tasklist: Auto-call set_client on all template widgets

This commit also update one of the example to remove its now
redundant boilerplate code.

lib/awful/widget/tasklist.lua

@@ -401,6 +401,11 @@ local function tasklist_label(c, args, tb)
     return text, bg, bg_image, not tasklist_disable_icon and c.icon or nil, other_args
 end
 
+-- Remove some callback boilerplate from the user provided templates.
+local function create_callback(w, t)
+    common._set_common_property(w, "client", t)
+end
+
 local function tasklist_update(s, w, buttons, filter, data, style, update_function, args)
     local clients = {}
 
@@ -419,6 +424,7 @@ local function tasklist_update(s, w, buttons, filter, data, style, update_functi
 
     update_function(w, buttons, label, data, clients, {
         widget_template = args.widget_template,
+        create_callback = create_callback,
     })
 end
 

tests/examples/wibox/awidget/tasklist/windows10.lua

@@ -52,17 +52,11 @@ end --DOC_HIDE
                 widget        = wibox.container.background,
             },
             {
-                {
-                    id     = "clienticon",
-                    widget = awful.widget.clienticon,
-                },
+                awful.widget.clienticon,
                 margins = 5,
                 widget  = wibox.container.margin
             },
             nil,
-            create_callback = function(self, c, index, objects) --luacheck: no unused args
-                self:get_children_by_id("clienticon")[1].client = c
-            end,
             layout = wibox.layout.align.vertical,
         },
     }