How to check if a space on the form has an object

Question

I'm working on a mind-map project. I'm trying to get the "New Bubble" button to create a new textbox into a FREE space on the form. So I want to check if there is another bubble in the place where it's getting created. If it already has a textbox then I want it to find a new place and repeat the process.

How can I do this?

public partial class frmMap : Form
{
    private void btnProperties_Click(object sender, EventArgs e)
    {
        new frmProperties().Show();
    }

    private void btnNewBubble_Click(object sender, EventArgs e)
    {
        var tb = new TextBox();

        tb.Multiline = true;
        tb.BorderStyle = BorderStyle.FixedSingle;
        tb.Top = 100;
        tb.Left = 200;
        tb.Size = new Size(100, 100);

        this.Controls.Add(tb);
    }
}

You could just use a FlowLayoutPanel and you don't have to figure out a free space yourself. — Hans Passant, Dec 23 '14 at 22:48

score 1 · Answer 1 · answered Dec 23 '14 at 22:25

You can check "collision" with other controls like so:

foreach (Control checkControl in Controls)
{
   if (tb.Bounds.IntersectsWith(checkControl.Bounds))
      ...
}

Of course, thats a lot of checking to do! If you are just going to "grid" the controls, it would be faster/easier to just layout a bool array that holds the state of each "cell" (filled/empty) then pick the first empty one you find.

score 1 · Answer 2 · answered Dec 23 '14 at 22:31

Create dynamic textbox:

 var tb = new TextBox();
 tb.Multiline = true;
 tb.BorderStyle = BorderStyle.FixedSingle;

 tb.Top = 100;
 tb.Left = 200;
 tb.Size = new Size(100, 100);

Then use Rectangle.IntersectWith to check if new textbox intersects with other already added texboxes (you can remove control type filter, if you have other type of controls to check):

 while(Controls.OfType<TextBox>().Any(x => tb.Bounds.IntersectsWith(x.Bounds))
 {
    // adjust tb size or position here
 }

And last step - add textbox to form:

 Controls.Add(tb);

How to check if a space on the form has an object

2 Answers2