porting Windows C++ to D, a few questions

[Regan Heath]

BLS wrote:
> Regan Heath schrieb:
>> BLS wrote:
>>> Hi,
>>>
>>> I have/would like to translate a Windows C++ source into D and I have 
>>> questions regarding
>>> Class pointer, casting, and CALLBACK
>>>
>>> Okay, here a C++ fragment.
>>> class CWin : public CMsg
>>
>> Don't need 'public' in there.
>>
>>> {
>>>
>>> WNDCLASSEX    wcex;
>>> wcex.hbrBackground= (HBRUSH) (COLOR_BTNFACE+1);
>>> // How to translate this into D ?
>>> // I guess :
>>>
>>> //wcex.hbrBackground = cast(HBRUSH) (COLOR_BTNFACE+1);
>>> // Is this correct ????
>>
>> It looks correct to me.
>>
>>> //Later :
>>> static LRESULT CALLBACK WndProc(HWND hWnd, UINT uID, WPARAM wParam, 
>>> LPARAM lParam)
>>> // Actually I have no idea how to convert this construct into D...
>>
>> By including std.c.windows.windows you will get most of HWND, etc 
>> defined for you, so you can just leave them there.
>>
>> If you're:
>>
>> 1. re-writing this in D then "CALLBACK" can be removed (as it resolves 
>> to __stdcall which is not needed in D)
>>
>> 2. Trying to call this D function from a C application then you need 
>> to remove CALLBACK and place extern(Windows) on the front of it, i.e.
>>
>> extern(Windows) LRESULT WndProc(HWND hWnd, UINT uID, WPARAM wParam, 
>> LPARAM lParam)
>>
>> 3. Likewise if you're trying to call a C function from D you need to 
>> define it as #2
>>
>>> {
>>>
>>>   CWin* pWnd=NULL;
>>>   // I think in D using a pointer to a class is not nessesary.
>>>   // Do you agree ? However the next pb. I have is here :
>>
>> Yes.  Change this to "CWin pWnd = null;".  Classes are automatically 
>> "by reference" (which is like a pointer)
>>
>>> pWnd = 
>>> reinterpret_cast<CWin*>((long)((LPCREATESTRUCT)lParam)->lpCreateParams);
>>
>> Change this to:
>>
>> pWnd = cast(CWin)(cast(LPCREATESTRUCT)lParam)->lpCreateParams;
>>
>> You could put a cast(int) in there (where the (long) was) but I don't 
>> believe you need it.  The reason you would use 'int' and not 'long' is 
>> that long in C++ is typically 32 bits and long in D is 64 bits.
>>
>> I'm not 100% certain that it is guaranteed to work if you cast class 
>> references to void and back again.  Someone else might be able to 
>> confirm/deny this for us.
>>
>> Note: LPVOID is defined as void* in D
>>
>>> // Now it seems to become difficult. In case that I define
>>> CWin pWind; // instead off CWin* pWnd;
>>> //then casting is impossible. So what can I do ?
>>
>> Hope I got that all correct.
>>
>> Regan
> Thanks a lot Regan!
> 
>  > Change this to:
>  >
>  > pWnd = cast(CWin)(cast(LPCREATESTRUCT)lParam)->lpCreateParams;
> 
> It is the ->lpCreateParams which makes me wonder..

Doh!  Change -> to . :)

Regan