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ScrollPane.java
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1998-09-22
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/*
* @(#)ScrollPane.java 1.59 98/07/14
*
* Copyright 1995-1998 by Sun Microsystems, Inc.,
* 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
* All rights reserved.
*
* This software is the confidential and proprietary information
* of Sun Microsystems, Inc. ("Confidential Information"). You
* shall not disclose such Confidential Information and shall use
* it only in accordance with the terms of the license agreement
* you entered into with Sun.
*/
package java.awt;
import java.awt.peer.ScrollPanePeer;
import java.awt.event.*;
import java.io.Serializable;
/**
* A container class which implements automatic horizontal and/or
* vertical scrolling for a single child component. The display
* policy for the scrollbars can be set to:
* <OL>
* <LI>as needed: scrollbars created and shown only when needed by scrollpane
* <LI>always: scrollbars created and always shown by the scrollpane
* <LI>never: scrollbars never created or shown by the scrollpane
* </OL>
* <P>
* The state of the horizontal and vertical scrollbars is represented
* by two objects (one for each dimension) which implement the
* Adjustable interface. The API provides methods to access those
* objects such that the attributes on the Adjustable object (such as unitIncrement,
* value, etc.) can be manipulated.
* <P>
* Certain adjustable properties (minimum, maximum, blockIncrement,
* and visibleAmount) are set internally by the scrollpane in accordance
* with the geometry of the scrollpane and its child and these should
* not be set by programs using the scrollpane.
* <P>
* If the scrollbar display policy is defined as "never", then the
* scrollpane can still be programmatically scrolled using the
* setScrollPosition() method and the scrollpane will move and clip
* the child's contents appropriately. This policy is useful if the
* program needs to create and manage its own adjustable controls.
* <P>
* The placement of the scrollbars is controlled by platform-specific
* properties set by the user outside of the program.
* <P>
* The initial size of this container is set to 100x100, but can
* be reset using setSize().
* <P>
* Insets are used to define any space used by scrollbars and any
* borders created by the scroll pane. getInsets() can be used
* to get the current value for the insets. If the value of
* scrollbarsAlwaysVisible is false, then the value of the insets
* will change dynamically depending on whether the scrollbars are
* currently visible or not.
*
* @version 1.59 07/14/98
* @author Tom Ball
* @author Amy Fowler
* @author Tim Prinzing
*/
public class ScrollPane extends Container {
/**
* Specifies that horizontal/vertical scrollbar should be shown
* only when the size of the child exceeds the size of the scrollpane
* in the horizontal/vertical dimension.
*/
public static final int SCROLLBARS_AS_NEEDED = 0;
/**
* Specifies that horizontal/vertical scrollbars should always be
* shown regardless of the respective sizes of the scrollpane and child.
*/
public static final int SCROLLBARS_ALWAYS = 1;
/**
* Specifies that horizontal/vertical scrollbars should never be shown
* regardless of the respective sizes of the scrollpane and child.
*/
public static final int SCROLLBARS_NEVER = 2;
private int scrollbarDisplayPolicy;
private ScrollPaneAdjustable vAdjustable;
private ScrollPaneAdjustable hAdjustable;
private static final String base = "scrollpane";
private static int nameCounter = 0;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = 7956609840827222915L;
/**
* Create a new scrollpane container with a scrollbar display policy of
* "as needed".
*/
public ScrollPane() {
this(SCROLLBARS_AS_NEEDED);
}
/**
* Create a new scrollpane container.
* @param scrollbarDisplayPolicy policy for when scrollbars should be shown
*/
public ScrollPane(int scrollbarDisplayPolicy) {
this.layoutMgr = null;
this.width = 100;
this.height = 100;
switch (scrollbarDisplayPolicy) {
case SCROLLBARS_NEVER:
case SCROLLBARS_AS_NEEDED:
case SCROLLBARS_ALWAYS:
this.scrollbarDisplayPolicy = scrollbarDisplayPolicy;
break;
default:
throw new IllegalArgumentException("illegal scrollbar display policy");
}
vAdjustable = new ScrollPaneAdjustable(this, new PeerFixer(this),
Adjustable.VERTICAL);
hAdjustable = new ScrollPaneAdjustable(this, new PeerFixer(this),
Adjustable.HORIZONTAL);
}
/**
* Construct a name for this component. Called by getName() when the
* name is null.
*/
String constructComponentName() {
return base + nameCounter++;
}
/**
* Adds the specified component to this scroll pane container.
* If the scroll pane has an existing child component, that
* component is removed and the new one is added.
