Eclipse Platform
Release 3.7

org.eclipse.swt.widgets
Class Composite

java.lang.Object
  extended by org.eclipse.swt.widgets.Widget
      extended by org.eclipse.swt.widgets.Control
          extended by org.eclipse.swt.widgets.Scrollable
              extended by org.eclipse.swt.widgets.Composite
All Implemented Interfaces:
Drawable
Direct Known Subclasses:
Browser, Canvas, CBanner, CCombo, Combo, CoolBar, CTabFolder, DateTime, DrillDownComposite, ExpandBar, FilteredList, FilteredTree, Form, Group, ImageAndMessageArea, OleClientSite, OleFrame, PageBook, ProgressIndicator, ProgressMonitorPart, SashForm, ScrolledComposite, Spinner, TabFolder, Table, TableTree, ToolBar, Tree, ViewForm

public class Composite
extends Scrollable

Instances of this class are controls which are capable of containing other controls.

Styles:
NO_BACKGROUND, NO_FOCUS, NO_MERGE_PAINTS, NO_REDRAW_RESIZE, NO_RADIO_GROUP, EMBEDDED, DOUBLE_BUFFERED
Events:
(none)

Note: The NO_BACKGROUND, NO_FOCUS, NO_MERGE_PAINTS, and NO_REDRAW_RESIZE styles are intended for use with Canvas. They can be used with Composite if you are drawing your own, but their behavior is undefined if they are used with subclasses of Composite other than Canvas.

Note: The CENTER style, although undefined for composites, has the same value as EMBEDDED which is used to embed widgets from other widget toolkits into SWT. On some operating systems (GTK, Motif), this may cause the children of this composite to be obscured.

This class may be subclassed by custom control implementors who are building controls that are constructed from aggregates of other controls.

See Also:
Canvas, Composite snippets, Sample code and further information

Field Summary
 
Fields inherited from class org.eclipse.swt.widgets.Control
handle
 
Constructor Summary
Composite(Composite parent, int style)
          Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.
 
Method Summary
 void changed(Control[] changed)
          Clears any data that has been cached by a Layout for all widgets that are in the parent hierarchy of the changed control up to and including the receiver.
protected  void checkSubclass()
          Checks that this class can be subclassed.
 Point computeSize(int wHint, int hHint, boolean changed)
          Returns the preferred size of the receiver.
 void drawBackground(GC gc, int x, int y, int width, int height, int offsetX, int offsetY)
          Fills the interior of the rectangle specified by the arguments, with the receiver's background.
 int getBackgroundMode()
          Returns the receiver's background drawing mode.
 Control[] getChildren()
          Returns a (possibly empty) array containing the receiver's children.
 Layout getLayout()
          Returns layout which is associated with the receiver, or null if one has not been set.
 boolean getLayoutDeferred()
          Returns true if the receiver has deferred the performing of layout, and false otherwise.
 Control[] getTabList()
          Gets the (possibly empty) tabbing order for the control.
 boolean isLayoutDeferred()
          Returns true if the receiver or any ancestor up to and including the receiver's nearest ancestor shell has deferred the performing of layouts.
 void layout()
          If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children.
 void layout(boolean changed)
          If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children.
 void layout(boolean changed, boolean all)
          If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children.
 void layout(Control[] changed)
          Forces a lay out (that is, sets the size and location) of all widgets that are in the parent hierarchy of the changed control up to and including the receiver.
 void layout(Control[] changed, int flags)
          Forces a lay out (that is, sets the size and location) of all widgets that are in the parent hierarchy of the changed control up to and including the receiver.
 void setBackgroundMode(int mode)
          Sets the background drawing mode to the argument which should be one of the following constants defined in class SWT: INHERIT_NONE, INHERIT_DEFAULT, INHERIT_FORCE.
 boolean setFocus()
          Causes the receiver to have the keyboard focus, such that all keyboard events will be delivered to it.
 void setLayout(Layout layout)
          Sets the layout which is associated with the receiver to be the argument which may be null.
 void setLayoutDeferred(boolean defer)
          If the argument is true, causes subsequent layout operations in the receiver or any of its children to be ignored.
 void setTabList(Control[] tabList)
          Sets the tabbing order for the specified controls to match the order that they occur in the argument list.
 
