Option to automatically save sessions every few minutes (issue #26)

Issue #26 on GitHub:

  autosave the current session every few minutes
  #26

README.md

@@ -6,7 +6,7 @@ To persist your current editing session you can execute the `:SaveSession` comma
 
 ![Screenshot of auto-save prompt](http://peterodding.com/code/vim/session/autosave.png)
 
-When you start Vim without editing any files and the default session exists, you'll be prompted whether you want to restore the default session:
+If you want, the plug-in can also automatically save your session every few minutes (see the `g:session_autosave_periodic` option). When you start Vim without editing any files and the default session exists, you'll be prompted whether you want to restore the default session:
 
 ![Screenshot of auto-open prompt](http://peterodding.com/code/vim/session/autoopen.png)
 
@@ -109,6 +109,12 @@ By default this option is set to `'prompt'`. This means that when you start Vim
 
 By default this option is set to `'prompt'`. When you've opened a session and you quit Vim, the session plug-in will ask whether you want to save the changes to your session. Set this option to `'yes'` to always automatically save open sessions when you quit Vim. To completely disable automatic saving you can set this option to `'no'`.
 
+### The `g:session_autosave_periodic` option
+
+This option sets the interval in minutes for automatic, periodic saving of active sessions. The default is zero which disables the feature.
+
+Note that when the plug-in automatically saves a session (because you enabled this feature) the plug-in will not prompt for your permission.
+
 ### The `g:session_verbose_messages` option
 
 The session load/save prompts are quite verbose by default because they explain how to disable the prompts. If you find the additional explanation distracting you can lower the verbosity by setting this option to 0 (false) in your [vimrc script] [vimrc].

autoload/xolox/session.vim

@@ -1,9 +1,9 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: May 4, 2013
+" Last Change: May 5, 2013
 " URL: http://peterodding.com/code/vim/session/
 
-let g:xolox#session#version = '1.7.3'
+let g:xolox#session#version = '1.8'
 
 call xolox#misc#compat#check('session', 2)
 
@@ -246,6 +246,7 @@ endfunction
 " Automatic commands to manage the default session. {{{1
 
 function! xolox#session#auto_load() " {{{2
+  " Automatically load the default / last used session when Vim starts.
   if g:session_autoload == 'no'
     return
   endif
@@ -313,7 +314,31 @@ function! xolox#session#auto_save() " {{{2
   endif
 endfunction
 
+function! xolox#session#auto_save_periodic() " {{{2
+  " Automatically save the session every few minutes?
+  let interval = g:session_autosave_periodic * 60
+  let next_save = s:session_last_flushed + interval
+  if next_save < localtime()
+    call xolox#misc#msg#debug("session.vim %s: Skipping this beat of 'updatetime' (it's not our time yet).", g:xolox#session#version)
+  else
+    call xolox#misc#msg#debug("session.vim %s: This is our beat of 'updatetime'!", g:xolox#session#version)
+    let name = s:get_name('', 0)
+    if !empty(name)
+      call xolox#session#save_cmd(name, '')
+    endif
+  endif    
+endfunction
+
+function! s:flush_session()
+  let s:session_last_flushed = localtime()
+endfunction
+
+if !exists('s:session_last_flushed')
+  call s:flush_session()
+endif
+
 function! xolox#session#auto_unlock() " {{{2
+  " Automatically unlock all sessions when Vim quits.
   let i = 0
   while i < len(s:lock_files)
     let lock_file = s:lock_files[i]
@@ -359,6 +384,7 @@ function! xolox#session#open_cmd(name, bang) abort " {{{2
       call s:lock_session(path)
       execute 'source' fnameescape(path)
       call s:last_session_persist(name)
+      call s:flush_session()
       call xolox#misc#timer#stop("session.vim %s: Opened %s session in %s.", g:xolox#session#version, string(name), starttime)
       call xolox#misc#msg#info("session.vim %s: Opened %s session from %s.", g:xolox#session#version, string(name), fnamemodify(path, ':~'))
     endif
@@ -395,6 +421,7 @@ function! xolox#session#save_cmd(name, bang) abort " {{{2
       call xolox#misc#msg#warn(msg, g:xolox#session#version, string(name), friendly_path)
     else
       call s:last_session_persist(name)
+      call s:flush_session()
       call xolox#misc#timer#stop("session.vim %s: Saved %s session in %s.", g:xolox#session#version, string(name), starttime)
       call xolox#misc#msg#info("session.vim %s: Saved %s session to %s.", g:xolox#session#version, string(name), friendly_path)
       let v:this_session = path
@@ -458,6 +485,7 @@ function! xolox#session#close_cmd(bang, silent, save_allowed) abort " {{{2
     execute s:oldcwd
     unlet s:oldcwd
   endif
+  call s:flush_session()
   if v:this_session == ''
     if !a:silent
       let msg = "session.vim %s: Closed session."

