Add support for capslock plugin

docs/source/configuration/segments/vim.rst

@@ -32,3 +32,9 @@ NERDTree segments
 
 .. automodule:: powerline.segments.vim.plugin.nerdtree
    :members:
+
+Capslock segments
+-----------------
+
+.. automodule:: powerline.segments.vim.plugin.capslock
+   :members:

powerline/bindings/vim/__init__.py

@@ -124,6 +124,22 @@ else:
 	vim_get_func = VimFunc
 
 
+if hasattr(vim, 'Function'):
+	def vim_func_exists(f):
+		try:
+			vim.Function(f)
+		except ValueError:
+			return False
+		else:
+			return True
+else:
+	def vim_func_exists(f):
+		try:
+			return bool(int(vim.eval('type(function("{0}")) == 2'.format(f))))
+		except vim.error:
+			return False
+
+
 if type(vim) is object:
 	vim_get_func = lambda *args, **kwargs: None
 

powerline/config_files/colorschemes/vim/__main__.json

@@ -18,6 +18,7 @@
 		"bufnr":              "file_directory",
 		"winnr":              "information:unimportant",
 		"tabnr":              "file_directory",
+		"capslock_indicator": "paste_indicator",
 
 		"csv:column_number": "line_current",
 		"csv:column_name":   "line_current_symbol",

powerline/config_files/themes/vim/default.json

@@ -15,6 +15,11 @@
 				"exclude_modes": ["nc"],
 				"priority": 10
 			},
+			{
+				"function": "powerline.segments.vim.plugin.capslock.capslock_indicator",
+				"include_modes": ["i", "R", "Rv"],
+				"priority": 10
+			},
 			{
 				"function": "branch",
 				"exclude_modes": ["nc"],

powerline/segments/vim/plugin/capslock.py

@@ -0,0 +1,30 @@
+# vim:fileencoding=utf-8:noet
+from __future__ import (unicode_literals, division, absolute_import, print_function)
+
+try:
+	import vim
+except ImportError:
+	vim = object()
+
+from powerline.bindings.vim import vim_func_exists
+from powerline.theme import requires_segment_info
+
+
+@requires_segment_info
+def capslock_indicator(pl, segment_info, text='CAPS'):
+	'''Shows the indicator if tpope/vim-capslock plugin is enabled
+
+	.. _note::
+		In the current state plugin automatically disables itself when leaving 
+		insert mode. So trying to use this segment not in insert or replace 
+		modes is useless.
+
+	:param str text:
+		String to show when software capslock presented by this plugin is 
+		active.
+	'''
+	if not vim_func_exists('CapsLockStatusline'):
+		return None
+	# CapsLockStatusline() function returns an empty string when plugin is 
+	# disabled. If it is not then string is non-empty.
+	return text if vim.eval('CapsLockStatusline()') else None