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windows programming

Started by Ahmet Apr 28, 2006 at 7:44 AM 5 replies 850+ views

Original Post

Apr 28, 2006 at 7:44 AM

I am a newbie in game programing and ask you a quesstion about creating a window. Windows use WndProc( HWND hWnd , UINT msg ,WPARAM wParam, LPARAM lParam) function to handle windows' messages which has below structure typedef struct tagMSG { HWND hwnd; UINT message; WPARAM wParam; LPARAM lParam; DWORD time; POINT pt; } MSG; msg structure already has the window handle , wParam and lParam . Why we have to resend the hWnd , wParam and lParam parameters?WndProc can't be satisfied with a single msg parameter?Same thing is valid for DefWindowProc() . thanks for all help :)

Evil Steve

382

Evil Steve

Apr 28, 2006 at 7:50 AM

The WndProc doesn't actually get the MSG variable, it just gets a few members of it. I'd like to know why WnyProc doesn't just get passed the MSG that's getting handled in the message loop, actually...

EDIT: Oh, I think that's what you're saying... never mind then [smile]

cenix

Apr 28, 2006 at 7:52 AM

Quote:
Original post by Ahmet
Why we have to resend the hWnd , wParam and lParam parameters?WndProc can't be satisfied with a single msg parameter?Same thing is valid for DefWindowProc() .
thanks for all help :)

You don't.
You don't send the msg struct to wndproc.
The 'UINT msg' parameter in WndProc is the message, e.g. WM_PAINT.
Look on MSDN if you want more information.

Ahmet

Author

Ahmet

Apr 28, 2006 at 7:57 AM

ofcourse cenix but if we send the WM_PAINT we have already sent lParam..

Evil Steve

382

Evil Steve

Apr 28, 2006 at 8:02 AM

WM_PAINT is sent as a UINT, which is just an integer. The message also needs the lParam to be passed to the window proc with it.

Emmanuel Deloget

431

Emmanuel Deloget

Apr 28, 2006 at 8:17 AM

Rewrite to make things more obvious:

WndProc( HWND hwnd, UINT message ,WPARAM wParam, LPARAM lParam)

Compare to

typedef struct tagMSG {  HWND hwnd;  UINT message;  WPARAM wParam;  LPARAM lParam;  DWORD time;  POINT pt;} MSG;

Your high level code gets the MSG structure from GetMessage or PeekMessage, and DispatchMessage feeds WndProc with the hwnd, the message and the params.

HTH,

Ahmet

Author

Ahmet

Apr 28, 2006 at 8:41 AM

Thanks all , especially Emmanuel Deloget , you are the best :)

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