drag and drop issue...

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Lloyd Dupont - 24 Nov 2006 03:44 GMT

If I use software like OpenOffice and try to drag text I could notice that
1. when I drag inside the document I'm moving the text
2. when I drag outside the document I'm copying the text

Yet it all looks like one smooth operation. With correct cursor feedback
(the little + marker next to the icon).
My problem is, once I call DoDragDrop() it's blocking, I have no other
opportunities to change the AllowedEffect to only Copy if I drag over, say,
an other control

And QueryContinueDrag:
1. don't allow me to change the efect
2. don't inform me about the current drop target

How could I do that?
(i.e. how could I modify the allowed efffect depending on the target (i.e.
wether it's me or not))

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Ciaran O''Donnell - 24 Nov 2006 09:42 GMT

The DragDropEffects enum is a Flags enum so when DoDrapDrop'ing at the
source, if the data can be moved or copied then you set the effect to
DragDropEffects.Copy | DragDropEffects.Move
The when the destination handles drag enter, that can decide whether it
should be copied or moved to it.
I generally like to make a struct or class to hold more information that the
dragdrop'd data like the source object and anythign else used in the
descision. Then if dragging to another part of my app then i can handle it
easily.

HTH

Ciaran O'Donnell

> If I use software like OpenOffice and try to drag text I could notice that
> 1. when I drag inside the document I'm moving the text
[quoted text clipped - 13 lines]
> (i.e. how could I modify the allowed efffect depending on the target (i.e.
> wether it's me or not))

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Lloyd Dupont - 24 Nov 2006 13:31 GMT

No, it didn't H!

Perhaps I was not clear enough?
I'm trying to do something which looks impossible with the public .NET API,
yet Word and OpenOffice manage it.

In pseudo code it will look like that:

if(target == this)
AllowedEffect = Copy | Move;
else
AllowedEffect = Copy;

Of course the source should update the AllowedEffect every time the target
change. Which is not possible with the API, yet Word manage to do it.
So I wonder how it does it...

> The DragDropEffects enum is a Flags enum so when DoDrapDrop'ing at the
> source, if the data can be moved or copied then you set the effect to
[quoted text clipped - 31 lines]
>> (i.e.
>> wether it's me or not))

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Jeff Gaines - 24 Nov 2006 15:18 GMT

On 24/11/2006 in message <##xYcz8DHHA.3520@TK2MSFTNGP04.phx.gbl> Lloyd
Dupont wrote:

>No, it didn't H!
>
>Perhaps I was not clear enough?
>I'm trying to do something which looks impossible with the public .NET
>API, yet Word and OpenOffice manage it.

I do that with a TreeView as follows:

private void tvFav_DragOver(object sender, DragEventArgs e)
{
    //    Control key moves
    if (e.Data.GetDataPresent(typeof(JExLVItem)))
    {
        if ((e.KeyState & 8) == 8)
            e.Effect = DragDropEffects.Move;
        else
            e.Effect = DragDropEffects.Copy;
    }
    else
        e.Effect = DragDropEffects.None;
}

Can you trap DragOver in whatever control you are dropping on? You could
then test for the type of data.

Signature

Jeff Gaines

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Dave Sexton - 26 Nov 2006 05:53 GMT

Hi Lloyd,

The key is that your drop targets must be aware of the source, not the other
way around.

You may want to read the following article:

"Performing Drag and Drop Operations"
http://msdn2.microsoft.com/en-gb/library/ms973845.aspx

(The article uses VB.NET; sorry :)

Signature

Dave Sexton

> No, it didn't H!
>
[quoted text clipped - 49 lines]
>>> (i.e.
>>> wether it's me or not))

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drag and drop issue...

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