* @param comp the component to be added
* @param constraints not applicable
* @param index position of child component (must be <= 0)
*/
protected final void addImpl(Component comp, Object constraints, int index) {
synchronized (getTreeLock()) {
if (getComponentCount() > 0) {
remove(0);
}
if (index > 0) {
throw new IllegalArgumentException("position greater than 0");
}
super.addImpl(comp, constraints, index);
}
}
/**
* Returns the display policy for the scrollbars.
* @return the display policy for the scrollbars
*/
public int getScrollbarDisplayPolicy() {
return scrollbarDisplayPolicy;
}
/**
* Returns the current size of the scroll pane's view port.
* @return the size of the view port in pixels
*/
public Dimension getViewportSize() {
Insets i = getInsets();
return new Dimension(width - i.right - i.left,
height - i.top - i.bottom);
}
/**
* Returns the height that would be occupied by a horizontal
* scrollbar, which is independent of whether it is currently
* displayed by the scroll pane or not.
* @return the height of a horizontal scrollbar in pixels
*/
public int getHScrollbarHeight() {
int h = 0;
if (scrollbarDisplayPolicy != SCROLLBARS_NEVER) {
ScrollPanePeer peer = (ScrollPanePeer)this.peer;
if (peer != null) {
h = peer.getHScrollbarHeight();
}
}
return h;
}
/**
* Returns the width that would be occupied by a vertical
* scrollbar, which is independent of whether it is currently
* displayed by the scroll pane or not.
* @return the width of a vertical scrollbar in pixels
*/
public int getVScrollbarWidth() {
int w = 0;
if (scrollbarDisplayPolicy != SCROLLBARS_NEVER) {
ScrollPanePeer peer = (ScrollPanePeer)this.peer;
if (peer != null) {
w = peer.getVScrollbarWidth();
}
}
return w;
}
/**
* Returns the Adjustable object which represents the state of
* the vertical scrollbar. If the scrollbar display policy is "never",
* this method returns null.
*/
public Adjustable getVAdjustable() {
return vAdjustable;
}
/**
* Returns the Adjustable object which represents the state of
* the horizontal scrollbar. If the scrollbar display policy is "never",
* this method returns null.
*/
public Adjustable getHAdjustable() {
return hAdjustable;
}
/**
* Scrolls to the specified position within the child component.
* A call to this method is only valid if the scroll pane contains
* a child. Specifying a position outside of the legal scrolling bounds
* of the child will scroll to the closest legal position.
* Legal bounds are defined to be the rectangle:
* x = 0, y = 0, width = (child width - view port width),
* height = (child height - view port height).
* This is a convenience method which interfaces with the Adjustable
* objects which represent the state of the scrollbars.
* @param x the x position to scroll to
* @param y the y position to scroll to
* @exception IllegalArgumentException if specified coordinates are
* not within the legal scrolling bounds of the child component.
*/
public void setScrollPosition(int x, int y) {
synchronized (getTreeLock()) {
if (ncomponents <= 0) {
throw new NullPointerException("child is null");
}
hAdjustable.setValue(x);
vAdjustable.setValue(y);
}
}
/**
* Scrolls to the specified position within the child component.
* A call to this method is only valid if the scroll pane contains
* a child and the specified position is within legal scrolling bounds
* of the child. Legal bounds are defined to be the rectangle:
* x = 0, y = 0, width = (child width - view port width),
* height = (child height - view port height).
* This is a convenience method which interfaces with the Adjustable
* objects which represent the state of the scrollbars.
* @param p the Point representing the position to scroll to
* @exception IllegalArgumentException if specified coordinates are
* not within the legal scrolling bounds of the child component.
*/
public void setScrollPosition(Point p) {
setScrollPosition(p.x, p.y);
}
/**
* Returns the current x,y position within the child which is displayed
* at the 0,0 location of the scrolled panel's view port.
* This is a convenience method which interfaces with the adjustable
* objects which represent the state of the scrollbars.
* @return the coordinate position for the current scroll position
*/
public Point getScrollPosition() {
if (ncomponents <= 0) {
throw new NullPointerException("child is null");
}
return new Point(hAdjustable.getValue(), vAdjustable.getValue());
}
/**
* Sets the layout manager for this container. This method is
* overridden to prevent the layout mgr from being set.
* @param mgr the specified layout manager
*/
public final void setLayout(LayoutManager mgr) {
throw new AWTError("ScrollPane controls layout");
}
/**
* Lays out this container by resizing its child to its preferred size.
* If the new preferred size of the child causes the current scroll
* position to be invalid, the scroll position is set to the closest
* valid position.
*
* @see Component#validate
*/
public void doLayout() {
layout();
}
/**
* Determine the size to allocate the child component.
