add feature to format automatically on InsertLeave

This feature has some side effects.  So you should be careful if you
introduce this feature.

- Sometime, screen is moved on auto-formatting.
- Cursor position history is changed (Issue #8)

README.md

@@ -77,7 +77,16 @@ When this variable's value is `1`, vim-clang-format automatically detects the st
 - `g:clang_format#auto_format`
 
 When the value is 1, a current buffer is automatically formatted on saving the buffer.
-Formatting is executed at `BufWritePre` event.
+Formatting is executed on `BufWritePre` event.
+
+- `g:clang_format#auto_format_on_insert_leave`
+
+When the value is 1, inserted lines are automatically formatted on leaving insert mode.
+Formatting is executed on `InsertLeave` event.
+
+![auto formatting on InsertLeave](http://gifzo.net/CPrVbHnKMe.gif)
+
+In above screenshot, inserted 'if' statement are automatically formated on leaving insert mode.
 
 ### Vimrc Example
 

autoload/clang_format.vim

@@ -106,6 +106,7 @@ let g:clang_format#style_options = s:getg('clang_format#style_options', {})
 
 let g:clang_format#detect_style_file = s:getg('clang_format#detect_style_file', 1)
 let g:clang_format#auto_format = s:getg('clang_format#auto_format', 0)
+let g:clang_format#auto_format_on_insert_leave = s:getg('clang_format#auto_format_on_insert_leave', 0)
 " }}}
 
 " check version of clang-format "{{{
@@ -159,5 +160,26 @@ function! clang_format#replace(line1, line2)
 endfunction
 " }}}
 
+" auto formatting on insert leave {{{
+let s:pos_on_insertenter = []
+
+function! s:format_inserted_area()
+    let pos = getpos('.')
+    " When in the same buffer
+    if &modified && ! empty(s:pos_on_insertenter) && s:pos_on_insertenter[0] == pos[0]
+        call clang_format#replace(s:pos_on_insertenter[1], line('.'))
+        let s:pos_on_insertenter = []
+    endif
+endfunction
+
+function! clang_format#enable_format_on_insert()
+    augroup plugin-clang-format-auto-format-insert
+        autocmd!
+        autocmd InsertEnter <buffer> let s:pos_on_insertenter = getpos('.')
+        autocmd InsertLeave <buffer> call s:format_inserted_area()
+    augroup END
+endfunction
+" }}}
+
 let &cpo = s:save_cpo
 unlet s:save_cpo

plugin/clang_format.vim

@@ -15,6 +15,7 @@ command! -range=% -nargs=0 ClangFormatEchoFormattedCode echo clang_format#format
 augroup plugin-clang-format-auto-format
     autocmd!
     autocmd BufWritePre * if &ft ==# 'cpp' && g:clang_format#auto_format | call clang_format#replace(1, line('$')) | endif
+    autocmd FileType c,cpp,objc if 1 || g:clang_format#auto_format_on_insert_leave | call clang_format#enable_format_on_insert() | endif
 augroup END
 
 let g:loaded_clang_format = 1

t/clang_format_spec.vim

@@ -67,6 +67,8 @@ describe 'default settings'
         Expect exists('g:clang_format#style_options') to_be_true
         Expect exists('g:clang_format#command') to_be_true
         Expect exists('g:clang_format#detect_style_file') to_be_true
+        Expect exists('g:clang_format#auto_format') to_be_true
+        Expect exists('g:clang_format#auto_format_on_insert_leave') to_be_true
         Expect g:clang_format#extra_args to_be_empty
         Expect g:clang_format#code_style ==# 'google'
         Expect g:clang_format#style_options to_be_empty
@@ -235,3 +237,27 @@ describe 'g:clang_format#auto_format'
     end
 end
 " }}}
+
+" test for auto formatting on insert leave {{{
+
+describe 'g:clang_format#auto_format_on_insert_leave'
+
+    before
+        let g:clang_format#auto_format_on_insert_leave = 1
+        new
+        execute 'silent' 'edit!' './'.s:root_dir.'t/test.cpp'
+    end
+
+    after
+        bdelete!
+    end
+
+    it 'formats a inserted area on InsertLeave if the value is 1'
+        SKIP because somehow InsertEnter and InsertLeave events aren't fired
+        execute 10
+        execute 'normal' "iif(1+2)return 4;\<Esc>"
+        Expect getline('.') ==# '    if (1 + 2) return 4;'
+    end
+end
+
+" }}}