Drawstring on a panel change when other panel move over

Question

I draw a rectangle panel with every button click. After that add a line on the edge of the rectangle and text on the center. But when I drag a panel move over other panel. The panel string will change. Please advice. I can't upload an image. How can I upload an image like that can show my problem more clearly.

This link http://i3.photobucket.com/albums/y53/ctkhai/1-4.png show the gui of my software. The upper left and lower left are picturebox. User add a "box" when click on button once and the "box" will show on upper left. User can drag the box to lower right and arrange all the box.

now the problem is when user drag the new added "box" and move over some other "box", the text i draw on previous box will change. like this http://i3.photobucket.com/albums/y53/ctkhai/2-4.png.

Update: I try to create a class for the tag. but it won't work, the number change again. It is the way I create class for the tag and read is wrong? code like below

Product _box = new Product();
List<Panel>product = new List<Panel>();

public  class Product
{        
    public  float X { set; get; }     //box coordinate
    public  float Y { set; get; }     //box coordinate
    public  int rotate { set; get; }
    public  int entryP { set; get; }
    public  int boxName { set; get; }

}

private void button_RecAdd_Click(object sender, EventArgs e)
{


   locX = pictureBox_conveyor.Left + (pictureBox_conveyor.Width / 2 - box_y / 2);
   locY = pictureBox_conveyor.Top + (pictureBox_conveyor.Height / 2 - box_x / 2);

   _box.boxName = panelBoxNo;
   _box.entryP = 1;
   _box.rotate = 0;
   _box.X = locX;
   _box.Y = locY;


   Panel box = new Panel();
   box.Location = new Point(locX, locY);
   box.Name = "box" + panelBoxNo;
   box.Tag = _box;  
   box.Size = new Size(box_y, box_x);
   box.BackColor = boxColor;
   pbW = box.Width;
   pbH = box.Height;
   box.MouseDown += panelBox_MouseDown;
   box.MouseMove += panelBox_MouseMove;               


   box.Paint += new PaintEventHandler((s, m) =>
   {

       Graphics g = m.Graphics;
       g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;]

       Product b = box.Tag as Product;

       string text = b.boxName.ToString();

       SizeF textSize = m.Graphics.MeasureString(text, Font);
       PointF locationToDraw = new PointF();
       locationToDraw.X = (pbW / 2) - (textSize.Width / 2);
       locationToDraw.Y = (pbH / 2) - (textSize.Height / 2);

       g.DrawString(text, Font, Brushes.Black, locationToDraw);
       g.DrawRectangle(new Pen(Color.Black), 0, 0, pbW - 1, pbH - 1);
       g.DrawLine(drawLine, 0, 0, 0, pbH);                      

   });

   product.Add(box);
   panel_pelletLayout.Controls.Add(box);
   box.BringToFront();
   label_boxNo.Text = panelBoxNo.ToString();
   panelBoxNo++;

}

private void panelBox_MouseDown(object sender, MouseEventArgs e)
    {
        Panel p = sender as Panel;

        if (e.Button == MouseButtons.Left)
        {
            xPos = e.X;
            yPos = e.Y;

            if (p != null)
            {
                activePnlBox = p.Name;                                     
                textBox_selectedName.Text = p.Name;                    
                textBox_selectedX.Text = p.Left.ToString();
                textBox_selectedY.Text = p.Top.ToString();

            }
        }
    }

private void panelBox_MouseMove(object sender, MouseEventArgs e)
    {
        Panel p = sender as Panel;      

        if (p != null)
        {

            if (e.Button == MouseButtons.Left)
            {

                p.Left = ((e.X + p.Left - (p.Width / 2)) / gripGap) * gripGap;                    
                p.Top = ((e.Y + p.Top - (p.Height / 2)) / gripGap) * gripGap;

                textBox_selectedX.Text = p.Left.ToString();
                textBox_selectedY.Text = p.Top.ToString();

            }        
        }
    }

Answer 1

Your title has got all of us confused.. You don't draw Rectangles, you create new Panels on each ButtonClick, right?

The code for the Paint event is not quite right, though. Just like in any Paint event you should use the built-in Graphics object. And as Hans has noted, you should not destroy/dispose things you didn't create.

The main problem you describe seems to be that your boxes have to paint themselves without referring to their real numbers. You should store their numbers e.g. in their Tags..

(Or you could extract it from their Names, like you do it in the MouseDown!)

box[panelBoxNo].Name = "box" + panelBoxNo;
box[panelBoxNo].Tag =  panelBoxNo;                     // < === !!
//..

box[panelBoxNo].Paint += new PaintEventHandler((s, m) =>
{
   Graphics g = m.Graphics;                            // < === !!
   g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;
   string text = box[panelBoxNo].Tag.ToString();       // < ===
   SizeF textSize = g.MeasureString(text, Font);
   PointF locationToDraw = new PointF();
   locationToDraw.X = (pbW / 2) - (textSize.Width / 2);
   locationToDraw.Y = (pbH / 2) - (textSize.Height / 2);

   g.DrawString(text, Font, Brushes.Black, locationToDraw);
   g.DrawRectangle(new Pen(Color.Black), 0, 0, pbW - 1, pbH - 1);
   g.DrawLine(drawLine, 0, 0, 0, pbH);
   //  g.Dispose();                       // < === !!

  //  m.Graphics.DrawImageUnscaled(drawBox, new Point(0, 0));         // < === !!
  // m.Dispose();                       // < === !!
});

And, as I have noted you should only use arrays if you (or the code) really knows the number of elements. In your case a List<Panel> will be flexible to hold any number of elements without changing any other part of the code, except the adding. You can access the List just like an Array. (Which it is behind the scenes..)

Update: The way I see it now, your problems all are about scope in one way or another.

Scope in its most direct meaning is the part of your code where a variable is known and accessible. In a slightly broader meaning it is also about the time when it has the value your need.

Your original problem was of the latter kind: You accessed the partNo in thr Paint event of the Panels, when it had long changed to a new, probably higher value.

Your current problem is to understand the scope of the variables in the ButtonClick event.

Usually this is no problem; looking at the pairs of braces, the scope is obvious. But: Here we have a dynamically created Lambda event and this is completely out of the scope of the Click event!! Behind the scenes this Paint event is removed from the Click code, placed in a new event and replaced by a line that simply adds a delegate to the Paint handler just like any regular event.

So: nothing you declare in the ButtonClick is known in the Paint code!

To access these data you must place them in the Panel properties, in our case in the Tag and access them via casting from the Sender parameter s!

So you need to change this line in the Paint event

Product b = box.Tag as Product;

to something like this:

Product b = ( (Panel) s ).Tag as Product;

Answer 2

Your Paint event handler has to be responsible for drawing everything each time. Your code looks like it only draws one object.

When you drag something over your box, the box becomes invalid and needs to be painted from scratch which means it erases everything and calls your Paint handler. Your Paint event handler then just draws one object.

I suspect that what you want to do is keep a data structure of each item you draw and then have a loop in your Paint event handler that will draw all the objects you add.

Answer 3

Don't use variables that you defined outside a loop, in the paint event. That might be your problem. Try to paint ((Panel)s).Name. Does this work properly?