javax.swing
Class JViewport

java.lang.Object
  java.awt.Component
      java.awt.Container
          javax.swing.JComponent
              javax.swing.JViewport

All Implemented Interfaces:

javax.accessibility.Accessible, ImageObserver, MenuContainer, Serializable

Direct Known Subclasses:

BasicTabbedPaneUI.ScrollableTabViewport

public class JViewport

extends JComponent

implements javax.accessibility.Accessible

The "viewport" or "porthole" through which you see the underlying information. When you scroll, what moves is the viewport. It is like peering through a camera's viewfinder. Moving the viewfinder upwards brings new things into view at the top of the picture and loses things that were at the bottom.

By default, JViewport is opaque. To change this, use the setOpaque method.

NOTE:We have implemented a faster scrolling algorithm that does not require a buffer to draw in. The algorithm works as follows:

1. The view and parent view and checked to see if they are JComponents, if they aren't, stop and repaint the whole viewport.
2. If the viewport is obscured by an ancestor, stop and repaint the whole viewport.
3. Compute the region that will become visible, if it is as big as the viewport, stop and repaint the whole view region.
4. Obtain the ancestor Window's graphics and do a copyArea on the scrolled region.
5. Message the view to repaint the newly visible region.
6. The next time paint is invoked on the viewport, if the clip region is smaller than the viewport size a timer is kicked off to repaint the whole region.

In general this approach is much faster. Compared to the backing store approach this avoids the overhead of maintaining an offscreen buffer and having to do two copyAreas. Compared to the non backing store case this approach will greatly reduce the painted region.

This approach can cause slower times than the backing store approach when the viewport is obscured by another window, or partially offscreen. When another window obscures the viewport the copyArea will copy garbage and a paint event will be generated by the system to inform us we need to paint the newly exposed region. The only way to handle this is to repaint the whole viewport, which can cause slower performance than the backing store case. In most applications very rarely will the user be scrolling while the viewport is obscured by another window or offscreen, so this optimization is usually worth the performance hit when obscured.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans^TM has been added to the java.beans package. Please see XMLEncoder.

Author:

Hans Muller, Philip Milne

See Also:

JScrollPane, Serialized Form

Nested Class Summary

protected class	JViewport.AccessibleJViewport This class implements accessibility support for the JViewport class.
protected class	JViewport.ViewListener A listener for the view.

Nested classes inherited from class javax.swing.JComponent

JComponent.AccessibleJComponent, JComponent.ActionStandin, JComponent.IntVector, JComponent.KeyboardState

Nested classes inherited from class java.awt.Container

Container.AccessibleAWTContainer

Nested classes inherited from class java.awt.Component

Component.AccessibleAWTComponent, Component.BltBufferStrategy, Component.FlipBufferStrategy

Field Summary

protected boolean	backingStore Deprecated. As of Java 2 platform v1.3
static int	BACKINGSTORE_SCROLL_MODE Draws viewport contents into an offscreen image.
protected Image	backingStoreImage The view image used for a backing store.
static int	BLIT_SCROLL_MODE Use graphics.copyArea to implement scrolling.
private ChangeEvent	changeEvent
(package private) static Object	EnableWindowBlit Property used to indicate window blitting should not be done.
protected boolean	isViewSizeSet True when the viewport dimensions have been determined.
protected Point	lastPaintPosition The last viewPosition that we've painted, so we know how much of the backing store image is valid.
private boolean	repaintAll This is set to true in setViewPosition if doing a window blit and the viewport is obscured.
private Timer	repaintTimer Instead of directly invoking repaint, a Timer is started and when it fires, repaint is invoked.
private int	scrollMode
protected boolean	scrollUnderway The scrollUnderway flag is used for components like JList.
static int	SIMPLE_SCROLL_MODE This mode uses the very simple method of redrawing the entire contents of the scrollpane each time it is scrolled.
private static String	uiClassID
private ComponentListener	viewListener
private boolean	waitingForRepaint This is set to true in paint, if repaintAll is true and the clip rectangle does not match the bounds.

