OLE Drag Drop related queries

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Hi,

There is a code which uses OLE drag-drop for drag from application to windows explorer. It uses delayed rendering and uses CFSTR_FILEDESCRIPTOR and CFSTR_FILECONTENTS formats. It is pretty much doing the normal stuffs:

i) It creates a Global Memory on LbuttonDown and stores the file/s selected.

ii) It is storing both the formats to be called for rendering.

iii) On calling RenderData, it is calling the over-ridden functions for GetData depending on the format specified.

The problem I am facing are two fold :

i) GetData for CFSTR_FILECONTENTS is not getting called always. the behavior is inconsistent. Anything I am missing that is causing this inconsistency ? Has it got to do by any chance with some kind of marshaling/unmarshaling.

ii) When GetData for CFSTR_FILECONTENTS is called, it gives me back an error "invalid memory location" and then bails out. The progress appears though with the proper file-name until I click ok.
When it is not called, progress bar appears but nothing happens [even file-name of the file to be transferred does not appear]. I will have to restart the explorer to get rid of it.

Has some one encountered any of the above problems or have suggestions for me to try out ?

Also, I have a question. How does the explorer get to know the file-name it is transferring ? I am not able to figure out where in the code file-name is being sent.

The code is too huge to post even the relevant stuffs. Please let me know if any particular is needed. Please Help. I am badly stuck.

Thanks,
Shishir

Posted 31-Aug-10 9:13am

GoonerGator

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GoonerGator · Answer 1 · 2010-09-01T12:03:00

Just found out what was wrong. Or atleast I think.

I dunno what to say.. I mean, I still can't get myself to accept that it was the reason. It may not be; but atleast it seemed to solve the problem for me.

Apparently, I was writing the file-name explicitly of the LPSTGMEDIUM structure in the over-ridden OnRenderData method of COleDataSource; which was btw empty if I remember properly. Like I said, it sounds plain stupid and should not be the reason.. But for what its worth, if someone encounters the same problem, they might want to try it out.