Methods inherited from class org.eclipse.swt.widgets.Scrollable
computeTrim, getClientArea, getHorizontalBar, getVerticalBar
 
Methods inherited from class org.eclipse.swt.widgets.Control
addControlListener, addDragDetectListener, addFocusListener, addGestureListener, addHelpListener, addKeyListener, addMenuDetectListener, addMouseListener, addMouseMoveListener, addMouseTrackListener, addMouseWheelListener, addPaintListener, addTouchListener, addTraverseListener, computeSize, dragDetect, dragDetect, forceFocus, getAccessible, getBackground, getBackgroundImage, getBorderWidth, getBounds, getCursor, getDragDetect, getEnabled, getFont, getForeground, getLayoutData, getLocation, getMenu, getMonitor, getOrientation, getParent, getRegion, getShell, getSize, getToolTipText, getTouchEnabled, getVisible, internal_dispose_GC, internal_new_GC, isEnabled, isFocusControl, isReparentable, isVisible, moveAbove, moveBelow, pack, pack, print, redraw, redraw, removeControlListener, removeDragDetectListener, removeFocusListener, removeGestureListener, removeHelpListener, removeKeyListener, removeMenuDetectListener, removeMouseListener, removeMouseMoveListener, removeMouseTrackListener, removeMouseWheelListener, removePaintListener, removeTouchListener, removeTraverseListener, setBackground, setBackgroundImage, setBounds, setBounds, setCapture, setCursor, setDragDetect, setEnabled, setFont, setForeground, setLayoutData, setLocation, setLocation, setMenu, setOrientation, setParent, setRedraw, setRegion, setSize, setSize, setToolTipText, setTouchEnabled, setVisible, toControl, toControl, toDisplay, toDisplay, traverse, traverse, traverse, update
 
Methods inherited from class org.eclipse.swt.widgets.Widget
addDisposeListener, addListener, checkWidget, dispose, getData, getData, getDisplay, getListeners, getStyle, isDisposed, isListening, notifyListeners, removeDisposeListener, removeListener, removeListener, reskin, setData, setData, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Composite

public Composite(Composite parent,
                 int style)
Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.

The style value is either one of the style constants defined in class SWT which is applicable to instances of this class, or must be built by bitwise OR'ing together (that is, using the int "|" operator) two or more of those SWT style constants. The class description lists the style constants that are applicable to the class. Style bits are also inherited from superclasses.

Parameters:
parent - a widget which will be the parent of the new instance (cannot be null)
style - the style of widget to construct
Throws:
IllegalArgumentException -
  • ERROR_NULL_ARGUMENT - if the parent is null
SWTException -
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent
See Also:
SWT.NO_BACKGROUND, SWT.NO_FOCUS, SWT.NO_MERGE_PAINTS, SWT.NO_REDRAW_RESIZE, SWT.NO_RADIO_GROUP, SWT.EMBEDDED, SWT.DOUBLE_BUFFERED, Widget.getStyle()
Method Detail

changed

public void changed(Control[] changed)
Clears any data that has been cached by a Layout for all widgets that are in the parent hierarchy of the changed control up to and including the receiver. If an ancestor does not have a layout, it is skipped.

Parameters:
changed - an array of controls that changed state and require a recalculation of size
Throws:
IllegalArgumentException -
  • ERROR_INVALID_ARGUMENT - if the changed array is null any of its controls are null or have been disposed
  • ERROR_INVALID_PARENT - if any control in changed is not in the widget tree of the receiver
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.1

checkSubclass

protected void checkSubclass()
Description copied from class: Widget
Checks that this class can be subclassed.

The SWT class library is intended to be subclassed only at specific, controlled points (most notably, Composite and Canvas when implementing new widgets). This method enforces this rule unless it is overridden.

IMPORTANT: By providing an implementation of this method that allows a subclass of a class which does not normally allow subclassing to be created, the implementer agrees to be fully responsible for the fact that any such subclass will likely fail between SWT releases and will be strongly platform specific. No support is provided for user-written classes which are implemented in this fashion.

The ability to subclass outside of the allowed SWT classes is intended purely to enable those not on the SWT development team to implement patches in order to get around specific limitations in advance of when those limitations can be addressed by the team. Subclassing should not be attempted without an intimate and detailed understanding of the hierarchy.

Overrides:
checkSubclass in class Widget

computeSize

public Point computeSize(int wHint,
                         int hHint,
                         boolean changed)
Description copied from class: Control
Returns the preferred size of the receiver.

The preferred size of a control is the size that it would best be displayed at. The width hint and height hint arguments allow the caller to ask a control questions such as "Given a particular width, how high does the control need to be to show all of the contents?" To indicate that the caller does not wish to constrain a particular dimension, the constant SWT.DEFAULT is passed for the hint.

If the changed flag is true, it indicates that the receiver's contents have changed, therefore any caches that a layout manager containing the control may have been keeping need to be flushed. When the control is resized, the changed flag will be false, so layout manager caches can be retained.

