* 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: *
JComponents,
* if they aren't, stop and repaint the whole viewport.
* Window's graphics and
* do a copyArea on the scrolled region.
* 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: Swing is not thread safe. For more * information see Swing's Threading * Policy. *
* 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™
* has been added to the java.beans package.
* Please see {@link java.beans.XMLEncoder}.
*
* @author Hans Muller
* @author Philip Milne
* @see JScrollPane
* @since 1.2
*/
@SuppressWarnings("serial") // Same-version serialization only
public class JViewport extends JComponent implements Accessible
{
/**
* @see #getUIClassID
* @see #readObject
*/
private static final String uiClassID = "ViewportUI";
/** Property used to indicate window blitting should not be done.
*/
static final Object EnableWindowBlit = "EnableWindowBlit";
/**
* True when the viewport dimensions have been determined.
* The default is false.
*/
protected boolean isViewSizeSet = false;
/**
* The last viewPosition that we've painted, so we know how
* much of the backing store image is valid.
*/
protected Point lastPaintPosition = null;
/**
* 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.
*
* @deprecated As of Java 2 platform v1.3
* @see #setScrollMode
*/
@Deprecated
protected boolean backingStore = false;
/** The view image used for a backing store. */
transient protected Image backingStoreImage = null;
/**
* 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.
*/
protected boolean scrollUnderway = false;
/*
* Listener that is notified each time the view changes size.
*/
private ComponentListener viewListener = null;
/* Only one ChangeEvent is needed per
* JViewport instance since the
* event's only (read-only) state is the source property. The source
* of events generated here is always "this".
*/
private transient ChangeEvent changeEvent = null;
/**
* Use graphics.copyArea to implement scrolling.
* This is the fastest for most applications.
*
* @see #setScrollMode
* @since 1.3
*/
public static final int BLIT_SCROLL_MODE = 1;
/**
* 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.
*
* @see #setScrollMode
* @since 1.3
*/
public static final int BACKINGSTORE_SCROLL_MODE = 2;
/**
* 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.
*
* @see #setScrollMode
* @since 1.3
*/
public static final int SIMPLE_SCROLL_MODE = 0;
/**
* @see #setScrollMode
* @since 1.3
*/
private int scrollMode = BLIT_SCROLL_MODE;
//
// Window blitting:
//
// As mentioned in the javadoc when using windowBlit a paint event
// will be generated by the system if copyArea copies a non-visible
// portion of the view (in other words, it copies garbage). We are
// not guaranteed to receive the paint event before other mouse events,
// so we can not be sure we haven't already copied garbage a bunch of
// times to different parts of the view. For that reason when a blit
// happens and the Component is obscured (the check for obscurity
// is not supported on all platforms and is checked via ComponentPeer
// methods) the ivar repaintAll is set to true. When paint is received
// if repaintAll is true (we previously did a blit) it is set to
// false, and if the clip region is smaller than the viewport
// waitingForRepaint is set to true and a timer is started. When
// the timer fires if waitingForRepaint is true, repaint is invoked.
// In the mean time, if the view is asked to scroll and waitingForRepaint
// is true, a blit will not happen, instead the non-backing store case
// of scrolling will happen, which will reset waitingForRepaint.
// waitingForRepaint is set to false in paint when the clip rect is
// bigger (or equal) to the size of the viewport.
// A Timer is used instead of just a repaint as it appeared to offer
// better performance.
/**
* This is set to true in setViewPosition
* if doing a window blit and the viewport is obscured.
*/
private transient boolean repaintAll;
/**
* 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.
*/
private transient boolean waitingForRepaint;
/**
* Instead of directly invoking repaint, a Timer
* is started and when it fires, repaint is invoked.
*/
private transient Timer repaintTimer;
/**
* Set to true in paintView when paint is invoked.
*/
private transient boolean inBlitPaint;
/**
* Whether or not a valid view has been installed.
*/
private boolean hasHadValidView;
/**
* When view is changed we have to synchronize scrollbar values
* with viewport (see the BasicScrollPaneUI#syncScrollPaneWithViewport method).
* This flag allows to invoke that method while ScrollPaneLayout#layoutContainer
* is running.
*/
private boolean viewChanged;
/** Creates a JViewport. */
public JViewport() {
super();
setLayout(createLayoutManager());
setOpaque(true);
updateUI();
setInheritsPopupMenu(true);
}
/**
* Returns the L&F object that renders this component.
*
* @return a ViewportUI object
* @since 1.3
*/
public ViewportUI getUI() {
return (ViewportUI)ui;
}
/**
* Sets the L&F object that renders this component.
*
* @param ui the ViewportUI L&F object
* @see UIDefaults#getUI
* @beaninfo
* bound: true
* hidden: true
* attribute: visualUpdate true
* description: The UI object that implements the Component's LookAndFeel.
* @since 1.3
*/
public void setUI(ViewportUI ui) {
super.setUI(ui);
}
/**
* Resets the UI property to a value from the current look and feel.
