Mappings can now be easily remapped

README.md

@@ -229,7 +229,10 @@ TODO, still WIP
 - If the offered completions are too broad, keep typing characters; YCM will
   continue refining the offered completions based on your input.
 - Use the TAB key to accept a completion and continue pressing TAB to cycle
-  through the completions. Use Ctrl+TAB (or Shift-TAB) to cycle backwards.
+  through the completions. Use Shift-TAB to cycle backwards. Note that if you're
+  using console Vim (that is, not Gvim or MacVim) then it's likely that the
+  Shift-TAB binding will not work because the console will not pass it to Vim.
+  You can remap the keys; see the options section below.
 
 ### Semantic Completion Engine Usage
 
@@ -385,6 +388,47 @@ Default: `30`
 
     let g:ycm_max_diagnostics_to_display = 30
 
+### The `g:ycm_key_select_completion` option
+
+This option controls the key mapping used to select the first completion string.
+Invoking it repeatedly cycles forward through the completion list.
+
+Default: `<TAB>`
+
+    let g:ycm_key_select_completion = '<TAB>'
+
+### The `g:ycm_key_previous_completion` option
+
+This option controls the key mapping used to select the previous completion
+string. Invoking it repeatedly cycles backwards through the completion list.
+
+Note that the default of `<S-TAB>` means Shift-TAB. Also note that the default
+mapping will probably only work in GUI Vim (Gvim or MacVim) and not in plain
+console Vim because the terminal usually does not forward modifier key
+combinations to Vim.
+
+Default: `<S-TAB>`
+
+    let g:ycm_key_previous_completion = '<S-TAB>'
+
+### The `g:ycm_key_invoke_completion` option
+
+This option controls the key mapping used to invoke the completion menu for
+semantic completion. By default, semantic completion is trigged automatically
+after typing `.`, `->` and `::` in insert mode (if semantic completion support
+has been compiled in). This key mapping can be used to trigger semantic
+completion anywhere. Useful for searching for top-level functions and classes.
+
+Note that the default of `<C-Space>` means Ctrl-Space. Also note that the
+default mapping will probably only work in GUI Vim (Gvim or MacVim) and not in
+plain console Vim because the terminal usually does not forward modifier key
+combinations to Vim.
+
+
+Default: `<C-Space>`
+
+    let g:ycm_key_invoke_completion = '<C-Space>'
+
 
 FAQ
 ---

autoload/youcompleteme.vim

@@ -58,14 +58,22 @@ function! youcompleteme#Enable()
     set ut=2000
   endif
 
-  " With this command, when the completion window is visible, the tab key will
-  " select the next candidate in the window. In vim, this also changes the
-  " typed-in text to that of the candidate completion.
-  inoremap <expr><TAB>  pumvisible() ? "\<C-n>" : "\<TAB>"
+  " With this command, when the completion window is visible, the tab key
+  " (default) will select the next candidate in the window. In vim, this also
+  " changes the typed-in text to that of the candidate completion.
+  exe 'inoremap <expr>' . g:ycm_key_select_completion .
+        \ ' pumvisible() ? "\<C-n>" : "\' . g:ycm_key_select_completion .'"'
 
-  " This selects the previous candidate for ctrl-tab or shift-tab
-  inoremap <expr><C-TAB>  pumvisible() ? "\<C-p>" : "\<TAB>"
-  inoremap <expr><S-TAB>  pumvisible() ? "\<C-p>" : "\<TAB>"
+  " This selects the previous candidate for shift-tab (default)
+  exe 'inoremap <expr>' . g:ycm_key_previous_completion .
+        \ ' pumvisible() ? "\<C-p>" : "\' . g:ycm_key_previous_completion .'"'
+
+  " <c-x><c-o> trigger omni completion, <c-p> deselects the first completion
+  " candidate that vim selects by default
+  exe 'inoremap <unique> ' . g:ycm_key_invoke_completion . ' <C-X><C-O><C-P>'
+
+  " TODO: make this a nicer, customizable map
+  nnoremap <unique> <leader>d :call <sid>ShowDetailedDiagnostic()<cr>
 
   py import sys
   py import vim
@@ -73,13 +81,6 @@ function! youcompleteme#Enable()
   py import ycm
   py ycm_state = ycm.YouCompleteMe()
 
-  " <c-x><c-o> trigger omni completion, <c-p> deselects the first completion
-  " candidate that vim selects by default
-  inoremap <unique> <C-Space> <C-X><C-O><C-P>
-
-  " TODO: make this a nicer, customizable map
-  nnoremap <unique> <leader>d :call <sid>ShowDetailedDiagnostic()<cr>
-
   " Calling this once solves the problem of BufRead/BufEnter not triggering for
   " the first loaded file. This should be the last command executed in this
   " function!

plugin/youcompleteme.vim

@@ -76,6 +76,15 @@ let g:ycm_autoclose_preview_window_after_completion =
 let g:ycm_max_diagnostics_to_display =
       \ get( g:, 'ycm_max_diagnostics_to_display', 30 )
 
+let g:ycm_key_select_completion =
+      \ get( g:, 'ycm_key_select_completion', '<TAB>' )
+
+let g:ycm_key_previous_completion =
+      \ get( g:, 'ycm_key_previous_completion', '<S-TAB>' )
+
+let g:ycm_key_invoke_completion =
+      \ get( g:, 'ycm_key_invoke_completion', '<C-Space>' )
+
 " This is basic vim plugin boilerplate
 let s:save_cpo = &cpo
 set cpo&vim