Re: New module proposal: LightDM

[Robert Ancell <robert ancell gmail com>]

>> Why replace GDM?
>>
>> - LightDM is a cross-platform solution.  Ubuntu is planning to switch
>> to it this cycle, and other distributions have expressed interest in
>> the project.  By sharing this piece of infrastructure GNOME can spend
>> more time working on important GNOME components.
>
> I am pretty sure more platforms currently use GDM than use lightdm, how
> can you claim this as a reason that lightdm was better? In fact, what
> you claim here could be used as a good reason to convince Ubuntu to use
> GDM, since that is what the majority uses, not as a reason to convince
> the others to use lightdm, since that is only used by one relevant
> distro so far, Ubuntu?

I'm not too sure what you're getting at here...  My points are:

- Ubuntu is going to use it, and others are interested so I think the
project has some credibility (i.e. it's not just me supporting it).
- LightDM is the only cross-platform display manager that I know of,
so now we have a choice between a cross-platform solution and a GNOME
specific one.
- Shared infrastructure means shared resources.

My point is not to switch to LightDM because Ubuntu is a major user.

>> LightDM is aligned with freedesktop.org.
>
> What is this supposed to mean?

This reflects I can't work out what defines a freedesktop project.  I
have since been told I should just state "LightDM IS a FreeDesktop.org
project" until someone corrects me otherwise.

>> - I am confident that the LightDM architecture is simpler than GDM.
>> Some indicators of this:
>>   - Smaller code size
>>   - Well defined interface between greeter and session
>>   - Less dependencies
>>   - Less internal interfaces
>
> But do you support everything that gdm supports, too? Like all the a11y
> stuff? Or the fprint auth, the extensibility and stuff like that?

I think this is being sufficiently covered in other posts to this thread.

>> - By having a well defined interface between the greeter and daemon,
>> it is significantly easier to develop a greeter without knowledge of
>> how display management works.  This is useful as the skillset and
>> motivations of these two sets of developers are different.
>
> But why is that a benefit? I think we want one good one, instead of a
> lot of bad ones?

GNOME will continue to need to maintain and improve greeters over
time.  I think this will be easier to do in LightDM.

> Modern forms of authentication, like the biometric stuff, or auth tokens
> usually need some kind of specific UI integration. Why do you think that
> it is in our interest to complicate that even further, by requiring that
> 10 greeters need to be updated for this, instead of just one?

This would not be GNOME's problem - GNOME would only be interested in
it's own greeter.

> In general I do believe it is completely OK to replace existing
> components with complete rewrites from time to time. I have pushed that
> through myself more than once. But if you do you better have your
> arguments ready for this. You must have a very good case. You must
> support everything the old software you are replacing can provide, or
> have very good reasons why you do not want to support specific features
> (I have not seen such a list from you). You must support a lot of new
> features. You must have made clear that you fully understood the
> problem, you must show that you tried to fix the existing component, or
> you must have a good reason why you think the current solution is so
> broken that there is no value in trying to fix it. You must be able to
> deal with criticism and respond to it. You must show that you can
> rethink the set of problems, and that you have a good idea where you
> want to go with this. You need a vision.

Sure, and this is part of the process in making that case.