OSD above fullscreen windows

[Thomas Pfeiffer]

On Monday 11 August 2014 11:51:49 Martin Gräßlin wrote:
> > Should it be? I would also expect the OSD to always be on top of active
> > fullscreen windows, whatever that window might be. We also have OSD for
> > changing the keyboard layout for example, not showing it in some
> > fullscreen
> > app could be quite limiting.
> > 
> > Can we reconsider that?
> 
> honestly: no. There's a reason for the way it is and I'm quite sure we
> discussed it. If the arguments (e.g. private chat going over presentation)
> do not apply for OSD then we have to realize that a OSD needs a dedicated
> window type with a dedicated layer. But changing notification type handling
> is wrong.

I now regret that we have not yet written an HIG for OSDs, but we'll fix that 
soon, and it will be quite similar to what I'm writing in this email.

Notifications and OSDs serve fundamentally different purposes. Notifications 
inform users about events (triggered by an application or a system component) 
which are not directly related to their current task. 
OSDs  are used to provide feedback for user actions that change global 
parameters and therefore cannot be given in any specific application UI. 
That's why we decided not to show an OSD when the display brightness is 
changed automatically by the power management, but show one if the users 
changes brightness manually (because then they'd like to know whether the 
screen can get any brighter).

Notifications must not overlay full-screen applications (I'm sure we all have 
experienced the embarrassment when someone does a presentation on a Windows 
machine and suddenly a "Hi cutie, how are you?" pops up in the lower right 
corner of the screen.).

OSDs, however, don't have that problem, because they are always triggered by a 
user action. It's not embarrassing if the user changes the volume during a 
presentation and an OSD pops up showing that the volume is already at max, so 
there is nothing they can do to make it any louder.

If feedback for an action is not relevant if an application is running full-
screen, then an OSD is not the right format for it, period.
So, yes, notifications and OSDs must not share the same window type.

I hope my arguments are clear, otherwise feel free to ask and I'll provuide 
further clarification.

Cheers,
Thomas