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Classes and windows callback...

Started by Prankster Jan 3, 2003 at 6:27 AM 2 replies 1.3k views

Original Post

Jan 3, 2003 at 6:27 AM

Cheers, I have a question about something that's been tearing my mind for some time... Is it possible to make the windows callback a class member...? Or to access class members via the callback if it's not a class member...? I've tried a few times, without any luck. Some pseudo code from the top of my head --- Main wrapper

        
//winmain.cpp

//

int WINAPI WinMain(etc...)
{
  // Class registration and main window creation is done in the

  // foobar class constructor

  CFoobar* foo = new CFoobar();

  ...
  ...
}

Foobar class header

  
//foobar.h

//

class CFoobar{
  CFoobar();
  virtual~ CFoobar();

  // Possible??

  LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
};

Foobar class

        
//foobar.cpp

//

CFoobar::CFoobar()
{
  WNDCLASS wc;
  ZeroMemory(...);
  ...
  ...
  wc.WndProc = WndProc; // Doesn't work, i've tried casting as well (bad idéa :))

}

So if i instead try to get to the class member in the callback...

  
LRESULT CALLBACK WndProc(...)
{
  CFoobar *foo = (CFoobar*)GetWindowLong(hwnd, GWL_USERDATA);

  ...
  ...

  case WM_BLAH:
  {
    foo->DoSomething(); // Access violation...

  } break;

  ...
  ...
}

Well, I need to get this working in someway, and my only option at this time is to pick out the functions i access from the callback out of the classes and make them 'global' (can't find the word i'm looking for...). Can't find any tutorials on it either... Thanks in advance. [edited by - prankster on January 3, 2003 7:30:13 AM] [edited by - prankster on January 3, 2003 7:30:52 AM] [edited by - prankster on January 3, 2003 7:31:59 AM]

billybob

Jan 3, 2003 at 6:36 AM

i''ve had a lot of trouble with this as well, and the way i eventaully solved it was just have one global AppWndProc(...). i also have (my only global variable) is a pointer to the instance of my app. all my wndclass and wndclassex have AppWndProc as their wndproc arg. the AppWndProc looks like this:


LRESULT CALLBACK AppWndProc(HWND hWnd, UINT Message, WPARAM wParam, LPARAM lParam)
{
	return pAppInst->WndProc(hWnd, Message, wParam, lParam);
}

the pAppInst also has several LRESULT BlahBlahProcs(..), and the general WndProc checks which HWND is recieving the message, and then sends it off to the correct process, also a member of the class. it looks like this:


LRESULT CApp::WndProc(HWND hWnd, UINT Message, WPARAM wParam, LPARAM lParam)
{
	if(hWnd == hMainWnd)
		return MainWndProc(hWnd, Message, wParam, lParam);
	else if(hWnd == hViewClient)
		return ViewClientProc(hWnd, Message, wParam, lParam);

	else if(hWnd == hViewWndTop)
		return ViewTopProc(hWnd, Message, wParam, lParam);
...
...
...
        else
                return DefWndProc(hWnd, Message, wParam, lParam);
}

i know its crappy with the if else if else if stuff, but the compiler doesn''t like switch(HWND)

this is how i avoid having a bunch of global window processes, and it also allows me to make general WNDCLASSes. i have 3 or 4 classes, like ones with the IDC_CROSS cursor, stuff like that.

original vesoljc

Jan 3, 2003 at 6:36 AM

try searching for a window wrapper...
well here''s what i did (with big help from gd)

  
// in class header

	static LRESULT CALLBACK Router				(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam);
	LRESULT CALLBACK	WindowProc			(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam);

// implementation

LRESULT CALLBACK	WinApp::Router(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
	if (msg == WM_NCCREATE)
	{
		LPCREATESTRUCT lpcs = LPCREATESTRUCT(lparam);
		SetWindowLong(hwnd, GWL_USERDATA, (long) lpcs->lpCreateParams);
	}
	WinApp *pThis = (WinApp *) GetWindowLong(hwnd, GWL_USERDATA);
	if (pThis)
	{
		return pThis->WindowProc(hwnd, msg, wparam, lparam);
	}
	else
	{
		return DefWindowProc(hwnd, msg, wparam, lparam);
	}
}

LRESULT CALLBACK	WinApp::WindowProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
    switch (msg)
    {
		case WM_DESTROY:
			Destroy();
			PostQuitMessage(0);
			break;
		case WM_ACTIVATE:
			if(LOWORD(wparam))
			{
				Activate(true);
			}
			else
			{
				Activate(false);
			}
            break;
        default:
            return DefWindowProc(hwnd, msg, wparam, lparam);
    }
    return 0;
}

// and when creating WNDCLASS

m_class.lpfnWndProc   = WinApp::Router;

Abnormal behavior of abnormal brain makes me normal...

Prankster

Author

Prankster

Jan 3, 2003 at 11:58 AM

Thanks for your replies. I''ll give it a try.

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