[PATCH weston 10/17] xdg-shell: Clarify the meaning of app ID and give example

[Jasper St. Pierre]

It's described as murky because it is super murky.

In the brave new world, apps are supposed to be D-Bus Activatable.
That means setting DBusActivatable=true in their desktop file. A
requirement for this is that desktop file name needs to match their
bus name. D-Bus doesn't require this -- the desktop file specification
does.

If you don't follow that convention, you don't have one app ID you can
pass to this. You have multiple. In the X11 world, this includes your
resource and application class you set with the WM_CLASS property,
your Exec line / prgname, your bus name, your PID, and plenty more
(startup-notification ID, _GTK_APPLICATION_ID, your ICCCM window group
leader, X11 Client ID).

The best way to not be in that situation is to not be in it: you have
one app ID, and that's it. That's what I was trying to say in the
original specification.

If you don't have that, there's no great answer for what to say your
ID is. GNOME would prefer what matches your .desktop filename. I don't
know what other DEs might prefer.

On Tue, Apr 7, 2015 at 7:01 PM, Bryce Harrington <bryce at osg.samsung.com> wrote:
> On Tue, Apr 07, 2015 at 05:01:25PM +0800, Jonas Ådahl wrote:
>> Signed-off-by: Jonas Ådahl <jadahl at gmail.com>
>> ---
>>  protocol/xdg-shell.xml | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/protocol/xdg-shell.xml b/protocol/xdg-shell.xml
>> index 3db76ab..c2e1443 100644
>> --- a/protocol/xdg-shell.xml
>> +++ b/protocol/xdg-shell.xml
>> @@ -197,6 +197,18 @@
>>       the surface belongs. The compositor can use this to group multiple
>>       surfaces together, or to determine how to launch a new application.
>>
>> +     When applicable, a client should set the app ID to the basename of the
>> +     .desktop file associated with the application, for example
>> +     "org.freedesktop.FooViewer" where the .desktop file is
>> +     "org.freedesktop.FooViewer.desktop".
>> +
>> +     For D-Bus activatble applications, this will also be D-Bus service
>
> typo
>
> Also:  'be *the* D-Bus service'
>
>> +     name used for activation of the application.
>
> Does D-Bus depend on having the service name constructed to match the
> .desktop file name?  If not, perhaps this paragraph should be moved
> ahead of the prior one.  I'm guessing the intention is that we're trying
> to say that the D-Bus service name will be the same as the app ID.
>
> "used for activation of the application" sounds redundant.
>
>> +     It is not a hard requirement to specify a well formed (as described
>> +     above) app ID, but the compositor shell may group the surface
>> +     inadequately if the client fail to do so.
>
> s/fail/fails/
>
> The way this is written it sounds like a requirement, that's optional,
> but has weird side effects if you don't follow it.  So it's a bit
> ambiguous whether you really do need to follow it or not.
> You might want to elaborate a bit on the implications of not having
> things grouped properly, so it's clear what the trade-off is.
>
> It might help if it was expressed as optional, but with extra features
> if you follow it.  Maybe something like:
>
>     The app ID identifies the general class of applications to which
>     the surface belongs. The compositor can use this to group multiple
>     applications together, or to determine how to launch a new
>     application.
>
>     For D-Bus activatable applications, the app ID is used as the D-Bus
>     service name.
>
>     The compositor shell will try to group application surfaces together
>     by their app ID.  As a best practice, it is suggested to select app
>     ID's that match the basename of the application's .desktop file.
>     For example, "org.freedesktop.FooViewer" where the .desktop file is
>     "org.freedesktop.FooViewer.desktop".
>
>     See the desktop-entry specification [0] for more details on
>     application identifiers and how they relate to well-known DBus
>     names and .desktop files.
>
>
>>       See the desktop-entry specification [0] for more details on
>>       application identifiers and how they relate to well-known D-Bus
>>       names and .desktop files.
>> --
>> 2.1.4
>>
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-- 
  Jasper