wibox.widget: Add `set_children` method

Provide a generic method to set the widget content

lib/wibox/layout/align.lua

@@ -171,6 +171,17 @@ function align:get_children()
     return util.from_sparse {self.first, self.second, self.third}
 end
 
+--- Replace the layout children
+-- This layout only accept three children, all others will be ignored
+-- @tparam table children A table composed of valid widgets
+function align:set_children(children)
+    if not children then return self:reset() end
+    self.first  = children[1]
+    self.second = children[2]
+    self.third  = children[3]
+    self:emit_signal("widget::layout_changed")
+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.
@@ -243,6 +254,9 @@ local function get_layout(dir, first, second, third)
     ret:set_second(second)
     ret:set_third(third)
 
+    -- An align layout allow set_children to have empty entries
+    ret.allow_empty_widget = true
+
     return ret
 end
 

lib/wibox/layout/constraint.lua

@@ -50,6 +50,14 @@ function constraint:get_children()
     return {self.widget}
 end
 
+--- Replace the layout children
+-- This layout only accept one children, all others will be ignored
+-- @tparam table children A table composed of valid widgets
+function constraint:set_children(children)
+    self.widget = children and children[1]
+    self:emit_signal("widget::layout_changed")
+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/fixed.lua

@@ -110,6 +110,14 @@ function fixed:get_children()
     return self.widgets
 end
 
+--- Replace the layout children
+-- @tparam table children A table composed of valid widgets
+function fixed:set_children(children)
+    if not children then return self:reset() end
+    self.widgets = children
+    self:emit_signal("widget::layout_changed")
+end
+
 --- Replace the first instance of `widget` in the layout with `widget2`
 -- @param widget The widget to replace
 -- @param widget2 The widget to replace `widget` with

lib/wibox/layout/flex.lua

@@ -31,6 +31,11 @@ local flex = {}
 -- @name get_children
 -- @class function
 
+--- Replace the layout children
+-- @tparam table children A table composed of valid widgets
+-- @name set_children
+-- @class function
+
 --- Add some widgets to the given fixed layout
 -- @param layout The layout you are modifying.
 -- @tparam widget ... Widgets that should be added (must at least be one)

lib/wibox/layout/margin.lua

@@ -78,6 +78,14 @@ function margin:get_children()
     return {self.widget}
 end
 
+--- Replace the layout children
+-- This layout only accept one children, all others will be ignored
+-- @tparam table children A table composed of valid widgets
+function margin:set_children(children)
+    self.widget = children and children[1]
+    self:emit_signal("widget::layout_changed")
+end
+
 --- Set all the margins to val.
 function margin:set_margins(val)
     self.left = val

lib/wibox/layout/mirror.lua

@@ -64,6 +64,14 @@ function mirror:get_children()
     return {self.widget}
 end
 
+--- Replace the layout children
+-- This layout only accept one children, all others will be ignored
+-- @tparam table children A table composed of valid widgets
+function mirror:set_children(children)
+    self.widget = children and children[1]
+    self:emit_signal("widget::layout_changed")
+end
+
 --- Reset this layout. The widget will be removed and the axes reset.
 function mirror:reset()
     self.horizontal = false

lib/wibox/layout/rotate.lua

@@ -72,6 +72,14 @@ function rotate:get_children()
     return {self.widget}
 end
 
+--- Replace the layout children
+-- This layout only accept one children, all others will be ignored
+-- @tparam table children A table composed of valid widgets
+function rotate:set_children(children)
+    self.widget = children and children[1]
+    self:emit_signal("widget::layout_changed")
+end
+
 --- Reset this layout. The widget will be removed and the rotation reset.
 function rotate:reset()
     self.direction = nil

lib/wibox/layout/scroll.lua

@@ -267,6 +267,14 @@ function scroll:get_children()
     return {self.widget}
 end
 
+--- Replace the layout children
+-- This layout only accept one children, all others will be ignored
+-- @tparam table children A table composed of valid widgets
+function scroll:set_children(children)
+    self.widget = children and children[1]
+    self:emit_signal("widget::layout_changed")
+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

@@ -101,6 +101,14 @@ function background:get_children()
     return {self.widget}
 end
 
+--- Replace the layout children
+-- This layout only accept one children, all others will be ignored
+-- @tparam table children A table composed of valid widgets
+function background:set_children(children)
+    self.widget = children and children[1]
+    self:emit_signal("widget::layout_changed")
+end
+
 --- Set the background to use
 function background:set_bg(bg)
     if bg then

lib/wibox/widget/base.lua

@@ -80,6 +80,14 @@ function base.widget:get_children()
     return {}
 end
 
+--- Replace the layout children
+-- The default implementation does nothing, this must be re-implemented by
+-- all layout and container widgets.
+-- @tparam table children A table composed of valid widgets
+function base.widget:set_children(children)
+    -- Nothing on purpose
+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