* If the viewport area is bigger than the childs
* preferred size then the child is allocated enough
* to fill the viewport, otherwise the child is given
* it's preferred size.
*/
Dimension calculateChildSize() {
//
// calculate the view size, accounting for border but not scrollbars
// - don't use right/bottom insets since they vary depending
// on whether or not scrollbars were displayed on last resize
//
Dimension size = getSize();
Insets insets = getInsets();
int viewWidth = size.width - insets.left*2;
int viewHeight = size.height - insets.top*2;
//
// determine whether or not horz or vert scrollbars will be displayed
//
boolean vbarOn;
boolean hbarOn;
Component child = getComponent(0);
Dimension childSize = new Dimension(child.getPreferredSize());
if (scrollbarDisplayPolicy == SCROLLBARS_AS_NEEDED) {
vbarOn = childSize.height > viewHeight;
hbarOn = childSize.width > viewWidth;
} else if (scrollbarDisplayPolicy == SCROLLBARS_ALWAYS) {
vbarOn = hbarOn = true;
} else { // SCROLLBARS_NEVER
vbarOn = hbarOn = false;
}
//
// adjust predicted view size to account for scrollbars
//
int vbarWidth = getVScrollbarWidth();
int hbarHeight = getHScrollbarHeight();
if (vbarOn) {
viewWidth -= vbarWidth;
}
if(hbarOn) {
viewHeight -= hbarHeight;
}
//
// if child is smaller than view, size it up
//
if (childSize.width < viewWidth) {
childSize.width = viewWidth;
}
if (childSize.height < viewHeight) {
childSize.height = viewHeight;
}
return childSize;
}
/**
* @deprecated As of JDK version 1.1,
* replaced by <code>doLayout()</code>.
*/
public void layout() {
if (ncomponents > 0) {
Component c = getComponent(0);
Point p = getScrollPosition();
Dimension cs = calculateChildSize();
Dimension vs = getViewportSize();
Insets i = getInsets();
c.reshape(i.left - p.x, i.top - p.y, cs.width, cs.height);
ScrollPanePeer peer = (ScrollPanePeer)this.peer;
if (peer != null) {
peer.childResized(cs.width, cs.height);
}
// update adjustables... the viewport size may have changed
// with the scrollbars coming or going so the viewport size
// is updated before the adjustables.
vs = getViewportSize();
hAdjustable.setSpan(0, cs.width, vs.width);
vAdjustable.setSpan(0, cs.height, vs.height);
}
}
/**
* Prints the component in this scroll pane.
* @param g the specified Graphics window
* @see Component#print
* @see Component#printAll
*/
public void printComponents(Graphics g) {
if (ncomponents > 0) {
Component c = component[0];
Point p = c.getLocation();
Dimension vs = getViewportSize();
Insets i = getInsets();
Graphics cg = g.create();
try {
cg.clipRect(i.left, i.top, vs.width, vs.height);
cg.translate(p.x, p.y);
c.printAll(cg);
} finally {
cg.dispose();
}
}
}
/**
* Creates the scroll pane's peer.
*/
public void addNotify() {
synchronized (getTreeLock()) {
int vAdjustableValue = 0;
int hAdjustableValue = 0;
// Bug 4124460. Save the current adjustable values,
// so they can be restored after addnotify. Set the
// adjustibles to 0, to prevent crashes for possible
// negative values.
if (getComponentCount() > 0) {
vAdjustableValue = vAdjustable.getValue();
hAdjustableValue = hAdjustable.getValue();
vAdjustable.setValue(0);
hAdjustable.setValue(0);
}
if (peer == null)
peer = getToolkit().createScrollPane(this);
super.addNotify();
// Bug 4124460. Restore the adjustable values.
if (getComponentCount() > 0) {
vAdjustable.setValue(vAdjustableValue);
hAdjustable.setValue(hAdjustableValue);
}
if (getComponentCount() > 0) {
Component comp = getComponent(0);
if (comp.peer instanceof java.awt.peer.LightweightPeer) {
// The scrollpane won't work with a windowless child... it assumes
// it is moving a child window around so the windowless child is
// wrapped with a window.
remove(0);
Panel child = new Panel();
child.setLayout(new BorderLayout());
child.add(comp);
add(child);
}
}
}
}
public String paramString() {
String sdpStr;
switch (scrollbarDisplayPolicy) {
case SCROLLBARS_AS_NEEDED:
sdpStr = "as-needed";
break;
case SCROLLBARS_ALWAYS:
sdpStr = "always";
break;
case SCROLLBARS_NEVER:
sdpStr = "never";
break;
default:
sdpStr = "invalid display policy";
}
Point p = ncomponents > 0? getScrollPosition() : new Point(0,0);
Insets i = getInsets();
return super.paramString()+",ScrollPosition=("+p.x+","+p.y+")"+
",Insets=("+i.top+","+i.left+","+i.bottom+","+i.right+")"+
",ScrollbarDisplayPolicy="+sdpStr;
}
class PeerFixer implements AdjustmentListener, java.io.Serializable {
PeerFixer(ScrollPane scroller) {
this.scroller = scroller;
}
/**
* Invoked when the value of the adjustable has changed.
