wibox.widget: Add new `get_children(recursive)` method to all widgets

lib/wibox/layout/align.lua

@@ -10,6 +10,7 @@ local table = table
 local pairs = pairs
 local type = type
 local floor = math.floor
+local util = require("awful.util")
 local base = require("wibox.widget.base")
 
 local align = {}
@@ -164,6 +165,12 @@ function align:set_third(widget)
     self:emit_signal("widget::layout_changed")
 end
 
+--- Get all children of this layout
+-- @treturn table a list of all widgets
+function align:get_children()
+    return util.from_sparse {self.first, self.second, self.third}
+end
+
 --- Fit the align layout into the given space. The align layout will
 -- ask for the sum of the sizes of its sub-widgets in its direction
 -- and the largest sized sub widget in the other direction.

lib/wibox/layout/constraint.lua

@@ -44,6 +44,12 @@ function constraint:set_widget(widget)
     self:emit_signal("widget::layout_changed")
 end
 
+--- Get the number of children element
+-- @treturn table The children
+function constraint:get_children()
+    return {self.widget}
+end
+
 --- Set the strategy to use for the constraining. Valid values are 'max',
 -- 'min' or 'exact'. Throws an error on invalid values.
 function constraint:set_strategy(val)

lib/wibox/layout/margin.lua

@@ -72,6 +72,12 @@ function margin:set_widget(widget)
     self:emit_signal("widget::layout_changed")
 end
 
+--- Get the number of children element
+-- @treturn table The children
+function margin:get_children()
+    return {self.widget}
+end
+
 --- Set all the margins to val.
 function margin:set_margins(val)
     self.left = val

lib/wibox/layout/mirror.lua

@@ -58,6 +58,12 @@ function mirror:set_widget(widget)
     self:emit_signal("widget::layout_changed")
 end
 
+--- Get the number of children element
+-- @treturn table The children
+function mirror:get_children()
+    return {self.widget}
+end
+
 --- Reset this layout. The widget will be removed and the axes reset.
 function mirror:reset()
     self.horizontal = false

lib/wibox/layout/rotate.lua

@@ -66,6 +66,12 @@ function rotate:set_widget(widget)
     self:emit_signal("widget::layout_changed")
 end
 
+--- Get the number of children element
+-- @treturn table The children
+function rotate:get_children()
+    return {self.widget}
+end
+
 --- Reset this layout. The widget will be removed and the rotation reset.
 function rotate:reset()
     self.direction = nil

lib/wibox/layout/scroll.lua

@@ -261,6 +261,12 @@ function scroll:set_widget(widget)
     self:emit_signal("widget::redraw_needed")
 end
 
+--- Get the number of children element
+-- @treturn table The children
+function scroll:get_children()
+    return {self.widget}
+end
+
 --- Specify the expand mode that is used for extra space.
 -- @tparam boolean expand If true, the widget is expanded to include the extra
 -- space. If false, the extra space is simply left empty.

lib/wibox/widget/background.lua

@@ -69,6 +69,12 @@ function background:set_widget(widget)
     self:emit_signal("widget::layout_changed")
 end
 
+--- Get the number of children element
+-- @treturn table The children
+function background:get_children()
+    return {self.widget}
+end
+
 --- Set the background to use
 function background:set_bg(bg)
     if bg then

lib/wibox/widget/base.lua

@@ -73,6 +73,32 @@ function base.widget:set_height(s)
     end
 end
 
+--- Get all direct children widgets
+-- This method should be re-implemented by the relevant widgets
+-- @treturn table The children
+function base.widget:get_children()
+    return {}
+end
+
+-- It could have been merged into `get_all_children`, but it's not necessary
+local function digg_children(ret, tlw)
+    for k, w in ipairs(tlw:get_children()) do
+        table.insert(ret, w)
+        digg_children(ret, w)
+    end
+end
+
+--- Get all direct and indirect children widgets
+-- This will scan all containers recursively to find widgets
+-- Warning: This method it prone to stack overflow id the widget, or any of its
+-- children, contain (directly or indirectly) itself.
+-- @treturn table The children
+function base.widget:get_all_children()
+    local ret = {}
+    digg_children(ret, self)
+    return ret
+end
+
 -- }}}
 
 -- {{{ Caches