RFC : xdg_surface_present() look-and-feel and implementation

[Jason Ekstrand]

On Tue, Jul 29, 2014 at 12:16 PM, Bill Spitzak <spitzak at gmail.com> wrote:

> On 07/29/2014 11:40 AM, Manuel Bachmann wrote:
>
>  When creating a xdg_surface, the surface will not be mapped (i.e. shown)
>> by desktop-shell anymore. It will only be if xdg_surface_present() has
>> been called once.
>>
>
> There seems to be a design goal in Wayland to prevent clients from making
> surfaces that they never map. So it would be better if creation + commit of
> a surface did the same thing as present. Also this does not break existing
> clients.
>

That's the way it has worked in the past.  There's nothing requiring this
behavior in xdg_shell as we haven't stabilized it fully yet.  Really, it
doesn't matter whether the client has to call an additional request beyond
just creating the xdg_surface.

Another question for Manuel: Does present() interact with the surface
commit?  Should it?


>
> There is nothing special about the first time the surface wants attention
> (other than historical legacy). The desktop should be allowed to turn this
> into a notification just like it would on subsequent calls.
>
>
True.  We shouldn't claim to guarantee any "window showing up behavior" on
the first or subsequent calls.


>
>  If called twice, or more, the request will send an event to
>> desktop-shell, so it can display a notification.
>>
>
> This is not controlled by a count, but by whether a window is already
> visible or already in the notification state. Clients should be able to
> send a lot of these in a row. They cannot reliably test if they are
> invisible and send the request only then, as there is a race condition.
>
>
Yes, talking about it in terms of a count is a bad plan.


> I also think the term "present" is not a great idea. This should be
> exactly the same as "raise" or "show" or "activate" or any number of other
> terms, but I have never seen the word "present" used before. I would reuse
> an existing term. One reason is to prevent somebody else from adding a
> redundant api for that term, because they did not realize "present" is the
> thing they are looking for.
>

We also discussed the name "attention".  The reason why we didn't go with
"raise" or "show" is that it implies a specific action on the part of the
compositor, namely showing the user the window.  The term "activate" is
used for something else in xdg_shell so that one's out too.

--Jason Ekstrand
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