Fields inherited from class javax.swing.JComponent

_bounds, accessibleContext, listenerList, paintingChild, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW

Fields inherited from class java.awt.Container

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Fields inherited from interface java.awt.image.ImageObserver

ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH

Constructor Summary

JViewport()
Creates a JViewport.

Method Summary

void	addChangeListener(ChangeListener l) Adds a ChangeListener to the list that is notified each time the view's size, position, or the viewport's extent size has changed.
protected void	addImpl(Component child, Object constraints, int index) Sets the JViewport's one lightweight child, which can be null.
private void	blitDoubleBuffered(JComponent view, Graphics g, int clipX, int clipY, int clipW, int clipH, int blitFromX, int blitFromY, int blitToX, int blitToY, int blitW, int blitH, Image off)
private void	blitWindowGraphics(int x, int y, int w, int h, int ox, int oy) Blits the parent windows graphics from the given region offset to ox, oy.
private boolean	canUseWindowBlitter() Returns true if the viewport is not obscured by one of its ancestors, or its ancestors children and if the viewport is showing.
protected boolean	computeBlit(int dx, int dy, Point blitFrom, Point blitTo, Dimension blitSize, Rectangle blitPaint) Computes the parameters for a blit where the backing store image currently contains oldLoc in the upper left hand corner and we're scrolling to newLoc.
protected LayoutManager	createLayoutManager() Subclassers can override this to install a different layout manager (or null) in the constructor.
private Timer	createRepaintTimer()
protected JViewport.ViewListener	createViewListener() Creates a listener for the view.
protected void	firePropertyChange(String propertyName, Object oldValue, Object newValue) Notifies listeners of a property change.
protected void	fireStateChanged() Notifies all ChangeListeners when the views size, position, or the viewports extent size has changed.
private void	flushViewDirtyRegion(Graphics g) If the repaint manager has a dirty region for the view, the view is asked to paint.
javax.accessibility.AccessibleContext	getAccessibleContext() Gets the AccessibleContext associated with this JViewport.
private Graphics	getBackingStoreGraphics(Graphics g)
ChangeListener[]	getChangeListeners() Returns an array of all the ChangeListeners added to this JViewport with addChangeListener().
Dimension	getExtentSize() Returns the size of the visible part of the view in view coordinates.
Insets	getInsets() Returns the insets (border) dimensions as (0,0,0,0), since borders are not supported on a JViewport.
Insets	getInsets(Insets insets) Returns an Insets object containing this JViewports inset values.
int	getScrollMode() Returns the current scrolling mode.
ViewportUI	getUI() Returns the L&F object that renders this component.
String	getUIClassID() Returns a string that specifies the name of the L&F class that renders this component.
Component	getView() Returns the JViewport's one child or null.
private Point	getViewLocation() Only used by the paint method below.
Point	getViewPosition() Returns the view coordinates that appear in the upper left hand corner of the viewport, or 0,0 if there's no view.
Rectangle	getViewRect() Returns a rectangle whose origin is getViewPosition and size is getExtentSize.
Dimension	getViewSize() If the view's size hasn't been explicitly set, return the preferred size, otherwise return the view's current size.
boolean	isBackingStoreEnabled() Deprecated. As of Java 2 platform v1.3, replaced by getScrollMode().
private boolean	isBlitting()
boolean	isOptimizedDrawingEnabled() The JViewport overrides the default implementation of this method (in JComponent) to return false.
(package private) boolean	isPaintingOrigin() Returns true if scroll mode is a BACKINGSTORE_SCROLL_MODE to cause painting to originate from JViewport, or one of its ancestors.
private boolean	needsRepaintAfterBlit() Returns true if the component needs to be completely repainted after a blit and a paint is received.
void	paint(Graphics g) Depending on whether the backingStore is enabled, either paint the image through the backing store or paint just the recently exposed part, using the backing store to "blit" the remainder.
private void	paintViaBackingStore(Graphics g)
private void	paintViaBackingStore(Graphics g, Rectangle oClip)
private void	paintView(Graphics g) Called to paint the view, usually when blitPaint can not blit.
private void	paintViewDoubleBuffered(JComponent view, Graphics g, int clipX, int clipY, int clipW, int clipH, Image off)
protected String	paramString() Returns a string representation of this JViewport.
private int	positionAdjustment(int parentWidth, int childWidth, int childAt)
void	remove(Component child) Removes the Viewports one lightweight child.
void	removeChangeListener(ChangeListener l) Removes a ChangeListener from the list that's notified each time the views size, position, or the viewports extent size has changed.
void	repaint(long tm, int x, int y, int w, int h) Always repaint in the parents coordinate system to make sure only one paint is performed by the RepaintManager.
void	reshape(int x, int y, int w, int h) Sets the bounds of this viewport.
void	scrollRectToVisible(Rectangle contentRect) Scrolls the view so that Rectangle within the view becomes visible.
void	setBackingStoreEnabled(boolean enabled) Deprecated. As of Java 2 platform v1.3, replaced by setScrollMode().
void	setBorder(Border border) The viewport "scrolls" its child (called the "view") by the normal parent/child clipping (typically the view is moved in the opposite direction of the scroll).
void	setExtentSize(Dimension newExtent) Sets the size of the visible part of the view using view coordinates.
void	setScrollMode(int mode) Used to control the method of scrolling the viewport contents.
void	setUI(ViewportUI ui) Sets the L&F object that renders this component.
void	setView(Component view) Sets the JViewport's one lightweight child (view), which can be null.
void	setViewPosition(Point p) Sets the view coordinates that appear in the upper left hand corner of the viewport, does nothing if there's no view.
void	setViewSize(Dimension newSize) Sets the size of the view.
Dimension	toViewCoordinates(Dimension size) Converts a size in pixel coordinates to view coordinates.
Point	toViewCoordinates(Point p) Converts a point in pixel coordinates to view coordinates.
void	updateUI() Resets the UI property to a value from the current look and feel.
private void	validateView() Ascends the Viewport's parents stopping when a component is found that returns true to isValidateRoot.
private boolean	windowBlitPaint(Graphics g) Used when blitting.