*
* @see JComponent#updateUI
*/
public void updateUI() {
setUI((ViewportUI)UIManager.getUI(this));
}
/**
* Returns a string that specifies the name of the L&F class
* that renders this component.
*
* @return the string "ViewportUI"
*
* @see JComponent#getUIClassID
* @see UIDefaults#getUI
*/
public String getUIClassID() {
return uiClassID;
}
/**
* 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.)
*
* @param child the lightweight child of the viewport
* @param constraints the constraints to be respected
* @param index the index
* @see #setView
*/
protected void addImpl(Component child, Object constraints, int index) {
setView(child);
}
/**
* Removes the Viewports one lightweight child.
*
* @see #setView
*/
public void remove(Component child) {
child.removeComponentListener(viewListener);
super.remove(child);
}
/**
* 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.
*
* @param contentRect the Rectangle to display
* @see JComponent#isValidateRoot
* @see java.awt.Component#isValid
*/
public void scrollRectToVisible(Rectangle contentRect) {
Component view = getView();
if (view == null) {
return;
} else {
if (!view.isValid()) {
// If the view is not valid, validate. scrollRectToVisible
// may fail if the view is not valid first, contentRect
// could be bigger than invalid size.
validateView();
}
int dx, dy;
dx = positionAdjustment(getWidth(), contentRect.width, contentRect.x);
dy = positionAdjustment(getHeight(), contentRect.height, contentRect.y);
if (dx != 0 || dy != 0) {
Point viewPosition = getViewPosition();
Dimension viewSize = view.getSize();
int startX = viewPosition.x;
int startY = viewPosition.y;
Dimension extent = getExtentSize();
viewPosition.x -= dx;
viewPosition.y -= dy;
// Only constrain the location if the view is valid. If the
// the view isn't valid, it typically indicates the view
// isn't visible yet and most likely has a bogus size as will
// we, and therefore we shouldn't constrain the scrolling
if (view.isValid()) {
if (getParent().getComponentOrientation().isLeftToRight()) {
if (viewPosition.x + extent.width > viewSize.width) {
viewPosition.x = Math.max(0, viewSize.width - extent.width);
} else if (viewPosition.x < 0) {
viewPosition.x = 0;
}
} else {
if (extent.width > viewSize.width) {
viewPosition.x = viewSize.width - extent.width;
} else {
viewPosition.x = Math.max(0, Math.min(viewSize.width - extent.width, viewPosition.x));
}
}
if (viewPosition.y + extent.height > viewSize.height) {
viewPosition.y = Math.max(0, viewSize.height -
extent.height);
}
else if (viewPosition.y < 0) {
viewPosition.y = 0;
}
}
if (viewPosition.x != startX || viewPosition.y != startY) {
setViewPosition(viewPosition);
// NOTE: How JViewport currently works with the
// backing store is not foolproof. The sequence of
// events when setViewPosition
// (scrollRectToVisible) is called is to reset the
// views bounds, which causes a repaint on the
// visible region and sets an ivar indicating
// scrolling (scrollUnderway). When
// JViewport.paint is invoked if scrollUnderway is
// true, the backing store is blitted. This fails
// if between the time setViewPosition is invoked
// and paint is received another repaint is queued
// indicating part of the view is invalid. There
// is no way for JViewport to notice another
// repaint has occurred and it ends up blitting
// what is now a dirty region and the repaint is
// never delivered.
// It just so happens JTable encounters this
// behavior by way of scrollRectToVisible, for
// this reason scrollUnderway is set to false
// here, which effectively disables the backing
// store.
scrollUnderway = false;
}
}
}
}
/**
* 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.
*/
private void validateView() {
Component validateRoot = SwingUtilities.getValidateRoot(this, false);
if (validateRoot == null) {
return;
}
// Validate the root.
validateRoot.validate();
// And let the RepaintManager it does not have to validate from
// validateRoot anymore.
RepaintManager rm = RepaintManager.currentManager(this);
if (rm != null) {
rm.removeInvalidComponent((JComponent)validateRoot);
}
}
/* Used by the scrollRectToVisible method to determine the
* proper direction and amount to move by. The integer variables are named
* width, but this method is applicable to height also. The code assumes that
* parentWidth/childWidth are positive and childAt can be negative.
*/
private int positionAdjustment(int parentWidth, int childWidth, int childAt) {
// +-----+
// | --- | No Change
// +-----+
if (childAt >= 0 && childWidth + childAt <= parentWidth) {
return 0;
}
// +-----+
// --------- No Change
// +-----+
if (childAt <= 0 && childWidth + childAt >= parentWidth) {
return 0;
}
// +-----+ +-----+
// | ---- -> | ----|
// +-----+ +-----+
if (childAt > 0 && childWidth <= parentWidth) {
return -childAt + parentWidth - childWidth;
}
// +-----+ +-----+
// | -------- -> |--------
// +-----+ +-----+
if (childAt >= 0 && childWidth >= parentWidth) {
return -childAt;
}
// +-----+ +-----+
// ---- | -> |---- |
// +-----+ +-----+
if (childAt <= 0 && childWidth <= parentWidth) {
return -childAt;
}
// +-----+ +-----+
//-------- | -> --------|
// +-----+ +-----+
if (childAt < 0 && childWidth >= parentWidth) {
return -childAt + parentWidth - childWidth;
}
return 0;
}
/**
* 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.
