From 078537f1e220a585dff463be9056ac05436ab6aa Mon Sep 17 00:00:00 2001
From: Jorrit Visser <jorrit.jan.visser@gmail.com>
Date: Thu, 16 Feb 2017 19:51:30 +0100
Subject: [PATCH] Add interface fallback (Powerline>Unicode>ASCII)

Basically what the title says. First check if the user has Powerline,
fall back to Unicode symbols if he doesn't and fall back to ASCII
symbols if he doesn't have that either.
---
 autoload/airline/init.vim | 80 +++++++++++++++++++++++++++++----------
 1 file changed, 61 insertions(+), 19 deletions(-)

diff --git a/autoload/airline/init.vim b/autoload/airline/init.vim
index 1a74cca..02f1c49 100644
--- a/autoload/airline/init.vim
+++ b/autoload/airline/init.vim
@@ -17,10 +17,10 @@ function! airline#init#bootstrap()
   let s:loaded = 1
 
   let g:airline#init#bootstrapping = 1
-  call s:check_defined('g:airline_left_sep', get(g:, 'airline_powerline_fonts', 0) ? "\ue0b0" : " ")
-  call s:check_defined('g:airline_left_alt_sep', get(g:, 'airline_powerline_fonts', 0) ? "\ue0b1" : "|")
-  call s:check_defined('g:airline_right_sep', get(g:, 'airline_powerline_fonts', 0) ? "\ue0b2" : " ")
-  call s:check_defined('g:airline_right_alt_sep', get(g:, 'airline_powerline_fonts', 0) ? "\ue0b3" : "|")
+
+  let g:airline#util#async = v:version >= 800 && has('job')
+  let g:airline#util#is_windows = has('win32') || has('win64')
+
   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_crypt', 1)
@@ -32,9 +32,6 @@ function! airline#init#bootstrap()
   call s:check_defined('g:airline_exclude_preview', 0)
   call s:check_defined('g:airline_gui_mode', airline#init#gui_mode())
 
-  let g:airline#util#async = v:version >= 800 && has('job')
-  let g:airline#util#is_windows = has('win32') || has('win64')
-
   call s:check_defined('g:airline_mode_map', {})
   call extend(g:airline_mode_map, {
         \ '__' : '------',
@@ -64,19 +61,64 @@ function! airline#init#bootstrap()
         \ }, 'keep')
 
   call s:check_defined('g:airline_symbols', {})
+  " First define the symbols,
+  " that are common in Powerline/Unicode/ASCII mode,
+  " then add specific symbols for either mode
   call extend(g:airline_symbols, {
-        \ 'paste': 'PASTE',
-        \ 'spell': 'SPELL',
-        \ 'readonly': get(g:, 'airline_powerline_fonts', 0) ? "\ue0a2" : 'RO',
-        \ 'whitespace': get(g:, 'airline_powerline_fonts', 0) ? "\u2632" : "\u2632",
-        \ 'linenr': get(g:, 'airline_powerline_fonts', 0) ? "\ue0a1" : "\u33D1",
-        \ 'maxlinenr': get(g:, 'airline_powerline_fonts', 0) ? "\u2630" : "\u2630",
-        \ 'branch': get(g:, 'airline_powerline_fonts', 0) ? "\ue0a0" : "\u16A0",
-        \ 'notexists': "\u2204",
-        \ 'modified': '+',
-        \ 'space': ' ',
-        \ 'crypt': get(g:, 'airline_crypt_symbol', nr2char(0x1F512)),
-        \ }, 'keep')
+          \ 'paste': 'PASTE',
+          \ 'spell': 'SPELL',
+          \ 'modified': '+',
+          \ 'space': ' '
+          \  }, 'keep')
+
+  if exists('g:airline_powerline_fonts')
+    " Symbols for Powerline terminals
+    call s:check_defined('g:airline_left_sep', "\ue0b0")      " 
+    call s:check_defined('g:airline_left_alt_sep', "\ue0b1")  " 
+    call s:check_defined('g:airline_right_sep', "\ue0b2")     " 
+    call s:check_defined('g:airline_right_alt_sep', "\ue0b3") " 
+    " ro=, ws=☲, lnr=☰, mlnr=, br=, nx=Ɇ, crypt=🔒
+    call extend(g:airline_symbols, {
+          \ 'readonly': "\ue0a2",
+          \ 'whitespace': "\u2632",
+          \ 'linenr': "\u2630",
+          \ 'maxlinenr': "\ue0a1",
+          \ 'branch': "\ue0a0",
+          \ 'notexists': "\u0246",
+          \ 'crypt': nr2char(0x1F512),
+          \ }, 'keep')
+  elseif &encoding==?'utf-8'
+    " Symbols for Unicode terminals
+    call s:check_defined('g:airline_left_sep', "")
+    call s:check_defined('g:airline_left_alt_sep', "")
+    call s:check_defined('g:airline_right_sep', "")
+    call s:check_defined('g:airline_right_alt_sep', "")
+    " ro=⊝, ws=☲, lnr=☰, mlnr=㏑, br=ᚠ, nx=Ɇ, crypt=🔒
+    call extend(g:airline_symbols, {
+          \ 'readonly': "\u229D",
+          \ 'whitespace': "\u2632",
+          \ 'linenr': "\u2630",
+          \ 'maxlinenr': "\u33D1",
+          \ 'branch': "\u16A0",
+          \ 'notexists': "\u0246",
+          \ 'crypt': nr2char(0x1F512),
+          \ }, 'keep')
+  else
+    " Symbols for ASCII terminals
+    call s:check_defined('g:airline_left_sep', "")
+    call s:check_defined('g:airline_left_alt_sep', "")
+    call s:check_defined('g:airline_right_sep', "")
+    call s:check_defined('g:airline_right_alt_sep', "")
+    call extend(g:airline_symbols, {
+          \ 'readonly': 'RO',
+          \ 'whitespace': '!',
+          \ 'linenr': 'ln',
+          \ 'maxlinenr': ':',
+          \ 'branch': '',
+          \ 'notexists': '?',
+          \ 'crypt': 'cr',
+          \ }, 'keep')
+  endif
 
   call airline#parts#define('mode', {
         \ 'function': 'airline#parts#mode',