porting Windows C++ to D, a few questions

[Regan Heath]

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