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The IDirectDraw4::GetAvailableVidMemmethod retrieves the total amount of display memory available and the amount of display memory currently free for a given type of surface.
HRESULT GetAvailableVidMem( LPDDSCAPS2 lpDDSCaps2 , LPDWORD lpdwTotal , LPDWORD lpdwFree );
Parameters
- lpDDSCaps2
- Address of a DDSCAPS2structure that indicates the hardware capabilities of the proposed surface.
- lpdwTotal
- Address of a variable that will be filled with the total amount of display memory available, in bytes. The value retrieved reflects the total video memory, less the video memory required for the primary surface and any private caches the display driver reserves.
- lpdwFree
- Address of a variable that will be filled with the amount of
display memory currently free that can be allocated for a surface
that matches the capabilities specified by the structure at
lpDDSCaps2.
Return Values
If the method succeeds, the return value is DD_OK.
If the method fails, the return value may be one of the following error values:
If NULL is passed to either lpdwTotalor lpdwFree, the value for that parameter is not returned.
Remarks
The following C++ example demonstrates using IDirectDraw4::GetAvailableVidMemto determine both the total and free display memory available for texture-map surfaces:
// For this example, the lpDD variable is a valid // pointer to an IDirectDraw interface. LPDIRECTDRAW4 lpDD4; DDSCAPS2 ddsCaps2; DWORD dwTotal; DWORD dwFree; HRESULT hr; hr = lpDD->QueryInterface(IID_IDirectDraw4, &lpDD4); if (FAILED(hr)) return hr; // Initialize the structure. ZeroMemory(&ddsCaps2, sizeof(ddsCaps2)); ddsCaps2.dwCaps = DDSCAPS_TEXTURE; hr = lpDD4->GetAvailableVidMem(&ddsCaps2, &dwTotal, &dwFree); if (FAILED(hr)) return hr;
This method provides only a snapshot of the current display-memory state. The amount of free display memory is subject to change as surfaces are created and released. Therefore, you should use the free memory value only as an approximation. In addition, a particular display adapter card may make no distinction between two different memory types. For example, the adapter might use the same portion of display memory to store Z-buffers and textures. So, allocating one type of surface (for example, a Z-buffer) can affect the amount of display memory available for another type of surface (for example, textures). For best results, first allocate an application's fixed resources (such as front and back buffers, and Z-buffers) before determining how much memory is available for dynamic use (such as texture mapping).
This method was not implemented in the IDirectDrawinterface.
Requirements
Runs on Versions Declared in Link to Windows CE OS 2.12 or later. Version 2.12 requires DXPAK 1.0 or later. ddraw.h ddraw.lib