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On 26/04/2014 16:41, Philipp Janda wrote:

Am 26.04.2014 12:38 schröbte David Demelier:

Hi there,


Hi!



I'm very happy to announce the first release candidate of Lua-SDL2
[1]. As I already announced a few
months ago, Lua-SDL2 is a pure C binding against SDL 2.0.3.

[...]

* A few functions are not implemented, it's the case of Texture:lock
for instance which is terribly
   hard to implement from Lua because the C side expect to cast the
pixel pointer to the underlyling
   sized array which in Lua is impossible to do. Please provide me
feedback on how you want it to
   be implemented.
That depends on what you want the Lua code to do with a locked texture. For my own binding I considered using something along the lines of 

    myTexture:with_lock( function( modifypixels )
      -- code using the modifypixels function ...
    end )
but in the end I simply didn't implement direct access to pixel data in my binding (it has a rather narrow focus). `with_lock` would `pcall` (not `pcallk`![*]) the given function and pass a closure that has access to the pixel data and the pitch as argument. The Lua code would only access the pixel data via that function. After the `pcall` returns the upvalues of `modifypixels` get nil'ed using `lua_setupvalue` (for safety), and `SDL_UnlockTexture` is called before `with_lock` returns ... 


That's a really interesting way of doing it :-).


* Feedback, provide me some enhancement you may find obvious or
better. In the code or in the documentation :-).
I don't know if that's intended, but your binding is rather low-level: It can crash in certain situations (e.g. if a renderer is collected before its textures, or window before renderer, etc.), and it would be easy to call `SDL_Quit` automatically via garbage-collection so that the binding doesn't leak if there is a non-local exit (e.g. an error, or a yielded coroutine that gets collected). Another minor point: If `lua_newuserdata` ever raises an error you will leak the corresponding SDL object.
Ah I didn't know that the program crash is a renderer is destroyed before textures. But I can easily fix that by keeping references until the renderer is destroyed it "owns" a reference to the texture and may not be collected. (It's also done in the SDL_net Set object which "owns" sockets).
Yes, the binding is rather low-level, because I wanted it to be a SDL binding and not a game engine :-). However it is still a bit higher level than C with the object orientation and some other convenient stuff.
Aside from that it looks very good (and I probably would have used it instead of rolling my own if had known about it a week ago)! 


Thanks :-).


Enjoy this binding :-).

Kind regards,
David.



Philipp
[*]: This is one of those rare cases where you *don't* want a yieldable `pcall` ...