Methods inherited from class javax.swing.JComponent

_paintImmediately, addAncestorListener, addNotify, addPropertyChangeListener, addPropertyChangeListener, addVetoableChangeListener, alwaysOnTop, checkIfChildObscuredBySibling, componentInputMapChanged, computeVisibleRect, computeVisibleRect, compWriteObjectNotify, contains, createToolTip, disable, enable, enableSerialization, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getActionForKeyStroke, getActionMap, getActionMap, getAlignmentX, getAlignmentY, getAncestorListeners, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getCreatedDoubleBuffer, getDebugGraphicsOptions, getDefaultLocale, getGraphics, getHeight, getInputMap, getInputMap, getInputMap, getInputVerifier, getListeners, getLocation, getManagingFocusBackwardTraversalKeys, getManagingFocusForwardTraversalKeys, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getTransferHandler, getVerifyInputWhenFocusTarget, getVetoableChangeListeners, getVisibleRect, getWidth, getWriteObjCounter, getX, getY, grabFocus, isDoubleBuffered, isLightweightComponent, isManagingFocus, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPaintingTile, isPreferredSizeSet, isRequestFocusEnabled, isValidateRoot, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, print, printAll, printBorder, printChildren, printComponent, processComponentKeyEvent, processKeyBinding, processKeyBindings, processKeyBindingsForAllComponents, processKeyEvent, processMouseMotionEvent, putClientProperty, rectangleIsObscured, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, removeVetoableChangeListener, repaint, requestDefaultFocus, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, resetKeyboardActions, revalidate, setActionMap, setAlignmentX, setAlignmentY, setAutoscrolls, setBackground, setCreatedDoubleBuffer, setDebugGraphicsOptions, setDefaultLocale, setDoubleBuffered, setEnabled, setFont, setForeground, setInputMap, setInputVerifier, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPaintingChild, setPreferredSize, setRequestFocusEnabled, setToolTipText, setTransferHandler, setUI, setVerifyInputWhenFocusTarget, setVisible, setWriteObjCounter, shouldDebugGraphics, superProcessMouseMotionEvent, unregisterKeyboardAction, update

