feat(icons): use virtual text if possible (has('nvim') or has('textprop'))

Closes justinmk#145, justinmk#253

Author: brianhuster

autoload/dirvish.vim

@@ -426,7 +426,19 @@ func! s:apply_icons() abort
   if 0 == len(s:cb_map)
     return
   endif
-  highlight clear Conceal
+  if has('nvim')
+    if !exists('s:ns_id')
+      let s:ns_id = nvim_create_namespace('dirvish.icons')
+    endif
+  elseif v:version >= 901 && has('textprop')
+    if !exists('s:prop_type')
+      let s:prop_type = 'dirvish.icons'
+      call prop_type_add(s:prop_type, {})
+    endif
+  else
+    highlight clear Conceal
+  endif
+
   let i = 0
   for f in getline(1, '$')
     let i += 1
@@ -438,11 +450,17 @@ func! s:apply_icons() abort
       endif
     endfor
     if icon != ''
-      let isdir = (f[-1:] == s:sep)
-      let f = substitute(s:f(f), escape(s:sep,'\').'$', '', '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
+			if has('nvim')
+				call nvim_buf_set_extmark(0, s:ns_id, i-1, 0, #{virt_text: [[icon, 'DirvishColumnHead']], virt_text_pos: 'inline'})
+			elseif v:version >= 901 && has('textprop')
+				call prop_add(i, 1, #{type: s:prop_type, text: icon})
+			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
+		endif
   endfor
 endf