Allow expanding the vim window when opening Tagbar

doc/tagbar.txt

@@ -304,6 +304,18 @@ Example:
 >
 	let g:tagbar_compact = 1
 <
+
+							*g:tagbar_expand*
+g:tagbar_expand~
+If this option is set the Vim window will be expanded by the width of the
+Tagbar window if using a GUI version of Vim. The default is not to expand the
+window.
+
+Example:
+>
+	let g:tagbar_expand = 1
+<
+
 ==============================================================================
 6. Extending Tagbar					*tagbar-extend*
 
@@ -607,3 +619,6 @@ anything else that's free, taglist.vim is provided *as is* and comes with no
 warranty of any kind, either expressed or implied. In no event will the
 copyright holder be liable for any damamges resulting from the use of this
 software.
+
+==============================================================================
+ vim: tw=78 ts=8 sw=8 sts=8 noet ft=help

plugin/tagbar.vim

@@ -62,9 +62,14 @@ if !exists('g:tagbar_compact')
     let g:tagbar_compact = 0
 endif
 
+if !exists('g:tagbar_expand')
+    let g:tagbar_expand = 0
+endif
+
 let s:type_init_done    = 0
 let s:key_mapping_done  = 0
 let s:autocommands_done = 0
+let s:window_expanded   = 0
 
 " s:InitTypes() {{{2
 function! s:InitTypes()
@@ -837,6 +842,12 @@ function! s:OpenWindow(autoclose)
         return
     endif
 
+    " Expand the Vim window to accomodate for the Tagbar window if requested
+    if g:tagbar_expand && !s:window_expanded && has('gui_running')
+        let &columns += g:tagbar_width + 1
+        let s:window_expanded = 1
+    endif
+
     let openpos = g:tagbar_left ? 'topleft vertical ' : 'botright vertical '
     exe 'silent! keepalt ' . openpos . g:tagbar_width . 'split ' . '__Tagbar__'
 
@@ -915,6 +926,8 @@ function! s:CloseWindow()
         return
     endif
 
+    let tagbarbufnr = winbufnr(tagbarwinnr)
+
     if winnr() == tagbarwinnr
         if winbufnr(2) != -1
             " Other windows are open, only close the tagbar one
@@ -933,6 +946,20 @@ function! s:CloseWindow()
             exe winnum . 'wincmd w'
         endif
     endif
+
+    " If the Vim window has been expanded, and Tagbar is not open in any other
+    " tabpages, shrink the window again
+    if s:window_expanded
+        let tablist = []
+        for i in range(tabpagenr('$'))
+            call extend(tablist, tabpagebuflist(i + 1))
+        endfor
+
+        if index(tablist, tagbarbufnr) == -1
+            let &columns -= g:tagbar_width + 1
+            let s:window_expanded = 0
+        endif
+    endif
 endfunction
 
 " s:ZoomWindow() {{{2
@@ -1661,6 +1688,7 @@ endfunction
 " s:CleanUp() {{{2
 function! s:CleanUp()
     silent! autocmd! TagbarAutoCmds
+
     unlet s:current_file
     unlet s:is_maximized
     unlet s:compare_typeinfo