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, applyComponentOrientation, areFocusTraversalKeysSet, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getContainerListeners, getFocusTraversalKeys, getFocusTraversalPolicy, getLayout, insets, invalidate, isAncestorOf, isFocusCycleRoot, isFocusCycleRoot, isFocusTraversalPolicySet, layout, list, list, locate, minimumSize, paintComponents, preferredSize, printComponents, processContainerEvent, processEvent, remove, removeAll, removeContainerListener, setFocusCycleRoot, setFocusTraversalKeys, setFocusTraversalPolicy, setLayout, transferFocusBackward, transferFocusDownCycle, validate, validateTree

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addMouseWheelListener, bounds, checkImage, checkImage, coalesceEvents, contains, createImage, createImage, createVolatileImage, createVolatileImage, disableEvents, dispatchEvent, enable, enableEvents, enableInputMethods, getBackground, getBounds, getColorModel, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphicsConfiguration, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocationOnScreen, getMouseListeners, getMouseMotionListeners, getMouseWheelListeners, getName, getParent, getPeer, getSize, getToolkit, getTreeLock, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isBackgroundSet, isCursorSet, isDisplayable, isEnabled, isFocusable, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processMouseEvent, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, repaint, repaint, repaint, resize, resize, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setFocusable, setFocusTraversalKeysEnabled, setIgnoreRepaint, setLocale, setLocation, setLocation, setName, setSize, setSize, show, show, size, toString, transferFocus, transferFocusUpCycle

Methods inherited from class java.lang.Object

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

Field Detail

uiClassID

private static final String uiClassID

See Also:

getUIClassID(), JComponent.readObject(java.io.ObjectInputStream), Constant Field Values

EnableWindowBlit

static final Object EnableWindowBlit

Property used to indicate window blitting should not be done.

isViewSizeSet

protected boolean isViewSizeSet

True when the viewport dimensions have been determined. The default is false.

lastPaintPosition

protected Point lastPaintPosition

The last viewPosition that we've painted, so we know how much of the backing store image is valid.

backingStore

protected boolean backingStore

Deprecated. As of Java 2 platform v1.3

True when this viewport is maintaining an offscreen image of its contents, so that some scrolling can take place using fast "bit-blit" operations instead of by accessing the view object to construct the display. The default is false.

See Also:

setScrollMode(int)

backingStoreImage

protected transient Image backingStoreImage

The view image used for a backing store.

scrollUnderway

protected boolean scrollUnderway

The scrollUnderway flag is used for components like JList. When the downarrow key is pressed on a JList and the selected cell is the last in the list, the scrollpane autoscrolls. Here, the old selected cell needs repainting and so we need a flag to make the viewport do the optimized painting only when there is an explicit call to setViewPosition(Point). When setBounds is called through other routes, the flag is off and the view repaints normally. Another approach would be to remove this from the JViewport class and have the JList manage this case by using setBackingStoreEnabled. The default is false.

viewListener

private ComponentListener viewListener

changeEvent

private transient ChangeEvent changeEvent

BLIT_SCROLL_MODE

public static final int BLIT_SCROLL_MODE

Use graphics.copyArea to implement scrolling. This is the fastest for most applications.

Since:

1.3

See Also:

setScrollMode(int), Constant Field Values

BACKINGSTORE_SCROLL_MODE

public static final int BACKINGSTORE_SCROLL_MODE

Draws viewport contents into an offscreen image. This was previously the default mode for JTable. This mode may offer advantages over "blit mode" in some cases, but it requires a large chunk of extra RAM.

