[2005] Mousemove vs. DoubleClick - who will win?

[dolot]

It appears that mousemove wins, at least when I implement the following code:

Private Sub EitherListview_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles lstFrom.MouseMove, lstTo.MouseMove

        Dim itmClick As Windows.Forms.ListViewItem

        'make sure the left mouse button is clicked
        'and that we have a listview to work with
        If e.Button = Windows.Forms.MouseButtons.Left Then
            If TypeOf sender Is Windows.Forms.ListView Then
                With CType(sender, Windows.Forms.ListView)

                    'get the node here
                    itmClick = .GetItemAt(e.X, e.Y)
                    If Not itmClick Is Nothing Then

                        'allow a drag drop of this node
                        .DoDragDrop(itmClick, DragDropEffects.All)

                    End If

                End With
            End If
        End If

    End Sub

When this code is in effect, the double click event for the handled listview never gets raised. Does anybody know why?

[stimbo]

where have you handled the Double Click event??

[FourBlades]

It's possible, depending on what you are thinking, that the problem lies in the following line of code. What do you think this line of code is doing for you?

If Not itmClick Is Nothing Then

Edit: Never mind. I did not read your post carefully enough.

[FourBlades]

Ok, well I get it.
What's happening is that when the mouse enters the control the control begins to emit numerous mousemove events prior to any double click event being raised. So yes, the mousemove will always fire first.

[dolot]

If you take out the code in the mousemove event, then the control will raise a double click event. So it isn't the handling of the mousemove event per se that cancels out the double click event, but something that I'm doing within the event that causes the double click event not to raise.

It isn't a big deal, really. I either have drag and drop or I have double click ability. I'll probably just stick with drag and drop. Still, it seems to me there has to be a way around it, and it sounds like a good question for the brilliant minds on this forum.

[FourBlades]

You can't stop an event from being "raised".
If the control exists you can be sure that the event is being raised and also that it is not being "blocked".

It is entirely possible though that:
1) your own code is not properly registered to listen to the event
2) the code you have within an event handler is not written to correctly do what you think it is supposed to do; and therefore you get the impression that the event is not raised.

The object that raises the event will continue to function internally just as it was written to do. When the conditions occur that trigger that object's event the event will fire. That's certain.

[dolot]

If you put a breakpoint at the beginning of the code for the double click event, and comment out the code in the mousemove event, the breakpoint in the double click event will be hit and the code will stop. If you uncomment the code in the mousemove event, the breakpoint in the double click event will not be hit.

Try it yourself. Put my code into the mousemove event of a listview and then handle the double click event for the listview with something simple like a msgbox("hello"). You'll see.

My guess is that something in the mousemove code is modifying conditions so that the double click event never fires.

[dbasnett]

I am a lot confused. In the mousemove event, which occurs anytime the cursor moves over the control, you check to see if the left button was clicked? BTW - If you hold the left button down and move the mouse the event fires numerous times.

The control for the code appears to be a listview, but you check it anyway, and then you do whatever it is you are trying to do.

Can you doubleclick the mouse and move the mouse at the same time? Think about it? The code I see is in the mousemove event.

So, what are you trying to do? Drag and drop?

[dolot]

The code I use in the mousemove event was actually supplied to me by another developer, who had used it to handle mousemoves from multiple different types of controls. You're right - I could probably remove that 'typeof sender' check.

The code - along with the corresponding dragover and dragdrop event code - works fine in implementing drag and drop. It's just that something in the drag code is causing the listview to not raise the double click event.

It occurs to me that I probably should post the other two events' code as well. So here is the full thing:

Private Sub EitherListview_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles lstFrom.MouseMove, lstTo.MouseMove

        Dim itmClick As Windows.Forms.ListViewItem

        'make sure the left mouse button is clicked
        'and that we have a listview to work with
        If e.Button = Windows.Forms.MouseButtons.Left Then
            If TypeOf sender Is Windows.Forms.ListView Then
                With CType(sender, Windows.Forms.ListView)

                    'get the node here
                    itmClick = .GetItemAt(e.X, e.Y)
                    If Not itmClick Is Nothing Then

                        'allow a drag drop of this node
                        .DoDragDrop(itmClick, DragDropEffects.All)

                    End If

                End With
            End If
        End If

    End Sub

    ''' <summary>
    ''' Responding to DragOver Events
    ''' </summary>
    Private Sub EitherListview_DragOver(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles lstFrom.DragOver, lstTo.DragOver

