FIX: DelayRenderFileData() Does Not Call OnRenderFileData() (185675)
The information in this article applies to:
- The Microsoft Foundation Classes (MFC), when used with:
- Microsoft Visual C++, 32-bit Editions 2.0
- Microsoft Visual C++, 32-bit Editions 2.1
- Microsoft Visual C++, 32-bit Editions 2.2
- Microsoft Visual C++, 32-bit Editions 4.0
- Microsoft Visual C++, 32-bit Editions 4.1
- Microsoft Visual C++, 32-bit Enterprise Edition 4.2
- Microsoft Visual C++, 32-bit Enterprise Edition 5.0
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 4.2
- Microsoft Visual C++, 32-bit Professional Edition 5.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0
- Microsoft Visual C++ for Windows, 16-bit edition 1.52
This article was previously published under Q185675 SYMPTOMS
In OLE drag-and-drop, when using COleDataSource::DelayRenderFileData() with
the default second parameter of NULL, COleDataSource::OnRenderFileData()
may not be called to request the actual data.
CAUSE
When you call COleDataSource::DelayRenderFileData() with a clipboard format
such as CF_TEXT (or any other clipboard format) and the second parameter
FORMATETC is not specified (defaulting to NULL), _AfxFillFormatEtc() gets
called. This function creates a FORMATETC structure and populates it with
default values--it fills the "tymed" member of the FORMATETC structure with
-1. Because the "tymed" member is a DWORD, the value is effectively
0xffffffff, and therefore all TYMED enumerations are supported.
However, COleDataSource::OnRenderFileData() or your override for this
function, is called only if the user of this data requests the data with a
TYMED value of TYMED_ISTREAM or TYMED_HGLOBAL.
Because DelayRenderFileData() specified that all the TYMED enumerations are
acceptable, a client may in fact ask for data with a TYMED value other than
TYMED_ISTREAM or TYMED_HGLOBAL. This results in an HRESULT of
DATA_E_FORMATETC being returned from IDataObject::GetData().
RESOLUTION
The workaround is to call COleDataSource::DelayRenderFileData() with the
second parameter explicitly specified. For example:
FORMATETC fmt = {CF_TEXT, NULL, DVASPECT_CONTENT, -1,
TYMED_ISTREAM|TYMED_HGLOBAL};
// Class derived from ColeDataSource.
COleMyDataSource *pDataSrc;
pDataSrc = new COleMyDataSource();
pDataSrc->DelayRenderFileData(CF_TEXT, &fmt);
STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed
at the beginning of this article.
This problem was corrected in Microsoft Visual C++ .NET.
(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by
Jaganathan Thangavelu, Microsoft Corporation
| Modification Type: | Major | Last Reviewed: | 12/10/2003 |
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| Keywords: | kbBug kbfix kbNoUpdate KB185675 |
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