in Delphi TIPS
:: If you are creating MDI applications using Delphi, you must have noticed some "quirks" or issues that you cannot simply handle / fix from your code. When creating (to show) an MDI child an animation of resizing will take place. This animation might look ugly if the code executed during the creation of your MDI child takes some time to process. Here's how to prevent window updating when creating new MDI child forms.
Read the full article to learn how to Lock (Prevent) Window Updating When Creating New MDI Child Forms