XOR Drawing

Remember in VB6 when you could set a picturebox's drawmode to XOR, then if you draw a line and then draw it again, the line would dissapear?

How can this be achieved in .Net without having to refresh the entire picturebox area?

I need to be able to drag a line using the mouse and I need rapid responding code without flicker.

How is it done?

Help!

Hi.

You can't do it, using normal GDI+.
But you can use the ControlPaint object.
There's a method to draw a reversible line.

Problem is, that it draws to the screen DC and not a normal graphics object, so you have to clip your mouse to stay within the borders of your picturebox.

Also, if the picturebox is refreshed the line disappears.

I you're talking about a rubberband, then none of this should really be a problem, as long as you clip your mouse.

Hi.

Try this code:

VB Code:

Dim OldLineStart As Point
    Dim OldLineEnd As Point
 
    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        Dim R As Rectangle = PictureBox1.ClientRectangle
        R.Offset(PictureBox1.PointToScreen(PictureBox1.ClientRectangle.Location))
        Cursor.Clip = R
        OldLineStart = PictureBox1.PointToScreen(New Point(e.X, e.Y))
        OldLineEnd = OldLineStart
    End Sub
 
    Private Sub PictureBox1_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        Cursor.Clip = Nothing
        PictureBox1.Invalidate()
    End Sub
 
    Private Sub PictureBox1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        If e.Button = MouseButtons.Left Then
            ControlPaint.DrawReversibleLine(OldLineStart, OldLineEnd, PictureBox1.BackColor)
            OldLineEnd = PictureBox1.PointToScreen(New Point(e.X, e.Y))
            ControlPaint.DrawReversibleLine(OldLineStart, OldLineEnd, PictureBox1.BackColor)
        End If
    End Sub

Ok, I'll just have to do the math myself with setpixel() and so on.