        'allow the dragover if it is from a listview on this form
        If e.Data.GetDataPresent(GetType(Windows.Forms.ListViewItem)) Then

            'get the item
            'and make sure it's from this form
            With CType(e.Data.GetData(GetType(Windows.Forms.ListViewItem)), Windows.Forms.ListViewItem)
                If .ListView.FindForm Is Me.FindForm Then

                    'supported dragdrop
                    e.Effect = DragDropEffects.All

                    'also highlight the nearest node
                    'to show a context to the dragdrop event
                    If TypeOf sender Is Windows.Forms.ListView Then
                        With CType(sender, Windows.Forms.ListView)

                            Dim itmContext As Windows.Forms.ListViewItem
                            Dim pClient As Drawing.Point

                            pClient = .PointToClient(New Drawing.Point(e.X, e.Y))
                            itmContext = .GetItemAt(pClient.X, pClient.Y)

                            .SelectedItems.Clear()
                            If Not itmContext Is Nothing Then itmContext.Selected = True

                        End With
                    End If

                Else

                    'not supported
                    e.Effect = DragDropEffects.None

                End If
            End With

        Else

            'not supported
            e.Effect = DragDropEffects.None

        End If

    End Sub

    ''' <summary>
    ''' Responding to DragDrop Events
    ''' </summary>
    ''' <param name="sender"></param>
    ''' <param name="e"></param>
    ''' <remarks></remarks>
    Private Sub EitherListview_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles lstFrom.DragDrop, lstTo.DragDrop

        Dim lvwTarget As Windows.Forms.ListView
        Dim itmDrop As Windows.Forms.ListViewItem
        Dim itmContext As Windows.Forms.ListViewItem
        Dim pClient As Drawing.Point


        'make sure the dropped data is a listview item
        'and that we have a proper drop target
        If e.Data.GetDataPresent(GetType(Windows.Forms.ListViewItem)) Then
            If TypeOf sender Is Windows.Forms.ListView Then

                'get the target listview
                lvwTarget = sender

                'get the dragged listviewitem
                'and make sure it's from this form
                itmDrop = e.Data.GetData(GetType(Windows.Forms.ListViewItem))
                If itmDrop.ListView.FindForm Is Me.FindForm Then

                    'get the context item from the drop target, if any
                    pClient = lvwTarget.PointToClient(New Drawing.Point(e.X, e.Y))
                    itmContext = lvwTarget.GetItemAt(pClient.X, pClient.Y)

                    'see if we are dragging it onto the same listview, or another
                    If itmDrop.ListView Is sender Then

                        If itmContext Is itmDrop Then
                            'nothing to do; dropped onto self
                        ElseIf itmContext Is Nothing Then
                            'move to the end
                            itmDrop.ListView.Items.Remove(itmDrop)
                            lvwTarget.Items.Add(itmDrop)
                        Else
                            'move before selection
                            itmDrop.ListView.Items.Remove(itmDrop)
                            lvwTarget.Items.Insert(itmContext.Index, itmDrop)
                        End If

                    Else

                        'moving from one listview to another
                        itmDrop.ListView.Items.Remove(itmDrop)
                        If itmContext Is Nothing Then
                            lvwTarget.Items.Add(itmDrop)
                        Else
                            lvwTarget.Items.Insert(itmContext.Index, itmDrop)
                        End If

                    End If

                End If

            End If
        End If

    End Sub

[dbasnett]

Let me try again. Why do you expect a double-click when the mouse is moving? Can you physically do it, move the mouse and doubleclick at the same time, and if you can, is that what this code does?

And what, just a brief description, is the mousemove code supposed to do?

[dolot]

I wanted the user to be able to move the selected listview item from one listview to another, and I wanted to allow a couple of different ways of doing it. One was to drag an item from one listview to another. The other was by double clicking an item in a listview. I can get either of the move ways working, but not both at the same time. If the drag and drop code is in place, then I can double click on an item all day long and the double click event simply won't raise. If the drag and drop code is removed, the double click event raises and I can move items just fine.

Here's the double click code, just in case you are interested.

Private Sub lstFrom_DoubleClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles lstFrom.DoubleClick
        ListViewTransfer(Me.lstFrom, Me.lstTo)
    End Sub

    Private Sub ListViewTransfer(ByRef FromListView As ListView, ByRef ToListView As ListView)
        For Each item As Windows.Forms.ListViewItem In FromListView.SelectedItems
            FromListView.Items.Remove(item)
            ToListView.Items.Add(item)
        Next
    End Sub

Edit: Sorry, I should have explained this better up front rather than just jumping into the middle of the problem.

