Merge pull request #394 from lambdalisue/fix-session

Properly restore fern on a different tab through session

autoload/fern/helper/sync.vim

@@ -11,6 +11,18 @@ endfunction
 
 let s:sync = {}
 
+function! s:sync_winid() abort dict
+  let helper = self.helper
+  if win_id2tabwin(helper.winid) != [0, 0]
+    return helper.winid
+  endif
+  " Original window has disappeared
+  let winids = win_findbuf(helper.bufnr)
+  let helper.winid = len(winids) is# 0 ? -1 : winids[0]
+  return helper.winid
+endfunction
+let s:sync.winid = funcref('s:sync_winid')
+
 function! s:sync_echo(message, ...) abort dict
   let hl = a:0 ? a:1 : 'None'
   try
@@ -73,14 +85,22 @@ let s:sync.get_selected_nodes = funcref('s:sync_get_selected_nodes')
 function! s:sync_get_cursor() abort dict
   let helper = self.helper
   let fern = helper.fern
-  return s:WindowCursor.get_cursor(helper.winid)
+  let winid = self.winid()
+  if winid is# -1
+    return [0, 0]
+  endif
+  return s:WindowCursor.get_cursor(winid)
 endfunction
 let s:sync.get_cursor = funcref('s:sync_get_cursor')
 
 function! s:sync_set_cursor(cursor) abort dict
   let helper = self.helper
   let fern = helper.fern
-  call s:WindowCursor.set_cursor(helper.winid, a:cursor)
+  let winid = self.winid()
+  if winid is# -1
+    return
+  endif
+  call s:WindowCursor.set_cursor(winid, a:cursor)
   call setbufvar(helper.bufnr, 'fern_cursor', a:cursor)
 endfunction
 let s:sync.set_cursor = funcref('s:sync_set_cursor')

autoload/fern/internal/viewer.vim

@@ -57,6 +57,7 @@ function! s:init() abort
     autocmd! * <buffer>
     autocmd BufEnter <buffer> setlocal nobuflisted
     autocmd BufReadCmd <buffer> nested call s:BufReadCmd()
+    autocmd Syntax <buffer> call s:Syntax()
     autocmd ColorScheme <buffer> call s:ColorScheme()
     autocmd CursorMoved,CursorMovedI,BufLeave <buffer> let b:fern_cursor = getcurpos()[1:2]
   augroup END
@@ -99,9 +100,6 @@ function! s:init() abort
 
   " now the buffer is ready so set filetype to emit FileType
   setlocal filetype=fern
-  call helper.fern.renderer.syntax()
-  call fern#hook#emit('viewer:syntax', helper)
-  doautocmd <nomodeline> User FernSyntax
   call fern#action#_init()
 
   let l:Profile = fern#profile#start('fern#internal#viewer:init')
@@ -129,9 +127,6 @@ endfunction
 function! s:BufReadCmd() abort
   let helper = fern#helper#new()
   setlocal filetype=fern
-  call helper.fern.renderer.syntax()
-  call fern#hook#emit('viewer:syntax', helper)
-  doautocmd <nomodeline> User FernSyntax
   setlocal modifiable
   call setline(1, get(b:, 'fern_viewer_cache_content', []))
   setlocal nomodifiable
@@ -144,6 +139,13 @@ function! s:BufReadCmd() abort
         \.catch({ e -> fern#logger#error(e) })
 endfunction
 
+function! s:Syntax() abort
+  let helper = fern#helper#new()
+  call helper.fern.renderer.syntax()
+  call fern#hook#emit('viewer:syntax', helper)
+  doautocmd <nomodeline> User FernSyntax
+endfunction
+
 function! s:ColorScheme() abort
   let helper = fern#helper#new()
   call helper.fern.renderer.highlight()

doc/fern-develop.txt

@@ -316,11 +316,12 @@ VARIABLE				*fern-develop-helper-variable*
 
 			*fern-develop-helper.bufnr*
 .bufnr
-	A buffer number where the target fern instance binded.
+	A buffer number where the target fern instance is associated.
 
 			*fern-develop-helper.winid*
 .winid
-	A window number where a target fern instance binded.
+	A window number where a target fern instance is associated.
+	Use |fern-develop-helper.sync.winid()| to get proper value.
 
 			*fern-develop-helper.STATUS_NONE*
 			*fern-develop-helper.STATUS_COLLAPSED*
@@ -335,6 +336,10 @@ SYNC METHODS				*fern-develop-helper.sync*
 
 Following methods are executed synchronously.
 
+			*fern-develop-helper.sync.winid()*
+.sync.winid()
+	Return |winid| where a target fern instance is associated.
+
 			*fern-develop-helper.sync.echo()*
 .sync.echo({message})
 	Display a temporary |String| {message}.

plugin/fern.vim

@@ -25,8 +25,19 @@ function! s:BufReadCmd() abort
         \.catch({ e -> fern#logger#error(e) })
 endfunction
 
+function! s:SessionLoadPost() abort
+  let bufnr = bufnr()
+  call s:BufReadCmd()
+  " Re-apply required window options
+  for winid in win_findbuf(bufnr)
+    let [tabnr, winnr] = win_id2tabwin(winid)
+    call settabwinvar(tabnr, winnr, '&concealcursor', 'nvic')
+    call settabwinvar(tabnr, winnr, '&conceallevel', 2)
+  endfor
+endfunction
+
 augroup fern_internal
   autocmd! *
   autocmd BufReadCmd fern://* nested call s:BufReadCmd()
-  autocmd SessionLoadPost fern://* nested call s:BufReadCmd()
+  autocmd SessionLoadPost fern://* nested call s:SessionLoadPost()
 augroup END