Lock Issue While using DirectDraw

Iam using DirectDraw Component to create primary surface in windowed mode , when i try to lock
the primary surface to acess the primary surface memory , it works,  but some times it won't allow me to lock the surface it gives me DDERR_GENERIC. This problem persists until i exit from the application.  Can any one help me.

Here is the code


      hr = lpDDSPrimary->Lock( NULL , &ddsd, DDLOCK_WAIT |DDLOCK_SURFACEMEMORYPTR    | DDLOCK_READONLY , NULL );
      if(hr ==DD_OK)
      {
         if(ddsd.lpSurface !=NULL)
          {
                // i will do processing of surface here
                    }
                   lpDDSPrimary->Unlock(ddsd.lpSurface);

      }
      else
      {
            CString eMsg="Error in lock  ";
            GetErrorMsg(hr,eMsg);
            throw "Error Unable to Lock Surface";      
      }
 

Thnaks in advance

SHariAsked:
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bredboredCommented:
In theory you ought to use
if( SUCCEEDED( hr ) )
rather than
if( hr == DD_OK )

Also in theory, IDirectDrawSurface7::Lock does not return DDERR_GENERIC.

Did you set ddsd.dwSize to sizeof ddsd?

Finally, IDirectDrawSurface7::Unlock takes a pointer to a rectangle as its parameter.  This rectangle must be the same rectangle specified in the call to IDirectDrawSurface7::Lock.  Therefore you should change
lpDDSPrimary->Unlock( ddsd.lpSurface );
to
lpDDSPrimary->Unlock( NULL );

All of there points are applicable to versions of DirectDraw other than 7.

Nick

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davebytesCommented:
Sounds strange.

My brain says many cards and drivers will not allow access to the primary buffer via locking.

What are you trying to do that you need to lock the primary?  and not double-buffering and locking down the back-buffer instead?

-d
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