C++ cast to D cast again :)

[BLS]

div0 schrieb:
> div0 wrote:
>> BLS wrote:
>>> div0 schrieb:
>>>> BLS wrote:
>>>>> Hi and sorry about picking on your nerves again  :(
>>>>> // C++
>>>>> class CWin
>>>>> {
>>>>> //
>>>>> static LRESULT CALLBACK WndProc(HWND hWnd, UINT uID, WPARAM wParam, 
>>>>> LPARAM lParam)
>>>>> {
>>>>>   CWin* pWnd=NULL;  // init pWnd
>>>>> }
>>>>>
>>>>> // later ...
>>>>> CWin* pChild=reinterpret_cast<CWin*>((HWND)
>>>>> ::GetWindowLong(pWnd->GetDlgItem( ((( LPDRAWITEMSTRUCT 
>>>>> )lParam)->CtlID) ),GWL_USERDATA) );
>>>>>
>>>>>
>>>>> }
>>>>>
>>>>> //our D class
>>>>> class CWin
>>>>> {
>>>>> static LRESULT WndProc(HWND hWnd, UINT uID, WPARAM wParam, LPARAM 
>>>>> lParam)
>>>>> {
>>>>>   CWin pWnd=null;  // init pWnd as    ---reference !
>>>>> }
>>>>> /* instead of :
>>>>> CWin* pChild=reinterpret_cast<CWin*>
>>>>> we use
>>>>> CWin pChild = cast(CWin) cast(void*)
>>>>>
>>>>> But I am not sure how to translate :
>>>>> ((HWND)
>>>>> ::GetWindowLong(pWnd->GetDlgItem( ((( LPDRAWITEMSTRUCT 
>>>>> )lParam)->CtlID) ),GWL_USERDATA) );
>>>>> */
>>>>>
>>>>> // Later we have
>>>>> if (HIWORD(pWnd))
>>>>>
>>>>> /*Since we are working with a ref. instead of a pointer this will 
>>>>> not work.
>>>>> I guess I can use :
>>>>> */
>>>>>
>>>>> if (HIWORD(cast(void*)pWnd))
>>>>> // can you confirm
>>>>> }
>>>>>
>>>>> GetWindowLong() is a Windows Api func., sure you know it.
>>>>> So what the correct translation ?
>>>>> Bjoern
>>>>> Beside, I still wonder : Having a class A, Is A* pA a legal 
>>>>> construct in D.
>>>>> What is pA from a technical view; a pointer to a reference ?
>>>>
>>>> Even if you get this to compile it won't work.
>>>> (well it will till one day until it just crashes mysteriously)
>>>>
>>>> At some point the garbage collector might decide move your Cwin 
>>>> object, invalidating the pointer you are trying to store with 
>>>> SetWindowLong/GetWindowLong.
>>>>
>>>
>>> Thanks div0,
>>> I am allready afraid that this is the case...
>>>
>>>> You'll have to either allocation your cwin objects outside the 
>>>> garbage collectors control or pin the objects. (Don't know how you 
>>>> do this, depends on whether you are using phobos or tango)
>>>>
>>>
>>> Tango.
>>>
>>> What means "pin the object", please explain.
>>> Bjoern
>>
>> Marks the object as not movable.
>> It looks like getAttr/setAttr is what you want, but I've not used it 
>> myself so don't blame me if your program crashes. ;)
>>
>> http://www.dsource.org/projects/tango/browser/trunk/lib/common/tango/core/Memory.d 
>>
>>
>>
>>>
>>>> You should probably look at how dfl interfaces with the Win32 API, 
>>>> http://www.dprogramming.com/dfl.ph as that library has solved these 
>>>> issues and you should be able to work out how it's doing all the 
>>>> necessary casting/pinning.
> 
> And to actually answer your original question:
> 
> 
> class CWin {
>     int    m_a;
> 
>     this() {
>     }
> }
> 
> extern(Windows){
>     typedef void* HWND;
>     int GetWindowLongA(HWND wnd, int indx);
>     int GetWindowLongW(HWND wnd, int indx);
> }
> 
> 
> void main()
> {
>     // do the call (assume mbcs not unicode)
>     int    r = GetWindowLongA(cast(HWND)0, 0);
> 
>     // do the call & cast to CWin object pointer
>     CWin    *pWin = cast(CWin*)GetWindowLongA(cast(HWND)0, 0);
>     Stdout( r );
>     
> }
> 
> 
> Replace the 0's with the appropriate values, ie the window handle and 
> GWL_USERDATA (which is -21)
> 
> compile with:
>     dmd main.d user32.lib

We, means Bill B., Regan H., Jarret B. and me have discussed the C++ 
casting to D custing stuff a few days ago. Unfortunately our results 
regarding translating reinterpret_cast<CWin*> are different. Maybe we 
are wrong :(  ... Please have a look at :
http://www.prowiki.org/wiki4d/wiki.cgi?PortingFromCxx

Of course! your comments are welcome.
Bjoern
Beside it is this part :
pWnd->GetDlgItem( ((( LPDRAWITEMSTRUCT ))lParam)->CtlID

which makes me banging my head on the keyboard ;)