Created attachment 8834567 [details] Off-Screen Notification.png User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:51.0) Gecko/20100101 Firefox/51.0 Build ID: 20170125094131 Steps to reproduce: (These steps may not be exact:) • Go to the demo page at http://www.girliemac.com/html5-notifications-webOS-style/ containing a Notifications API demo. • Click the switch button to trigger a notifications request. • Enable notifications for that website in the browser UI. • Enable some or all types of notifications and repeatedly click the "Show Notifications" button to trigger notifications. Actual results: Notifications will first appear at the lower left of the viewport, then at the upper-right of the screen over the browser chrome (in a maximized browser window), then further to the upper-right of the viewport and off-screen leaving only the lower drop shadow of notification boxes visible. A screenshot has been attached showing the last state. Expected results: Notifications should have started appearing at the lower-right of viewport, then stacking vertically until reaching the top of the viewport. When there are too many notifications to fit in the viewport, it's not clear to me what should happen. However, notifications definitely shouldn’t appear off-screen.
It seems that the cause of this issue is calling the |browser.notifications.create| method multiple times with the same notification ID argument (as tested in Firefox Developer Edition 55.0b14). In theory, doing such a thing should either: (1) throw an error. (2) function the same as calling the unimplemented |browser.notifications.update| method as described in the email at https://mail.mozilla.org/pipermail/dev-addons/2017-February/002582.html (in which case one has to wonder what the point of a redundant |update| method is).