OpenEuphoria

Re: Gosu Wrapper

• Posted by ghaberek (admin) in July
• 486 views

GOSU_FFI_API void Gosu_Window_set_update(Gosu_Window* window, void function(void* data), 
                                         void* data); 

This function takes three parameters:

• Gosu_Window* window - a pointer to a Gosu_Window object
• void function(void* data) - a pointer to a function that accepts one parameter (this is our "callback")
• void* data - a generic pointer to any object (this is "user" object, a concept used by most callback-based systems)

If it helps, you can create alias constants to break up the sea of C_POINTER values everywhere. I find this helps weed out a lot of simple errors.

constant C_CALLBACK  = C_POINTER -- pointer to a callback function 
constant C_PVOID     = C_POINTER -- pointer to any object (void*) 
constant GOSU_WINDOW = C_POINTER -- pointer to a Gosu_Window object 
 
constant xGosu_Window_create = define_c_proc(gosu,"+Gosu_Window_create",{C_INT,C_INT,C_UINT,C_DOUBLE},GOSU_WINDOW) 
constant xGosu_Window_set_update = define_c_proc(gosu,"+Gosu_Window_set_update",{GOSU_WINDOW,C_CALLBACK,C_PVOID}) 
 
public function Gosu_Window_create(integer width, integer height, atom window_flags, atom update_interval) 
    return c_func(xGosu_Window_create,{width,height,window_flags,update_interval}) 
end function 
 
public procedure Gosu_Window_set_update(atom window,object func,atom data) 
    c_proc(xGosu_Window_set_update,{window,func,data}) 
end procedure 

And it should come together something like this:

function update_callback(atom data) 
    return 0 
end function 
constant update_callback_id = routine_id("update_callback") 
constant update_callback_cb = call_back(update_callback) 
 
atom window = Gosu_Window_create(800, 450, 0, 1/60) 
Gosu_Window_set_update(window, update_callback_cb, NULL) 

Disclaimer: I have not actually tried any of this to see if it works. I'm not sure how or if the callbacks are supposed to get knowledge about the window object.

-Greg