Re: [gtkmm] gtkmm 2.4 questions

[Frank Naumann <fnaumann cs uni-magdeburg de>]

Hello!

> I would be surprised if the recomputation you are doing requires a change in 
> the underlying data or the fundamental state of the CellRenderer; therefore 
> you should be able to do it inside a const method without a great deal of 
> difficulty, perhaps with the help of a few mutable data members (perhaps for 
> result caching where appropriate).

Yes, mainly the result is cached for the immediatly following render call. 
Ok, having the cache result mutable don't look so bad.

> It seems a good rule of API design to write methods as const whenever you 
> possibly can. This provides a clear and guarenteed interface to the user, 
> helping them to write code that doesn't have unexpected side effects. That 
> might be the Haskell programmer in me speaking.

Yes, I do so too for my own code.

> > Then my question, why is get_size_vfunc const? What's the difference 
> > compared to render_vfunc for example?
>
> I can't answer that question, as I had no input on the design of the API 
> there. I would have expected render_vfunc to be const, but it may operate in 
> a way which surprises me and forces it to be non-const.

render_vfunc should be const too, then I aggree on the logic :-) Otherwise 
something is not consequent and logical.


Regards,
Frank