title: How to create a delphi form containing multiple 'child' forms that can be moved/sized and show activated
body: <p>I've created a form that hosts one or more 'child' forms. In my edit mode, each child form shows its border and caption bar allowing it to be moved and sized (a bit like the old MDI app). Out of my edit mode, the borders disappear and the child forms are fixed in position. For my simple demo, I'm creating the child forms thus:</p>
  
  <pre><code>procedure TForm1.Button1Click(Sender: TObject);
  var
    Frm : TForm;
  begin
    Frm := TForm3.Create( Self );
    Frm.Parent := Self;
    Frm.Visible := True;
  </code></pre>
  
  <p>The result is a layout like this:
  <img src="https://i.stack.imgur.com/I14q5.jpg" alt="Layout"></p>
  
  <p>I notice that the edit controls in the child forms are never active. I would like to have the 'clicked' form show an active caption bar colour just like active apps move around when clicked. I presume my 'corpse' behaviour of the child forms is because they are inactive but attempts to do things like ChildForm.SetFocus do nothing.</p>
  
  <p>What do I need to do to get these edit controls alive and to show one of the forms as 'selected' please?</p>
  
  <p>(I'd really like to 'select' more than one form too if possible)</p>