Since:

1.3

See Also:

setScrollMode(int), Constant Field Values

SIMPLE_SCROLL_MODE

public static final int SIMPLE_SCROLL_MODE

This mode uses the very simple method of redrawing the entire contents of the scrollpane each time it is scrolled. This was the default behavior in Swing 1.0 and Swing 1.1. Either of the other two options will provide better performance in most cases.

Since:

1.3

See Also:

setScrollMode(int), Constant Field Values

scrollMode

private int scrollMode

Since:

1.3

See Also:

setScrollMode(int)

repaintAll

private transient boolean repaintAll

This is set to true in setViewPosition if doing a window blit and the viewport is obscured.

waitingForRepaint

private transient boolean waitingForRepaint

This is set to true in paint, if repaintAll is true and the clip rectangle does not match the bounds. If true, and scrolling happens the repaint manager is not cleared which then allows for the repaint previously invoked to succeed.

repaintTimer

private transient Timer repaintTimer

Instead of directly invoking repaint, a Timer is started and when it fires, repaint is invoked.

Constructor Detail

JViewport

public JViewport()

Creates a JViewport.

Method Detail

getUI

public ViewportUI getUI()

Returns the L&F object that renders this component.

Returns:

a ViewportUI object

setUI

public void setUI(ViewportUI ui)

Sets the L&F object that renders this component.

Parameters:

ui - the ViewportUI L&F object

See Also:

UIDefaults.getUI(javax.swing.JComponent)

updateUI

public void updateUI()

Resets the UI property to a value from the current look and feel.

Overrides:

updateUI in class JComponent

See Also:

JComponent.updateUI()

getUIClassID

public String getUIClassID()

Returns a string that specifies the name of the L&F class that renders this component.

Overrides:

getUIClassID in class JComponent

Returns:

the string "ViewportUI"

See Also:

JComponent.getUIClassID(), UIDefaults.getUI(javax.swing.JComponent)

addImpl

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

Sets the JViewport's one lightweight child, which can be null. (Since there is only one child which occupies the entire viewport, the constraints and index arguments are ignored.)

Overrides:

addImpl in class Container

Parameters:

child - the lightweight child of the viewport

constraints - the constraints to be respected

index - the index

See Also:

setView(java.awt.Component)

remove

public void remove(Component child)

Removes the Viewports one lightweight child.

Overrides:

remove in class Container

Parameters:

child - the component to be removed

See Also:

setView(java.awt.Component)

scrollRectToVisible

public void scrollRectToVisible(Rectangle contentRect)

Scrolls the view so that Rectangle within the view becomes visible.

This attempts to validate the view before scrolling if the view is currently not valid - isValid returns false. To avoid excessive validation when the containment hierarchy is being created this will not validate if one of the ancestors does not have a peer, or there is no validate root ancestor, or one of the ancestors is not a Window or Applet.

Note that this method will not scroll outside of the valid viewport; for example, if contentRect is larger than the viewport, scrolling will be confined to the viewport's bounds.

Overrides:

scrollRectToVisible in class JComponent

Parameters:

contentRect - the Rectangle to display

See Also:

JComponent.isValidateRoot(), Component.isValid(), Component.getPeer()

validateView

private void validateView()

Ascends the Viewport's parents stopping when a component is found that returns true to isValidateRoot. If all the Component's parents are visible, validate will then be invoked on it. The RepaintManager is then invoked with removeInvalidComponent. This is the synchronous version of a revalidate.

positionAdjustment

private int positionAdjustment(int parentWidth,
                               int childWidth,
                               int childAt)

setBorder

public final void setBorder(Border border)

The viewport "scrolls" its child (called the "view") by the normal parent/child clipping (typically the view is moved in the opposite direction of the scroll). A non-null border, or non-zero insets, isn't supported, to prevent the geometry of this component from becoming complex enough to inhibit subclassing. To create a JViewport with a border, add it to a JPanel that has a border.

Note: If border is non-null, this method will throw an exception as borders are not supported on a JViewPort.

