wibox: Support the declarative container syntax

Also support it for titlebars

lib/awful/titlebar.lua

@@ -26,6 +26,12 @@ local titlebar = {
     widget = {}
 }
 
+--- Set a declarative widget hierarchy description.
+-- See [The declarative layout system](../documentation/03-declarative-layout.md.html)
+-- @param args An array containing the widgets disposition
+-- @name setup
+-- @class function
+
 --- Show tooltips when hover on titlebar buttons (defaults to 'true')
 titlebar.enable_tooltip = true
 
@@ -108,6 +114,9 @@ local function new(c, args)
     -- Make sure the titlebar has the right colors applied
     bars[position].update_colors()
 
+    -- Handle declarative/recursive widget container
+    ret.setup = base.widget.setup
+
     return ret
 end
 

lib/wibox/init.lua

@@ -21,6 +21,7 @@ local sort = require("gears.sort")
 local beautiful = require("beautiful")
 local surface = require("gears.surface")
 local cairo = require("lgi").cairo
+local base = require("wibox.widget.base")
 
 --- This provides widget box windows. Every wibox can also be used as if it were
 -- a drawin. All drawin functions and properties are also available on wiboxes!
@@ -36,6 +37,13 @@ function wibox:set_widget(widget)
     self._drawable:set_widget(widget)
 end
 
+--- Set a declarative widget hierarchy description.
+-- See [The declarative layout system](../documentation/03-declarative-layout.md.html)
+-- @param args An array containing the widgets disposition
+-- @name setup
+-- @class function
+wibox.setup = base.widget.setup
+
 --- Set the background of the wibox
 -- @param c The background to use. This must either be a cairo pattern object,
 --   nil or a string that gears.color() understands.