Overrides:
computeSize in class Control
Parameters:
wHint - the width hint (can be SWT.DEFAULT)
hHint - the height hint (can be SWT.DEFAULT)
changed - true if the control's contents have changed, and false otherwise
Returns:
the preferred size of the control.
See Also:
Layout, Control.getBorderWidth(), Control.getBounds(), Control.getSize(), Control.pack(boolean), "computeTrim, getClientArea for controls that implement them"

drawBackground

public void drawBackground(GC gc,
                           int x,
                           int y,
                           int width,
                           int height,
                           int offsetX,
                           int offsetY)
Fills the interior of the rectangle specified by the arguments, with the receiver's background.

The offsetX and offsetY are used to map from the gc origin to the origin of the parent image background. This is useful to ensure proper alignment of the image background.

Parameters:
gc - the gc where the rectangle is to be filled
x - the x coordinate of the rectangle to be filled
y - the y coordinate of the rectangle to be filled
width - the width of the rectangle to be filled
height - the height of the rectangle to be filled
offsetX - the image background x offset
offsetY - the image background y offset
Throws:
IllegalArgumentException -
  • ERROR_NULL_ARGUMENT - if the gc is null
  • ERROR_INVALID_ARGUMENT - if the gc has been disposed
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.6

getBackgroundMode

public int getBackgroundMode()
Returns the receiver's background drawing mode. This will be one of the following constants defined in class SWT: INHERIT_NONE, INHERIT_DEFAULT, INHERTIT_FORCE.

Returns:
the background mode
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.2
See Also:
SWT

getChildren

public Control[] getChildren()
Returns a (possibly empty) array containing the receiver's children. Children are returned in the order that they are drawn. The topmost control appears at the beginning of the array. Subsequent controls draw beneath this control and appear later in the array.

Note: This is not the actual structure used by the receiver to maintain its list of children, so modifying the array will not affect the receiver.

Returns:
an array of children
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
See Also:
Control.moveAbove(org.eclipse.swt.widgets.Control), Control.moveBelow(org.eclipse.swt.widgets.Control)

getLayout

public Layout getLayout()
Returns layout which is associated with the receiver, or null if one has not been set.

Returns:
the receiver's layout or null
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

getTabList

public Control[] getTabList()
Gets the (possibly empty) tabbing order for the control.

Returns:
tabList the ordered list of controls representing the tab order
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
See Also:
setTabList(org.eclipse.swt.widgets.Control[])

getLayoutDeferred

public boolean getLayoutDeferred()
Returns true if the receiver has deferred the performing of layout, and false otherwise.

Returns:
the receiver's deferred layout state
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.1
See Also:
setLayoutDeferred(boolean), isLayoutDeferred()

isLayoutDeferred

public boolean isLayoutDeferred()
Returns true if the receiver or any ancestor up to and including the receiver's nearest ancestor shell has deferred the performing of layouts. Otherwise, false is returned.

Returns:
the receiver's deferred layout state
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.1
See Also:
setLayoutDeferred(boolean), getLayoutDeferred()

layout

public void layout()
If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children. If the receiver does not have a layout, do nothing.

This is equivalent to calling layout(true).

Note: Layout is different from painting. If a child is moved or resized such that an area in the parent is exposed, then the parent will paint. If no child is affected, the parent will not paint.

Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

layout

public void layout(boolean changed)
If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children. If the argument is true the layout must not rely on any information it has cached about the immediate children. If it is false the layout may (potentially) optimize the work it is doing by assuming that none of the receiver's children has changed state since the last layout. If the receiver does not have a layout, do nothing.

If a child is resized as a result of a call to layout, the resize event will invoke the layout of the child. The layout will cascade down through all child widgets in the receiver's widget tree until a child is encountered that does not resize. Note that a layout due to a resize will not flush any cached information (same as layout(false)).

Note: Layout is different from painting. If a child is moved or resized such that an area in the parent is exposed, then the parent will paint. If no child is affected, the parent will not paint.

Parameters:
changed - true if the layout must flush its caches, and false otherwise
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

layout

public void layout(boolean changed,
                   boolean all)
If the receiver has a layout, asks the layout to lay out (that is, set the size and location of) the receiver's children. If the changed argument is true the layout must not rely on any information it has cached about its children. If it is false the layout may (potentially) optimize the work it is doing by assuming that none of the receiver's children has changed state since the last layout. If the all argument is true the layout will cascade down through all child widgets in the receiver's widget tree, regardless of whether the child has changed size. The changed argument is applied to all layouts. If the all argument is false, the layout will not cascade down through all child widgets in the receiver's widget tree. However, if a child is resized as a result of a call to layout, the resize event will invoke the layout of the child. Note that a layout due to a resize will not flush any cached information (same as layout(false)).

