feat(icon): support using highlight group in add_icon_fn()

.editorconfig

@@ -0,0 +1,4 @@
+[*]
+indent_style = space
+indent_size = 2
+tab_width = 2

autoload/dirvish.vim

@@ -4,6 +4,7 @@ let s:noswapfile = (2 == exists(':noswapfile')) ? 'noswapfile' : ''
 let s:noau       = 'silent noautocmd keepjumps'
 let s:cb_map = {}   " callback map
 let s:rel = get(g:, 'dirvish_relative_paths', 0)
+let s:virttext_feat = has('nvim-0.8') ? 'extmark' : ((v:version >= 901 && has('textprop'))? 'textprop': 'conceal')
 
 " Debug:
 "     echo '' > dirvish.log ; tail -F dirvish.log
@@ -426,12 +427,11 @@ func! s:apply_icons() abort
   if 0 == len(s:cb_map)
     return
   endif
-  let l:feat = has('nvim-0.8') ? 'extmark' : ((v:version >= 901 && has('textprop'))? 'textprop': 'conceal')
-  if l:feat ==# 'extmark'
+  if s:virttext_feat ==# 'extmark'
     if !exists('s:ns_id')
       let s:ns_id = nvim_create_namespace('dirvish.icons')
     endif
-  elseif l:feat ==# 'textprop'
+  elseif s:virttext_feat ==# 'textprop'
     if !exists('s:prop_type')
       let s:prop_type = 'dirvish.icons'
       call prop_type_add(s:prop_type, {})
@@ -443,24 +443,36 @@ func! s:apply_icons() abort
   let i = 0
   for f in getline(1, '$')
     let i += 1
-    let icon = ''
     for id in sort(keys(s:cb_map))
       let icon = s:cb_map[id](f)
-      if -1 != match(icon, '\S')
-        break
+      if type(icon) == type('')
+        if -1 != match(icon, '\S')
+          unlet icon
+          break
+        endif
       endif
     endfor
-    if icon != ''
-      if l:feat ==# 'extmark'
-        call nvim_buf_set_extmark(0, s:ns_id, i-1, 0, #{virt_text: [[icon, 'DirvishColumnHead']], virt_text_pos: 'inline'})
-      elseif l:feat ==# 'textprop'
-        call prop_add(i, 1, #{type: s:prop_type, text: icon})
+    if exists('l:icon')
+      if s:virttext_feat ==# 'extmark'
+        let l:virt_text = type(icon) == type({}) ? [[icon.icon, icon.hl]] : [[icon, 'DirvishColumnHead']]
+        call nvim_buf_set_extmark(0, s:ns_id, i-1, 0, #{virt_text: l:virt_text, virt_text_pos: 'inline'})
+      elseif s:virttext_feat ==# 'textprop'
+        if type(icon) == type('')
+          call prop_add(i, 1, #{type: s:prop_type, text: icon})
+        else
+          let l:prop_type = prop_type_get('dirvish.'.icon.hl, {})
+          if l:prop_type == {}
+            call prop_type_add('dirvish.'.icon.hl, #{highlight: icon.hl})
+          endif
+          call prop_add(i, 1, #{type: 'dirvish.'.icon.hl, text: icon.icon})
+        endif
       else
         let isdir = (f[-1:] == s:sep)
         let f = substitute(s:f(f), escape(s:sep,'\').'$', '', 'g')  " Full path, trim slash.
         let tail_esc = escape(fnamemodify(f,':t').(isdir?(s:sep):''), '[,*.^$~\')
         exe 'syntax match DirvishColumnHead =\%'.i.'l^.\{-}\ze'.tail_esc.'$= conceal cchar='.icon
       endif
+      unlet icon
     endif
   endfor
 endf

doc/dirvish.txt

@@ -114,12 +114,27 @@ dirvish#add_icon_fn(fn)
     a given path, wins. Best practice: if you don't have anything meaningful
     to show for a given path, return empty string (or whitespace).
 
-    {fn} is any |Funcref| that takes a path (string) and returns a string
-    (the "icon"). Example: >vim
+    {fn} is any |Funcref| that takes a path (string) and returns an `icon-item` as
+    a |string| or a |dict| with the following keys:
+        - "icon" (|string|): the string representing the icon.
+        - "hl"   (|string|): the highlight group to use for the icon.
+
+    Note: If your Vim isn't Vim 9.1+ with |+textprop| or Nvim 0.8+, `icon-item`
+    can only be a character.
+
+    Example that returns a string: >vim
         call dirvish#add_icon_fn({p -> p[-1:]=='/'?'📂':'📄'})
 <
-    Note: multi-character icons are only supported on Nvim 0.8+ or Vim 9.1+
-    with |+textprop|.
+    Example that uses |mini.icons| <https://github.com/echasnovski/mini.icons>
+    0.15.0 as icon provider >lua
+        --- NOTE: mini.icons must be loaded before vim-dirvish
+        vim.fn['dirvish#add_icon_fn'](function(p)
+          local get = require('mini.icons').get
+          local icon, hl = get(p:sub(-1) == '/' and 'directory' or 'file', p)
+          icon = icon .. ' '
+          return { icon = icon, hl = hl }
+        end)
+<
 
                                                     *dirvish#remove_icon_fn()*
 dirvish#remove_icon_fn(fn_id)