Re: DirectX Blues

[Donald Halloran <donaldha@ozemail.com.au>]

Neil wrote:
> 
> I'm having a few problems with my DirectX program. I was wondering if
> someone could please help me with a few questions:
> 1. How do I check Windows messages to see when the program becomes avtive
> (i.e. not minimized). I've read "just look for the WM_ACTIVATE message, so
> I tried toggling a "BOOL Active" every time I get that message, but it
> doesn't seem to work.

When your app is deactivated you may lose the memory allocated for your
directx program. Therefore if your program detects a WM_ACTIVATE, you
should call functions which restore your draw surfaces and sound
buffers, and reloads the data you want into those surfaces and buffers.

> 2. Can I safely assume that the screen's pitch as stored in the surface
> descreption after locking a surface will remain constant? I.e. Can I get it
> once and save it, or do I have to check it every frame?

Not sure about this one, I didn't deal with the pitch in my game (my
first one, its at http://www.ozemail.com.au/~donaldha/eradicator ).

> 3. How do I align my page-flips with the monitor's refresh? Is this done
> automatically? Can I continue calculating something else while I wait?
> 4. Why does the following code not work? I'm using page-flipping, but the
> screen is still flashing psychedellically and exhibiting massive tearing. I
> can see pixels I've drawn over as semi-transparent just as though I were
> writing directly to the screen even though I'm pretty sure I'm not; I know
> I'm not trying to.

I think all of this will be solved by including the DDSFLIP_WAIT flag in
your call to IDirectDrawSurface::Flip, and DDBLT_WAIT in your call to
IDirectDrawSurface7::Blt. However, the DDBLT_WAIT flag can be rather
inefficient... I believe there is a better alternative given somewhere
in the DirectX.chm help file in the sdk. IDirectDrawSurface7::Flip by
default waits for the vertical retrace. It will only flip other than
during a vertical retrace if you specify DDFLIP_NOVSYNC.

--
Don Halloran
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