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 , LPDWORD , LPDWORD );
If the method succeeds, the return value is DD_OK.
If it fails, the method can return one of the following error values:
The following C++ example demonstrates how to use GetAvailableVidMem to 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 IDirectDraw7 interface. LPDIRECTDRAW7 lpDD; DDSCAPS2 ddsCaps2; DWORD dwTotal; DWORD dwFree; HRESULT hr; hr = lpDD->QueryInterface(IID_IDirectDraw7, &lpDD); if (FAILED(hr)) return hr; // Initialize the structure. ZeroMemory(&ddsCaps2, sizeof(ddsCaps2)); ddsCaps2.dwCaps = DDSCAPS_TEXTURE; hr = lpDD->GetAvailableVidMem(&ddsCaps2, &dwTotal, &dwFree); if (FAILED(hr)) return hr;
GetAvailableVidMem 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 might 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 (textures). Therefore, it is best to 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).
GetAvailableVidMem was not implemented in the previous DirectX IDirectDraw interface version.