Thank you for your answer, as you said, this pattern makes things quite clear for the user. I like it :) SDL is of course a somewhat special case, at it itself is an abstraction
over different backends, and there's little functionality there that could not be part of a standard window API...
Yeah, that's true. But actually SDL is not even really a GUI / Windowing API. As stated ont heir website it is "[...]designed to provide low level access to audio, keyboard, mouse, joystick, and graphics hardware [...]" So I guess it's the other way arround. You can probably do things with a real window API that you cannot do with SDL. What made me think of this "issue" is a new functionnality coming with the next version of SDL2 : https://wiki.libsdl.org/SDL_SetWindowHitTest I implemented this in OSWindow and then I asked myself if all the other libraries could do the same. I mean, it is always possible to move a window without decorations by using the mouse position and calls to "set window position" or whatever. Same goes for resizing. But the SDL way is so easy and painless that I wanted to know if the exact same way was doable with other libraries. After some basic researches on GTK+ I was not really able to tell if it was possible to do so. So a new question arose : Should I really look at every possible backend to know if a functionnality is general or backend-specific ? :/ 2015-06-16 12:15 GMT+02:00 Henrik Johansen <henrik.s.johansen@veloxit.no>:
On 16 Jun 2015, at 9:58 , Matthieu Lacaton <matthieu.lacaton@gmail.com> wrote:
Hello everybody,
The question I have concerns OSWindow and its backend : SDL. However, even if I'll speak about these two, i think the question is quite general and can apply to every API.
There are some functions that we are sure we will find in every backend possible (for instance the possibility to create a new window, to resize it etc.) and for these ones it is totally fine to abstract the backend from the user because you know that even if the backend has to change the API will be usable the same way.
But there are some functions that are quite specific to a certain backend and you cannot always find it in others. But this function is cool so it would be a shame not to implement it just for the sake of uniformity. In this case I see two options :
1) You abstract these functions exactly the same way you did for the others and the user is not informed at all. In this case the risk is that if the backend changes it may break the API for the user because he won't be able to use this function anymore.And he may feel a bit sad because he was not warned about it.
2) You make *something* to let the user know that this or that function is specific to this or that backend. By doing so the user knows that there is a small risk that he won't be able to use this function anymore if the backend changes. He has been warned.
Now I prefer the second option but I wanted to ask you about that "something". What is the best way to warn the user ?
- Should I let the name of the backend in the name of the method ? "SDL_MySpecificMethod" - Should I put all these methods in a specific package and name / comment that package accordingly ? - Some other things ?
Basically my question is : what is the best way to let the user know he is dealing with a specific function for a specific backend ?
Thanks,
Matthieu
A recent idea I had, translated to your case, was doing this by providing accessors to specific backend extension classes. Personally, I'd prefer to use a class separate from that which implements the common interface, so one doesn't accidentally end up doing common calls on only specific backends, here's a purely theoretical example of how that may look:
window := OSWindow new. window title: 'Test window'. "With SDL, we support making window unbordered" window SDL bordered: false. window openInWorld.
With a few example implementations: OSWindow >> #SDL "Could cache in instvar, but that would not as modular, as you can't package that with the rest of the backend, with methods all you need is *SDL-Windows categorization" currentBackEnd isSDL ifTrue: [SDL_ExtWindow target: self] ifFalse: [NoopWindow target: self]
SDLExtendedWindow >> #bordered: aBoolean <primitive: #primitiveNativeCall module: #NativeBoostPlugin error: errorCode> ^ self nbCall: #( int SDL_SetWindowBordered ( SDL_Window * target , SDL_bool aBoolean ) )
Haven't actually used this pattern yet, but at least to me, it yields a clear distinction between what is common between backends, and what will only work on some. SDL is of course a somewhat special case, at it itself is an abstraction over different backends, and there's little functionality there that could not be part of a standard window API...
Cheers, Henry