Returns an object to enumerate the FORMATETC
structures that can be used with IDataObject::GetData
. You use this method when you want to enumerate the FORMATETC
structures for a data object.
| DWORD dwDirection,
||//Specifies a value from the enumeration DATADIR
| IEnumFORMATETC ** ppenumFormatetc
||//Location for IEnumFORMATETC
[in]Specifies a value from the enumeration DATADIR
typedef enum tagDATADIR
DATADIR_GET = 1,
DATADIR_SET = 2,
The value DATADIR_GET enumerates the formats that can be passed in IDataObject::GetData
. The value DATADIR_SET enumerates those formats that can be passed in IDataObject::SetData
[out]Points to the location where the new enumerator object should be returned.
Enumerator object was successfully returned.
One or more arguments are invalid.
Enumerator object was not returned because the system ran out of memory.
The direction specified by dwDirection
is not supported.
Requests that OLE enumerate the formats from the registry.
This method creates and returns an enumerator object that can be used to
determine all of the ways the data object can describe data in a FORMATETC
structure. The enumerator object implements IEnumFORMATETC
, one of the standard enumerator interfaces. The caller is responsible for
when it is finished with the enumeration.
If a FORMATETC
structure is enumerated by IDataObject::EnumFormatEtc
, there is no guarantee that the format is supported because the formats can
change over time. Accordingly, applications should treat the enumeration as a
hint of the format types that can be passed.
is called when one of the following actions occurs:
- An application calls OleSetClipboard. OLE must determine what data to place on the Clipboard and whether it is
necessary to put OLE 1 compatibility formats on the Clipboard.
- Data is being pasted from the Clipboard or dropped. An application uses the
first acceptable format.
- The Paste Special dialog box is displayed. The target application builds the
list of formats from the FORMATETC entries.
Formats can be registered statically in the registration database or
dynamically during object initialization. If an object has an unchanging list of formats
and these formats are registered in the registration database, it can ask OLE
to perform the enumeration using the registration database by calling the
helper function OleRegEnumFormatEtc
or by returning OLE_S_USEREG.
OLE_S_USEREG instructs the default object handler to call OleRegEnumFormatEtc
. Object applications that are implemented as DLL object applications cannot
return OLE_S_USEREG. They must call OleRegEnumFormatEtc
Private formats can be enumerated for OLE 1 objects, if they are registered
with the RequestDataFormats or SetDataFormats keys in the registration database.
Also, private formats can be enumerated for OLE 2 objects, if they are
registered with the GetDataFormats or SetDataFormats keys.
For OLE 1 objects whose servers do not have RequestDataFormats or
SetDataFormats information registered in the registration database, a call to EnumFormatEtc
with DATADIR_GET only enumerates the Native and Metafile formats, regardless
of whether they support these formats or others. Calling EnumFormatEtc
with DATADIR_SET on such objects only enumerates Native, regardless of
whether the object supports being set with other formats.
structure returned by the enumeration usually indicates a NULL target device (ptd
). This is appropriate because, unlike the other members of FORMATETC
, the target device does not participate in the object's decision as to
whether it can accept or provide the data in either a SetData
member of FORMATETC
often indicates that more than one kind of storage medium is acceptable. You
should always mask and test for it by using a Boolean OR operator.
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