lex:tag(lexer.LINK, P('!')^-1 * link_text * link_target + link_url))
+
+local link_ref = lex:tag(lexer.REFERENCE, link_text * S(' \t')^0 * lexer.range('[', ']', true))
+local ref_link_label = lex:tag(lexer.REFERENCE, lexer.range('[', ']', true) * ':')
+local ws = lex:get_rule('whitespace')
+local ref_link_url = lex:tag(lexer.LINK, (lexer.any - lexer.space)^1)
+local ref_link_title = lex:tag(lexer.STRING, lexer.range('"', true, false) +
+  lexer.range("'", true, false) + lexer.range('(', ')', true))
+lex:add_rule('link_ref', link_ref + ref_link_label * ws * ref_link_url * (ws * ref_link_title)^-1)
+
+local punct_space = lexer.punct + lexer.space
+
+-- Handles flanking delimiters as described in
+-- https://github.github.com/gfm/#emphasis-and-strong-emphasis in the cases where simple
+-- delimited ranges are not sufficient.
+local function flanked_range(s, not_inword)
+  local fl_char = lexer.any - s - lexer.space
+  local left_fl = B(punct_space - s) * s * #fl_char + s * #(fl_char - lexer.punct)
+  local right_fl = B(lexer.punct) * s * #(punct_space - s) + B(fl_char) * s
+  return left_fl * (lexer.any - blank_line - (not_inword and s * #punct_space or s))^0 * right_fl
+end
+
+local asterisk_strong = flanked_range('**')
+local underscore_strong = (B(punct_space) + #lexer.starts_line('_')) * flanked_range('__', true) *
+  #(punct_space + -1)
+lex:add_rule('strong', lex:tag(lexer.BOLD, asterisk_strong + underscore_strong))
+
+local asterisk_em = flanked_range('*')
+local underscore_em = (B(punct_space) + #lexer.starts_line('_')) * flanked_range('_', true) *
+  #(punct_space + -1)
+lex:add_rule('em', lex:tag(lexer.ITALIC, asterisk_em + underscore_em))
+
+-- Embedded LaTeX.
+local latex = lexer.load('latex')
+local latex_start_rule = lexer.starts_line(P(' ')^-3) * #P('\\') * latex:get_rule('environment') -- P(' ')^4 starts code_line
+local latex_end_rule = #blank_line * ws
+lex:embed(latex, latex_start_rule, latex_end_rule)
+
+-- Embedded yaml.
+local yaml = lexer.load('yaml')
+local yaml_start_rule = #lexer.starts_line('---') * ws
+local yaml_end_rule = #lexer.starts_line('---') * ws
+lex:embed(yaml, yaml_start_rule, yaml_end_rule)
+
+return lex
diff --git a/config/vis/visrc.lua b/config/vis/visrc.lua
index b20ab91..fd118cb 100644
--- a/config/vis/visrc.lua
+++ b/config/vis/visrc.lua
@@ -87,6 +87,8 @@ vis.events.subscribe(vis.events.WIN_OPEN, function(win)
       win:set_syntax("diff")
     elseif win.file.name:find('meson.build') and win.syntax ~= 'meson' then
       win:set_syntax('python')
+    elseif win.file.name:find('slides.md') then
+      win:set_syntax('slides')
     end
 
     if win.syntax == "python" or win.syntax == "rust" then