L0018 - SWT - The Standard Widget Toolkit

The graphical sub-system of the Eclipse platform is made up of two components: SWT, the Standard Widget Toolkit; and JFace, an architecture independent modeling layer. This module describes how to use SWT in views and editors and how different resources must be managed.

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SWT - The Standard Widget Toolkit
The graphical sub-system of the Eclipse platform is made up of two
components: SWT, the Standard Widget Toolkit; and JFace, an
architecture independent modeling layer. This module describes how to
use SWT in views and editors and how different resources must be
managed.

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Eclipse User Interface Layers
Four Layers:
The Eclipse Workbench
Overall look-n-feel
JFace
Architecture-independent models
SWT
Platform independent API yet rather close to the metal
Native widgets
Platform dependent: Windows, Linux, Mac, Unix
The “Eclipse User Interface Guidelines” govern the look-n-feel of the
workbench and JFace
Consequently (nearly) all Eclipse RCP based applications look the same!
Use the SWT Bible “The Definitive Guide to SWT and JFace” by Robert Harris
and Rob Warner
2Eclipse RCP
OSGi/Run-time
SWT
JFace
Workbench
PreferencesJobs RegistryICUCommands

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SWT and the Native Widgets
SWT is short for ”The Standard Widget Toolkit”
SWT is a sub-project of the Eclipse project
SWT has a common API on all target platforms – the implementation is
different
Base plug-in org.eclipse.swt contains only MANIFEST.MF plus some
configuration files
A set of platform specific fragments implements all of SWT–
org.eclipse.swt.win32.win32.x86 for 32-bit Windows on x86 (not Vista
look-n-feel)
SWT is a thin layer on top of the native widgets
Windows, Mac, Motif, GTK and more
SWT can easily be used stand-alone
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SWT on Different Platforms
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Working with SWT
SWT API is not as regular as Swing
The SWT site contains a large repository of “SWT Snippets” that demonstrate
most of the abilities of SWT
To find leaks with graphical resources use sleak plug-in
It is possible to integrate SWT and Swing to a very large degree
But expect problems with shortcuts and focus management
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SWT Widgets
Basic
Button, Combo, Composite, Group, Label, Link, List, Menu, ProgressBar,
Shell, Slider, Scale, Spinner, TabFolder, Table, Text, ToolBar, and Tree
Advanced
Browser, Canvas, CBanner, CCombo, CLabel, CoolBar, CTabFolder,
DateTime, ExpandBar, GLCanvas, Sash, SashForm, ScrolledComposite,
StyledText, SWT_AWT, TableCursor, and Tray
Other Sources – e.g. Nebula, Sourceforge.net
FormattedText, Gallery, Grid, and many more
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SWT Widgets
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The Basic Widget Hierarchy
8 Widget Menu Item Control MenuItem TableItem TabItem Canvas Button Label Composite List Combo Form OleSiteClient Table

