XDG menu implementation

[Benedikt Meurer]

Jannis Pohlmann wrote:
>> a) It should be thread-aware (not necessarily thread-safe). That is
>>queries on the tree must be possible from various threads (not
>>necessarily on the same XfceMenu/Frap, as that would probably add too
>>much locking overhead).
> 
> Yes, that's something I didn't care about until now. But it should be
> doable. Perhaps you can point me to some thread-safe library code where
> I can get inspirations from? That would be cool, as I still only have a
> vague image of how this needs to look like.

Maybe start off with some "Operating System" lecture notes to get the
big picture. It's not really something that can be learned by looking at
other peoples code.

But in general, for the library to be thread-aware:

 1) Non-singleton GObject's aren't protected by the library.
 2) Singleton GObject's and all shared data (most probably the desktop
database, etc.) will need to be locked for every access (read/write).

>> b) Thunar (currently the "Open With" dialog) needs a way to query all
>>installed applications (-> .desktop files) that claim to handle
>>atleast one MimeType (the condition can be checked in Thunar, once we
>>have the application list). Currently, there's no clean way to
>>retrieve this list and structure it according to the menu definition.
>>This will also be needed for the application browser.
> 
> Of course, something like this will be implemented. All XfceMenuItems
> (which represent application desktop entries) will be stored in a kind
> of cache (database, DesktopFile-Id hash table) and it shouldn't be hard
> to add mime query functions for this.

Maybe just add a generic query interface, where the caller specifies a
callback predicate that is invoked on all desktop entries, and only
those are returned for which the predicate returns TRUE.

> Regards,
> Jannis

Benedikt