Chapter 3. PlainBaseDialog, PlainUserDialog, Base Mixin Classes

PlainBaseDialog is the base class of all dialog classes in the ooDialog framework. It implements methods that are common to every dialog. PlainBaseDialog should be considered an abstract class. Although, a programmer could instantiate a new PlainBaseDialog object, the class does not implement all the methods that are needed to execute a dialog. Therefore, not much can be done with a simple PlainBaseDialog object. The ooDialog programmer uses subclasses of PlainBaseDialog to actually create and execute a real dialog.

The PlainBaseDialog inherits from the WindowBase mixin class. The WindowBase mixin class implements methods that are common to all windows. Since both dialogs and dialog controls are windows, the DialogControl class also inherits from WindowBase.

The PlainUserDialog class subclasses from PlainBaseDialog class and provides all the methods that normally are required to execute a dialog that is either created dynamically or loaded from a resource script (.RC). Its purpose is to provide a simpler class that can be used for ordinary user interfaces, like the standard dialogs. The ooDialog programmer can subclass from the PlainUserDialog to produce straighforward, uncomplicated user interfaces.

The more advanced dialog classes, ResDialog, RcDialog, UserDialog, subclass the BaseDialog class. The BaseDialog class subclasses PlainBaseDialog, and like PlainBaseDialog should be considered an abstract class. BaseDialog inherits from the WindowExtensions and DialogExtensions mixin classes. These classes implement methods that cover asynchronous dialog execution, scroll bar support, resizing and repositioning, bitmaps, graphics (device context related methods), scrolling text, and menus (action bars). The ResDialog, RcDialog, UserDialog classes, and their subclasses, allow the programmer to produce very sophisticated graphical user interfaces.

Historically, the reason for providing the simpler PlainUserDialog class was to have a smaller package that required less system resources for ordinary user interfaces like the standard dialogs. That reason is probably not as valid in modern times as it was when ooDialog was being developed to run on Windows 3.1.