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:

AnimatedProgress, CLabel, Decorations, 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

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

Caret	getCaret() Returns the caret.
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.

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

checkSubclass, computeSize, getChildren, getLayout, getTabList, layout, layout, setFocus, setLayout, setTabList

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

computeTrim, getClientArea, getHorizontalBar, getVerticalBar

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

addControlListener, addFocusListener, addHelpListener, addKeyListener, addMouseListener, addMouseMoveListener, addMouseTrackListener, addPaintListener, addTraverseListener, computeSize, forceFocus, getAccessible, getBackground, getBorderWidth, getBounds, getDisplay, getEnabled, getFont, getForeground, getLayoutData, getLocation, getMenu, getParent, getShell, getSize, getToolTipText, getVisible, internal_dispose_GC, internal_new_GC, isDisposed, isEnabled, isFocusControl, isReparentable, isVisible, moveAbove, moveBelow, pack, pack, redraw, redraw, removeControlListener, removeFocusListener, removeHelpListener, removeKeyListener, removeMouseListener, removeMouseMoveListener, removeMouseTrackListener, removePaintListener, removeTraverseListener, setBackground, setBounds, setBounds, setCapture, setCursor, setEnabled, setForeground, setLayoutData, setLocation, setLocation, setMenu, setParent, setRedraw, setSize, setSize, setToolTipText, setVisible, toControl, toDisplay, traverse, update

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

addDisposeListener, addListener, checkWidget, dispose, getData, getData, getStyle, isListening, notifyListeners, removeDisposeListener, removeListener, removeListener, 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
• ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass

See Also:

SWT, Widget.checkSubclass(), Widget.getStyle()

Method Detail

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

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

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, 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)