Note: Layout is different from painting. If a child is moved or resized such that an area in the parent is exposed, then the parent will paint. If no child is affected, the parent will not paint.

Parameters:
changed - true if the layout must flush its caches, and false otherwise
all - true if all children in the receiver's widget tree should be laid out, and false otherwise
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.1

layout

public void layout(Control[] changed)
Forces a lay out (that is, sets the size and location) of all widgets that are in the parent hierarchy of the changed control up to and including the receiver. The layouts in the hierarchy must not rely on any information cached about the changed control or any of its ancestors. The layout may (potentially) optimize the work it is doing by assuming that none of the peers of the changed control have changed state since the last layout. If an ancestor does not have a layout, skip it.

Note: Layout is different from painting. If a child is moved or resized such that an area in the parent is exposed, then the parent will paint. If no child is affected, the parent will not paint.

Parameters:
changed - a control that has had a state change which requires a recalculation of its size
Throws:
IllegalArgumentException -
  • ERROR_INVALID_ARGUMENT - if the changed array is null any of its controls are null or have been disposed
  • ERROR_INVALID_PARENT - if any control in changed is not in the widget tree of the receiver
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.1

layout

public void layout(Control[] changed,
                   int flags)
Forces a lay out (that is, sets the size and location) of all widgets that are in the parent hierarchy of the changed control up to and including the receiver.

The parameter flags may be a combination of:

SWT.ALL
all children in the receiver's widget tree should be laid out
SWT.CHANGED
the layout must flush its caches
SWT.DEFER
layout will be deferred

When the changed array is specified, the flags SWT.ALL and SWT.CHANGED have no effect. In this case, the layouts in the hierarchy must not rely on any information cached about the changed control or any of its ancestors. The layout may (potentially) optimize the work it is doing by assuming that none of the peers of the changed control have changed state since the last layout. If an ancestor does not have a layout, skip it.

When the changed array is not specified, the flag SWT.ALL indicates that the whole widget tree should be laid out. And the flag SWT.CHANGED indicates that the layouts should flush any cached information for all controls that are laid out.

The SWT.DEFER flag always causes the layout to be deferred by calling Composite.setLayoutDeferred(true) and scheduling a call to Composite.setLayoutDeferred(false), which will happen when appropriate (usually before the next event is handled). When this flag is set, the application should not call Composite.setLayoutDeferred(boolean).

Note: Layout is different from painting. If a child is moved or resized such that an area in the parent is exposed, then the parent will paint. If no child is affected, the parent will not paint.

Parameters:
changed - a control that has had a state change which requires a recalculation of its size
flags - the flags specifying how the layout should happen
Throws:
IllegalArgumentException -
  • ERROR_INVALID_ARGUMENT - if any of the controls in changed is null or has been disposed
  • ERROR_INVALID_PARENT - if any control in changed is not in the widget tree of the receiver
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.6

setBackgroundMode

public void setBackgroundMode(int mode)
Sets the background drawing mode to the argument which should be one of the following constants defined in class SWT: INHERIT_NONE, INHERIT_DEFAULT, INHERIT_FORCE.

Parameters:
mode - the new background mode
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.2
See Also:
SWT

setFocus

public boolean setFocus()
Description copied from class: Control
Causes the receiver to have the keyboard focus, such that all keyboard events will be delivered to it. Focus reassignment will respect applicable platform constraints.

Overrides:
setFocus in class Control
Returns:
true if the control got focus, and false if it was unable to.
See Also:
Control.forceFocus()

setLayout

public void setLayout(Layout layout)
Sets the layout which is associated with the receiver to be the argument which may be null.

Parameters:
layout - the receiver's new layout or null
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setLayoutDeferred

public void setLayoutDeferred(boolean defer)
If the argument is true, causes subsequent layout operations in the receiver or any of its children to be ignored. No layout of any kind can occur in the receiver or any of its children until the flag is set to false. Layout operations that occurred while the flag was true are remembered and when the flag is set to false, the layout operations are performed in an optimized manner. Nested calls to this method are stacked.

Parameters:
defer - the new defer state
Throws:
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
Since:
3.1
See Also:
layout(boolean), layout(Control[])

setTabList

public void setTabList(Control[] tabList)
Sets the tabbing order for the specified controls to match the order that they occur in the argument list.

Parameters:
tabList - the ordered list of controls representing the tab order or null
Throws:
IllegalArgumentException -
  • ERROR_INVALID_ARGUMENT - if a widget in the tabList is null or has been disposed
  • ERROR_INVALID_PARENT - if widget in the tabList is not in the same widget tree
SWTException -
  • ERROR_WIDGET_DISPOSED - if the receiver has been disposed
  • ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

Eclipse Platform
Release 3.7

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