Add support for escape sequences

runtime/autoload/man.vim

@@ -161,7 +161,7 @@ function! s:put_page(page) abort
   while getline(1) =~# '^\s*$'
     silent keepjumps 1delete _
   endwhile
-  call man#highlight_backspaced_text()
+  call man#highlight_formatted_text()
   setlocal filetype=man
 endfunction
 
@@ -375,7 +375,7 @@ function! man#init_pager() abort
   else
     keepjumps 1
   endif
-  call man#highlight_backspaced_text()
+  call man#highlight_formatted_text()
   " This is not perfect. See `man glDrawArraysInstanced`. Since the title is
   " all caps it is impossible to tell what the original capitilization was.
   let ref = substitute(matchstr(getline(1), '^[^)]\+)'), ' ', '_', 'g')
@@ -387,12 +387,12 @@ function! man#init_pager() abort
   execute 'silent file man://'.fnameescape(ref)
 endfunction
 
-function! man#highlight_backspaced_text() abort
+function! man#highlight_formatted_text() abort
   let l:modifiable = &modifiable
   set modifiable
 
   lua man = require("man")
-  luado return man.highlight_backspaced(line, linenr)
+  luado return man.highlight_formatted(line, linenr)
 
   let &modifiable = l:modifiable
 endfunction

runtime/lua/man.lua

@@ -1,12 +1,60 @@
-local function highlight_backspaced(line, linenr)
+local function highlight_formatted(line, linenr)
   local chars = {}
   local prev_char = ''
-  local overstrike = false
+  local overstrike, escape = false, false
   local hls = {} -- Store highlight groups as { attr, start, end }
-  local NONE, BOLD, UNDERLINE = 0, 1, 2
+  local NONE, BOLD, UNDERLINE, ITALIC = 0, 1, 2, 3
+  local hl_groups = {[BOLD]="manBold", [UNDERLINE]="manUnderline", [ITALIC]="manItalic"}
   local attr = NONE
   local byte = 0 -- byte offset
 
+  local function end_attr_hl(attr)
+    for i, hl in ipairs(hls) do
+      if hl[1] == attr and hl[3] == -1 then
+        hl[3] = byte
+        hls[i] = hl
+      end
+    end
+  end
+
+  local function add_attr_hl(code)
+    local on = true
+    if code == 0 then
+      attr = NONE
+      on = false
+    elseif code == 1 then
+      attr = BOLD
+    elseif code == 21 or code == 22 then
+      attr = BOLD
+      on = false
+    elseif code == 3 then
+      attr = ITALIC
+    elseif code == 23 then
+      attr = ITALIC
+      on = false
+    elseif code == 4 then
+      attr = UNDERLINE
+    elseif code == 24 then
+      attr = UNDERLINE
+      on = false
+    else
+      attr = NONE
+      return
+    end
+
+    if on then
+      hls[#hls + 1] = {attr, byte, -1}
+    else
+      if attr == NONE then
+        for a, _ in pairs(hl_groups) do
+          end_attr_hl(a)
+        end
+      else
+        end_attr_hl(attr)
+      end
+    end
+  end
+
   -- Break input into UTF8 characters
   for char in line:gmatch("[^\128-\191][\128-\191]*") do
     if overstrike then
@@ -45,6 +93,24 @@ local function highlight_backspaced(line, linenr)
       prev_char = ''
       byte = byte + #char
       chars[#chars + 1] = char
+    elseif escape then
+      -- Use prev_char to store the escape sequence
+      prev_char = prev_char .. char
+      local sgr = prev_char:match("^%[([\020-\063]*)m$")
+      if sgr then
+        local match = ''
+        while sgr and #sgr > 0 do
+          match, sgr = sgr:match("^(%d*);?(.*)")
+          add_attr_hl(match + 0) -- coerce to number
+        end
+        escape = false
+      elseif not prev_char:match("^%[[\020-\063]*$") then
+        -- Stop looking if this isn't a partial CSI sequence
+        escape = false
+      end
+    elseif char == "\027" then
+      escape = true
+      prev_char = ''
     elseif char == "\b" then
       overstrike = true
       prev_char = chars[#chars]
@@ -61,7 +127,7 @@ local function highlight_backspaced(line, linenr)
       vim.api.nvim_buf_add_highlight(
         0,
         -1,
-        hl[1] == BOLD and "manBold" or "manUnderline",
+        hl_groups[hl[1]],
         linenr - 1,
         hl[2],
         hl[3]
@@ -72,4 +138,4 @@ local function highlight_backspaced(line, linenr)
   return table.concat(chars, '')
 end
 
-return { highlight_backspaced = highlight_backspaced }
+return { highlight_formatted = highlight_formatted }

runtime/syntax/man.vim

@@ -21,6 +21,7 @@ highlight default link manSubHeading     Function
 function! s:init_highlight_groups()
   highlight default manUnderline cterm=underline gui=underline
   highlight default manBold      cterm=bold      gui=bold
+  highlight default manItalic    cterm=italic    gui=italic
 endfunction
 
 augroup man_init_highlight_groups