COleDataSource::DoDragDrop
Tim Philip -- philip@cs.usask.ca
Wednesday, February 12, 1997
Environment: MSVC 4.0, NT 4.0
I am implementing drag and drop in an owner-draw CListCtrl subclass. I
am initiating a drag and drop operating using a COleDataSource object,
and calling the DoDragDrop member from my OnLButtonDown member.
I have two problems.
1. The drag and drop operation does not seem to start the same way the
documentation suggests. It says that if the user stays within a
certain bounding rectangle, the drag and drop operation is not
initiated. If there is no bounding rectangle, it waits for a short
period of time. However, this does not seem to be the case. I
have the following code in my OnLButtonDown function. I have tried
several different values for the rectangle, none of them seem to make
any difference.
RECT ItemRect;
GetItemRect(lvHitTest.iItem, &ItemRect, LVIR_BOUNDS); // get items rect
ClientToScreen(&ItemRect); // try screen coordinates
CWnd *pDesktop = GetDesktopWindow();
pDesktop->GetClientRect(&ItemRect); // heck, try the whole screen?
// allocate global string
HGLOBAL hGlobal = GlobalAlloc(0, 20);
LPVOID lpVoid = GlobalLock(hGlobal);
strcpy((LPSTR)lpVoid, "tim rox");
GlobalUnlock(hGlobal);
// initialize OLE data source and begin drag and drop
COleDataSource *pSource = new COleDataSource;
pSource->CacheGlobalData(CF_TEXT, hGlobal);
DROPEFFECT dropEffect = pSource->DoDragDrop(DROPEFFECT_COPY, &ItemRect);
What I find is that if I just click the button and let go (without
moving the mouse) it performs a drag and drop operation. If I move
the mouse within the items rectangle, it still does a drag and drop
operation. In other words, it always does a drag and drop operation.
This doesn't seem to be what the docs say. Can someone tell me what I
am doing wrong? Should I move this into an OnMouseMove and track when
to start a drag/drop operation myself?!
2. When it is in drag/drop mode, I don't get any OnMouseMove messages
so I cannot determine what element of my list control the user is
holding the mouse over. After the drag and drop operation the select
is the same as when it began.
Also, does anyone know how to change the cursor/drag image used? I
really like how internet explorer does it but I am not sure how they
do that.
Any information greatly appreciated!
Thanks!
Tim.
-------
Tim Philip, B.Sc. (Hon) philip@cs.usask.ca
Consultant, Graduate Student http://www.cs.usask.ca/grads/philip
"... magic has a habit of lying low, like a rake in the grass." - T. Pratchet
Oksana Lien -- lien@ares.csd.net
Friday, February 14, 1997
[Mini-digest: 2 responses]
At 04:28 PM 2/12/97 -0600, you wrote:
>
>
>Environment: MSVC 4.0, NT 4.0
>
>
>I am implementing drag and drop in an owner-draw CListCtrl subclass. I
>am initiating a drag and drop operating using a COleDataSource object,
>and calling the DoDragDrop member from my OnLButtonDown member.
Process the OnMouseMove message. When the left mouse button is pressed for
the first time, the MK_LBUTTON flag will be set in nFlags. When it is -
initiate your drag'n'drop. If it isn't set, call the base class method.
Here's the code:
void CYourListCtrl::OnMouseMove(UINT nFlags, CPoint point)
{
if (!(nFlags & MK_LBUTTON))
{
CListCtrl::OnMouseMove(nFlags, point);
return;
}
CRuntimeClass *pItemClass = RUNTIME_CLASS(CYourListItem);
int index;
if ((index = HitTest(point)) > -1)
{
CYourListItem *pItem = (CYourListItem *)GetItemData(index);
if (pRtu->IsKindOf(pItemClass))
{
HGLOBAL hItem = GlobalAlloc(GMEM_FIXED | GMEM_SHARE, sizeof(CYourListItem));
CYourListItem *pOleItem = (CYourListItem*)GlobalLock(hItem);
if (pOleItem)
{
// Do what you need to do - copy the item, etc.
// Cash the data
m_dataSource.CacheGlobalData(CF_TEXT, (void
*)hItem);
// drag & drop
DROPEFFECT dropEffect = m_dataSource.DoDragDrop(
DROPEFFECT_COPY | DROPEFFECT_MOVE );
CListCtrl::OnMouseMove(nFlags, point);
PostMessage(WM_LBUTTONUP, nFlags, MAKELONG(point.x, point.y));
}
}
}
}
I think this should be all you need, assuming the rest of your code -
OleDropTarget declaration, OnDragEnter, OnDragOver and OnDrop - is allright.
>Also, does anyone know how to change the cursor/drag image used? I
>really like how internet explorer does it but I am not sure how they
>do that.
I haven't done that. But have you tryed changing it on in OnDragEnter,
OnDragOver and OnDrop? Let me know if you get it working.
_________________________
Oksana Lien
Dimension Softek, Inc.
lien@ares.csd.net
-----From: "Hill, Les"
Tim,
>2. When it is in drag/drop mode, I don't get any OnMouseMove messages
>so I cannot determine what element of my list control the user is
>holding the mouse over. After the drag and drop operation the select
>is the same as when it began.