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The Basic Widget Hierarchy
Widget
Top-level abstract
super class for all
widgets
Support for
arbitrary
associated data
general event
management
disposal
management
Control
Top-level abstract
super class for
controls
Support for
foreground,
background
border
content menu
focus
management
layout
management –
layout, location
and size
Composite
Control that can
contain other controls
Support for layout
management
A Composite must
have a layout
manager, or the child
widgets will not be
shown!
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Using SWT Widgets
Common constructor form – e.g. new Text(parent, SWT.PASSWORD)
The parent
The style argument specifies the basic sub-function of the widget
Use Text controls for data values event when read-only, as this makes it
possible to select and copy the value
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Using SWT Styles
Second argument of all widget constructions – e.g. new Text(parent,
SWT.PASSWORD)
The most used styles are
SWT.NONE – no style needed
SWT.LEAD, SWT.CENTER, and SWT.TRAIL - the alignment of text in
labels, menus and buttons
SWT.ARROW, SWT.CHECK, SWT.PUSH, SWT.RADIO, and SWT.TOGGLE -
the sub-type of a button
SWT.PASSWORD - Text is used for password entry
SWT.V_SCROLL, SWT.H_SCROLL, and SWT.NO_SCROLL – Table or Tree
has vertical, horizontal or no scroll bar (3.4 and later)
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Using SWT Styles
Some special considerations regarding styles
Some style arguments cannot be changed once specified in the
constructor (e.g. SWT.CHECK for a Button), whereas others can (e.g.
SWT.LEAD for Label)
Some style arguments have different meaning for different widgets –
e.g. SWT.MULTI for Table and Text
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Managing Composites (Composite)
Children are added to a composite during the construction of the children
new Text(composite, SWT.BORDER)
Children are retrieved using
comp.getChildren()
Children are removed using
child.dispose()
Children can be moved in the parent using
child.moveAbove(otherChild)
child.moveBelow(otherChild)
When a composite is changed, remember to re-layout
comp.layout()
Setting the background of children of a composite:
comp.setBackgroundMode(SWT.INHERIT_DEFAULT)
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SWT Layout Managers
The positioning and sizing of controls in a Composite (and subclasses) is
performed using layout managers
SWT includes a rather complete set of standard layout managers
FillLayout and RowLayout: layout is a single row or column
GridLayout: layout in a grid with size constraints
FormLayout: layout in canvas with size and edge-to-edge constraints
Most GUI designer can handle these
A new layout manager can be created fairly easily
computeSize: computes the “natural” size of the Composite
layout: lays out the controls of the Compositepublic abstract class Layout {
protected abstract Point computeSize(Composite composite, int wHint, int hHint, boolean flushCache);
protected abstract void layout(Composite composite, boolean flushCache);
}
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Using the Grid Layout (GridLayout)
Grid Layout is the most used layout manager in Eclipse
It works by adding the child widgets to the cells in a grid
Widgets are added in sequence
When using a Grid Layout, the parent uses the GridLayout and all children
use GridData
final Composite composite = new Composite(parent, SWT.NONE);
final GridLayout gridLayout = new GridLayout(3, false);
composite.setLayout(gridLayout);
...
label = new Label(composite, SWT.NONE);
label.setText("Label");
text = new Text(composite, SWT.BORDER);
text.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false, 2, 1));
// …
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TextLabel

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Using the Grid Layout (GridLayout)
The GridLayout class has two arguments
numColumns – the number of columns in the grid (defaults to 1)
makeColumnsEqualWidth – whether all columns in the grid have equal
width (defaults to false)
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Using the Grid Data (GridData)
GridData specifies how a child widget is laid out in the parent grid
A GridData holds the following primary information
Grab Excess Space (horizontal and vertical) – describes whether the grid
column or row should expand to grab any excess space (defaults to no
grab)
Span (horizontal and vertical) – describes the number of cells the
widget should span (defaults to 1,1)
Alignment (horizontal and vertical) – placement of widget within the
cells – one of SWT.BEGINNING, SWT.CENTER, SWT.END or SWT.FILL
(defaults to BEGINNING, BEGINNING)
A GridData also contains information about indentation, minimum size
and size hints
Don’t use the two-argument constructor!
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Using the Grid Data (GridData)
Grab Excess Space (horizontal and vertical)
describes whether the grid column or row should expand to grab any
excess space (defaults to no grab)
18Outer
Composite GridLayout with 3
columns and 3 rows Control to be
positioned

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Using the Grid Data (GridData)
Span (horizontal and vertical)
describes the number of cells the widget should span (defaults to 1,1)
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1,1 2,1
2,2

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Using the Grid Data (GridData)
Alignment (horizontal and vertical)
placement of widget within the cells – one of SWT.BEGINNING,
SWT.CENTER, SWT.END or SWT.FILL (defaults to BEGINNING, BEGINNING)
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C,C F,C
E,E

