OpenEuphoria

2. Re: Help wrapping SDL2.0

• Posted by ghaberek (admin) Oct 14, 2014
• 1863 views

Close! The allocate_string() function actually accepts a string and pokes it into memory for you. Just use allocate_string() directly. You could use allocate() and poke_string() but that's just twice the work.

A few other points on this as well...

• It doesn't look like you're free()-ing the values you've allocated. Always make sure to free anything you allocate.
• You can also use automatic cleanup on any allocate function by adding a 1 as the second parameter.
• Thanks to the magic of automatic cleanup, you can one-line the entire function call.
• You can return the value from c_func() directly without storing it. Unless you need it for some reason.
• Since you're using Euphoria 4.0, you should be using public, not global, which is generally discouraged (see Defining the scope of an identifier).

public constant SDL_HINT_WINRT_HANDLE_BACK_BUTTON  = "SDL_HINT_WINRT_HANDLE_BACK_BUTTON" 
 
-- I have already opened the SDL in another header so I have this 
 
constant xSDL_SetHint = define_c_func( sdl, "SDL_SetHint", {C_POINTER, C_POINTER}, C_BOOL) 
 
public function SDL_SetHint( sequence name, sequence value ) 
 
    -- allocate the strings into memory with automatic cleanup 
    atom p_name = allocate_string( name, 1 ) 
    atom p_value = allocate_string( value, 1 ) 
 
    -- don't bother storing the return value, 
    -- just return whatever c_func() gives us 
    return c_func( xSDL_SetHint, {p_name,p_value} ) 
end function 
 
-- Thanks to automatic cleanup, you can also one-line this whole function call... 
 
public function SDL_SetHint( sequence name, sequence value ) 
    return c_func( xSDL_SetHint, {allocate_string(name,1),allocate_string(value,1)} ) 
end function 

Hope that helps,

-Greg

4. Re: Help wrapping SDL2.0

• Posted by Icy_Viking Oct 18, 2014
• 1772 views

I believe I still have the 32-bit version on my computer somewhere. If I can find it, I'll upload it. You're welcome to improve/edit upon my wrapper if you'd like.

6. Re: Help wrapping SDL2.0

• Posted by ghaberek (admin) Oct 18, 2014
• 1769 views

typedef struct SDL_RWops 
{ 
    Sint64 (SDLCALL * size) (struct SDL_RWops * context); 
. 
. 
. 
} 

According to the SDL Wiki, that structure is a set of callbacks for low-level SDL programming with some additional data tacked on then end (a "type" and some "hidden" data). You can probably skip wrapping it.

If you do want to wrap it, each function callback should be a pointer (e.g. C_POINTER), in which you will store (using poke4()) a value from call_back() that points to a routine_id() of a function with the matching parameters (which are always atoms). In this case, that first callback wants to accept a single parameter that is a pointer to a "SDL_RWopts" struct called "context".

function SDL_RWops_size_callback( atom context ) 
 
    -- 'context' is a pointer to an SDL_RWops structure, use it here as you need 
 
    return 0 -- callbacks must return a value, see relevant documentation for possible values 
end function 
atom SDL_RWops_size_callback_cb = call_back( routine_id("SDL_RWops_size_callback") ) 

Here's a good StackOverflow discussion on Understanding typedefs for function pointers in C.

-Greg

8. Re: Help wrapping SDL2.0

• Posted by Icy_Viking Oct 18, 2014
• 1695 views

typedef struct SDL_RWops 
{ 
    Sint64 (SDLCALL * size) (struct SDL_RWops * context); 
. 
. 
. 
} 

I had forgot about Greg's struct.e I could have used that to wrap the Rect functions in SDL. It would come in handy for when you need to declare Rect variables in SDL. Since Euphoria has no native support for structs at this time, hopefully with the next release, struct support will be added.

10. Re: Help wrapping SDL2.0

• Posted by ghaberek (admin) Oct 20, 2014
• 1685 views

I just realized you guys were talking about this: http://openeuphoria.org/forum/109791.wc#109791. I had forgotten all about that until now. Good to see it's actually getting tested, since I had said this...

It's basically the same idea as the memory management routines in Win32Lib, but slimmed down and re-using the C_* constants from std/dll.e.

If it seems useful, then I can update it and added to my Euphoria Advanced Library. This will open up a lot more available types that I have added to adv/dll.e.

-Greg