Overrides:

setBorder in class JComponent

Parameters:

border - the Border to set

Throws:

IllegalArgumentException - this method is not implemented

See Also:

Border, CompoundBorder

getInsets

public final Insets getInsets()

Returns the insets (border) dimensions as (0,0,0,0), since borders are not supported on a JViewport.

Overrides:

getInsets in class JComponent

Returns:

a Rectange of zero dimension and zero origin

See Also:

setBorder(javax.swing.border.Border)

getInsets

public final Insets getInsets(Insets insets)

Returns an Insets object containing this JViewports inset values. The passed-in Insets object will be reinitialized, and all existing values within this object are overwritten.

Overrides:

getInsets in class JComponent

Parameters:

insets - the Insets object which can be reused

Returns:

this viewports inset values

See Also:

getInsets()

getBackingStoreGraphics

private Graphics getBackingStoreGraphics(Graphics g)

paintViaBackingStore

private void paintViaBackingStore(Graphics g)

paintViaBackingStore

private void paintViaBackingStore(Graphics g,
                                  Rectangle oClip)

isOptimizedDrawingEnabled

public boolean isOptimizedDrawingEnabled()

The JViewport overrides the default implementation of this method (in JComponent) to return false. This ensures that the drawing machinery will call the Viewport's paint implementation rather than messaging the JViewport's children directly.

Overrides:

isOptimizedDrawingEnabled in class JComponent

Returns:

false

isPaintingOrigin

boolean isPaintingOrigin()

Returns true if scroll mode is a BACKINGSTORE_SCROLL_MODE to cause painting to originate from JViewport, or one of its ancestors. Otherwise returns false.

Overrides:

isPaintingOrigin in class JComponent

Returns:

true if if scroll mode is a BACKINGSTORE_SCROLL_MODE.

See Also:

JComponent.isPaintingOrigin()

getViewLocation

private Point getViewLocation()

Only used by the paint method below.

paint

public void paint(Graphics g)

Depending on whether the backingStore is enabled, either paint the image through the backing store or paint just the recently exposed part, using the backing store to "blit" the remainder.

The term "blit" is the pronounced version of the PDP-10 BLT (BLock Transfer) instruction, which copied a block of bits. (In case you were curious.)

Overrides:

paint in class JComponent

Parameters:

g - the Graphics context within which to paint

See Also:

JComponent.paintComponent(java.awt.Graphics), JComponent.paintBorder(java.awt.Graphics), JComponent.paintChildren(java.awt.Graphics), JComponent.getComponentGraphics(java.awt.Graphics), JComponent.repaint(long, int, int, int, int)

reshape

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

Sets the bounds of this viewport. If the viewport's width or height has changed, fire a StateChanged event.

Overrides:

reshape in class JComponent

Parameters:

x - left edge of the origin

y - top edge of the origin

w - width in pixels

h - height in pixels

See Also:

JComponent.reshape(int, int, int, int)

setScrollMode

public void setScrollMode(int mode)

Used to control the method of scrolling the viewport contents. You may want to change this mode to get maximum performance for your use case.

Parameters:

mode - one of the following values:

• JViewport.BLIT_SCROLL_MODE
• JViewport.BACKINGSTORE_SCROLL_MODE
• JViewport.SIMPLE_SCROLL_MODE

Since:

1.3

See Also:

BLIT_SCROLL_MODE, BACKINGSTORE_SCROLL_MODE, SIMPLE_SCROLL_MODE

getScrollMode

public int getScrollMode()

Returns the current scrolling mode.

Returns:

the scrollMode property

Since:

1.3

See Also:

setScrollMode(int)

isBackingStoreEnabled

public boolean isBackingStoreEnabled()

Deprecated. As of Java 2 platform v1.3, replaced by getScrollMode().

Returns true if this viewport is maintaining an offscreen image of its contents.

