[PATCHv2] Add name event to xdg-output

[Pekka Paalanen]

On Mon, 09 Apr 2018 16:00:35 +0200
Philipp Kerling <pkerling at casix.org> wrote:

> Hey,
> 
> I'll just reiterate one point from the prior discussion.
> 
> > On Mon, 9 Apr 2018 08:13:15 -0400
> > Drew DeVault <sir at cmpwn.com> wrote:
> >   
> > > Good feedback.
> > > 
> > > On 2018-04-09 11:09 AM, Pekka Paalanen wrote:  
> > > > Does this name correspond to the physical connector or to the
> > > > specific
> > > > monitor connected? Or some abstract "output" concept, see the
> > > > next
> > > > paragraph about clone mode.    
> > > 
> > > Doesn't matter, whatever the compositor wants. Should be unique to
> > > each
> > > wl_output.  
> > 
> > If it is unique to each wl_output, then it is referring to either a
> > connector or a monitor, ok.
> >   
> > > > [...] Would xdg_outputs for the cloned wl_outputs report
> > > > identical
> > > > names to signify they in fact always show the exact same image?    
> > > 
> > > No.  
> > 
> > This is consistent with the above, good.
> >   
> > > > Is this name intended to be stable and persistent, so that
> > > > applications
> > > > can expect to save it in a config and find the same one later,
> > > > after a
> > > > machine reboot, at least if the configuration of that output has
> > > > not
> > > > changed and the compositor is still the same version?    
> > > 
> > > Yes.  
> > 
> > But if it is undefined whether the name refers to a connector or a
> > monitor, would that not cause problems for apps to decide how to use
> > it?
> > 
> > If a user unplugs one monitor and then plugs in a different monitor
> > to
> > the same connector, should the name change or stay the same?
> > 
> > If the name is defined to stay the same, the app can look at
> > wl_output
> > make/model to see if the monitor is different.  

> No, this does not work. Having multiple instances of the same make and
> model is common in desktop multi-monitor setups. The app has no option
> to recognize specific ones as long as there is no serial number or
> other additional identifier involved that is not currently part of the
> wl_output and xdg_output info.

Oh yes, that's a good point. This is actually a good reason to repeat
the question:

Does the name identify the connector or the monitor?

I feel that we should have both a connector name and a monitor name
separately and explicitly defined, so that applications that care about
the identity can pick which one they want to match to.

I would hesitate to simply add a "monitor serial" event because I don't
think it's always available and there might be other ways to identify a
unit if it even is a physical monitor to begin with. Hence I'd go with
"monitor name" which could simply be the serial plus maybe make+model
when those are available and something else at other times. Then there
is the special case of what to do when you just cannot identify the
unit uniquely at all.

The very least the current proposal for a "name" should specify whether
it refers to the connector or the monitor, because if it is ambiguous,
then we need to add two more events that are not ambiguous when the
need to make the difference arises.


Thanks,
pq
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