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package gjt;
import java.awt.*;
/**
* Each Scroller contains a Panel (viewport) and two Scrollbars
* (horizontal and vertical). Works in conjunction with a
* ScrollerLayout, that lays out the viewport and two
* scrollbars.<p>
*
* Subclasses must override:<p>
* <dl>
* <dd> abstract public void scrollTo(int x, int y)
* <dd> abstract public Dimension getScrollAreaSize()
* </dl>
*
* @version 1.0, Apr 1 1996
* @author David Geary
* @see ComponentScroller
* @see ImageScroller
* @see ScrollerLayout
* @see gjt.test.ComponentScrollerTest
* @see gjt.test.ImageScrollerTest
*/
public abstract class Scroller extends Panel {
protected Panel viewport;
protected Scrollbar hbar, vbar;
abstract public void scrollTo(int x, int y);
abstract public Dimension getScrollAreaSize();
public Scroller() {
setLayout(new ScrollerLayout(this));
add("Scroll", viewport = new Panel());
add("East", vbar = new Scrollbar(Scrollbar.VERTICAL));
add("South",hbar = new Scrollbar(Scrollbar.HORIZONTAL));
}
public Scrollbar getHorizontalScrollbar() {return hbar; }
public Scrollbar getVerticalScrollbar () {return vbar; }
public Panel getViewport () {return viewport;}
public boolean handleEvent(Event event) {
boolean handledEvent;
switch(event.id) {
case Event.SCROLL_LINE_UP: scrollLineUp(event);
break;
case Event.SCROLL_LINE_DOWN: scrollLineDown(event);
break;
case Event.SCROLL_PAGE_UP: scrollPageUp (event);
break;
case Event.SCROLL_PAGE_DOWN: scrollPageDown(event);
break;
case Event.SCROLL_ABSOLUTE: scrollAbsolute(event);
break;
}
handledEvent = event.id == Event.SCROLL_LINE_UP ||
event.id == Event.SCROLL_LINE_DOWN ||
event.id == Event.SCROLL_PAGE_UP ||
event.id == Event.SCROLL_PAGE_DOWN ||
event.id == Event.SCROLL_ABSOLUTE;
if(handledEvent) return true;
else return super.handleEvent(event);
}
public void paint (Graphics g) { scroll(); }
public void update(Graphics g) { paint(g); }
public void manageScrollbars() {
manageHorizontalScrollbar();
manageVerticalScrollbar ();
}
protected void manageHorizontalScrollbar() {
Dimension size = size();
Dimension scrollAreaSize = getScrollAreaSize();
if(vbar.isVisible())
size.width -= vbar.size().width;
if(scrollAreaSize.width > size.width) {
if( ! hbar.isVisible())
hbar.show();
}
else if(hbar.isVisible()) {
hbar.hide();
hbar.setValue(0);
repaint();
}
}
protected void manageVerticalScrollbar() {
Dimension size = size();
Dimension scrollAreaSize = getScrollAreaSize();
if(hbar.isVisible())
size.height -= hbar.size().height;
if(scrollAreaSize.height > size.height) {
if( ! vbar.isVisible())
vbar.show();
}
else if(vbar.isVisible()) {
vbar.hide();
vbar.setValue(0);
repaint();
}
}
public void setScrollbarValues() {
if(hbar.isVisible()) setHorizontalScrollbarValues();
if(vbar.isVisible()) setVerticalScrollbarValues();
}
protected void setHorizontalScrollbarValues() {
Dimension vsize = viewport.size();
Dimension scrollAreaSize = getScrollAreaSize();
int max = scrollAreaSize.width - vsize.width;
hbar.setValues(hbar.getValue(), // value
vsize.width, // amt visible/page
0, // minimum
max); // maximum
setHorizontalLineAndPageIncrements();
}
protected void setVerticalScrollbarValues() {
Dimension vsize = viewport.size();
Dimension scrollAreaSize = getScrollAreaSize();
int max = scrollAreaSize.height - vsize.height;
vbar.setValues(vbar.getValue(), // value
vsize.height, // amt visible/page
0, // minimum
max); // maximum
setVerticalLineAndPageIncrements();
}
protected void scrollLineUp (Event event) { scroll(); }
protected void scrollLineDown(Event event) { scroll(); }
protected void scrollPageUp (Event event) { scroll(); }
protected void scrollPageDown(Event event) { scroll(); }
protected void scrollAbsolute(Event event) { scroll(); }
protected void setHorizontalLineAndPageIncrements() {
Dimension size = getScrollAreaSize();
hbar.setLineIncrement(size.width/10);
hbar.setPageIncrement(size.width/5);
}
protected void setVerticalLineAndPageIncrements() {
Dimension size = getScrollAreaSize();
vbar.setLineIncrement(size.height/10);
vbar.setPageIncrement(size.height/5);
}
protected void scroll() {
scrollTo(hbar.getValue(), vbar.getValue());
}
}
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