*
* @param border the Border to set
* @exception IllegalArgumentException this method is not implemented
*/
public final void setBorder(Border border) {
if (border != null) {
throw new IllegalArgumentException("JViewport.setBorder() not supported");
}
}
/**
* Returns the insets (border) dimensions as (0,0,0,0), since borders
* are not supported on a JViewport.
*
* @return a Rectangle of zero dimension and zero origin
* @see #setBorder
*/
public final Insets getInsets() {
return new Insets(0, 0, 0, 0);
}
/**
* 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.
*
* @param insets the Insets object which can be reused
* @return this viewports inset values
* @see #getInsets
* @beaninfo
* expert: true
*/
public final Insets getInsets(Insets insets) {
insets.left = insets.top = insets.right = insets.bottom = 0;
return insets;
}
private Graphics getBackingStoreGraphics(Graphics g) {
Graphics bsg = backingStoreImage.getGraphics();
bsg.setColor(g.getColor());
bsg.setFont(g.getFont());
bsg.setClip(g.getClipBounds());
return bsg;
}
private void paintViaBackingStore(Graphics g) {
Graphics bsg = getBackingStoreGraphics(g);
try {
super.paint(bsg);
g.drawImage(backingStoreImage, 0, 0, this);
} finally {
bsg.dispose();
}
}
private void paintViaBackingStore(Graphics g, Rectangle oClip) {
Graphics bsg = getBackingStoreGraphics(g);
try {
super.paint(bsg);
g.setClip(oClip);
g.drawImage(backingStoreImage, 0, 0, this);
} finally {
bsg.dispose();
}
}
/**
* 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.
*
* @return false
*/
public boolean isOptimizedDrawingEnabled() {
return false;
}
/**
* Returns true if scroll mode is a {@code BACKINGSTORE_SCROLL_MODE} to cause
* painting to originate from {@code JViewport}, or one of its
* ancestors. Otherwise returns {@code false}.
*
* @return true if scroll mode is a {@code BACKINGSTORE_SCROLL_MODE}.
* @see JComponent#isPaintingOrigin()
*/
protected boolean isPaintingOrigin() {
return scrollMode == BACKINGSTORE_SCROLL_MODE;
}
/**
* Only used by the paint method below.
*/
private Point getViewLocation() {
Component view = getView();
if (view != null) {
return view.getLocation();
}
else {
return new Point(0,0);
}
}
/**
* 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.) ** * @param g the
Graphics context within which to paint
*/
public void paint(Graphics g)
{
int width = getWidth();
int height = getHeight();
if ((width <= 0) || (height <= 0)) {
return;
}
if (inBlitPaint) {
// We invoked paint as part of copyArea cleanup, let it through.
super.paint(g);
return;
}
if (repaintAll) {
repaintAll = false;
Rectangle clipB = g.getClipBounds();
if (clipB.width < getWidth() ||
clipB.height < getHeight()) {
waitingForRepaint = true;
if (repaintTimer == null) {
repaintTimer = createRepaintTimer();
}
repaintTimer.stop();
repaintTimer.start();
// We really don't need to paint, a future repaint will
// take care of it, but if we don't we get an ugly flicker.
}
else {
if (repaintTimer != null) {
repaintTimer.stop();
}
waitingForRepaint = false;
}
}
else if (waitingForRepaint) {
// Need a complete repaint before resetting waitingForRepaint
Rectangle clipB = g.getClipBounds();
if (clipB.width >= getWidth() &&
clipB.height >= getHeight()) {
waitingForRepaint = false;
repaintTimer.stop();
}
}
if (!backingStore || isBlitting() || getView() == null) {
super.paint(g);
lastPaintPosition = getViewLocation();
return;
}
// If the view is smaller than the viewport and we are not opaque
// (that is, we won't paint our background), we should set the
// clip. Otherwise, as the bounds of the view vary, we will
// blit garbage into the exposed areas.
Rectangle viewBounds = getView().getBounds();
if (!isOpaque()) {
g.clipRect(0, 0, viewBounds.width, viewBounds.height);
}
if (backingStoreImage == null) {
// Backing store is enabled but this is the first call to paint.
// Create the backing store, paint it and then copy to g.