*/
public void adjustmentValueChanged(AdjustmentEvent e) {
Adjustable adj = e.getAdjustable();
int value = e.getValue();
ScrollPanePeer peer = (ScrollPanePeer) scroller.peer;
if (peer != null) {
peer.setValue(adj, value);
}
Component c = scroller.getComponent(0);
switch(adj.getOrientation()) {
case Adjustable.VERTICAL:
c.move(c.getLocation().x, -(value));
break;
case Adjustable.HORIZONTAL:
c.move(-(value), c.getLocation().y);
break;
default:
throw new IllegalArgumentException("Illegal adjustable orientation");
}
}
private ScrollPane scroller;
}
}
class ScrollPaneAdjustable implements Adjustable, java.io.Serializable {
private ScrollPane sp;
private int orientation;
private int minimum;
private int maximum;
private int visibleAmount;
private int unitIncrement = 1;
private int blockIncrement = 1;
private int value;
private AdjustmentListener adjustmentListener;
private static final String SCROLLPANE_ONLY =
"Can be set by scrollpane only";
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = -3359745691033257079L;
public ScrollPaneAdjustable(ScrollPane sp, AdjustmentListener l, int orientation) {
this.sp = sp;
this.orientation = orientation;
addAdjustmentListener(l);
}
/**
* This is called by the scrollpane itself to update the
* min,max,visible values. The scrollpane is the only one
* that should be changing these since it is the source of
* these values.
*/
void setSpan(int min, int max, int visible) {
// adjust the values to be reasonable
minimum = min;
maximum = Math.max(max, minimum + 1);
visibleAmount = Math.min(visible, maximum - minimum);
visibleAmount = Math.max(visibleAmount, 1);
blockIncrement = Math.max((int)(visible * .90), 1);
setValue(value);
}
public int getOrientation() {
return orientation;
}
public void setMinimum(int min) {
throw new AWTError(SCROLLPANE_ONLY);
}
public int getMinimum() {
return 0;
}
public void setMaximum(int max) {
throw new AWTError(SCROLLPANE_ONLY);
}
public int getMaximum() {
return maximum;
}
public synchronized void setUnitIncrement(int u) {
if (u != unitIncrement) {
unitIncrement = u;
if (sp.peer != null) {
ScrollPanePeer peer = (ScrollPanePeer) sp.peer;
peer.setUnitIncrement(this, u);
}
}
}
public int getUnitIncrement() {
return unitIncrement;
}
public synchronized void setBlockIncrement(int b) {
blockIncrement = b;
}
public int getBlockIncrement() {
return blockIncrement;
}
public void setVisibleAmount(int v) {
throw new AWTError(SCROLLPANE_ONLY);
}
public int getVisibleAmount() {
return visibleAmount;
}
public void setValue(int v) {
// bounds check
v = Math.max(v, minimum);
v = Math.min(v, maximum - visibleAmount);
if (v != value) {
value = v;
// Synchronously notify the listeners so that they are
// guaranteed to be up-to-date with the Adjustable before
// it is mutated again.
AdjustmentEvent e =
new AdjustmentEvent(this, AdjustmentEvent.ADJUSTMENT_VALUE_CHANGED,
AdjustmentEvent.TRACK, value);
adjustmentListener.adjustmentValueChanged(e);
}
}
public int getValue() {
return value;
}
public synchronized void addAdjustmentListener(AdjustmentListener l) {
adjustmentListener = AWTEventMulticaster.add(adjustmentListener, l);
}
public synchronized void removeAdjustmentListener(AdjustmentListener l){
adjustmentListener = AWTEventMulticaster.remove(adjustmentListener, l);
}
public String toString() {
return getClass().getName() + "[" + paramString() + "]";
}
public String paramString() {
return ((orientation==Adjustable.VERTICAL?"vertical,":"horizontal,")+
"[0.."+maximum+"],"+"val="+value+",vis="+visibleAmount+
",unit="+unitIncrement+",block="+blockIncrement);
}
}