What a drag: Dragging a virtual file (IStorage edition)

re: What a drag: Dragging a virtual file (IStorage edition)

Anthony Wieser — Wed, 26 Mar 2008 17:44:03 GMT

I see from msdn online this works on XP and later systems. oops.

re: What a drag: Dragging a virtual file (IStorage edition)

Anthony Wieser — Wed, 26 Mar 2008 17:42:21 GMT

Now all I need to do is figure out how to implement the other end of the drop target so that I can register file associations.

MSDN says this:

On Microsoft Windows XP systems, enhanced support is added for applications that implement drag-and-drop features and expose their IDropTarget interface. With this method, the Shell communicates with the application through the Component Object Model (COM) subsystem. This method offers a significant performance gain over both the command line method and DDE. To use this method, add a DropTarget subkey under a verb's key. Under the DropTarget, add a registry string named Clsid, and set the value of this string to a valid CLSID Key.

MSDN online also adds this helpful advice:

Implementations of IDropTarget::Drop need to return quickly to the caller avoid causing an unresponsive state. There are two ways to accomplish this:

Marshall the input IDropTarget to a new thread.

Take a reference to the data object, set a short timer, and process the drop against that timer. If you use this method, you must ensure that you do not begin processing a second drop while the first is still being processed.

http://msdn2.microsoft.com/en-us/library/bb776883.aspx

What it doesn't say is: Does this work on Vista?

I assume all I need to do is expose on object on my exe with the specified CLSID that supports an IDropTarget interface.

re: What a drag: Dragging a virtual file (IStorage edition)

Matt Green — Sat, 22 Mar 2008 01:31:29 GMT

If you want to integrate with Windows, you will probably have to learn it. If you're not aiming to do that, then learn the concepts behind it and why it developed the way it did.

I know the basics and how to use it in a pinch, but I probably couldn't write a COM component easily, and I consider myself a fairly competent Windows developer. Maybe I'm not if I try to avoid COM... ;)

re: What a drag: Dragging a virtual file (IStorage edition)

Rivari — Fri, 21 Mar 2008 06:14:25 GMT

@Anon

I am a computer science student and I wonder if it still a good idea to learn COM!

What do you think?

re: What a drag: Dragging a virtual file (IStorage edition)

Anon — Fri, 21 Mar 2008 05:49:34 GMT

@gb

You can't fool me. I've seen lots of movies where esoteric computer knowledge saves the world. When the aliens attack, a knowledge of COM and OLE may save the world. It's certainly more likely than them using Macs like the aliens in Independence Day. Watch the skys but make sure you read Dale Rogerson!

More to the point, I could hack up an explorer style application with a treeview/splitter/listview/menu bar that lets me drag and drop files from my PTP device. Or anything else for that matter.

re: What a drag: Dragging a virtual file (IStorage edition)

Chris Charabaruk — Fri, 21 Mar 2008 02:01:52 GMT

@gb When you need it, you'll be able to use it.

re: What a drag: Dragging a virtual file (IStorage edition)

gb — Fri, 21 Mar 2008 01:46:19 GMT

god dammit it's so boring, what's the purpose raymond?

re: What a drag: Dragging a virtual file (IStorage edition)

Dan — Fri, 21 Mar 2008 00:20:51 GMT

Steve: Are you nitpicking? I don't think those are virtual files (or real files; doesn't outlook use one large file for all your e-mail?)

re: What a drag: Dragging a virtual file (IStorage edition)

JamesNT — Thu, 20 Mar 2008 18:34:27 GMT

Mr. Chen,

Thank you for this series. It has been one of the most fun so far.

JamesNT

re: What a drag: Dragging a virtual file (IStorage edition)

Steve Thresher — Thu, 20 Mar 2008 17:14:48 GMT

I may be missing the obvious but doesn't outlook use structured storage when dragging messages around.