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Display mode changing problem


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#1 Aeetes   Members   -  Reputation: 122

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Posted 07 December 1999 - 02:51 AM

I have written a GUI class library using DD and DI. So far it only runs in 640x480x8 mode. However, when I attempted to add support for mode changing (different resolutions, still 8-bit though) my programs crashes on exit (page fault). After this, any DDraw program that I run (including the samples) always crashes on loading with a page fault. I can only run a DDraw program again after rebooting.

My library has surfaces for primary and back buffer. When I change the mode I first release both the primary and back buffers, switch the mode, then finally create new primary and back buffer surfaces.

If I ignore the surfaces, and just switch the mode, not releasing and recreating the primary and back buffer, the program runs fine. I stripped the program down to the point where it does nothing but change the mode, so I am certain that the problem has to do with it... Namely the surfaces I believe.

Here is the code for changing the mode:

code:
ARESULT AccessDisplay::SetDisplayMode(int nWidth, int nHeight, int nBPP) {
if (m_pDDSPrimary != NULL) {
m_pDDSPrimary->Release();
m_pDDSPrimary = NULL;
}
if (m_pDDSBuffer != NULL) {
m_pDDSBuffer->Release();
m_pDDSBuffer = NULL;
}

if (m_pDD->SetDisplayMode(nWidth, nHeight, nBPP, 0, 0) != DD_OK)
return AERROR;

DDSURFACEDESC2 ddsd;
ZeroMemory(&ddsd, sizeof(ddsd));
ddsd.dwSize = sizeof(ddsd);
ddsd.dwFlags = DDSD_CAPS | DDSD_BACKBUFFERCOUNT;
ddsd.ddsCaps.dwCaps = DDSCAPS_PRIMARYSURFACE | DDSCAPS_FLIP | DDSCAPS_COMPLEX;
ddsd.dwBackBufferCount = 1;
if (m_pDD->CreateSurface(&ddsd, &m_pDDSPrimary, NULL) != DD_OK)
return AERROR;

DDSCAPS2 ddscaps;
ZeroMemory(&ddscaps, sizeof(ddscaps));
ddscaps.dwCaps = DDSCAPS_BACKBUFFER;
if (m_pDDSPrimary->GetAttachedSurface(&ddscaps, &m_pDDSBuffer) != DD_OK)
return AERROR;

DDBLTFX ddbltfx;
ZeroMemory(&ddbltfx, sizeof(ddbltfx));
ddbltfx.dwSize = sizeof(ddbltfx);
ddbltfx.dwFillColor = 0;
if (m_pDDSPrimary->Blt(NULL, NULL, NULL, DDBLT_COLORFILL | DDBLT_WAIT, &ddbltfx) != DD_OK)
return AERROR;
if (m_pDDSBuffer->Blt(NULL, NULL, NULL, DDBLT_COLORFILL | DDBLT_WAIT, &ddbltfx) != DD_OK)
return AERROR;

return AOK;
}


Does anyone have any ideas as to what could be causing this?

[This message has been edited by Aeetes (edited December 06, 1999).]


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#2 Tuan   Members   -  Reputation: 122

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Posted 06 December 1999 - 02:56 PM

When you create the primary surface in full screen mode, the back surface is a member of primary. So, when you release primary surface, the back is release automatically. You release the back surface manually when you run in window mode.
Goodluck!

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#3 Aeetes   Members   -  Reputation: 122

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Posted 07 December 1999 - 02:51 AM

Thank you. I got it working a little later by just releasing the back buffer before the primary surface. Thanks, since I didn't really know that the reference was held by the primary surface (I'm new to COM programming, switching from good old DPMI under DJGPP). At least now I know why it worked when I switched the release order, thanks.

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