// The backing store image will be created with the size of
// the viewport. We must make sure the clip region is the
// same size, otherwise when scrolling the backing image
// the region outside of the clipped region will not be painted,
// and result in empty areas.
backingStoreImage = createImage(width, height);
Rectangle clip = g.getClipBounds();
if (clip.width != width || clip.height != height) {
if (!isOpaque()) {
g.setClip(0, 0, Math.min(viewBounds.width, width),
Math.min(viewBounds.height, height));
}
else {
g.setClip(0, 0, width, height);
}
paintViaBackingStore(g, clip);
}
else {
paintViaBackingStore(g);
}
}
else {
if (!scrollUnderway || lastPaintPosition.equals(getViewLocation())) {
// No scrolling happened: repaint required area via backing store.
paintViaBackingStore(g);
} else {
// The image was scrolled. Manipulate the backing store and flush it to g.
Point blitFrom = new Point();
Point blitTo = new Point();
Dimension blitSize = new Dimension();
Rectangle blitPaint = new Rectangle();
Point newLocation = getViewLocation();
int dx = newLocation.x - lastPaintPosition.x;
int dy = newLocation.y - lastPaintPosition.y;
boolean canBlit = computeBlit(dx, dy, blitFrom, blitTo, blitSize, blitPaint);
if (!canBlit) {
// The image was either moved diagonally or
// moved by more than the image size: paint normally.
paintViaBackingStore(g);
} else {
int bdx = blitTo.x - blitFrom.x;
int bdy = blitTo.y - blitFrom.y;
// Move the relevant part of the backing store.
Rectangle clip = g.getClipBounds();
// We don't want to inherit the clip region when copying
// bits, if it is inherited it will result in not moving
// all of the image resulting in garbage appearing on
// the screen.
g.setClip(0, 0, width, height);
Graphics bsg = getBackingStoreGraphics(g);
try {
bsg.copyArea(blitFrom.x, blitFrom.y, blitSize.width, blitSize.height, bdx, bdy);
g.setClip(clip.x, clip.y, clip.width, clip.height);
// Paint the rest of the view; the part that has just been exposed.
Rectangle r = viewBounds.intersection(blitPaint);
bsg.setClip(r);
super.paint(bsg);
// Copy whole of the backing store to g.
g.drawImage(backingStoreImage, 0, 0, this);
} finally {
bsg.dispose();
}
}
}
}
lastPaintPosition = getViewLocation();
scrollUnderway = false;
}
/**
* Sets the bounds of this viewport. If the viewport's width
* or height has changed, fire a StateChanged event.
*
* @param x left edge of the origin
* @param y top edge of the origin
* @param w width in pixels
* @param h height in pixels
*
* @see JComponent#reshape(int, int, int, int)
*/
@SuppressWarnings("deprecation")
public void reshape(int x, int y, int w, int h) {
boolean sizeChanged = (getWidth() != w) || (getHeight() != h);
if (sizeChanged) {
backingStoreImage = null;
}
super.reshape(x, y, w, h);
if (sizeChanged || viewChanged) {
viewChanged = false;
fireStateChanged();
}
}
/**
* 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.
*
* @param mode one of the following values:
* scrollMode property
* @see #setScrollMode
* @since 1.3
*/
public int getScrollMode() {
return scrollMode;
}
/**
* Returns true if this viewport is maintaining
* an offscreen image of its contents.
*
* @return true if scrollMode is
* BACKINGSTORE_SCROLL_MODE
*
* @deprecated As of Java 2 platform v1.3, replaced by
* getScrollMode().
*/
@Deprecated
public boolean isBackingStoreEnabled() {
return scrollMode == BACKINGSTORE_SCROLL_MODE;
}
/**
* 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.
*
* @param enabled if true, maintain an offscreen backing store
*
* @deprecated As of Java 2 platform v1.3, replaced by
* setScrollMode().
*/
@Deprecated
public void setBackingStoreEnabled(boolean enabled) {
if (enabled) {
setScrollMode(BACKINGSTORE_SCROLL_MODE);
} else {
setScrollMode(BLIT_SCROLL_MODE);
}
}
private boolean isBlitting() {
Component view = getView();
return (scrollMode == BLIT_SCROLL_MODE) &&
(view instanceof JComponent) && view.isOpaque();
}
/**
* Returns the JViewport's one child or null.
*
* @return the viewports child, or null if none exists
*
* @see #setView
*/
public Component getView() {
return (getComponentCount() > 0) ? getComponent(0) : null;
}
/**
* Sets the JViewport's one lightweight child
* (view), which can be null.
*
* @param view the viewport's new lightweight child
*
* @see #getView
*/
public void setView(Component view) {
/* Remove the viewport's existing children, if any.
* Note that removeAll() isn't used here because it
* doesn't call remove() (which JViewport overrides).
*/
int n = getComponentCount();
for(int i = n - 1; i >= 0; i--) {
remove(getComponent(i));
}
isViewSizeSet = false;
if (view != null) {
super.addImpl(view, null, -1);
viewListener = createViewListener();
view.addComponentListener(viewListener);
}
if (hasHadValidView) {
// Only fire a change if a view has been installed.
fireStateChanged();
}
else if (view != null) {
hasHadValidView = true;
}
viewChanged = true;
revalidate();
repaint();
}
/**
* 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.
