IWiaItem2::CheckExtension method
Checks whether a specified extension is available on the machine and can be used by the IWiaItem2::GetExtension method.
Syntax
HRESULT CheckExtension(
[in] LONG lFlags,
[in] BSTR bstrName,
[in] REFIID riidExtensionInterface,
[out] BOOL *pbExtensionExists
);
Parameters
-
lFlags [in]
-
Type: LONG
Currently unused. Should be set to zero.
-
bstrName [in]
-
Type: BSTR
Specifies the name of the extension.
-
riidExtensionInterface [in]
-
Type: REFIID
Currently unused.
-
pbExtensionExists [out]
-
Type: BOOL*
Receives a pointer to a BOOL.
-
FALSE
-
The specified extension is not available.
-
TRUE
-
The specified extension is available.
Return value
Type: HRESULT
If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.
Remarks
Using this method, applications can check whether an extension is available before calling the IWiaItem2::GetExtension method. Also, the application can check which extensions are available without co-creating each of them, and then decide which one to use.
Examples
CheckImgFilter checks if the driver has an image processing filter. Before calling into the preview component, an application should ensure that the driver has an image processing filter.
HRESULT
CheckImgFilter(
IN IWiaItem2 *pWiaItem2,
OUT BOOL *pbHasImgFilter)
{
HRESULT hr = S_OK;
if (!pWiaItem2 || !pbHasImgFilter)
{
hr = E_INVALIDARG;
}
if (SUCCEEDED(hr))
{
*pbHasImgFilter = FALSE;
}
if (SUCCEEDED(hr))
{
BSTR bstrFilterString = SysAllocString(WIA_IMAGEPROC_FILTER_STR);
if (bstrFilterString)
{
hr = pWiaItem2->CheckExtension(0,
bstrFilterString,
IID_IWiaSegmentationFilter,
pbHasImgFilter);
SysFreeString(bstrFilterString);
bstrFilterString = NULL;
}
else
{
hr = E_OUTOFMEMORY;
}
}
return hr;
}
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client |
Windows Vista [desktop apps only] |
| Minimum supported server |
Windows Server 2008 [desktop apps only] |
| Header |
|
| IDL |
|