Thread: A few questions

Hi there.
i'm relatively new to directx.

I have a message loop from a book called Introduction to 3d Game Programming with Directx 9.0

here it is:

Code:

int d3d::EnterMsgLoop( bool (*ptr_display)(float timeDelta) )
{
	MSG msg;
	::ZeroMemory(&msg, sizeof(MSG));

	static float lastTime = (float)timeGetTime(); 

	while(msg.message != WM_QUIT)
	{
		if(::PeekMessage(&msg, 0, 0, 0, PM_REMOVE))
		{
			::TranslateMessage(&msg);
			::DispatchMessage(&msg);
		}
		else
        {	
			float currTime  = (float)timeGetTime();
			float timeDelta = (currTime - lastTime)*0.001f;

			ptr_display(timeDelta);

			lastTime = currTime;
        }
    }
    return msg.wParam;
}

could someone clear this up for me please.
i understand a little, but not all of it.

thanks if anyone replies.

EDIT:
Oh yes, and what is HRESULT?

This loop is the message pump. And it also takes care of some timer housekeeping so you can pass the frame delta to the render function. I completely changed the one in the book to my own version b/c I did not agree with some of the architecture and framework. I removed the pointer to the render function as well but I won't get into my architecture here as it will certainly differ from yours.

Interesting to note that in the second edition of the book the author made many of the same changes. In order to fit this into an object oriented design you will have to make some significant alterations to what you see in the book.

But it is a very good book and I highly recommend it as well as the second edition. If you have questions you can go to www.moon-labs.com. There are forums and FAQs about the book as well as more code, more information, and the author frequents the site as well and is more than happy to help new programmers with DirectX.

ZeroMemory sets everything in the MSG structure to 0. HRESULT is the return type that the guys at DirectX came up with. It's designed to tell whether the function completed properly. There are several different things that HRESULT could be to give specific errors. There are 2 macros that are designed to simplify those into either success or failure.

Code:

HRESULT MyResult;
MyResult = SomeFunction();
if (SUCCEED(MyResult))
{
     // function ran fine
}

if (FAILED(MyResult))
{
     // handle some errors
     // possibly exit program
}

// or directly:
if (FAILED(SomeFunction()))
{
     // SomeFunction failed
}