[RESOLVED] Tab control - Change cursor while dragging

Hi,

I've implemented Drag & Drop in Tab control and I want cursor to be changed while dragging Tabs. I got that part too, but with one slight problem - normally you change cursor on GiveFeedback event when you allready started drag drop action. Unfortunally I also set start of drag/drop in Mousedown, so when I click to change Tab page my new dragging cursor also appears for a moment, because left mouse click was done. Is there any way that I could start drag/drop with left mouse after I changed Tab page, and then change cursor ?

My code:

Code:

---

  Protected Overrides Sub OnMouseDown(e As MouseEventArgs)
        MyBase.OnMouseDown(e)

    'Current tab is checked in MouseMove, and It's added into Tag
            If Not Me.Tag Is Nothing Then

                Dim clickedTab As TabPage = DirectCast(Me.Tag, TabPage)
                Dim clicked_index As Integer = Me.TabPages.IndexOf(clickedTab)

                ' start drag n drop
                Me.DoDragDrop(clickedTab, DragDropEffects.All)

            End If

    End Sub


    Protected Overrides Sub OnGiveFeedback(gfbevent As GiveFeedbackEventArgs)
        MyBase.OnGiveFeedback(gfbevent)

        ' Set the custom cursor based upon the effect.
        gfbevent.UseDefaultCursors = False

        If ((gfbevent.Effect And DragDropEffects.Move) = DragDropEffects.Move) Then
            Cursor.Current = Cursors.Hand
        Else
            Cursor.Current = Cursors.Default
            End If

    End Sub

---

Generally you shouldn't start a "drag" operation on MouseDown because of problems like this. Every click starts a drag and drop operation, and that can cause weird things to happen.

The more correct way to start a drag and drop operation is to start it after the mouse is down *and* has moved by a certain margin. It turns out "a certain margin" is defined by SystemParameters.MinimumHorizontalDragDistance and SystemParameters.MinimumVerticalDragDistance. So you need to write something like this:

Code:

---

When MouseDown happens:
    * Note the position of the cursor.

When MouseUp happens:
    * If a drag/drop is in progress:
        * Do the thing.
    * Note a drag/drop can't be happening anymore.

When MouseMove happens:
    * If the user is holding the button and a drag/drop isn't already in progress:
        * If the mouse has moved far enough:
            * Note a drag/drop is happening, update the cursor, and save any information you might need.

---

The documentation for DoDragDrop() has a pretty good implementation, though it looks like in theirs they drag things during MouseMove (which is sensible sometimes.)

Thanks Sitten,

very good example, didn't notice this solution at all. I've implemented drag operation in simmilar (but much simpler) way and It works good :)