javax.swing

Class JViewport

public class JViewport extends JComponent implements Accessible

                                                     _
   +-------------------------------+    ...........Y1 \
   |  view                         |                .  \
   |  (this component's child)     |                .   > VY
   |                               |                .  / = Y2-Y1
   |         +------------------------------+  ....Y2_/
   |         | viewport            |        |       .
   |         | (this component)    |        |       .
   |         |                     |        |       .
   |         |                     |        |       .
   |         |                     |        |       .
   |         |                     |        |       .
   |         +------------------------------+  ....Y3
   |                               |                .
   |         .                     |        .       .
   |         .                     |        .       .
   +---------.---------------------+    ...........Y4
   .         .                     .        .
   .         .                     .        .
   .         .                     .        .
   X1.......X2.....................X3.......X4
   \____  ___/
        \/
        VX = X2-X1

A viewport is, like all swing components, located at some position in the swing component tree; that location is exactly the same as any other components: the viewport's "bounds".

But in terms of drawing its child, the viewport thinks of itself as covering a particular position of the view's coordinate space. For example, the {@link #getViewPosition} method returns the position (VX,VY) shown above, which is an position in "view space", even though this is implemented by positioning the underlying child at position (-VX,-VY)

Nested Class Summary
protected class	JViewport.AccessibleJViewport Provides accessibility support for `JViewport`.
protected class	JViewport.ViewListener A {@link java.awt.event.ComponentListener} that listens for changes of the view's size.

Field Summary
protected boolean	backingStore This flag indicates whether we use a backing store for drawing.
protected Image	backingStoreImage The backingstore image used for the backingstore and blit scroll methods.
static int	BACKINGSTORE_SCROLL_MODE
static int	BLIT_SCROLL_MODE
protected boolean	isViewSizeSet
protected Point	lastPaintPosition The position at which the view has been drawn the last time.
protected boolean	scrollUnderway
static int	SIMPLE_SCROLL_MODE

Constructor Summary
	JViewport() Initializes the default setting for the scrollMode property.

Method Summary
void	addChangeListener(ChangeListener listener)
protected void	addImpl(Component comp, Object constraints, int index)
protected boolean	computeBlit(int dx, int dy, Point blitFrom, Point blitTo, Dimension blitSize, Rectangle blitPaint) Computes the parameters for the blitting scroll method.
protected LayoutManager	createLayoutManager() Creates the LayoutManager that is used for this viewport.
protected JViewport.ViewListener	createViewListener() Creates a {@link ViewListener} that is supposed to listen for size changes on the view component.
protected void	fireStateChanged()
AccessibleContext	getAccessibleContext() Returns the accessible context for this `JViewport`.
ChangeListener[]	getChangeListeners()
Dimension	getExtentSize()
Insets	getInsets()
Insets	getInsets(Insets insets)
int	getScrollMode()
ViewportUI	getUI() This method returns the viewport's UI delegate.
String	getUIClassID() This method returns the String ID of the UI class of Separator.
Component	getView()
Point	getViewPosition() Get the viewport's position in view space.
Rectangle	getViewRect()
Dimension	getViewSize() Returns the viewSize when set, or the preferred size of the set Component view.
boolean	isBackingStoreEnabled()
boolean	isOptimizedDrawingEnabled() Overridden to return `false`, so the JViewport's paint method gets called instead of directly calling the children.
void	paint(Graphics g)
void	removeChangeListener(ChangeListener listener)
void	repaint(long tm, int x, int y, int w, int h) Forward repaint to parent to make sure only one paint is performed by the RepaintManager.
void	reshape(int x, int y, int w, int h)
void	scrollRectToVisible(Rectangle contentRect) Scrolls the view so that contentRect becomes visible.
void	setBackingStoreEnabled(boolean b)
void	setBorder(Border border)
void	setExtentSize(Dimension newSize)
void	setScrollMode(int mode)
void	setUI(ViewportUI ui) This method sets the viewport's UI delegate.
void	setView(Component v)
void	setViewPosition(Point p)
void	setViewSize(Dimension newSize)
Dimension	toViewCoordinates(Dimension size)
Point	toViewCoordinates(Point p)
void	updateUI() This method resets the UI used to the Look and Feel defaults..

Field Detail

backingStore

protected boolean backingStore

Deprecated: since JDK 1.3

This flag indicates whether we use a backing store for drawing.

backingStoreImage

protected Image backingStoreImage

The backingstore image used for the backingstore and blit scroll methods.

