Package org.eclipse.swt.widgets

Class Canvas

java.lang.Object

org.eclipse.swt.widgets.Widget

org.eclipse.swt.widgets.Control

org.eclipse.swt.widgets.Scrollable

org.eclipse.swt.widgets.Composite

org.eclipse.swt.widgets.Canvas

All Implemented Interfaces:

Drawable

Direct Known Subclasses:

AbstractHyperlink, AnimatedProgress, CLabel, Decorations, ExpandableComposite, FormText, GLCanvas, HyperlinkLabel, ImageBasedFrame, StyledText, TableCursor, TreeCursor

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

Fields inherited from class org.eclipse.swt.widgets.Widget

nativeZoom

Constructor Summary

Constructors

Constructor	Description
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

Modifier and Type	Method	Description
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, drawBackground, getBackgroundMode, getChildren, getLayout, getLayoutDeferred, getTabList, isLayoutDeferred, layout, layout, layout, layout, layout, setBackgroundMode, setFocus, setLayout, setLayoutDeferred, setTabList, toString

Methods inherited from class org.eclipse.swt.widgets.Scrollable

computeTrim, getClientArea, getHorizontalBar, getScrollbarsMode, getVerticalBar, setScrollbarsMode

Methods inherited from class org.eclipse.swt.widgets.Control

addControlListener, addDragDetectListener, addFocusListener, addGestureListener, addHelpListener, addKeyListener, addMenuDetectListener, addMouseListener, addMouseMoveListener, addMouseTrackListener, addMouseWheelListener, addPaintListener, addTouchListener, addTraverseListener, computeSize, computeSize, dragDetect, dragDetect, forceFocus, getAccessible, getBackground, getBackgroundImage, getBorderWidth, getBounds, getCursor, getDragDetect, getEnabled, getFont, getForeground, getLayoutData, getLocation, getMenu, getMonitor, getOrientation, getParent, getRegion, getShell, getSize, getTextDirection, 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, requestLayout, setBackground, setBackgroundImage, setBounds, setBounds, setCapture, setCursor, setDragDetect, setEnabled, setForeground, setLayoutData, setLocation, setLocation, setMenu, setOrientation, setParent, setRedraw, setRegion, setSize, setSize, setTextDirection, setToolTipText, setTouchEnabled, setVisible, toControl, toControl, toDisplay, toDisplay, traverse, traverse, traverse, update

Methods inherited from class org.eclipse.swt.widgets.Widget

addDisposeListener, addListener, addTypedListener, checkWidget, dispose, getData, getData, getDisplay, getListeners, getStyle, getTypedListeners, isAutoDirection, isDisposed, isListening, notifyListeners, removeDisposeListener, removeListener, removeListener, removeTypedListener, reskin, setData, setData

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.eclipse.swt.graphics.Drawable

isAutoScalable

Constructor Details

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.getStyle()

Method Details

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