porting Windows C++ to D, a few questions

[BLS]

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..