The MDI (multiple document interface) is designed for applications that need to have two or more documents open at the same time. The documents are independent of each other and have different content, but they're the same type of document, such as an Excel workbook or a Photoshop image. An MDI application provides a single parent window?called the MDI parent form?with each open document represented by a child form. This arrangement has some special characteristics:
* Child forms are restricted to the parent form's client area.
* Minimizing/restoring the parent automatically minimizes/restores the children.
* The application's menu and/or toolbar are hosted in the parent form.
* Only one child can be active at a time, and user input and commands are automatically routed to that active child form.
An MDI child form can contain controls and other components, just like a regular form. The parent form is typically limited to menu and toolbars. In most MDI applications, all child forms ...