Proposal and RFC: DAL, the Desktop Abstraction Layer

[Jamie McCracken]

Havoc Pennington wrote:
> On Wed, 2005-01-19 at 16:03 +0000, Jamie McCracken wrote:
> 
>>>You should get a list of all services that export a particular interface
>>>and then activate the service you want.  We should fix D-Bus if it
>>>doesn't do what we want or create another daemon that keeps track of
>>>these things.  A spec which aims to be a standard should not try and
>>>workaround deficiencies.
>>
>>Thats what I asked for earlier in this thread but Havoc is reluctant to 
>>implement that and not wishing to upset Havoc I accepted the compromise 
>>of multiple services for that.
>>
>>I agree its much better to use interfaces here than services after all 
>>an interface is an agreed well defined contract so it seems pointless to 
>>make a service a well defined contract too in those cases. I should also 
>>add that only public (pre-defined) interfaces should be exported as you 
>>suggested (theres obviously no point asking for a propriety interface).
> 
> 
> As soon as someone explains how an application (rather than an object
> instance) can implement an interface, then I'm happy to listen.
> 
> In the meantime you are suggesting the equivalent of this function:
> 
>  bool process_implements_gtk_editable (pid_t process_id);
> 
> If you can explain how that makes any sense *at all* then I'm all ears.
> Processes are not editable text fields.
> 
> Havoc

Firstly I'm not insisting on this functionality - Its okay with me to 
have it implemented at the service level though I *prefer* to have it at 
the interface level as thats more consistent with what im used to namely 
COM (and Corba too) and it avoids all the confusion between interfaces 
and services.

A COM server is an application and it implements interfaces. The concept 
of object instances is not really relevant because the COM server's 
interfaces are a contract and you dont have any knowledge of whether any 
actual instances of the underlying objects exist. When a COM server is 
activated all its interfaces are available - its not like some 
interfaces are only available if a document is open rather its a case of 
the COM server saying I dont have an open document therefore I cant 
perform function X if an instance does not exist (EG if I tried to do a 
word search and there was no open document, the text editor's search 
method should return an error indicating there's no doc open). In 
essence that means the interface is a separate object to the actual 
object that performs the function on it. If it was not then obviously 
you would seg fault if you called a method on an object that was not 
instantiated. That does not and should not happen in COM so should it 
not be the same with Dbus?


jamie.