From 0a015e53050a21b802cfdda414ee057995dd240d Mon Sep 17 00:00:00 2001
From: Bailey Ling <bling@live.ca>
Date: Tue, 6 Aug 2013 21:48:00 -0400
Subject: [PATCH] use autocmds to detect whitespace, shouldn't need max anymore

---
 autoload/airline/extensions/whitespace.vim | 42 +++++++++++++---------
 plugin/airline.vim                         |  1 -
 2 files changed, 25 insertions(+), 18 deletions(-)

diff --git a/autoload/airline/extensions/whitespace.vim b/autoload/airline/extensions/whitespace.vim
index 0f0f751..ad964e7 100644
--- a/autoload/airline/extensions/whitespace.vim
+++ b/autoload/airline/extensions/whitespace.vim
@@ -1,36 +1,44 @@
 " MIT license. Copyright (c) 2013 Bailey Ling.
 " vim: ts=2 sts=2 sw=2 fdm=indent
 
+" http://got-ravings.blogspot.com/2008/10/vim-pr0n-statusline-whitespace-flags.html
+
 function! airline#extensions#whitespace#check()
-  if line('$') > g:airline_whitespace_max_lines
-    return ''
-  endif
+  if !exists('b:airline_whitespace_check')
+    let b:airline_whitespace_check = ''
+    let trailing = search(' $', 'nw') != 0
+    let mixed = search('^ ', 'nw') != 0 && search('^\t', 'nw') != 0
 
-  let trailing = search(' $', 'nw') != 0
-  let mixed = search('^ ', 'nw') != 0 && search('^\t', 'nw') != 0
-
-  if trailing || mixed
-    let text = g:airline_whitespace_symbol." "
-    if g:airline_detect_whitespace == 1
-      if trailing
-        let text .= 'trailing '
-      endif
-      if mixed
-        let text .= 'mixed-indent '
+    if trailing || mixed
+      let b:airline_whitespace_check = g:airline_whitespace_symbol." "
+      if g:airline_detect_whitespace == 1
+        if trailing
+          let b:airline_whitespace_check .= 'trailing '
+        endif
+        if mixed
+          let b:airline_whitespace_check .= 'mixed-indent '
+        endif
       endif
     endif
-    return text
   endif
-  return ''
+  return b:airline_whitespace_check
 endfunction!
 
 function! airline#extensions#whitespace#apply()
   if exists('w:airline_active') && w:airline_active
-    let w:airline_section_warning = '%{airline#extensions#whitespace#check()}'
+    if !exists('w:airline_section_warning')
+      let w:airline_section_warning = ' '
+    endif
+    let w:airline_section_warning .= '%{airline#extensions#whitespace#check()}'
   endif
 endfunction
 
 function! airline#extensions#whitespace#init(ext)
   call a:ext.add_statusline_funcref(function('airline#extensions#whitespace#apply'))
+
+  augroup airline_whitespace
+    autocmd!
+    autocmd CursorHold,BufWritePost * unlet! b:airline_whitespace_check
+  augroup END
 endfunction
 
diff --git a/plugin/airline.vim b/plugin/airline.vim
index 6df2204..2d47cc6 100644
--- a/plugin/airline.vim
+++ b/plugin/airline.vim
@@ -29,7 +29,6 @@ call s:check_defined('g:airline_detect_modified', 1)
 call s:check_defined('g:airline_detect_paste', 1)
 call s:check_defined('g:airline_detect_whitespace', 1)
 call s:check_defined('g:airline_whitespace_symbol', '✹')
-call s:check_defined('g:airline_whitespace_max_lines', 3000)
 call s:check_defined('g:airline_branch_prefix', exists('g:airline_powerline_fonts')?' ':'')
 call s:check_defined('g:airline_readonly_symbol', exists('g:airline_powerline_fonts')?'':'RO')
 call s:check_defined('g:airline_linecolumn_prefix', exists('g:airline_powerline_fonts')?' ':':')