Windows Dev Center

PSFormatForDisplayAlloc function

Gets a formatted, Unicode string representation of a property value stored in a PROPVARIANT structure. This function allocates memory for the output string.


HRESULT PSFormatForDisplayAlloc(
  _In_  REFPROPERTYKEY        key,
  _In_  REFPROPVARIANT        propvar,
  _Out_ PWSTR                 *ppszDisplay


key [in]


Reference to a PROPERTYKEY that names the property whose value is being retrieved.

propvar [in]


Reference to a PROPVARIANT structure that contains the type and value of the property.

pdfFlags [in]


One or more flags that specify the format to apply to the property string. See PROPDESC_FORMAT_FLAGS for possible values.

ppszDisplay [out]

Type: PWSTR*

When the function returns, contains a pointer to a null-terminated, Unicode string representation of the requested property value.

Return value


Returns one of the following values.

Return codeDescription

The formatted string was successfully created. S_OK together with an empty return string indicates that there was an empty input string or a non-empty value that was formatted as an empty string.


The formatted string was not created. S_FALSE together with an empty return string indicates that the empty string resulted from a VT_EMPTY.


Indicates allocation failed.



This function calls the schema subsystem's implementation of IPropertySystem::FormatForDisplayAlloc. That call provides a Unicode string representation of a property value, with additional formatting based on one or more PROPDESC_FORMAT_FLAGS. If the PROPERTYKEY is not recognized by the schema subsystem, IPropertySystem::FormatForDisplayAlloc attempts to format the value according to the value's VARTYPE.

You must initialize Component Object Model (COM) with CoInitialize or OleInitialize before you call PSFormatForDisplayAlloc.

The function allocates memory through CoTaskMemAlloc and returns a pointer to that memory through the ppszDisplay parameter. The calling application must use CoTaskMemFree to release that resource when it is no longer needed.

The purpose of this function is to convert data into a string suitable for display to the user. The value is formatted according to the current locale, the language of the user, the PROPDESC_FORMAT_FLAGS, and the property description specified by the property key. For information on how the property description schema influences the formatting of the value, see the following topics:

Typically, the PROPDESC_FORMAT_FLAGS are used to modify the format prescribed by the property description.

The output string can contain Unicode directional characters. These nonspacing characters influence the Unicode bidirectional algorithm so that the values appear correctly when a left-to-right (LTR) language is drawn on a right-to-left (RTL) window, or an RTL is drawn on a LTR window. These characters include the following: "\x200e", "\x200f", "\x202a", "\x202b", "\x202c", "\x202d", "\x202e".

The following properties use special formats and are unaffected by the PROPDESC_FORMAT_FLAGS. Note that examples cited are for strings with a current locale set to English; typically, output is localized except where noted.

System.FileAttributesThe following file attributes are converted to letters and appended to create a string (for example, a value of 0x1801 (FILE_ATTRIBUTE_READONLY | FILE_ATTRIBUTE_COMPRESSED | FILE_ATTRIBUTE_OFFLINE) is converted to "RCO"):
  • FILE_ATTRIBUTE_READONLY (0x00000001) - 'R'
  • FILE_ATTRIBUTE_SYSTEM (0x00000004) - 'S'
  • FILE_ATTRIBUTE_ARCHIVE (0x00000020) -'A'
  • FILE_ATTRIBUTE_COMPRESSED (0x00000800) - 'C'
  • FILE_ATTRIBUTE_ENCRYPTED (0x00004000) - 'E'
  • FILE_ATTRIBUTE_OFFLINE (0x00001000) - 'O'
System.Photo.ISOSpeedFor example, "ISO-400".

The APEX value is converted to an exposure time using this formula:

Exposure_time = 2^(-APEX_value)

For example, "2 sec."or "1/125 sec.".

System.Photo.ExposureTimeFor example, "2 sec."or "1/125 sec."

The APEX value is converted to an F number using this formula:

F_Number = 2^(APEX_Value / 2)

For example, "f/5.6".

System.Photo.FNumberFor example, "f/5.6".
System.Photo.SubjectDistanceFor example, "15 m"or "250 mm".
System.Photo.FocalLengthFor example, "50 mm".
System.Photo.FlashEnergyFor example, "500 bpcs".
System.Photo.ExposureBiasFor example, "-2 step", " 0 step", or "+3 step".
System.Computer.DecoratedFreeSpaceFor example, "105 MB free of 13.2 GB".
System.ItemTypeFor example, "Application" or "JPEG Image".
System.ControlPanel.CategoryFor example, "Appearance and Personalization".
System.ComputerNameFor example, "LITWARE05 (this computer)" or "testbox07".


If the property key does not correspond to a property description in any of the registered property schemas, then this function chooses a format based on the type of the value.

Type of the valueFormat
VT_BOOLEANNot supported.
VT_FILETIMEDate/time string as specified by PROPDESC_FORMAT_FLAGS and the current locale. PDFF_SHORTTIME and PDFF_SHORTDATE are the default. For example, "11/13/2006 3:22 PM".
Numeric VARTYPEDecimal string in the current locale. For example, "42".
VT_LPWSTR or otherConverted to a string. Sequences of "\r", "\t", or "\n" are replaced with a single space.
VT_VECTOR | anythingSemicolon separated values. A semicolon is used regardless of locale.



The following example, to be included as part of a larger program, demonstrates how to use PSFormatForDisplayAlloc to format a rating value.


HRESULT hr = InitPropVariantFromUInt32(RATING_THREE_STARS_SET, &propvar);

if (SUCCEEDED(hr))
    PWSTR pszValue;

    hr = PSFormatForDisplayAlloc(PKEY_Rating, propvar, PDFF_DEFAULT, &pszValue);

    if (SUCCEEDED(hr))
        // pszValue contains a formatted string similar to "3 stars".


Minimum supported client

Windows Vista [desktop apps only]

Minimum supported server

Windows Server 2008 [desktop apps only]


Windows Desktop Search (WDS) 3.0






Propsys.dll (version 6.0 or later)

See also

Property Description Schema



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