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Problem Initializing DirectDraw...

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I''ve got the book Tricks of the Game Programming Gurus, written by Andre LaMothe, and I can not get the method he uses in the book for initializing DirectDraw to work. Following the Documentation that came with the DirectX SDK works fine. Below is the calls LaMothe makes to initialize DD and then the calls according to the SDK docs (and all the tutorials I''ve seen today on the web also). I''ve removed all the error checking code to keep it short. LaMothe DirectDrawCreate(NULL, &lpdd, NULL) lpdd->QueryInterface(IID_IDirectDraw4, (LPVOID *)&lpdd4) lpdd4->SetCooperativeLevel(hwnd, COOP_FLAGS) lpdd4->SetDisplayMode(640, 480, 8, 0, 0) Everyone else DirectDrawCreate(NULL, &lpdd, NULL) lpdd->SetCooperativeLevel(hwnd, COOP_FLAGS) lpdd->SetDisplayMode(640, 480, 8) In LaMothes example, the two extra parameters in SetDisplayMode are supposed to be the refresh rate and extra flags. However, attempting to compile gives me a SetDisplayMode does not take 5 parameters error. Removing the two last parameters compiles just fine, but when I run, it simply fails to set the Display Mode. The non-LaMothe example compiles and works just fine. So I''m going to continue on using the non-LaMothe method, but what''s the deal? Why is he using QueryInterface and why isn''t it working on my system? I have the DX6.1 SDK that came with his book installed on my system. I''m using Developer Studio 97 (Visual C++ 5.0) I just don''t like leaving mysteries like this hanging.

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i beleive the SetDisplayMode() in laMothe''s code should have four parameters. just take out that last zero. LaMothe''s code uses the DX6-specific directdraw object. QueryInterface will essentially upgrade your generic lpdd from an IID_IDirectDraw object to the specified IID_IDirectDraw4 object (the DX6 one). hope it helps.


_________________Gecko___

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First off, take a look in the book on page 247 in the section titled ''Getting an Interface Lift". LaMothe explains the use of QueryInterface. DirectDrawCreate initializes an IDirectDraw interface. In order to get a pointer to the newer interface, you need to call QueryInterface and ask for a pointer to an IDrectDraw4 object. There is a typo on the page that may be causing you trouble. In the book, the first 2 lines of the example source look like this:

LPDIRECTDRAW lpdd = NULL;
LPDIRECTDRAW lpdd4 = NULL;

I believe that might be the root of your problems. Here''s how it should look:

LPDIRECTDRAW lpdd = NULL;
LPDIRECTDRAW4 lpdd4 = NULL;

IDirectDraw::SetDisplayMode takes 3 arguments, while IDirectDraw4::SetDisplayMode takes 5. It seems that you are not actually initializing the newer interface and are instead calling the older version of SetDisplayMode, thus the error message.

Take a look in the DirectX docs under DirectX Foundation->DirectDraw->DirectDraw Reference->Interfaces. There you can read more about IDirectDraw4 and it''s methods.

The sample source in the 6.1 documentation does not create an IDirectDraw4 object. Instead, a IDirectDraw object is created. That''s the difference between the sample and LaMothe''s code.

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haha, whoops. don''t bother listening to my post there. just forget it evvvveeeeer happened. post? what post?


_________________Gecko___

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It was indeed the typo that you pointed out that was causing my problems Aldacron. Thanks for the clarification.

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