C to D: please help translate this weird macro

[Dejan Lekic]

On Wednesday, 20 September 2023 at 13:55:14 UTC, Ki Rill wrote:
> On Wednesday, 20 September 2023 at 13:53:08 UTC, Ki Rill wrote:
>> Here is the macro:
>>
>> ```C
>> #define NK_CONTAINER_OF(ptr,type,member)\
>>     (type*)((void*)((char*)(1 ? (ptr): &((type*)0)->member) - 
>> NK_OFFSETOF(type, member)))
>> ```
>>
>> I'm trying to translate the Nuklear GUI library to D 
>> [here](https://github.com/rillki/nuklear-d/tree/nuklear-d-translation).
>
> Here is how `NK_OFFSETOF` is defined:
> ```c
> #define NK_OFFSETOF(st,m) ((nk_ptr)&(((st*)0)->m))
> ```

NK_OFFSETOF is the same as D's struct `.offsetof` attribute.

NK_CONTAINER_OF should probably be translated to:

`cast(T*)((cast(void*)ptr - __traits(getMember, T, 
member).offsetof))`

PS. I did not invent this. My original idea was far worse than 
this. - It was suggested on IRC by a much cleverer D programmer 
than myself - Herringway at IRC