Returns:

true if scrollMode is BACKINGSTORE_SCROLL_MODE

setBackingStoreEnabled

public void setBackingStoreEnabled(boolean enabled)

Deprecated. As of Java 2 platform v1.3, replaced by setScrollMode().

If true if this viewport will maintain an offscreen image of its contents. The image is used to reduce the cost of small one dimensional changes to the viewPosition. Rather than repainting the entire viewport we use Graphics.copyArea to effect some of the scroll.

Parameters:

enabled - if true, maintain an offscreen backing store

isBlitting

private final boolean isBlitting()

getView

public Component getView()

Returns the JViewport's one child or null.

Returns:

the viewports child, or null if none exists

See Also:

setView(java.awt.Component)

setView

public void setView(Component view)

Sets the JViewport's one lightweight child (view), which can be null.

Parameters:

view - the viewport's new lightweight child

See Also:

getView()

getViewSize

public Dimension getViewSize()

If the view's size hasn't been explicitly set, return the preferred size, otherwise return the view's current size. If there is no view, return 0,0.

Returns:

a Dimension object specifying the size of the view

setViewSize

public void setViewSize(Dimension newSize)

Sets the size of the view. A state changed event will be fired.

Parameters:

newSize - a Dimension object specifying the new size of the view

getViewPosition

public Point getViewPosition()

Returns the view coordinates that appear in the upper left hand corner of the viewport, or 0,0 if there's no view.

Returns:

a Point object giving the upper left coordinates

setViewPosition

public void setViewPosition(Point p)

Sets the view coordinates that appear in the upper left hand corner of the viewport, does nothing if there's no view.

Parameters:

p - a Point object giving the upper left coordinates

getViewRect

public Rectangle getViewRect()

Returns a rectangle whose origin is getViewPosition and size is getExtentSize. This is the visible part of the view, in view coordinates.

Returns:

a Rectangle giving the visible part of the view using view coordinates.

computeBlit

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

Computes the parameters for a blit where the backing store image currently contains oldLoc in the upper left hand corner and we're scrolling to newLoc. The parameters are modified to return the values required for the blit.

Parameters:

dx - the horizontal delta

dy - the vertical delta

blitFrom - the Point we're blitting from

blitTo - the Point we're blitting to

blitSize - the Dimension of the area to blit

blitPaint - the area to blit

Returns:

true if the parameters are modified and we're ready to blit; false otherwise

getExtentSize

public Dimension getExtentSize()

Returns the size of the visible part of the view in view coordinates.

Returns:

a Dimension object giving the size of the view

toViewCoordinates

public Dimension toViewCoordinates(Dimension size)

Converts a size in pixel coordinates to view coordinates. Subclasses of viewport that support "logical coordinates" will override this method.

Parameters:

size - a Dimension object using pixel coordinates

Returns:

a Dimension object converted to view coordinates

toViewCoordinates

public Point toViewCoordinates(Point p)

Converts a point in pixel coordinates to view coordinates. Subclasses of viewport that support "logical coordinates" will override this method.

Parameters:

p - a Point object using pixel coordinates

Returns:

a Point object converted to view coordinates

setExtentSize

public void setExtentSize(Dimension newExtent)

Sets the size of the visible part of the view using view coordinates.

Parameters:

newExtent - a Dimension object specifying the size of the view

createViewListener

protected JViewport.ViewListener createViewListener()

Creates a listener for the view.

Returns:

a ViewListener

createLayoutManager

protected LayoutManager createLayoutManager()

Subclassers can override this to install a different layout manager (or null) in the constructor. Returns a new ViewportLayout object.

Returns:

a LayoutManager

addChangeListener

public void addChangeListener(ChangeListener l)

Adds a ChangeListener to the list that is notified each time the view's size, position, or the viewport's extent size has changed.

Parameters:

l - the ChangeListener to add

See Also:

removeChangeListener(javax.swing.event.ChangeListener), setViewPosition(java.awt.Point), setViewSize(java.awt.Dimension), setExtentSize(java.awt.Dimension)

removeChangeListener

public void removeChangeListener(ChangeListener l)

Removes a ChangeListener from the list that's notified each time the views size, position, or the viewports extent size has changed.