doc/session.txt

@@ -20,12 +20,13 @@ Contents ~
   4. The |g:session_extension| option
   5. The |g:session_autoload| option
   6. The |g:session_autosave| option
-  7. The |g:session_verbose_messages| option
-  8. The |g:session_default_to_last| option
-  9. The |g:session_persist_globals| option
-  10. The |g:session_restart_environment| option
-  11. The |g:session_command_aliases| option
-  12. The |g:loaded_session| option
+  7. The |g:session_autosave_periodic| option
+  8. The |g:session_verbose_messages| option
+  9. The |g:session_default_to_last| option
+  10. The |g:session_persist_globals| option
+  11. The |g:session_restart_environment| option
+  12. The |g:session_command_aliases| option
+  13. The |g:loaded_session| option
  5. Compatibility with other plug-ins |session-compatibility-with-other-plug-ins|
  6. Known issues                                          |session-known-issues|
  7. Contact                                                    |session-contact|
@@ -52,8 +53,10 @@ prompted whether you want to save the open session before quitting Vim:
 
     Screenshot of auto-save prompt, see reference [1]
 
-When you start Vim without editing any files and the default session exists,
-you'll be prompted whether you want to restore the default session:
+If you want, the plug-in can also automatically save your session every few
+minutes (see the |g:session_autosave_periodic| option). When you start Vim
+without editing any files and the default session exists, you'll be prompted
+whether you want to restore the default session:
 
     Screenshot of auto-open prompt, see reference [2]
 
@@ -236,6 +239,15 @@ changes to your session. Set this option to 'yes' to always automatically save
 open sessions when you quit Vim. To completely disable automatic saving you
 can set this option to 'no'.
 
+-------------------------------------------------------------------------------
+The *g:session_autosave_periodic* option
+
+This option sets the interval in minutes for automatic, periodic saving of
+active sessions. The default is zero which disables the feature.
+
+Note that when the plug-in automatically saves a session (because you enabled
+this feature) the plug-in will not prompt for your permission.
+
 -------------------------------------------------------------------------------
 The *g:session_verbose_messages* option
 

plugin/session.vim

@@ -1,6 +1,6 @@
 " Vim script
 " Author: Peter Odding
-" Last Change: May 2, 2013
+" Last Change: May 5, 2013
 " URL: http://peterodding.com/code/vim/session/
 
 " Support for automatic update using the GLVS plug-in.
@@ -37,6 +37,13 @@ if !exists('g:session_autosave')
   let g:session_autosave = 'prompt'
 endif
 
+" Periodically save the active session automatically? Set this to the
+" auto-save interval in minutes. The value zero disables the feature
+" (this is the default).
+if !exists('g:session_autosave_periodic')
+  let g:session_autosave_periodic = 0
+endif
+
 " Define the verbosity of messages.
 if !exists('g:session_verbose_messages')
   let g:session_verbose_messages = 1
@@ -92,6 +99,7 @@ unlet s:directory
 augroup PluginSession
   autocmd!
   au VimEnter * nested call xolox#session#auto_load()
+  au CursorHold,CursorHoldI * call xolox#session#auto_save_periodic()
   au VimLeavePre * call xolox#session#auto_save()
   au VimLeavePre * call xolox#session#auto_unlock()
 augroup END