naughty: Replace request::icon by request::action_icon.

It wasn't a good idea to use ::icon because sometime the notification
themselves needs to request assistance for their icons.

lib/naughty/core.lua

@@ -561,9 +561,18 @@ naughty.connect_signal("request::screen", naughty.default_screen_handler)
 -- If an icon is found, the handler must set the `icon` property on the `action`
 -- object to a path or a `gears.surface`.
 --
--- @signal request::icon
+-- There is no implementation by default. To use the XDG-icon, the common
+-- implementation will be:
+--
+--    naughty.connect_signal("request::action_icon", function(a, context, hints)
+--         a.icon = menubar.utils.lookup_icon(hints.id)
+--    end)
+--
+-- @signal request::action_icon
 -- @tparam naughty.action action The action.
--- @tparam string icon_name The icon name.
+-- @tparam string context The context.
+-- @tparam table hints
+-- @tparam string args.id The action id. This will often by the (XDG) icon name.
 
 --- Emitted when the screen is not defined or being removed.
 -- @signal request::screen

lib/naughty/dbus.lua

@@ -173,7 +173,7 @@ function notif_methods.Notify(sender, object_path, interface, method, parameters
                 -- and `naughty` doesn't depend on `menubar`, so delegate the
                 -- icon "somewhere" using a request.
                 if hints["action-icons"] and action_id ~= "" then
-                    naughty.emit_signal("request::icon", a, action_id)
+                    naughty.emit_signal("request::action_icon", a, "dbus", {id = action_id})
                 end
 
                 a:connect_signal("invoked", function()

tests/test-naughty-legacy.lua

@@ -892,10 +892,9 @@ local icon_requests = {}
 table.insert(steps, function()
     assert(#active == 0)
 
-    naughty.connect_signal("request::icon", function(a, icon_name)
-        icon_requests[icon_name] = a
-
-        a.icon = icon_name == "list-add" and small_icon or big_icon
+    naughty.connect_signal("request::action_icon", function(a, context, hints)
+        icon_requests[hints.id] = a
+        a.icon = hints.id == "list-add" and small_icon or big_icon
     end)
 
     local hints = {