Answered Move and Disappear

[Zephlon]

I created a custom control called "DragPoint". It's a general-purpose moving/resizing tool. But whenever I move it, it disappears after I let go.

Imports System.Windows.Forms
Imports System.Drawing

Public Class DragPoint : Inherits Control
    Dim mouseOffset As Point
    Private DPS As DrawShape
    Private BGC As Color = Color.DodgerBlue
    Private BRC As Color = Color.Black
    Private BRW As Integer = 1

    Enum DrawShape
        Ellipse
        Rectangle
    End Enum

    Property Shape() As DrawShape
        Get
            Shape = DPS
        End Get
        Set(ByVal value As DrawShape)
            DPS = value
            Me.Refresh()
        End Set
    End Property

    Property BackgroundColor() As Color
        Get
            BackgroundColor = BGC
        End Get
        Set(ByVal value As Color)
            BGC = value
            Me.Refresh()
        End Set
    End Property

    Property BorderColor() As Color
        Get
            BorderColor = BRC
        End Get
        Set(ByVal value As Color)
            BRC = value
            Me.Refresh()
        End Set
    End Property

    Property BorderWidth() As Integer
        Get
            BorderWidth = BRW
        End Get
        Set(ByVal value As Integer)
            BRW = value
            Me.Refresh()
        End Set
    End Property

    Private Sub DragPoint_CursorChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.CursorChanged
        If Cursor = Cursors.Default Then
            Cursor = Cursors.SizeAll
        End If
    End Sub

    Private Sub DragPoint_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        If Cursor = Cursors.Default Then
            Cursor = Cursors.SizeAll
        End If

        Dim graphics As Graphics = e.Graphics
        Dim penWidth As Integer = BRW
        Dim pen As Pen = New Pen(BRC, BRW)

        If DPS = DrawShape.Ellipse Then
            Dim brush As SolidBrush = New SolidBrush(BackgroundColor)
            graphics.FillEllipse(brush, 0, 0, Width, Height)

            graphics.DrawEllipse(pen, CInt(penWidth / 2), _
              CInt(penWidth / 2), Width - penWidth, Height - penWidth)
        ElseIf DPS = DrawShape.Rectangle Then
            Dim brush As SolidBrush = New SolidBrush(BackgroundColor)
            graphics.FillRectangle(brush, 0, 0, Width, Height)

            graphics.DrawRectangle(pen, CInt(penWidth / 2), _
              CInt(penWidth / 2), Width - penWidth, Height - penWidth)
        End If



        'Dim textBrush As SolidBrush = New SolidBrush(Color.Black)
        'Dim fontHeight As Integer = 10
        'Dim font As Font = New Font("Arial", fontHeight)
        'graphics.DrawString(Text, font, textBrush, penWidth, _
        '  Height / 2 - fontHeight)

    End Sub

    Private Sub DragPoint_SizeChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.SizeChanged
        If Me.Width > Me.Height Then
            Me.Height = Me.Width
        ElseIf Me.Height > Me.Width Then
            Me.Width = Me.Height
        End If
    End Sub

    Private Sub DragPoint_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
        mouseOffset = New Point(-e.X, -e.Y)
    End Sub

    Private Sub DragPoint_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
        If e.Button = Windows.Forms.MouseButtons.Left Then
            Dim mousePos As Point = Control.MousePosition
            mousePos.Offset(mouseOffset.X, mouseOffset.Y)
            Location = mousePos
        End If
    End Sub

    Private Sub InitializeComponent()
        Me.SuspendLayout()
        Me.ResumeLayout(False)
    End Sub
End Class

 

[InertiaM]

Investigate the "Invalidate" command.

If the control then suffers from flickering when you move it, investigate SetStyle and OptimizedDoubleBuffer.

 

[Zephlon]

Ok. I did that, and found a better way to let it move. Problem solved.