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kirk

Flipping

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The DDRAW Flip method exchanges the pointer of the BackBuffer with the pointer of the PrimarySurface. Why if I exchange them by hand he does not work? For example: void MyFlip() { pPrimary->Lock(); pBack->Lock(); . . . // retrieve pointers DWORD *Temp = lpBackPn; lpBackPn = lpPrimaryPn; lpPrimaryPn = Temp; pPrimary->Unlock(); pBack->Unlock(); }

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All you are doing is grabbing copies of pointers to the memory. Just because you decide to copy the value of what was returned for the back buffer into a variable that you call the front buffer, and vice versa, has no effect on the video card whatsoever. All that changes is that you now have erroneous names for the buffers. Changing the names in your program doesn''t change anything on the video card. The DirectDraw flip method, on the other hand, tells the video card to start treating what was the back buffer as the front buffer, and vice versa.

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Why you would want to do this is beyond me.

Adding to what Kylotan said, too make your own home grown flip routine, you would need to have pointers to pointers. That way when you dereference once, you can change what the pointer points to (vs. the data a.k.a. regular pointer)

It would be more like the following:
(Not tested or compiled!)


void MyFlip(DDsurface **front, DDsurface **back)
{
(*front)->Lock();
(*back)->Lock();

DDsurface **Temp = *lpBackPn;
*lpBackPn = *lpPrimaryPn;
*lpPrimaryPn = *Temp;

(*front)->Unlock();
(*back)->Unlock();

}


That should work.




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