An automation server cannot pass a pointer to the picture object's IPictureDisp implementation across process boundaries (150034)
The information in this article applies to:
- The Microsoft Foundation Classes (MFC), when used with:
- 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 Professional Edition 4.2
- Microsoft Visual C++, 32-bit Enterprise Edition 5.0
- Microsoft Visual C++, 32-bit Professional Edition 5.0
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0
- Microsoft OLE Control Developer's Kit (CDK)
This article was previously published under Q150034 SYMPTOMS An automation server that implements a Picture object
wrapped by the CPictureHolder class in MFC fails when it attempts to pass a
pointer to the picture object's IPictureDisp implementation across process
boundaries. CAUSE IPictureDisp gains access to methods of the Picture object
that cannot be marshaled across process boundaries. For example, IPictureDisp
supports DISPID_PICT_RENDER to gain access to the Render method of the Picture
object. The Render method takes a handle to a device context as the first
parameter. Device context handles cannot be marshaled.
Dispatch
interfaces can normally be marshalled by using the IDispatch marshaling code,
but the Picture object implements IMarshal specifically to cause its marshaling
to fail. STATUS This behavior is by design. MORE INFORMATION The ClassWizard in Visual C++ allows you to select a return
type of LPPICTUREDISP for a method. This method might return the IPictureDisp
interface obtained by calling CPictureHolder::GetPictureDispatch. However, if
this method is called by a controller running in another process, the method
fails and returns an error code of E_FAIL.
Because the Picture object
causes the marshaling of IPictureDisp to fail, problems can also occur when
trying to obtain an IPictureDisp interface across thread boundaries in a
multiple-thread apartment model object. REFERENCES For more information on marshaling, please see "Inside
OLE," second edition, by Kraig Brockschmidt, Chapter 6, "Local/Remote
Transparency," published by Microsoft Press.
| Modification Type: | Major | Last Reviewed: | 6/4/2005 |
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| Keywords: | kbtshoot kbAutomation kbBitmap kbCtrl kbprb KB150034 kbAudDeveloper |
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