When Controls overlap

[Zmcpherson]

Alright my goal is to test to see if the user has dragged a label over a button. I have add event handlers for MouseMove and ButtonEnter, the trick is that i dont want the buttonEnter sub to fire unless the user is actually dragging a label.

Dim dragging As Boolean = False
 
   Public Sub Label_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs)
        Static lOffset As Point
        lbl = DirectCast(sender, Label)
        If e.Button = MouseButtons.None Then
            lOffset = New Point(e.Location)
            dragging = False
        ElseIf e.Button = MouseButtons.Left Then
            lbl.Location = lbl.Location + e.Location - lOffset
            dragging = True
        End If
    End Sub
 
    Private Sub Button_MouseEnter(sender As System.Object, e As System.EventArgs)
        If dragging = True Then
            MsgBox("This is a Test")
        End If
    End Sub

I thought would work but because the user is dragging the label the mouse never actually enters the button field.

I also tried doing lbl.location = button.location... but unless the label and the buttons are the exactly the same size in exactly the same location then the event wont trigger.

Is there an easy solution to this?

[Shaggy Hiker]

Is this drag and drop dragging, or are you doing your own? Drag and Drop dragging would be if you set AllowDrop to true for both controls. I ask because you get different events in each case.

Take a look at getting a Rectangle for each control (they have a couple). Rectangles have some method such as Intersects that will tell you if one is in the area of the other.

[Inferrd]

I'm sure I came across a more straight forward way of doing this, but I can't remember.....

Anyway, the following should do the job. Test if the rectangle occupied by the Label intersects with the rectangle occupied by the Button.

There are a couple of (minor) changes to your original code.

The first code triggers as soon as the Label overlaps the Button, but the Mouse Cursor may be off the Button.

The second code waits until the Mouse Cursor is also over the Button.

NOTE that (in this version) neither will work if the label and the Button have different parents (i.e. they both have to be on the Form itself or on the same Panel/GroupBox etc.)


EDIT note that I put the Handles Label1.MouseMove clause back in. Don't know if you need it. (and Shaggy's typing is getting quicker)

Dim dragging As Boolean = False
Public Sub Label_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Label1.MouseMove
 
    Static lOffset As Point
    Dim lbl As Label = DirectCast(sender, Label)
    If e.Button = MouseButtons.None Then
        lOffset = e.Location
        dragging = False
    ElseIf e.Button = MouseButtons.Left Then
        dragging = True
        lbl.Location = lbl.Location + New Size(e.Location) - New Size(lOffset)
 
        If dragging AndAlso lbl.Bounds.IntersectsWith(Button1.Bounds) Then
            MsgBox("This is a Test")
        End If
 
    End If
End Sub

Dim dragging As Boolean = False
Public Sub Label_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Label1.MouseMove
 
    Static lOffset As Point
    Dim lbl As Label = DirectCast(sender, Label)
    If e.Button = MouseButtons.None Then
        lOffset = e.Location
        dragging = False
    ElseIf e.Button = MouseButtons.Left Then
        dragging = True
        lbl.Location = lbl.Location + New Size(e.Location) - New Size(lOffset)
 
        If dragging AndAlso lbl.Bounds.IntersectsWith(Button1.Bounds) Then
            If Button1.ClientRectangle.Contains(Button1.PointToClient(MousePosition)) Then
                 MsgBox("This is a Test")
            End If
        End If
 
        End If
End Sub

[Zmcpherson]

You guys are good, I was missing the "bounds.IntersectsWith." I knew you guys would know : )

This is the code that Im using:

For Each but As Button In Me.Controls.OfType(Of Button)()
                If lbl.Bounds.IntersectsWith(but.Bounds) Then
                    MsgBox("This is a Test")
                End If
            Next