naughty: Expose 3 previously internal properties.

* app_name: To be used in filters when no clients are found.
 * max_width: Allow to set it from the rules, it might be different
    when a `widget_template` is used.
 * widget_template: Now it can be set from the rules without further
    boilerplate code.

lib/naughty/dbus.lua

@@ -141,9 +141,12 @@ function notif_methods.Notify(sender, object_path, interface, method, parameters
             return
         end
     end
+
     if appname ~= "" then
-        args.appname = appname
+        args.appname  = appname --TODO v6 Remove this.
+        args.app_name = appname
     end
+
     local preset = args.preset or cst.config.defaults
     local notification
     if actions then

lib/naughty/layout/box.lua

@@ -17,6 +17,7 @@ local popup      = require("awful.popup")
 local awcommon   = require("awful.widget.common")
 local placement  = require("awful.placement")
 local abutton    = require("awful.button")
+local dpi        = require("beautiful").xresources.apply_dpi
 
 local default_widget = require("naughty.widget._default")
 
@@ -136,9 +137,13 @@ end
 
 local function generate_widget(args, n)
     local w = wibox.widget.base.make_widget_from_value(
-        args.widget_template or default_widget
+        args.widget_template or (n and n.widget_template) or default_widget
     )
 
+    if w.set_width then
+        w:set_width(n.max_width or beautiful.notification_max_width or dpi(500))
+    end
+
     -- Call `:set_notification` on all children
     awcommon._set_common_property(w, "notification", n or args.notification)
 
@@ -224,7 +229,7 @@ local function new(args)
     new_args = args and setmetatable(new_args, {__index = args}) or new_args
 
     -- Generate the box before the popup is created to avoid the size changing
-    new_args.widget = generate_widget(new_args)
+    new_args.widget = generate_widget(new_args, new_args.notification)
 
     local ret = popup(new_args)
     ret._private.args = new_args

lib/naughty/notification.lua

@@ -407,6 +407,31 @@ local notification = {}
 -- @property clients
 -- @param table
 
+--- The maximum popup width.
+--
+-- Some notifications have overlong message, cap them to this width. Note that
+-- this is ignored by `naughty.list.notifications` because it delegate this
+-- decision to the layout.
+--
+-- @property[opt=500] max_width
+-- @param number
+
+--- The application name specified by the notification.
+--
+-- This can be anything. It is usually less relevant than the `clients`
+-- property, but can sometime to specified for remote or headless notifications.
+-- In these case, it helps to triage and detect the notification from the rules.
+-- @property app_name
+-- @param string
+
+--- The widget template used to represent the notification.
+--
+-- Some notifications, such as chat messages or music applications are better
+-- off with a specialized notification widget.
+--
+-- @property widget_template
+-- @param table
+
 --FIXME remove the screen attribute, let the handlers decide
 -- document all handler extra properties
 
@@ -526,7 +551,8 @@ local properties = {
     "shape"   , "opacity" , "margin"  , "ignore_suspend",
     "destroy" , "preset"  , "callback", "actions"       ,
     "run"     , "id"      , "ignore"  , "auto_reset_timeout",
-    "urgency" , "image"   , "images"  ,
+    "urgency" , "image"   , "images"  , "widget_template",
+    "max_width", "app_name",
 }
 
 for _, prop in ipairs(properties) do