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Layout Managers for Tables and Trees
Tables and Trees have a layout how columns are sized
TableLayout
Will only resize the columns the first time!
Applied to the Table or Tree
TableColumnLayout
Applied to the Composite of the Table or Tree
Column constraints saved as layout.setColumnData(column, constraint)
Both layout managers are based on the same column constraint objects:
ColumnPixelData – makes a column a specific width in pixels
ColumnWeightData – makes a column a specific percentage of the
summed width
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SWT Events
SWT events and listeners exist in two versions:
A simple very light-weight version
One event format and listener interface
A type-safe version
Multiple event formats and listener interfaces tailored to the specific
use
The difference is illustrated in the following examplefilter.addListener(SWT.KeyDown, new Listener() {
public void handleEvent(Event event) {
if (event.type == SWT.KeyDown) {
//...
}
}
}); filter.addKeyListener(new KeyAdapter() {
@Override
public void keyPressed(KeyEvent e) {
//...
}
});
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SWT Events
Key
KeyDown, KeyUp, HardKeyDown,
HardKeyUp
Mouse
MouseDown, MouseUp,
MouseMove, MouseEnter,
MouseExit, MouseDoubleClick,
MouseHover, MouseWheel
Control
Paint, Move, Resize, Dispose
Selection
Selection, DefaultSelection
Focus
FocusIn, FocusOut
Tree and Table
Expand, Collapse, EraseItem,
MeasureItem, PaintItem
Shell
Iconify, Deiconify, Close,
Activate, Deactivate
Menu
Show, Hide, Arm, MenuDetect
Basic Controls
Modify, Verify, SetData, Settings
Drag-n-Drop
DragDetect
Misc
Help
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Lab Exercise
Create a view with the following look using simple SWT controls
GridLayout, GridData
Label, Text, Button
…addSelectionListener(…)
Another extra lab for the fast ones:
add “stuff” to the lab to only allow “a” and “b” in the text field
and to only allow more “a” than “b”!
Use a Verify listenerpublic class View extends ViewPart {
public void createPartControl(Composite parent) {
Composite top = new Composite(parent, SWT.NONE);
// Add something here…
}
public void setFocus() {
}
}
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Button - spans two columns, RIGHT
aligned. SelectionListener that prints
current text of Text controlLabel
Text - FILL aligned + grab
Composite with GridLayout
with 2 columns

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Forms UI
A newer addition of the look-n-feel of the
Eclipse workbench is the Forms UI in
org.eclipse.ui.forms.
Provide a Web browser like look-n-feel to
forms
PDE is a good example of the increasing
use of this new technology
Have some of the same problems as seen in
ordinary Web applications: extensive use of the
mouse! Normally not welcome in office
applications
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More Information
“Eclipse User Interface Guidelines: Version 2.1”
http://www.eclipse.org/resources/resource.php?id=162
The Look-n-Feel guidelines for Eclipse – heavily influenced by the corresponding
Microsoft Windows Look-n-Feel guidelines
SWT home
http://www.eclipse.org/swt/
SWT versus Swing
http://www.developer.com/java/other/article.php/2179061
“Using SwingRCP (instead of SWT) in RCP”
http://www.eclipsezone.com/eclipse/forums/t104467.rhtm l
A discussion of different ways to integrate Eclipse RCP and Swing
“The Definitive Guide to SWT and JFace” by Robert Harris and Rob Warner (ISBN:
978-1590593257)
As it says – “The Definitive Guide…” – and needed due to the pure javadoc of SWT
“SWT Snippet” Repository
http://www.eclipse.org/swt/snippets/
A large repository of sample code for most uses of SWT!
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More Information
“Plug a Swing-based development tool into Eclipse”
http://www-128.ibm.com/developerworks/opensource/library/osswing/
“Eclipse Forms: Rich UI for the Rich Client”
http://www.eclipse.org/resources/resource.php?id=140
“Custom Drawing Table and Tree Items”
http://www.eclipse.org/resources/resource.php?id=122
“Using Images in the Eclipse UI”
http://www.eclipse.org/resources/resource.php?id=236
“Rich clients with the SWT and JFace”
http://www.javaworld.com/javaworld/jw-04-2004/jw-0426- swtjface.html?page=2
“SWT: The Standard Widget Toolkit”
http://www.eclipse.org/resources/resource.php?id=241
“Understanding Layouts in SWT”
http://www.eclipse.org/resources/resource.php?id=242
A good overview of the different basic layouts in Eclipse.
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More Information
“Drag and Drop in the Eclipse UI”
http://www.eclipse.org/resources/resource.php?id=202
“Adding Drag and Drop to an SWT Application”
http://www.eclipse.org/resources/resource.php?id=200
“Eclipse Data Binding Test Drive” (webinar)
http://www.eclipse.org/resources/resource.php?id=299
“Swing/SWT Integration”
http://www.eclipse.org/resources/resource.php?id=381
“Eclipse Forms: Rich UI for the Rich Client”
http://www.eclipse.org/articles/Article-Forms/article.html
The Forms UI explained with some good examples
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