Microsoft KB Archive/109545

= BUG: Retaining Clipboard IDataObject Causes Unexpected Result =

Article ID: 109545

Article Last Modified on 12/3/2003

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APPLIES TO

 Microsoft OLE 2.01 Microsoft OLE 4.0, when used with:  Microsoft Windows NT 4.0

 Microsoft Windows NT 3.51 Service Pack 5

 Microsoft Windows 95 </li></ul>

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This article was previously published under Q109545

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SYMPTOMS
An application holding on to a clipboard IDataObject pointer, and making repeated calls to IDataObject::EnumFormatEtc through that pointer, may find that the set of formats returned by EnumFormatEtc changes between calls.

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RESOLUTION
As noted in the Object Linking and Embedding SDK version 2.01 documentation, an application that calls OleGetClipboard to retrieve an IDataObject interface pointer should hold on to that IDataObject pointer only for a very short time.

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STATUS
Microsoft has confirmed this to be a problem in the products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

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Steps to Reproduce

 * 1) Copy an object from an OLE 1.0 server to the clipboard.
 * 2) Call OleGetClipboard to obtain an IDataObject pointer to the clipboard object.
 * 3) Call IDataObject::EnumFormatEtc to enumerate the available formats.
 * 4) Without calling IDataObject::Release, copy an object from an OLE 2.0 server to the clipboard.
 * 5) Call IDataObject::EnumFormatEtc again. The formats enumerated have changed to the formats provided by the new OLE 2.0 object.

The OLE2UI library's implementation of the Paste Special dialog box (provided in the Object Linking and Embedding SDK version 2.01) works around this problem. The Paste Special dialog box is launched by calling OleUIPasteSpecial. If the user changes the contents of the clipboard while this dialog is up, the OLE2UI code detects the change and responds by ending the dialog box. When this happens, OleUIPasteSpecial returns OLEUI_PSERR_CLIPBOARDCHANGED.

The dialog box detects changes to the clipboard contents by calling SetClipboardViewer to splice itself into the clipboard viewer chain.

Additional query words: 2.01 3.50 4.00 toolkit

Keywords: kbbug KB109545

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