>
>Also, does anyone know how to change the cursor/drag image used? I
>really like how internet explorer does it but I am not sure how they
>do that.
These are features of the COleDropTarget (wrapping IDropTarget). Simply
put, it is up to the target to handle these
issues. The mouse move messages are 'replaced' with calls to DragOver()
and the cursor can be manipulated there.
Les
leh@cybercom.net
John and Cecilia -- jandce@iglobal.net
Friday, February 14, 1997
[Mini-digest: 2 responses]
In an app I wrote, I check the message LVN_BEGINDRAG [OnBeginDrag()] to
start a drag and drop operation. I have not set up any bounding rectangles
and it seems to work just fine.
I also use a class derived from COleDropSource. In this class I override
QueryContinueDrag() which is continuously called until the operation is
complete and gives me a code on the last call that I can check to see if
the user has performed a drop. It does not give you the cursor position of
the drop however.
If you need some source, let me know. But by comparing your code to mine,
there is not much difference. Just try using LVN_BEGINDRAG instead. Good
luck.
John Boehme
http://www.iglobal.net/pub/johnandce/
For a really cool Windows 95 ftp client, check out:
http://www.iglobal.net/pub/johnandce/desktopftp.htm
----------
> From: Tim Philip
> To: MFC Mailing List
> Subject: COleDataSource::DoDragDrop
> Date: Wednesday, February 12, 1997 4:28 PM
>
>
>
> Environment: MSVC 4.0, NT 4.0
>
>
> I am implementing drag and drop in an owner-draw CListCtrl subclass. I
> am initiating a drag and drop operating using a COleDataSource object,
> and calling the DoDragDrop member from my OnLButtonDown member.
>
> I have two problems.
>
> 1. The drag and drop operation does not seem to start the same way the
> documentation suggests. It says that if the user stays within a
> certain bounding rectangle, the drag and drop operation is not
> initiated. If there is no bounding rectangle, it waits for a short
> period of time. However, this does not seem to be the case. I
> have the following code in my OnLButtonDown function. I have tried
> several different values for the rectangle, none of them seem to make
> any difference.
>
> RECT ItemRect;
> GetItemRect(lvHitTest.iItem, &ItemRect, LVIR_BOUNDS); // get items rect
> ClientToScreen(&ItemRect); // try screen coordinates
> CWnd *pDesktop = GetDesktopWindow();
> pDesktop->GetClientRect(&ItemRect); // heck, try the whole screen?
>
> // allocate global string
> HGLOBAL hGlobal = GlobalAlloc(0, 20);
> LPVOID lpVoid = GlobalLock(hGlobal);
> strcpy((LPSTR)lpVoid, "tim rox");
> GlobalUnlock(hGlobal);
>
> // initialize OLE data source and begin drag and drop
> COleDataSource *pSource = new COleDataSource;
> pSource->CacheGlobalData(CF_TEXT, hGlobal);
> DROPEFFECT dropEffect = pSource->DoDragDrop(DROPEFFECT_COPY, &ItemRect);
>
> What I find is that if I just click the button and let go (without
> moving the mouse) it performs a drag and drop operation. If I move
> the mouse within the items rectangle, it still does a drag and drop
> operation. In other words, it always does a drag and drop operation.
> This doesn't seem to be what the docs say. Can someone tell me what I
> am doing wrong? Should I move this into an OnMouseMove and track when
> to start a drag/drop operation myself?!
>
> 2. When it is in drag/drop mode, I don't get any OnMouseMove messages
> so I cannot determine what element of my list control the user is
> holding the mouse over. After the drag and drop operation the select
> is the same as when it began.
>
> Also, does anyone know how to change the cursor/drag image used? I
> really like how internet explorer does it but I am not sure how they
> do that.
>
> Any information greatly appreciated!
>
> Thanks!
>
> Tim.
>
> -------
> Tim Philip, B.Sc. (Hon) philip@cs.usask.ca
> Consultant, Graduate Student
http://www.cs.usask.ca/grads/philip
>
> "... magic has a habit of lying low, like a rake in the grass." - T.
Pratchet
-----From: "=?ISO-8859-1?Q?Ignacio_Nicol=E1s_Rodr=EDguez?="
Hi!
Windows 95 list controls send a LVN_BEGINDRAG message when the user is
moving one of the items.
With MFC's reflection, you can override the list's response to the user's
request, right on the subclass.
That should solve both your problems.
Ignacio.
I never said I didn't like Hockey.
----------
> From: Tim Philip
> To: MFC Mailing List
> Subject: COleDataSource::DoDragDrop
> Date: Wednesday, February 12, 1997 7:28 PM
>
> I have two problems.
>
> 1. The drag and drop operation does not seem to start the same way the
> documentation suggests. It says that if the user stays within a
>
> 2. When it is in drag/drop mode, I don't get any OnMouseMove messages
> so I cannot determine what element of my list control the user is
> holding the mouse over. After the drag and drop operation the select
> is the same as when it began.
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