Eclipse Platform
Release 3.7

org.eclipse.swt.widgets
Class Canvas

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
                  extended by org.eclipse.swt.widgets.Canvas
All Implemented Interfaces:
Drawable
Direct Known Subclasses:
AbstractHyperlink, AnimatedProgress, CLabel, Decorations, ExpandableComposite, FormText, GLCanvas, StyledText, TableCursor

public class Canvas
extends Composite

Instances of this class provide a surface for drawing arbitrary graphics.

Styles:
(none)
Events:
(none)

This class may be subclassed by custom control implementors who are building controls that are not constructed from aggregates of other controls. That is, they are either painted using SWT graphics calls or are handled by native methods.

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

Field Summary
 
Fields inherited from class org.eclipse.swt.widgets.Control
handle
 
Constructor Summary
Canvas(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 drawBackground(GC gc, int x, int y, int width, int height)
          Fills the interior of the rectangle specified by the arguments, with the receiver's background.
 Caret getCaret()
          Returns the caret.
 IME getIME()
          Returns the IME.
 void scroll(int destX, int destY, int x, int y, int width, int height, boolean all)
          Scrolls a rectangular area of the receiver by first copying the source area to the destination and then causing the area of the source which is not covered by the destination to be repainted.
 void setCaret(Caret caret)
          Sets the receiver's caret.
 void setFont(Font font)
          Sets the font that the receiver will use to paint textual information to the font specified by the argument, or to the default font for that kind of control if the argument is null.
 void setIME(IME ime)
          Sets the receiver's IME.
 
Methods inherited from class org.eclipse.swt.widgets.Composite
changed, checkSubclass, computeSize, drawBackground, getBackgroundMode, getChildren, getLayout, getLayoutDeferred, getTabList, isLayoutDeferred, layout, layout, layout, layout, layout, setBackgroundMode, setFocus, setLayout, setLayoutDeferred, setTabList
 
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, 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

Canvas

public Canvas(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 composite control which will be the parent of the new instance (cannot be null)
style - the style of control 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, Widget.checkSubclass(), Widget.getStyle()
Method Detail

drawBackground

public void drawBackground(GC gc,
                           int x,
                           int y,
                           int width,
                           int height)
Fills the interior of the rectangle specified by the arguments, with the receiver's 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
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:
3.2

getCaret

public Caret getCaret()
Returns the caret.

The caret for the control is automatically hidden and shown when the control is painted or resized, when focus is gained or lost and when an the control is scrolled. To avoid drawing on top of the caret, the programmer must hide and show the caret when drawing in the window any other time.

Returns:
the caret for the receiver, may be 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

getIME

public IME getIME()
Returns the IME.

Returns:
the IME
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:
3.4

scroll

public void scroll(int destX,
                   int destY,
                   int x,
                   int y,
                   int width,
                   int height,
                   boolean all)
Scrolls a rectangular area of the receiver by first copying the source area to the destination and then causing the area of the source which is not covered by the destination to be repainted. Children that intersect the rectangle are optionally moved during the operation. In addition, all outstanding paint events are flushed before the source area is copied to ensure that the contents of the canvas are drawn correctly.

Parameters:
destX - the x coordinate of the destination
destY - the y coordinate of the destination
x - the x coordinate of the source
y - the y coordinate of the source
width - the width of the area
height - the height of the area
all - trueif children should be scrolled, 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

setCaret

public void setCaret(Caret caret)
Sets the receiver's caret.

The caret for the control is automatically hidden and shown when the control is painted or resized, when focus is gained or lost and when an the control is scrolled. To avoid drawing on top of the caret, the programmer must hide and show the caret when drawing in the window any other time.

Parameters:
caret - the new caret for the receiver, may be null
Throws:
IllegalArgumentException -
  • ERROR_INVALID_ARGUMENT - if the caret 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

setFont

public void setFont(Font font)
Description copied from class: Control
Sets the font that the receiver will use to paint textual information to the font specified by the argument, or to the default font for that kind of control if the argument is null.

Overrides:
setFont in class Control
Parameters:
font - the new font (or null)

setIME

public void setIME(IME ime)
Sets the receiver's IME.

Parameters:
ime - the new IME for the receiver, may be null
Throws:
IllegalArgumentException -
  • ERROR_INVALID_ARGUMENT - if the IME 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:
3.4

Eclipse Platform
Release 3.7

Guidelines for using Eclipse APIs.

Copyright (c) Eclipse contributors and others 2000, 2011. All rights reserved.