*
* @return a Dimension object specifying the size of the view
*/
public Dimension getViewSize() {
Component view = getView();
if (view == null) {
return new Dimension(0,0);
}
else if (isViewSizeSet) {
return view.getSize();
}
else {
return view.getPreferredSize();
}
}
/**
* Sets the size of the view. A state changed event will be fired.
*
* @param newSize a Dimension object specifying the new
* size of the view
*/
public void setViewSize(Dimension newSize) {
Component view = getView();
if (view != null) {
Dimension oldSize = view.getSize();
if (!newSize.equals(oldSize)) {
// scrollUnderway will be true if this is invoked as the
// result of a validate and setViewPosition was previously
// invoked.
scrollUnderway = false;
view.setSize(newSize);
isViewSizeSet = true;
fireStateChanged();
}
}
}
/**
* Returns the view coordinates that appear in the upper left
* hand corner of the viewport, or 0,0 if there's no view.
*
* @return a Point object giving the upper left coordinates
*/
public Point getViewPosition() {
Component view = getView();
if (view != null) {
Point p = view.getLocation();
p.x = -p.x;
p.y = -p.y;
return p;
}
else {
return new Point(0,0);
}
}
/**
* Sets the view coordinates that appear in the upper left
* hand corner of the viewport, does nothing if there's no view.
*
* @param p a Point object giving the upper left coordinates
*/
public void setViewPosition(Point p)
{
Component view = getView();
if (view == null) {
return;
}
int oldX, oldY, x = p.x, y = p.y;
/* Collect the old x,y values for the views location
* and do the song and dance to avoid allocating
* a Rectangle object if we don't have to.
*/
if (view instanceof JComponent) {
JComponent c = (JComponent)view;
oldX = c.getX();
oldY = c.getY();
}
else {
Rectangle r = view.getBounds();
oldX = r.x;
oldY = r.y;
}
/* The view scrolls in the opposite direction to mouse
* movement.
*/
int newX = -x;
int newY = -y;
if ((oldX != newX) || (oldY != newY)) {
if (!waitingForRepaint && isBlitting() && canUseWindowBlitter()) {
RepaintManager rm = RepaintManager.currentManager(this);
// The cast to JComponent will work, if view is not
// a JComponent, isBlitting will return false.
JComponent jview = (JComponent)view;
Rectangle dirty = rm.getDirtyRegion(jview);
if (dirty == null || !dirty.contains(jview.getVisibleRect())) {
rm.beginPaint();
try {
Graphics g = JComponent.safelyGetGraphics(this);
flushViewDirtyRegion(g, dirty);
view.setLocation(newX, newY);
Rectangle r = new Rectangle(
0, 0, getWidth(), Math.min(getHeight(), jview.getHeight()));
g.setClip(r);
// Repaint the complete component if the blit succeeded
// and needsRepaintAfterBlit returns true.
repaintAll = (windowBlitPaint(g) &&
needsRepaintAfterBlit());
g.dispose();
rm.notifyRepaintPerformed(this, r.x, r.y, r.width, r.height);
rm.markCompletelyClean((JComponent)getParent());
rm.markCompletelyClean(this);
rm.markCompletelyClean(jview);
} finally {
rm.endPaint();
}
}
else {
// The visible region is dirty, no point in doing copyArea
view.setLocation(newX, newY);
repaintAll = false;
}
}
else {
scrollUnderway = true;
// This calls setBounds(), and then repaint().
view.setLocation(newX, newY);
repaintAll = false;
}
// we must validate the hierarchy to not break the hw/lw mixing
revalidate();
fireStateChanged();
}
}
/**
* Returns a rectangle whose origin is getViewPosition
* and size is getExtentSize.
* This is the visible part of the view, in view coordinates.
*
* @return a Rectangle giving the visible part of
* the view using view coordinates.
*/
public Rectangle getViewRect() {
return new Rectangle(getViewPosition(), getExtentSize());
}
/**
* 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.