[Shaggy Hiker]

My guess is that you are interferring with the interpretation of the double click event. Basically, the time taken in working the mouse move event is making the two clicks of the double click appear too far apart. Not sure if that is even possible.

Have you tried handling the click event, rather than the double click? I would try putting a listbox on the form and in the click event have a single line: Listbox1.Items.Add("Clicked Once") then run it and see what happens when you click once, and when you double click. If you just get two clicked once events, then you know what happened to your double click event.

[dbasnett]

I created a listview and verified the double click(mouse-down,mouse-up,mouse-down, mouse-up) fires. it does.

I also checked the mousemove event, and it appears normal also.

I then tried mouse-down,mouse-up,mouse-down.
Mousemove fired numerous times and when I finally did mouse-up the double click fired.

add this to mousemove event handler

dim recur as boolean = false

Public MouseMove sub
if recur then exit sub else recur = true
.
.
.
.
.
recur = false
exit sub

[dolot]

You are almost right SH. I got just one 'clicked once', whether I clicked or double clicked, but if I took out the code in the mousemove event, I would get a 'clicked once' and a 'double click', as added by the listview's double click event. But with the mousemove code in there I never got 'double click'

[dbasnett]

well shucks. I said "I then tried mouse-down,mouse-up,mouse-down.
Mousemove fired numerous times and when I finally did mouse-up the double click fired." This is only true if the mouse moves. If I

mouse-down,mouse-up,mouse-down
then wait without moving
then mouse-up the doubleclick does not fire

BUT

double click = mouse-down,mouse-up,mouse-down, mouse-up

the first part of the double-click is a MouseMove with LeftButton

[dbasnett]

Check this out

    Private Sub ListView1_DoubleClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles ListView1.DoubleClick
        Debug.WriteLine("D " & Date.Now.ToLongTimeString)
    End Sub
    Private Sub ListView1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ListView1.MouseMove
        Debug.WriteLine("MM " & Date.Now.ToLongTimeString)
        If e.Button = Windows.Forms.MouseButtons.Left Then
            Debug.WriteLine("L")
            For x = 0 To 500
                Thread.Sleep(10)
            Next
        End If
    End Sub

debug output
MM 2:12:54 PM
L
MM 2:12:59 PM
L
D 2:13:04 PM

It appears that mousemove with left button down fires twice, which makes sense.

[dolot]

I can duplicate your results DB, as long as I don't have

.DoDragDrop(itmClick, DragDropEffects.All)

in my mousemove event. If that's in place, then I can't get a double click.

[Shaggy Hiker]

You are almost right SH. I got just one 'clicked once', whether I clicked or double clicked, but if I took out the code in the mousemove event, I would get a 'clicked once' and a 'double click', as added by the listview's double click event. But with the mousemove code in there I never got 'double click'

Nope, I'd say from that that I was completely wrong. Interesting, though. Next thing to try is stripping out line after line to figure out which line causes the issue.

[dbasnett]

Aren't we in the wrong event, MouseMove?

[dolot]

Next thing to try is stripping out line after line to figure out which line causes the issue.

I tried that and it seems to be the following line in the mousemove event

.DoDragDrop(itmClick, DragDropEffects.All)

When it's present, the double click event won't raise. If it's commented out, then the double click event raises

[dbasnett]

How about something like this

    Dim itmClick As Windows.Forms.ListViewItem
    Dim stpW As New Stopwatch
    Const thresh As Integer = 200 'hmmm, what is good value
    Private Sub mDoubleClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles ListView1.DoubleClick
        Debug.WriteLine("D " & Date.Now.ToLongTimeString)
    End Sub
    Private Sub mMouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ListView1.MouseDown
        stpW.Reset() : stpW.Start()
    End Sub
    Private Sub mMouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ListView1.MouseUp
        Debug.WriteLine("MM " & Date.Now.ToLongTimeString & " " & stpW.ElapsedMilliseconds)
        If stpW.ElapsedMilliseconds < thresh Then Exit Sub
        With CType(sender, Windows.Forms.ListView)
            'get the node here
            itmClick = .GetItemAt(e.X, e.Y)
            If Not itmClick Is Nothing Then
                'allow a drag drop of this node
                .DoDragDrop(itmClick, DragDropEffects.Move)
            End If
        End With
    End Sub