Parameters:

l - the ChangeListener to remove

See Also:

addChangeListener(javax.swing.event.ChangeListener)

getChangeListeners

public ChangeListener[] getChangeListeners()

Returns an array of all the ChangeListeners added to this JViewport with addChangeListener().

Returns:

all of the ChangeListeners added or an empty array if no listeners have been added

Since:

1.4

fireStateChanged

protected void fireStateChanged()

Notifies all ChangeListeners when the views size, position, or the viewports extent size has changed.

See Also:

addChangeListener(javax.swing.event.ChangeListener), removeChangeListener(javax.swing.event.ChangeListener), EventListenerList

repaint

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

Always repaint in the parents coordinate system to make sure only one paint is performed by the RepaintManager.

Overrides:

repaint in class JComponent

Parameters:

tm - maximum time in milliseconds before update

x - the x coordinate (pixels over from left)

y - the y coordinate (pixels down from top)

w - the width

h - the height

See Also:

Component.update(java.awt.Graphics)

paramString

protected String paramString()

Returns a string representation of this JViewport. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

Overrides:

paramString in class JComponent

Returns:

a string representation of this JViewport

firePropertyChange

protected void firePropertyChange(String propertyName,
                                  Object oldValue,
                                  Object newValue)

Notifies listeners of a property change. This is subclassed to update the windowBlit property. (The putClientProperty property is final).

Overrides:

firePropertyChange in class JComponent

Parameters:

propertyName - a string containing the property name

oldValue - the old value of the property

newValue - the new value of the property

See Also:

PropertyChangeSupport

needsRepaintAfterBlit

private boolean needsRepaintAfterBlit()

Returns true if the component needs to be completely repainted after a blit and a paint is received.

createRepaintTimer

private Timer createRepaintTimer()

flushViewDirtyRegion

private void flushViewDirtyRegion(Graphics g)

If the repaint manager has a dirty region for the view, the view is asked to paint.

Parameters:

g - the Graphics context within which to paint

windowBlitPaint

private boolean windowBlitPaint(Graphics g)

Used when blitting.

Parameters:

g - the Graphics context within which to paint

Returns:

true if blitting succeeded; otherwise false

blitDoubleBuffered

private void blitDoubleBuffered(JComponent view,
                                Graphics g,
                                int clipX,
                                int clipY,
                                int clipW,
                                int clipH,
                                int blitFromX,
                                int blitFromY,
                                int blitToX,
                                int blitToY,
                                int blitW,
                                int blitH,
                                Image off)

paintView

private void paintView(Graphics g)

Called to paint the view, usually when blitPaint can not blit.

Parameters:

g - the Graphics context within which to paint

paintViewDoubleBuffered

private void paintViewDoubleBuffered(JComponent view,
                                     Graphics g,
                                     int clipX,
                                     int clipY,
                                     int clipW,
                                     int clipH,
                                     Image off)

blitWindowGraphics

private void blitWindowGraphics(int x,
                                int y,
                                int w,
                                int h,
                                int ox,
                                int oy)

Blits the parent windows graphics from the given region offset to ox, oy.

canUseWindowBlitter

private boolean canUseWindowBlitter()

Returns true if the viewport is not obscured by one of its ancestors, or its ancestors children and if the viewport is showing. Blitting when the view isn't showing will work, or rather copyArea will work, but will not produce the expected behavior.

getAccessibleContext

public javax.accessibility.AccessibleContext getAccessibleContext()

Gets the AccessibleContext associated with this JViewport. For viewports, the AccessibleContext takes the form of an AccessibleJViewport. A new AccessibleJViewport instance is created if necessary.

Specified by:

getAccessibleContext in interface javax.accessibility.Accessible

Overrides:

getAccessibleContext in class JComponent

Returns:

an AccessibleJViewport that serves as the AccessibleContext of this JViewport