*
* @param dx the horizontal delta
* @param dy the vertical delta
* @param blitFrom the Point we're blitting from
* @param blitTo the Point we're blitting to
* @param blitSize the Dimension of the area to blit
* @param blitPaint the area to blit
* @return true if the parameters are modified and we're ready to blit;
* false otherwise
*/
protected boolean computeBlit(
int dx,
int dy,
Point blitFrom,
Point blitTo,
Dimension blitSize,
Rectangle blitPaint)
{
int dxAbs = Math.abs(dx);
int dyAbs = Math.abs(dy);
Dimension extentSize = getExtentSize();
if ((dx == 0) && (dy != 0) && (dyAbs < extentSize.height)) {
if (dy < 0) {
blitFrom.y = -dy;
blitTo.y = 0;
blitPaint.y = extentSize.height + dy;
}
else {
blitFrom.y = 0;
blitTo.y = dy;
blitPaint.y = 0;
}
blitPaint.x = blitFrom.x = blitTo.x = 0;
blitSize.width = extentSize.width;
blitSize.height = extentSize.height - dyAbs;
blitPaint.width = extentSize.width;
blitPaint.height = dyAbs;
return true;
}
else if ((dy == 0) && (dx != 0) && (dxAbs < extentSize.width)) {
if (dx < 0) {
blitFrom.x = -dx;
blitTo.x = 0;
blitPaint.x = extentSize.width + dx;
}
else {
blitFrom.x = 0;
blitTo.x = dx;
blitPaint.x = 0;
}
blitPaint.y = blitFrom.y = blitTo.y = 0;
blitSize.width = extentSize.width - dxAbs;
blitSize.height = extentSize.height;
blitPaint.width = dxAbs;
blitPaint.height = extentSize.height;
return true;
}
else {
return false;
}
}
/**
* Returns the size of the visible part of the view in view coordinates.
*
* @return a Dimension object giving the size of the view
*/
@Transient
public Dimension getExtentSize() {
return getSize();
}
/**
* Converts a size in pixel coordinates to view coordinates.
* Subclasses of viewport that support "logical coordinates"
* will override this method.
*
* @param size a Dimension object using pixel coordinates
* @return a Dimension object converted to view coordinates
*/
public Dimension toViewCoordinates(Dimension size) {
return new Dimension(size);
}
/**
* Converts a point in pixel coordinates to view coordinates.
* Subclasses of viewport that support "logical coordinates"
* will override this method.
*
* @param p a Point object using pixel coordinates
* @return a Point object converted to view coordinates
*/
public Point toViewCoordinates(Point p) {
return new Point(p);
}
/**
* Sets the size of the visible part of the view using view coordinates.
*
* @param newExtent a Dimension object specifying
* the size of the view
*/
public void setExtentSize(Dimension newExtent) {
Dimension oldExtent = getExtentSize();
if (!newExtent.equals(oldExtent)) {
setSize(newExtent);
fireStateChanged();
}
}
/**
* A listener for the view.
*
* 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™
* has been added to the java.beans package.
* Please see {@link java.beans.XMLEncoder}.
*/
@SuppressWarnings("serial") // Same-version serialization only
protected class ViewListener extends ComponentAdapter implements Serializable
{
public void componentResized(ComponentEvent e) {
fireStateChanged();
revalidate();
}
}
/**
* Creates a listener for the view.
* @return a ViewListener
*/
protected ViewListener createViewListener() {
return new ViewListener();
}
/**
* Subclassers can override this to install a different
* layout manager (or null) in the constructor. Returns
* the LayoutManager to install on the JViewport.
*
* @return a LayoutManager
*/
protected LayoutManager createLayoutManager() {
return ViewportLayout.SHARED_INSTANCE;
}
/**
* Adds a ChangeListener to the list that is
* notified each time the view's
* size, position, or the viewport's extent size has changed.
*
* @param l the ChangeListener to add
* @see #removeChangeListener
* @see #setViewPosition
* @see #setViewSize
* @see #setExtentSize
*/
public void addChangeListener(ChangeListener l) {
listenerList.add(ChangeListener.class, l);
}
/**
* Removes a ChangeListener from the list that's notified each
* time the views size, position, or the viewports extent size
* has changed.
*
* @param l the ChangeListener to remove
* @see #addChangeListener
*/
public void removeChangeListener(ChangeListener l) {
listenerList.remove(ChangeListener.class, l);
}
/**
* Returns an array of all the ChangeListeners added
* to this JViewport with addChangeListener().
*
* @return all of the ChangeListeners added or an empty
* array if no listeners have been added
* @since 1.4
*/
public ChangeListener[] getChangeListeners() {
return listenerList.getListeners(ChangeListener.class);
}
/**
* Notifies all ChangeListeners when the views
* size, position, or the viewports extent size has changed.
*
* @see #addChangeListener
* @see #removeChangeListener
* @see EventListenerList
*/
protected void fireStateChanged()
{
Object[] listeners = listenerList.getListenerList();
for (int i = listeners.length - 2; i >= 0; i -= 2) {
if (listeners[i] == ChangeListener.class) {
if (changeEvent == null) {
changeEvent = new ChangeEvent(this);
}
((ChangeListener)listeners[i + 1]).stateChanged(changeEvent);
}
}
}
/**
* Always repaint in the parents coordinate system to make sure
* only one paint is performed by the RepaintManager.
*
* @param tm maximum time in milliseconds before update
* @param x the x coordinate (pixels over from left)
* @param y the y coordinate (pixels down from top)
* @param w the width
* @param h the height
* @see java.awt.Component#update(java.awt.Graphics)
*/
public void repaint(long tm, int x, int y, int w, int h) {
Container parent = getParent();
if(parent != null)
parent.repaint(tm,x+getX(),y+getY(),w,h);
else
super.repaint(tm,x,y,w,h);
}
/**
* 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.
