PropVariantToDoubleWithDefault function (propvarutil.h)

Extracts a double property value of a PROPVARIANT structure. If no value exists, then the specified default value is returned.

Syntax

PSSTDAPI_(DOUBLE) PropVariantToDoubleWithDefault(
  [in] REFPROPVARIANT propvarIn,
  [in] DOUBLE         dblDefault
);

Parameters

[in] propvarIn

Type: REFPROPVARIANT

Reference to a source PROPVARIANT structure.

[in] dblDefault

Type: DOUBLE

Specifies default property value, for use where no value currently exists.

Return value

Type: DOUBLE

Returns extracted double value, or default.

Remarks

This helper function is used in places where the calling application expects a PROPVARIANT to hold a double value and would like to use a default value if it does not. For instance, an application obtaining values from a property store can use this to safely extract the double value for double properties.

If the source PROPVARIANT has type VT_R8, this helper function extracts the double value. Otherwise, it attempts to convert the value in the PROPVARIANT structure into a double. If the source PROPVARIANT has type VT_EMPTY or a conversion is not possible, then PropVariantToDoubleWithDefault will return the default provided by dblDefault. See PropVariantChangeType for a list of possible conversions.

Examples

// IPropertyStore *ppropstore;
// Assume variable ppropstore is initialized and valid
PROPVARIANT propvar = {0};
HRESULT hr = ppropstore->GetValue(PKEY_Image_HorizontalResolution, &propvar);
if (SUCCEEDED(hr))
{
     // PKEY_Image_HorizontalResolution is expected to produce a VT_R8 or VT_EMPTY value.
     // The application developer decided to treat VT_EMPTY or invalid values as 72.0
     DOUBLE dblResolution = PropVariantToDoubleWithDefault(propvar, 72.0);
     // dblResolution is now valid.
     PropVariantClear(&propvar);
}

Requirements

See also

InitPropVariantFromDouble

PropVariantChangeType

PropVariantToDoubleVector

VariantToDouble