xkb: Added widget to display current keyboard layout

Widget shows current keyboard layout short name (usually two letters,
for example 'us', 'de'). Indicator will be hidden if only one layout
configured.  Layout can be switched either by clicking on widget or by
function keyboardlayout.next_layout()

awesomerc.lua.in

@@ -107,6 +107,10 @@ mylauncher = awful.widget.launcher({ image = beautiful.awesome_icon,
 menubar.utils.terminal = terminal -- Set the terminal for applications that require it
 -- }}}
 
+-- Keyboard map indicator and switcher
+mykeyboardlayout = awful.widget.keyboardlayout()
+-- }}}
+
 -- {{{ Wibox
 -- Create a textclock widget
 mytextclock = awful.widget.textclock()
@@ -189,6 +193,8 @@ for s = 1, screen.count() do
 
     -- Widgets that are aligned to the right
     local right_layout = wibox.layout.fixed.horizontal()
+    right_layout:add(mykeyboardlayout)
+
     if s == 1 then right_layout:add(wibox.widget.systray()) end
     right_layout:add(mytextclock)
     right_layout:add(mylayoutbox[s])

lib/awful/widget/init.lua.in

@@ -18,6 +18,7 @@ return
     graph = require("awful.widget.graph");
     layoutbox = require("awful.widget.layoutbox");
     textclock = require("awful.widget.textclock");
+    keyboardlayout = require("awful.widget.keyboardlayout");
 }
 
 -- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80

lib/awful/widget/keyboardlayout.lua.in

@@ -0,0 +1,104 @@
+---------------------------------------------------------------------------
+-- @author Aleksey Fedotov <lexa@cfotr.com>
+-- @copyright 2015 Aleksey Fedotov
+-- @release @AWESOME_VERSION@
+---------------------------------------------------------------------------
+
+local capi = {awesome = awesome,
+              awful = awful}
+local setmetatable = setmetatable
+local os = os
+local textbox = require("wibox.widget.textbox")
+local button = require("awful.button")
+local util = require("awful.util")
+local widget_base = require("wibox.widget.base")
+
+--- Keyboard Layout widget.
+-- awful.widget.keyboardlayout
+local keyboardlayout = { mt = {} }
+
+-- Callback for updaing current layout
+local function update_status (keyboardlayout)
+   keyboardlayout.current = awesome.xkb_get_layout_group();
+   local text = ""
+   if (#keyboardlayout.layout > 0) then
+      text = (" " .. keyboardlayout.layout[keyboardlayout.current] .. " ")
+   end
+   keyboardlayout.widget:set_text(text)
+end
+
+-- Callback for updating list of layouts
+local function update_layout(keyboardlayout)
+   keyboardlayout.layout = {};
+   local group_names = awesome.xkb_get_group_names();
+
+-- typical layout string looks like "pc+us+ru:2+de:3+ba:4+inet"
+-- and we want to get only three mathes: "us", "ru:2", "de:3" "ba:4"
+-- also please note, that numbers of groups reported by xkb_get_group_names
+-- is greater by one of the real group number
+
+
+   local first_group = string.match(group_names, "+(%a+)");
+   if (not first_group) then
+      error ("Failed to get list of keyboard groups");
+      return;
+   end
+   keyboardlayout.layout[0] = first_group;
+
+   for name, number_str in string.gmatch(group_names, "+(%a+):(%d)") do
+      group = tonumber(number_str);
+      keyboardlayout.layout[group - 1] = name;
+   end
+   update_status(keyboardlayout)
+end
+
+--- Create a keyboard layout widget. It shows current keyboard layout name in a textbox.
+-- @return A keyboard layout widget.
+function keyboardlayout.new()
+   local widget = textbox()
+   local keyboardlayout = widget_base.make_widget(widget)
+
+   keyboardlayout.widget = widget
+
+   update_layout(keyboardlayout);
+
+   keyboardlayout.next_layout = function()
+      new_layout = (keyboardlayout.current + 1) % (#keyboardlayout.layout + 1)
+      keyboardlayout.set_layout(new_layout)
+   end
+
+   keyboardlayout.set_layout = function(group_number)
+      if (0 > group_number) or (group_number > #keyboardlayout.layout) then
+         error("Invalid group number: " .. group_number ..
+                  "expected number from 0 to " .. #keyboardlayout.layout)
+         return;
+      end
+      awesome.xkb_set_layout_group(group_number);
+   end
+
+   -- callback for processing layout changes
+   capi.awesome.connect_signal("xkb::map_changed",
+                               function () update_layout(keyboardlayout) end)
+   capi.awesome.connect_signal("xkb::group_changed",
+                               function () update_status(keyboardlayout) end);
+
+   -- Mouse bindings
+   keyboardlayout:buttons(
+      util.table.join(button({ }, 1, keyboardlayout.next_layout))
+   )
+
+   return keyboardlayout
+end
+
+local _instance = nil;
+
+function keyboardlayout.mt:__call(...)
+   if _instance == nil then
+      _instance = keyboardlayout.new(...)
+   end
+   return _instance
+end
+
+return setmetatable(keyboardlayout, keyboardlayout.mt)
+
+-- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80