*
* @return a string representation of this JViewport
*/
protected String paramString() {
String isViewSizeSetString = (isViewSizeSet ?
"true" : "false");
String lastPaintPositionString = (lastPaintPosition != null ?
lastPaintPosition.toString() : "");
String scrollUnderwayString = (scrollUnderway ?
"true" : "false");
return super.paramString() +
",isViewSizeSet=" + isViewSizeSetString +
",lastPaintPosition=" + lastPaintPositionString +
",scrollUnderway=" + scrollUnderwayString;
}
//
// Following is used when doBlit is true.
//
/**
* Notifies listeners of a property change. This is subclassed to update
* the windowBlit property.
* (The putClientProperty property is final).
*
* @param propertyName a string containing the property name
* @param oldValue the old value of the property
* @param newValue the new value of the property
*/
protected void firePropertyChange(String propertyName, Object oldValue,
Object newValue) {
super.firePropertyChange(propertyName, oldValue, newValue);
if (propertyName.equals(EnableWindowBlit)) {
if (newValue != null) {
setScrollMode(BLIT_SCROLL_MODE);
} else {
setScrollMode(SIMPLE_SCROLL_MODE);
}
}
}
/**
* Returns true if the component needs to be completely repainted after
* a blit and a paint is received.
*/
private boolean needsRepaintAfterBlit() {
// Find the first heavy weight ancestor. isObscured and
// canDetermineObscurity are only appropriate for heavy weights.
Component heavyParent = getParent();
while (heavyParent != null && heavyParent.isLightweight()) {
heavyParent = heavyParent.getParent();
}
if (heavyParent != null) {
ComponentPeer peer = AWTAccessor.getComponentAccessor()
.getPeer(heavyParent);
if (peer != null && peer.canDetermineObscurity() &&
!peer.isObscured()) {
// The peer says we aren't obscured, therefore we can assume
// that we won't later be messaged to paint a portion that
// we tried to blit that wasn't valid.
// It is certainly possible that when we blited we were
// obscured, and by the time this is invoked we aren't, but the
// chances of that happening are pretty slim.
return false;
}
}
return true;
}
private Timer createRepaintTimer() {
Timer timer = new Timer(300, new ActionListener() {
public void actionPerformed(ActionEvent ae) {
// waitingForRepaint will be false if a paint came down
// with the complete clip rect, in which case we don't
// have to cause a repaint.
if (waitingForRepaint) {
repaint();
}
}
});
timer.setRepeats(false);
return timer;
}
/**
* If the repaint manager has a dirty region for the view, the view is
* asked to paint.
*
* @param g the Graphics context within which to paint
*/
private void flushViewDirtyRegion(Graphics g, Rectangle dirty) {
JComponent view = (JComponent) getView();
if(dirty != null && dirty.width > 0 && dirty.height > 0) {
dirty.x += view.getX();
dirty.y += view.getY();
Rectangle clip = g.getClipBounds();
if (clip == null) {
// Only happens in 1.2
g.setClip(0, 0, getWidth(), getHeight());
}
g.clipRect(dirty.x, dirty.y, dirty.width, dirty.height);
clip = g.getClipBounds();
// Only paint the dirty region if it is visible.
if (clip.width > 0 && clip.height > 0) {
paintView(g);
}
}
}
/**
* Used when blitting.
*
* @param g the Graphics context within which to paint
* @return true if blitting succeeded; otherwise false
*/
private boolean windowBlitPaint(Graphics g) {
int width = getWidth();
int height = getHeight();
if ((width == 0) || (height == 0)) {
return false;
}
boolean retValue;
RepaintManager rm = RepaintManager.currentManager(this);
JComponent view = (JComponent) getView();
if (lastPaintPosition == null ||
lastPaintPosition.equals(getViewLocation())) {
paintView(g);
retValue = false;
} else {
// The image was scrolled. Manipulate the backing store and flush
// it to g.
Point blitFrom = new Point();
Point blitTo = new Point();
Dimension blitSize = new Dimension();
Rectangle blitPaint = new Rectangle();
Point newLocation = getViewLocation();
int dx = newLocation.x - lastPaintPosition.x;
int dy = newLocation.y - lastPaintPosition.y;
boolean canBlit = computeBlit(dx, dy, blitFrom, blitTo, blitSize,
blitPaint);
if (!canBlit) {
paintView(g);
retValue = false;
} else {
// Prepare the rest of the view; the part that has just been
// exposed.
Rectangle r = view.getBounds().intersection(blitPaint);
r.x -= view.getX();
r.y -= view.getY();
blitDoubleBuffered(view, g, r.x, r.y, r.width, r.height,
blitFrom.x, blitFrom.y, blitTo.x, blitTo.y,
blitSize.width, blitSize.height);
retValue = true;
}
}
lastPaintPosition = getViewLocation();
return retValue;
}
//
// NOTE: the code below uses paintForceDoubleBuffered for historical
// reasons. If we're going to allow a blit we've already accounted for
// everything that paintImmediately and _paintImmediately does, for that
// reason we call into paintForceDoubleBuffered to diregard whether or
// not setDoubleBuffered(true) was invoked on the view.
