Common Widgets class hierarchy

Programmer Reference : Common Widgets : Common Widgets class hierarchy

This section describes the Common Widgets class hierarchy and provides an overview of the functionality provided by each class.

A is a user interface component, such as a top-level window (shell), button or list. A graphical user interface is built by creating a tree of widgets. Every widget except the topmost widget in a tree has a parent widget. In the user interface a child widget appears on top of the parent and is normally prevented from drawing outside the bounds of its parent. Each parent widget is responsible for sizing and positioning its children. The parent-child relationship defines the widget tree. The topmost widget in the tree is called a shell widget. Shell widgets are responsible for negotiating with the window manager for their position on the screen, and for the various window decorations that they display, such as a title, border, or close box.

All Common Widgets are subclasses of one of the following classes:

CwPrimitive

A primitive widget has no children.

CwComposite

A composite widget can have zero or more children.

CwShell

A shell widget has exactly one child.

Primitive widgets are the simplest building blocks in Common Widgets. A primitive widget is always the child of another widget. The following table provides brief descriptions of the CwPrimitive class and its subclasses. Classes in italics are abstract classes (they are never instantiated).

Note:

The parent-child relationship is not the same as the class-subclass relationship.

Table 28. Primitive hierarchy

Class hierarchy	Responsibility
CwWidget	Defines common behavior for all widgets
.CwBasicWidget	Defines common behavior for widgets implemented directly by the platform
..CwPrimitive	Defines common behavior for widgets that do not have children
…CwArrowButton	Displays an arrow button
.. CwComboBox	Combines a list and text area to provide a prompted entry field
…CwLabel	Displays a static label that can be a string, pixmap, or icon
....CwCascadeButton	Used as part of a menu system to trigger submenus
....CwDrawnButton	Displays a button drawn by the application
....CwPushButton	Displays a push button containing a string, pixmap, or icon
....CwToggleButton	Displays a button that has on and off state such as a radio or check button
…CwList	Displays a list of strings from which one or more can be selected
…CwScrollBar	Displays a vertical or horizontal scroll bar
.. .wSeparator	Displays a separator line, normally between menu items
...CwText	Displays and provides editing capability for text

Composite widgets can have zero or more child widgets. A composite widget's children can include other composite widgets, primitive widgets, or both. Different composite widgets provide various kinds of layout capabilities for arranging children. The following table briefly explains the CwComposite class and its subclasses. Classes in italics are abstract classes.

Table 29. Composite hierarchy

Class hierarchy	Responsibility
CwWidget	Defines common behavior for all widgets
..CwBasicWidget	Defines common behavior for widgets implemented directly by the platform
..CwComposite	Defines common behavior for widgets that contain child widgets
…CwBulletinBoard	Allows application-defined child widget positioning
....CwCompositeBox	Defines common behavior for CwMessageBox and CwSelectionBox
.....CwMessageBox	Provides a notification message, icon, and OK, Cancel, and Help buttons
.....CwSelectionBox	Provides a list of items to select, a text box showing the selection, and OK, Cancel, Apply, and Help buttons
....CwForm	Provides a constraint-based mechanism for laying out child widgets
…CwDrawingArea	Performs no child layout and provides an area for performing graphic operations
…CwFrame	Provides an optionally labeled frame around its single child widget
…CwRowColumn	Provides a mechanism for laying out child widgets in rows or columns
…CwScale	Displays a numeric scale with a position indicator
…CwScrolledWindow	Allows a child widget to be scrolled using scrollbars
....CwMainWindow	Provides layout management for a menu bar and optionally scrollable work area

Shell widgets provide the protocol between the application interface and the window manager. The following table provides brief descriptions of the CwShell class and its subclasses. Classes in italics are abstract classes.

Table 30. Shell hierarchy

Class hierarchy	Responsibility
CwWidget	Defines common behavior for all widgets
.CwBasicWidget	Defines common behavior for widgets implemented directly by the platform
..CwShell	Defines common behavior for the top-level widgets of windows and dialogs
...CwOverrideShell	A pop-up window that bypasses window management, and normally appears on top of all other widgets
...CwWMShell	Defines common behavior for shell widgets that do not bypass window management
....CwTopLevelShell	Provides a normal window with standard appearance and decorations
....CwTransientShell	A pop-up dialog window that does not bypass window management
.....CwDialogShell	A pop-up window used to implement modal and modeless dialog windows

Last modified date: 05/13/2020