[PATCHv2] Add name event to xdg-output

Pekka Paalanen ppaalanen at gmail.com
Mon Apr 9 12:54:21 UTC 2018

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. If the name is defined
to change, then apps cannot target a specific connector. It obviously
depends on apps or even users what they actually want.

If it is undefined, or if the name is defined to change in that case,
then there is no way to reliably target a connector. Is this acceptable?

I would be interested too hear if you can think of why it should not be
specified to refer to a connector specifically, because off-hand I
can't imagine any reason.

Even if the name refers to a connector, a compositor could name it as
it wishes.

> > The name is arbitrary, right? No standardization is inteneded? I.e.
> > switching compositors will likely result in different names.  
> Aye. Some compositors might find it useful to follow an informal
> standard, though, like all wlroots-based compositors use consistent
> names (e.g. DP-1).

Yeah, standardising on names would be difficult to write down right now.

> > Is the name enough, would you perhaps want to have a human-readable
> > description string as well? Perhaps something for a user to totally
> > customize and more verbose than just a name?  
> Eh, I'm not a fan of this idea.

Very good.

> > I think it would be good to explicitly answer most of these questions
> > in the spec, even if "configured by name" does imply some answers.  
> Yep, will send a v3 answering some of these.


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