Move some functions from VimL to python code

Should be faster with new interfaces, but that is not the case

Should remove zero that can be viewed temporary in place of statusline in new 
windows

Target: ressurect setup function like source_plugin (but in place of sourcing 
something code is moved to python) to make it possible to do the following 
sequence:

1. Install powerline via pip
2. Add a line to the vimrc like

        py from powerline.vim import setup as setup_powerline; setup_powerline(); del setup_powerline

3. See new fancy statusline

Currently there are no convenient options to use powerline installed by pip in 
vim. powerline/bindings/vim/plugin/powerline.vim will do what it does: check for 
appropriate python versions available, fix sys.path and so on, but it won’t 
create autocommands, set options or define PowerlinePyeval function.

Note: may be rebased on top of the develop.

powerline/bindings/vim/plugin/powerline.vim

@@ -41,39 +41,14 @@ finally
 endtry
 
 if !get(g:, 'powerline_debugging_pyeval') && exists('*'. s:powerline_pyeval)
-	let s:pyeval = function(s:powerline_pyeval)
+	let PowerlinePyeval = function(s:powerline_pyeval)
 else
 	exec s:powerline_pycmd 'import json, vim'
-	exec "function! s:pyeval(e)\n".
+	exec "function! PowerlinePyeval(e)\n".
 		\	s:powerline_pycmd." vim.command('return ' + json.dumps(eval(vim.eval('a:e'))))\n".
 		\"endfunction"
 endif
 
-let s:last_window_id = 0
-function! s:GetWinID(winnr)
-	let r = getwinvar(a:winnr, 'window_id')
-	if empty(r)
-		let r = s:last_window_id
-		let s:last_window_id += 1
-		call setwinvar(a:winnr, 'window_id', r)
-	endif
-	" Without this condition it triggers unneeded statusline redraw
-	if getwinvar(a:winnr, '&statusline') isnot# '%!Powerline('.r.')'
-		call setwinvar(a:winnr, '&statusline', '%!Powerline('.r.')')
-	endif
-	return r
-endfunction
-
-function! Powerline(window_id)
-	let winidx = index(map(range(1, winnr('$')), 's:GetWinID(v:val)'), a:window_id)
-	let current = w:window_id is# a:window_id
-	return s:pyeval('powerline.render('. a:window_id .', '. winidx .', '. current .')')
-endfunction
-
-function! PowerlineNew()
-	call map(range(1, winnr('$')), 's:GetWinID(v:val)')
-endfunction
-
 function! PowerlineRegisterCachePurgerEvent(event)
 	exec s:powerline_pycmd 'from powerline.segments.vim import launchevent as powerline_launchevent'
 	augroup Powerline
@@ -91,5 +66,4 @@ exec s:powerline_pycmd 'powerline = VimPowerline()'
 exec s:powerline_pycmd 'del VimPowerline'
 " Is immediately changed when PowerlineNew() function is run. Good for global 
 " value.
-set statusline=%!PowerlineNew()
-call PowerlineNew()
+set statusline=%!PowerlinePyeval('powerline.new_window()')

powerline/renderers/vim.py

@@ -68,17 +68,18 @@ class VimRenderer(Renderer):
 	def get_segment_info(self, segment_info):
 		return segment_info or self.segment_info
 
-	def render(self, window_id, winidx, current):
+	def render(self, window, window_id, winnr):
 		'''Render all segments.'''
-		if current:
+		if window is vim.current.window:
 			mode = vim_mode(1)
 			mode = mode_translations.get(mode, mode)
 		else:
 			mode = 'nc'
 		segment_info = {
-			'window': vim.windows[winidx],
+			'window': window,
 			'mode': mode,
 			'window_id': window_id,
+			'winnr': winnr,
 		}
 		segment_info['buffer'] = segment_info['window'].buffer
 		segment_info['bufnr'] = segment_info['buffer'].number

powerline/vim.py

@@ -7,9 +7,12 @@ from powerline import Powerline
 from powerline.lib import mergedicts
 from powerline.matcher import gen_matcher_getter
 import vim
+from itertools import count
 
 
 vim_exists = vim_get_func('exists', rettype=int)
+vim_getwinvar = vim_get_func('getwinvar')
+vim_setwinvar = vim_get_func('setwinvar')
 
 
 def _override_from(config, override_varname):
@@ -23,9 +26,13 @@ def _override_from(config, override_varname):
 	return config
 
 
+WINDOW_STASUSLINE = '%!PowerlinePyeval(\'powerline.statusline({0})\')'
+
+
 class VimPowerline(Powerline):
 	def __init__(self):
 		super(VimPowerline, self).__init__('vim')
+		self.last_window_id = 1
 
 	def add_local_theme(self, key, config):
 		'''Add local themes at runtime (during vim session).
@@ -93,3 +100,49 @@ class VimPowerline(Powerline):
 			# fine to ignore it: no renderer == no colors to reset == no need to 
 			# do anything.
 			pass
+
+	if all((hasattr(vim.current.window, attr) for attr in ('options', 'vars', 'number'))):
+		def win_idx(self, window_id):
+			r = None
+			for window in vim.windows:
+				try:
+					curwindow_id = window.vars['powerline_window_id']
+				except KeyError:
+					curwindow_id = self.last_window_id
+					self.last_window_id += 1
+					window.vars['powerline_window_id'] = curwindow_id
+				statusline = WINDOW_STASUSLINE.format(curwindow_id)
+				if window.options['statusline'] != statusline:
+					window.options['statusline'] = statusline
+				if curwindow_id == window_id if window_id else window is vim.current.window:
+					assert r is None, "Non-unique window ID"
+					r = (window, curwindow_id, window.number)
+			return r
+	else:
+		def win_idx(self, window_id):  # NOQA
+			r = None
+			for winnr, window in zip(count(1), vim.windows):
+				curwindow_id = vim_getwinvar(winnr, 'powerline_window_id')
+				if curwindow_id:
+					curwindow_id = int(curwindow_id)
+				else:
+					curwindow_id = self.last_window_id
+					self.last_window_id += 1
+					vim_setwinvar(winnr, 'powerline_window_id', curwindow_id)
+				statusline = WINDOW_STASUSLINE.format(curwindow_id)
+				if vim_getwinvar(winnr, '&statusline') != statusline:
+					vim_setwinvar(winnr, '&statusline', statusline)
+				if curwindow_id == window_id if window_id else window is vim.current.window:
+					assert r is None, "Non-unique window ID"
+					r = (window, curwindow_id, winnr)
+			return r
+
+	def statusline(self, window_id):
+		window, window_id, winnr = self.win_idx(window_id) or (None, None, None)
+		if not window:
+			return 'No window {0}'.format(window_id)
+		return self.render(window, window_id, winnr)
+
+	def new_window(self):
+		window, window_id, winnr = self.win_idx(None)
+		return self.render(window, window_id, winnr)