how to undo pictureBox drawline C# windows form using Microsoft Visual Studio

Question

And trying get working small paint application, that draws only lines with mouse event.

Could someone provide me with correct working example how to create undo functionality? I have picturebox1 with Events pictureBox1_MouseDown, pictureBox1_MouseMove, pictureBox1_MouseUp.

When I moving mouse and and clicking on picture box it is drawing lines as expected. But how to create undo functionality for example on undo button click?

     private void pictureBox1_MouseUp(object sender, MouseEventArgs e)
        {

            lx = e.X;
            ly = e.Y;

            Graphics g = pictureBox1.CreateGraphics();
            g.DrawLine(new Pen(new SolidBrush(paintcolor), 3), new Point(x, y), new Point(lx, ly));


            this.Invalidate();

        }




   private void pictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            x = e.X;
            y = e.Y;

        }




  private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
        {

        }

I create additionally

class Shape
{

    public string _font { get; set; }
    public string g { get; set; }
    public int x { get; set; }
    public int y { get; set; }
    public int lx { get; set; }
    public int ly { get; set; }
    public string paintcolor { get; set; }
    public string s { get; set; }


}

then added under public partial class Form1 : Form

private Stack<Shape> _shapes = new Stack<Shape>();

than add to pictureBox1_MouseUp

newShape._font = _font.ToString();
            newShape.g = g.ToString();
            newShape.x = x;
            newShape.y = y;
            newShape.lx = lx;
            newShape.ly = ly;
            newShape.paintcolor = paintcolor.ToString();




                _shapes.Push(newShape);


            this.Invalidate();

and for Undo button btnUndo

  private void btnUndo_Click(object sender, EventArgs e)
        {


            if (_shapes.Count > 0)
            {

                this.pictureBox1.Invalidate();
                _shapes.Pop();


            }
            else
            {
                MessageBox.Show("Nothing to remove.", "No Shapes",
                    MessageBoxButtons.OK, MessageBoxIcon.Warning);
                return;
            }

        }

and put break-point on _shapes.Push(newShape);

that _shapes are filed with values

and when I push button btnUndo

I see that _shapes.Pop(); removing values LIFO, but of course my lines did not disappears. So I'm confused because I have feeling that I need create lines on pictureBox1 not from mouse movements, but from Stack.

Yes, for **pictureBox1_MouseUp** _shapes.Push(newShape); //this.pictureBox1.Invalidate(); //this.pictureBox1.Invalidate(); this.Invalidate(); for **btnUndo_Click** tested if (_shapes.Count > 0) { // pictureBox1.Invalidate(); this.pictureBox1.Invalidate(); _shapes.Pop(); //this.pictureBox1.Invalidate(); } — Yanka, Aug 10 '17 at 10:16
Winforms = winapi, so you have to follow its design. Move all drawing logic into `Paint` event, you already have some collection to hold figures to paint, in `Paint` event you just **repaint** all of them (with clearing background). To add figure: add it to collection, call `Invalidate` (this will execute `Paint` event, so you will see your figure). To delete: remove it from collection, call `Invalidate` (`Paint` will draw less figures - it will looks like it's *undone*). — Sinatr, Aug 10 '17 at 10:17
Hi Sinatr, is behind your idea is something like this? http://www.c-sharpcorner.com/uploadfile/dbeniwal321/adding-a-paint-event-handler-to-a-form-and-controls-in-gdi/ — Yanka, Aug 10 '17 at 10:26
Thank You for advice, problem is solved. I create on pictureBox1 one more event **Appearance -> Paint pictureBox1_Paint** and create and add in to ` private void pictureBox1_Paint(object sender, PaintEventArgs e) { foreach (Shape shp in _shapes) { e.Graphics.DrawLine(new Pen(new SolidBrush(paintcolor), 3), shp.x, shp.y, shp.lx, shp.ly); } }` And then Pop() works as expected. Thanks for advice :) — Yanka, Aug 10 '17 at 13:30

how to undo pictureBox drawline C# windows form using Microsoft Visual Studio

0 Answers0