I've got a Help->About menu and I'm trying to make it so that when you select about it brings up a dialog box. I've gotten the dialog box made okay, but I'm having problems in the message loop (LRESULT CALLBACK). I've got a switch structure to select the message, here's the WM_COMMAND case that I'm having problems with:

case WM_COMMAND:
switch( wParam )
{
case IDM_ABOUT:
DialogBox(ghInstance, "AboutDlg", hWnd, (DLGPROC)AboutDlgProc);
break;
}
break;

The DialogBox call gives me these errors:

Error: generic.cpp(129,80):Cannot convert 'void *' to 'HINSTANCE__ *'
Error: generic.cpp(129,80):Type mismatch in parameter 'hInstance' in call to '__stdcall DialogBoxParamA(HINSTANCE__ *,const char *,HWND__ *,int (__stdcall *)(HWND__ *,unsigned int,unsigned int,long),long)'

I know the rest of the code is okay because if I comment out that case (WM_COMMAND) it compiles and executes perfectly (except that you can't select the about menu item, obviously)

Heres the dialog code if you need it:

1 DLGINCLUDE "generic.h"

AboutDlg DIALOG FIXED 6, 21, 198, 99
STYLE DS_MODALFRAME | WS_POPUP | WS_VISIBLE | WS_CAPTION | WS_SYSMENU
CAPTION "About Generic"
FONT 8, "MS Shell Dlg"
BEGIN
DEFPUSHBUTTON "&OK", IDOK, 72, 74, 40, 14
LTEXT "Generic Application", 104, 45, 14,
128, 8
LTEXT "Written as a sample", 105, 45, 35, 59, 8
LTEXT "Microsoft Corporation", 106, 45, 45, 98, 8
LTEXT "Copyright (c) 1996", 107, 45,
54, 138, 8
END

As you can see, it's taken directly from the MSDN, which is why I don't understand why it doesn't work. Thanks in advance

Well the text formatting obviously doesn't work, I hope you can still understand it.

What is the declaration of ghInstance? (Because the error says the error is in the hInstance parameter.)

- taubz

It's a global handle to an instance. It's declared globally as:

HANDLE ghInstance;

After the window is created it is set to hInstance:

ghInstance = hInstance;

Do you think I should just pass hInstance instead of ghInstance, would that make a difference?

Here is the message loop for the dialog box:

LRESULT CALLBACK AboutDlgProc( HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam )
{
switch( uMsg )
{
case WM_INITDIALOG:
return TRUE;
case WM_COMMAND:
switch( wParam )
{
case IDOK:
EndDialog( hDlg, TRUE );
return TRUE;
}
break;
}
return FALSE;
}

Maybe pass &ghInstance instead of ghInstance. The parameter expects HINSTANCE__ * and your passing a HANDLE. I'm not sure how HANDLE and HINSTANCE__ compare, though. I think that function might even be deprecated in the first place, as iirc hInstances aren't used anymore since Win95.

- taubz

Let's try a few things:

1) Change the definition of AboutDlgProc to
BOOL APIENTRY AboutDlgProc( HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam );

2) Inside your WinMain(HINSTANCE HInst, ...) function, call the DialogBox(...) function directly using HInst as the first variable. NOT IN A SUBROUTINE TO BEGIN WITH, but directly in WinMain(). When this works, change its location if you wish (with the proper global variables, of course).

3) Instead of specifying a HWnd value in the DialogBox() call, put NULL for that parameter. Really, you don't need the handle to the calling window at all unless you're doing some advanced applications work.

I hope this helps - tell us what happens!
- Danny

Thanks, but the problem was I was declaring ghInstance as a HANDLE for some reason when I should have been declaring it as an HINSTANCE. Works fine now. Actually that wasn't my problem, the code was copied directly from an example in the MSDN.