//
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) {
// NOTE:
// blitFrom/blitTo are in JViewport coordinates system
// not the views coordinate space.
// clip* are in the views coordinate space.
RepaintManager rm = RepaintManager.currentManager(this);
int bdx = blitToX - blitFromX;
int bdy = blitToY - blitFromY;
Composite oldComposite = null;
// Shift the scrolled region
if (g instanceof Graphics2D) {
Graphics2D g2d = (Graphics2D) g;
oldComposite = g2d.getComposite();
g2d.setComposite(AlphaComposite.Src);
}
rm.copyArea(this, g, blitFromX, blitFromY, blitW, blitH, bdx, bdy,
false);
if (oldComposite != null) {
((Graphics2D) g).setComposite(oldComposite);
}
// Paint the newly exposed region.
int x = view.getX();
int y = view.getY();
g.translate(x, y);
g.setClip(clipX, clipY, clipW, clipH);
view.paintForceDoubleBuffered(g);
g.translate(-x, -y);
}
/**
* Called to paint the view, usually when blitPaint
* can not blit.
*
* @param g the Graphics context within which to paint
*/
private void paintView(Graphics g) {
Rectangle clip = g.getClipBounds();
JComponent view = (JComponent)getView();
if (view.getWidth() >= getWidth()) {
// Graphics is relative to JViewport, need to map to view's
// coordinates space.
int x = view.getX();
int y = view.getY();
g.translate(x, y);
g.setClip(clip.x - x, clip.y - y, clip.width, clip.height);
view.paintForceDoubleBuffered(g);
g.translate(-x, -y);
g.setClip(clip.x, clip.y, clip.width, clip.height);
}
else {
// To avoid any problems that may result from the viewport being
// bigger than the view we start painting from the viewport.
try {
inBlitPaint = true;
paintForceDoubleBuffered(g);
} finally {
inBlitPaint = false;
}
}
}
/**
* 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.
*/
private boolean canUseWindowBlitter() {
if (!isShowing() || (!(getParent() instanceof JComponent) &&
!(getView() instanceof JComponent))) {
return false;
}
if (isPainting()) {
// We're in the process of painting, don't blit. If we were
// to blit we would draw on top of what we're already drawing,
// so bail.
return false;
}
Rectangle dirtyRegion = RepaintManager.currentManager(this).
getDirtyRegion((JComponent)getParent());
if (dirtyRegion != null && dirtyRegion.width > 0 &&
dirtyRegion.height > 0) {
// Part of the scrollpane needs to be repainted too, don't blit.
return false;
}
Rectangle clip = new Rectangle(0,0,getWidth(),getHeight());
Rectangle oldClip = new Rectangle();
Rectangle tmp2 = null;
Container parent;
Component lastParent = null;
int x, y, w, h;
for(parent = this; parent != null && isLightweightComponent(parent); parent = parent.getParent()) {
x = parent.getX();
y = parent.getY();
w = parent.getWidth();
h = parent.getHeight();
oldClip.setBounds(clip);
SwingUtilities.computeIntersection(0, 0, w, h, clip);
if(!clip.equals(oldClip))
return false;
if(lastParent != null && parent instanceof JComponent &&
!((JComponent)parent).isOptimizedDrawingEnabled()) {
Component comps[] = parent.getComponents();
int index = 0;
for(int i = comps.length - 1 ;i >= 0; i--) {
if(comps[i] == lastParent) {
index = i - 1;
break;
}
}
while(index >= 0) {
tmp2 = comps[index].getBounds(tmp2);
if(tmp2.intersects(clip))
return false;
index--;
}
}
clip.x += x;
clip.y += y;
lastParent = parent;
}
if (parent == null) {
// No Window parent.
return false;
}
return true;
}
/////////////////
// Accessibility support
////////////////
/**
* 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.
*
* @return an AccessibleJViewport that serves as the
* AccessibleContext of this JViewport
*/
public AccessibleContext getAccessibleContext() {
if (accessibleContext == null) {
accessibleContext = new AccessibleJViewport();
}
return accessibleContext;
}
/**
* This class implements accessibility support for the
* JViewport class. It provides an implementation of the
* Java Accessibility API appropriate to viewport user-interface elements.
*
* 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™
* has been added to the java.beans package.
* Please see {@link java.beans.XMLEncoder}.
*/
@SuppressWarnings("serial") // Same-version serialization only
protected class AccessibleJViewport extends AccessibleJComponent {
/**
* Get the role of this object.
*
* @return an instance of AccessibleRole describing the role of
* the object
*/
public AccessibleRole getAccessibleRole() {
return AccessibleRole.VIEWPORT;
}
} // inner class AccessibleJViewport
}