Error: “Cannot make a visible window modal”

Question: I’m trying to show a form modally; however, my application raises an exception: “Cannot make a visible window modal.” How do I solve this?

Answer: Set the form’s Visible design property to False.

To do this:

  1. Open your project in Delphi
  2. Open the form that raises the exception.
  3. In the Object Inspector, set the form’s Visible property to False.
  4. Save, compile, and run your application.

The creates the form as an invisible window, which lets you show it modally.

Thank’s to:  Lance Leonard
Source:  http://www.techtricks.com/delphi/makevisible.php

Error: “Cannot make a visible window modal”