Graphics Hidden Under A Panel

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VB

VB10

OK, new question as a follow up problem from my previous question about Bit Map Images Under A Panel
The advice to change to m_Graphics = Graphics.FromImage(m_Bitmap) and to use the Paint event seems to work. I have 20 small panels over the picture box to hide the randomly generated graphics. But the graphics will only draw on the picCanvas picture box if the overlaying panels are there. No panels, no graphics show up. And if you put one small panel anywhere on the picCanvas, the graphics only draw under the panel. when I debug the program with a breakpoint and check m_Bitmap.Width and m_Bitmap.Heght they are equal to the size of the picCanvas picture box. Now, I can make this work for my needs but I don't understand it???

Any thoughts???

Here is the revised code:

Public Class Form1
    Dim PenColor As New Pen(Color.Red, 2)
    Dim X As Long
    Dim Y As Long
    Dim W As Long
    Dim H As Long
    Dim NewFlag As Boolean
    ' The Bitmap and Graphics objects we will draw on.
    Private m_Bitmap As Bitmap
    Private m_Graphics As Graphics
    ' Make the initial blank image.
    Private Sub Form1_Load() Handles MyBase.Load
        NewFlag = True
        Call MakeNewBitmap()
    End Sub

    ' Make a new blank image.
    Private Sub mnuFileClear_Click() Handles mnuFileClear.Click
        Call MakeNewBitmap()
        Panel1.Visible = True
        'There are actually 20 Panels but I removed the code to make it more compact for the question
      
    End Sub

    ' Make a new Bitmap to fit the canvas.
    Private Sub MakeNewBitmap()
        ' Get the drawing surface's size.
        Dim wid As Integer = picCanvas.ClientSize.Width
        Dim hgt As Integer = picCanvas.ClientSize.Height

        ' Make a Bitmap and Graphics to fit.
        m_Bitmap = New Bitmap(wid, hgt)
        m_Graphics = Graphics.FromImage(m_Bitmap)

        ' Clear the drawing area.
        m_Graphics.Clear(Me.BackColor)

        ' Display the result.
        picCanvas.Image = m_Bitmap
    End Sub

    Private Sub MakeGraphics_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MakeGraphics.Click
        NewFlag = True
         Make some random elipses on screen when button is clicked
        m_Graphics = Graphics.FromImage(m_Bitmap)


        For Temp = 1 To 25
            Randomize()
            X = 5 + (Rnd() * (m_Bitmap.Width - 30))
            Y = 5 + (Rnd() * (m_Bitmap.Height - 30))
            'Minimum length,width = 20, max = 220
            H = 2 + (Rnd() * 20)
            W = 2 + (Rnd() * 20)
            m_Graphics.DrawEllipse(PenColor, X, Y, W, H)
        Next
        
    End Sub

    Private Sub picCanvas_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles picCanvas.Paint
        m_Graphics = Graphics.FromImage(m_Bitmap)


        
    End Sub
    Private Sub HidePanel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles HidePanel.Click
        Dim R As Integer
        Randomize()
        R = 1 + Rnd() * 20
        Label1.Text = R

        If R = 1 Then Panel1.Visible = False
       'There are actually 20 Panels but I removed the code to make it more compact for the question
      
    End Sub

    
End Class