[cairo] UserFontFace vs FtFontFace management (cairomm)

[Jonathon Jongsma]

Anne et Damien Carbonne wrote:
> Jonathon Jongsma a écrit :
>> In the current cairomm implementation, the lifetime of the wrapper 
>> object is managed by the smart pointer that it is created with.  When 
>> the wrapper object is deleted, the destructor simply calls 
>> cairo_font_face_destroy() on the wrapped object.  If I were to store 
>> an owning reference to the wrapper inside of the wrapped C object, the 
>> wrapper's destructor would never be called, so we'd never _destroy() 
>> the underlying font face, and it seems that we'd have circular 
>> reference issues.  Or am I missing something? (quite possible, I admit)
>>
>>   
> In the Ada solution I explained in another mail, the "Ada handle" never 
> destroys the "Ada object" itself.
> The "Ada handle" only calls ref and unref.
> It is cairo that calls destroy on the attached user data when the ref 
> count is 0.
> Then, I destroy the Ada create object(s).
> If I'm correct, there is no cycle here.
> I think this is applicable to C++: Replace "Ada handle" by "C++ smart 
> pointer" and "Ada object" by "C++ wrapper".


Yes, thank you.  This does seem like the proper way to do things, and I spent this weekend 
redesigning things to work this way.  With those changes, things work just as you would 
expect them to (e.g. Ian's issue with needing to keep a reference to the UserFontFace 
object no longer exists).  However, I have not pushed this out, because the changes are 
quite invasive, and it would mean that we'd essentially be breaking the API/ABI of 
cairomm, which is obviously a big deal for projects using cairomm.  So I'm still thinking 
about the proper way to proceed...

-- 
jonner