BACKINGSTORE_SCROLL_MODE

public static final int BACKINGSTORE_SCROLL_MODE

BLIT_SCROLL_MODE

public static final int BLIT_SCROLL_MODE

isViewSizeSet

protected boolean isViewSizeSet

lastPaintPosition

protected Point lastPaintPosition

The position at which the view has been drawn the last time. This is used to determine the bittable area.

scrollUnderway

protected boolean scrollUnderway

SIMPLE_SCROLL_MODE

public static final int SIMPLE_SCROLL_MODE

Constructor Detail

JViewport

public JViewport()

Initializes the default setting for the scrollMode property.

Method Detail

addChangeListener

public void addChangeListener(ChangeListener listener)

addImpl

protected void addImpl(Component comp, Object constraints, int index)

computeBlit

protected boolean computeBlit(int dx, int dy, Point blitFrom, Point blitTo, Dimension blitSize, Rectangle blitPaint)

Computes the parameters for the blitting scroll method. dx and dy specifiy the X and Y offset by which the viewport is scrolled. All other arguments are output parameters and are filled by this method. blitFrom holds the position of the blit rectangle in the viewport rectangle before scrolling, blitTo where the blitArea is copied to. blitSize holds the size of the blit area and blitPaint is the area of the view that needs to be painted. This method returns true if blitting is possible and false if the viewport has to be repainted completetly without blitting.

Parameters: dx the horizontal delta dy the vertical delta blitFrom the position from where to blit; set by this method blitTo the position where to blit area is copied to; set by this method blitSize the size of the blitted area; set by this method blitPaint the area that needs repainting; set by this method

Returns: true if blitting is possible, false otherwise

createLayoutManager

protected LayoutManager createLayoutManager()

Creates the LayoutManager that is used for this viewport. Override this method if you want to use a custom LayoutManager.

Returns: a LayoutManager to use for this viewport

createViewListener

protected JViewport.ViewListener createViewListener()

Creates a {@link ViewListener} that is supposed to listen for size changes on the view component.

Returns: a ViewListener instance

fireStateChanged

protected void fireStateChanged()

getAccessibleContext

public AccessibleContext getAccessibleContext()

Returns the accessible context for this JViewport. This will be an instance of {@link AccessibleJViewport}.

Returns: the accessible context for this JViewport

getChangeListeners

public ChangeListener[] getChangeListeners()

getExtentSize

public Dimension getExtentSize()

getInsets

public final Insets getInsets()

getInsets

public final Insets getInsets(Insets insets)

getScrollMode

public int getScrollMode()

getUI

public ViewportUI getUI()

This method returns the viewport's UI delegate.

Returns: The viewport's UI delegate.

getUIClassID

public String getUIClassID()

This method returns the String ID of the UI class of Separator.

Returns: The UI class' String ID.

getView

public Component getView()

getViewPosition

public Point getViewPosition()

Get the viewport's position in view space. Despite confusing name, this really does return the viewport's (0,0) position in view space, not the view's position.

getViewRect

public Rectangle getViewRect()

getViewSize

public Dimension getViewSize()

Returns the viewSize when set, or the preferred size of the set Component view. If no viewSize and no Component view is set an empty Dimension is returned.

isBackingStoreEnabled

public boolean isBackingStoreEnabled()

Deprecated: 1.4

isOptimizedDrawingEnabled

public boolean isOptimizedDrawingEnabled()

Overridden to return false, so the JViewport's paint method gets called instead of directly calling the children. This is necessary in order to get a useful clipping and translation on the children.

Returns: false

paint

public void paint(Graphics g)

removeChangeListener

public void removeChangeListener(ChangeListener listener)

repaint

public void repaint(long tm, int x, int y, int w, int h)

Forward repaint to parent to make sure only one paint is performed by the RepaintManager.

Parameters: tm number of milliseconds to defer the repaint request x the X coordinate of the upper left corner of the dirty area y the Y coordinate of the upper left corner of the dirty area w the width of the dirty area h the height of the dirty area

reshape

public void reshape(int x, int y, int w, int h)

scrollRectToVisible

public void scrollRectToVisible(Rectangle contentRect)

Scrolls the view so that contentRect becomes visible.

Parameters: contentRect the rectangle to make visible within the view

Parameters: ui The viewport's UI delegate.