Controls

So far we have used the term widget without a formal definition. In the SWT class hierarchy, a Widget is the abstract class for any UI object that can be placed inside another widget. A Control is a widget that typically has a counterpart representation, denoted by an OS window handle, in the underlying platform.

We tend to use the terms widget and control interchangeably. Although the distinction matters in the SWT implementation, we don't focus on this difference from an application's point of view. If you review the SWT widget hierarchy, you will see that a Control is something that you can create and place anywhere you want in your widget parent/child tree. Widgets that are not controls are typically more specialized UI objects that can be created only for certain types of parents.

The SWT API reference and examples are full of information about the different kinds of controls and their usage. The org.eclipse.swt.widgets package defines the core set of widgets in SWT. The following table summarizes the concrete types of controls provided in this package and their purpose. (Abstract classes are eliminated from this list).

Widget	Purpose	Styles	Events
Button	Selectable control that issues notification when pressed and/or released.	BORDER, CHECK, PUSH, RADIO, TOGGLE, FLAT, LEFT, RIGHT, CENTER, ARROW (with UP, DOWN)	Dispose, Control*, Selection
Canvas	Composite control that provides a surface for drawing arbitrary graphics. Often used to implement custom controls.	BORDER, H_SCROLL, V_SCROLL, NO_BACKGROUND, NO_FOCUS, NO_MERGE_PAINTS, NO_REDRAW_RESIZE, NO_RADIO_GROUP	Dispose, Control*
Caret	An i-beam that is typically used as the insertion point for text.		Dispose
Combo	Selectable control that allows the user to choose a string from a list of strings, or optionally type a new value into an editable text field. Often used when limited space requires a pop-down presentation of the available strings rather than using a single selection list box.	BORDER, DROP_DOWN, READ_ONLY, SIMPLE	Dispose, Control*, DefaultSelection, Modify, Selection
Composite	Control that is capable of containing other widgets.	BORDER, H_SCROLL, V_SCROLL	Dispose, Control*
CoolBar	Composite control that allows users to dynamically reposition the cool items contained in the bar.	BORDER	Dispose, Control*
CoolItem	Selectable user interface object that represents a dynamically positionable area of a cool bar.	DROP_DOWN	Dispose
Group	Composite control that groups other widgets and surrounds them with an etched border and/or label.	BORDER, SHADOW_ETCHED_IN, SHADOW_ETCHED_OUT, SHADOW_IN, SHADOW_OUT, SHADOW_NONE	Dispose, Control*
Label	Non-selectable control that displays a string or an image.	BORDER, CENTER, LEFT, RIGHT, WRAP, SEPARATOR (with HORIZONTAL, SHADOW_IN, SHADOW_OUT, SHADOW_NONE, VERTICAL)	Dispose, Control*
List	Selectable control that allows the user to choose a string or strings from a list of strings.	BORDER, H_SCROLL, V_SCROLL, SINGLE, MULTI	Dispose, Control*, Selection, DefaultSelection
Menu	User interface object that contains menu items.	BAR, DROP_DOWN, NO_RADIO_GROUP, POP_UP	Dispose, Help, Hide, Show
MenuItem	Selectable user interface object that represents an item in a menu.	CHECK, CASCADE, PUSH, RADIO, SEPARATOR	Dispose, Arm, Help, Selection
ProgressBar	Non-selectable control that displays progress to the user, typically in the form of a bar graph.	BORDER, INDETERMINATE, SMOOTH, HORIZONTAL, VERTICAL	Dispose, Control*
Sash	Selectable control that allows the user to drag a rubber banded outline of the sash within the parent window. Used to allow users to resize child widgets by repositioning their dividing line.	BORDER, HORIZONTAL, VERTICAL	Dispose, Control*, Selection
Scale	Selectable control that represents a range of numeric values.	BORDER, HORIZONTAL, VERTICAL	Dispose, Control*, Selection
ScrollBar	Selectable control that represents a range of positive numeric values. Used in a Composite that has V_SCROLL and/or H_SCROLL styles.	HORIZONTAL, VERTICAL	Dispose, Selection
Shell	Window that is managed by the OS window manager. Shells can be parented by a Display (top level shells) or by another shell (secondary shells).	BORDER, H_SCROLL, V_SCROLL, CLOSE, MIN, MAX, NO_TRIM, RESIZE, TITLE (see also SHELL_TRIM, DIALOG_TRIM)	Dispose, Control*, Activate, Close, Deactivate, Deiconify, Iconify
Slider	Selectable control that represents a range of numeric values. A slider is distinguished from a scale by providing a draggable thumb that can adjust the current value along the range.	BORDER, HORIZONTAL, VERTICAL	Dispose, Control*, Selection
TabFolder	Composite control that groups pages that can be selected by the user using labeled tabs.	BORDER	Dispose, Control*, Selection
TabItem	Selectable user interface object corresponding to a tab for a page in a tab folder.		Dispose
Table	Selectable control that displays a list of table items that can be selected by the user. Items are presented in rows that display multiple columns representing different aspects of the items.	BORDER, H_SCROLL, V_SCROLL, SINGLE, MULTI, CHECK, FULL_SELECTION, HIDE_SELECTION, VIRTUAL	Dispose, Control*, Selection, DefaultSelection
TableColumn	Selectable user interface object that represents a column in a table.	LEFT, RIGHT, CENTER	Dispose, Move, Resize, Selection
TableItem	Selectable user interface object that represents an item in a table.		Dispose
Text	Editable control that allows the user to type text into it.	BORDER, SINGLE,  READ_ONLY, LEFT, CENTER, RIGHT, WRAP, MULTI (with H_SCROLL, V_SCROLL)	Dispose, Control*, DefaultSelection, Modify, Verify
ToolBar	Composite control that supports the layout of selectable tool bar items.	BORDER, FLAT, WRAP, RIGHT, SHADOW_OUT HORIZONTAL, VERTICAL	Dispose, Control*,
ToolItem	Selectable user interface object that represents an item in a tool bar.	PUSH, CHECK, RADIO, SEPARATOR, DROP_DOWN	Dispose, Selection
Tracker	User interface object that implements rubber banding rectangles.	LEFT, RIGHT, UP, DOWN, RESIZE	Dispose, Move, Resize
Tree	Selectable control that displays a hierarchical list of tree items that can be selected by the user.	BORDER, H_SCROLL, V_SCROLL, SINGLE, MULTI, CHECK	Dispose, Control*, Selection, DefaultSelection, Collapse, Expand
TreeItem	Selectable user interface object that represents a hierarchy of tree items in a tree.		Dispose

Control* = Events inherited from Control:  FocusIn, FocusOut, Help, KeyDown, KeyUp, MouseDoubleClick, MouseDown, MouseEnter, MouseExit, MouseHover, MouseUp, MouseMove, Move, Paint, Resize