//The design of this program was an inspiration from an example in Sun's Java toutorial.

package misc;

import java.awt.*;

import java.applet.*;

import algebra.*;

//This class defines the canvas.

class Mycanvas extends Canvas {

int tx = 0;
int ty = 0;
int text_width = 0;
int text_height = 0;
Dimension D;
int numans = 1;
//The array that holds various trials.
answer ans[] = new answer[100];
public Mycanvas(int width, int height) {
super();
ans[0] = new answer();
ans[1] = new answer();
D = new Dimension(width,height);
}
public Dimension minimumSize() { return D; }
public Dimension preferredSize() { return minimumSize(); }
public void newanswer() {
++numans;
ans[numans] = new answer();
}
public void newline(entity ent) { ans[numans].add_line(ent); }
//The clear operation is easy because of the garbage collection
//in java. All we need to do is to set them to null!!
public void clear() {
for(int i = 0; i < numans; i++) {
ans[i] = null;
}
ans[0] = new answer();
ans[1] = new answer();
numans = 1;
repaint();
text_width = 0;
text_height = 0;
}
public void paint(Graphics g) {
//The width and height of the canvas.
int w = size().width;
int h = size().height;
//Boundary of the canvas is drawn
g.drawRect(0,0,w-1,h-1);
g.translate(-tx,-ty);
//The text begins from 30 units down.
int y = 30;
integer Y = new integer(y);
//This loops through each trial in the array.
for(int a = 1; a <= numans ; a++) {
int x = 30;
int width = 30;
int height = 0;
integer W = new integer(width);
integer H = new integer(height);
integer X = new integer(x);
String heading = "Trial #: " + String.valueOf( a );
Color Col = g.getColor();
g.setColor( Color.blue );
g.drawString( heading, x, Y.intValue() );
FontMetrics fm = g.getFontMetrics();
if( height < fm.getHeight() )
H.setValue( fm.getHeight() );
Y.setValue( Y.intValue() + H.intValue() );
g.setColor( Col );
//Loops through the lines in each answer.
for(int i = 0; i < (ans[a].noflines()); i++) {
W.setValue(30);
H.setValue(0);
X.setValue(x);
//The object is instantiated as a Drawable(interface).
Drawable D = ans[a].get_line(i);
D.draw(g, W, H, X, Y);
if (text_width <= W.intValue() )
text_width = W.intValue() + 20;
}// end of lines loop
if( a != numans ) Y.setValue( Y.intValue() + 20 );
text_height = Y.intValue();
}// end of the answer loop
return;
}
public void paint( entity ent) {
newline(ent);
repaint();
repaint();
return;
}

}

//This canvas has the Mycanvas defined above and positions

//it with the scrollbars.

public class ScrollableCanvas extends Panel {

Scrollbar vert;
Scrollbar horz;
Mycanvas canvas;
public ScrollableCanvas(int w, int h) {
canvas = new Mycanvas(w,h);
canvas.resize(canvas.minimumSize());
canvas.setBackground(this.getBackground() );
//Create horizontal scrollbar.
horz = new Scrollbar(Scrollbar.HORIZONTAL);
//Create vertical scrollbar.
vert = new Scrollbar(Scrollbar.VERTICAL);
//Add Components to the
Applet. setLayout(new BorderLayout());
add("Center",canvas);
add("East",vert);
add("South",horz);
resizeHorz();
resizeVert();
validate();
}
public void paint(entity ent) { //if (ent.equals(new sentence())){
canvas.paint(ent);
resizeHorz();
resizeVert();
}
public void newanswer() {
canvas.newanswer();
resizeHorz();
resizeVert();
}
public void clear() {
canvas.clear();
resizeHorz();
resizeVert();
}
public boolean handleEvent(Event evt) {
switch (evt.id) {
case Event.SCROLL_LINE_UP:
case Event.SCROLL_LINE_DOWN:
case Event.SCROLL_PAGE_UP:
case Event.SCROLL_PAGE_DOWN:
case Event.SCROLL_ABSOLUTE:
if (evt.target == vert) {
canvas.ty = ((Integer)evt.arg).intValue();
resizeVert();
canvas.repaint();
canvas.repaint();
}
if (evt.target == horz) {
canvas.tx = ((Integer)evt.arg).intValue();
resizeHorz();
canvas.repaint();
canvas.repaint();
}
default:
resizeVert();
resizeHorz();
}
return super.handleEvent(evt);
}
//Don't call this until the canvas size is valid.
void resizeHorz() {
int canvasWidth = canvas.size().width;
int tw = canvas.text_width;
if ((canvas.tx + canvasWidth) > tw) {
int newtx = tw - canvasWidth;
if (newtx < 0) { newtx = 0; }
canvas.tx = newtx;
}
horz.setValues(
//draw the part of the image that starts at this x:
canvas.tx,
//amount to scroll for a "page":
(int)(canvasWidth * 0.9),
//minimum image x to specify:
0,
//maximum image x to specify:
tw - canvasWidth);
//"visible" arg to setValues() has
//no effect after scrollbar is visible.
horz.setPageIncrement((int)(canvasWidth * 0.9));
return;
}
//Don't call this until the canvas size is valid.
void resizeVert() {
int canvasHeight = canvas.size().height;
int th = canvas.text_height;
if (canvasHeight <= 0) {
System.out.println("Canvas has no height" + " can't resize scrollbar"); return;
}
//Shift everything downward if we're displaying empty space
//on the bottom.
if ((canvas.ty + canvasHeight) > th) {
int newty = th - canvasHeight;
if (newty < 0) {
newty = 0;
}
canvas.ty = newty;
}
vert.setValues(
//initially draw part of image starting at this y:
canvas.ty,
//visible arg--amount to scroll for a "page":
(int)(canvasHeight * 0.9),
//minimum image y to specify:
0,
//maximum image y to specify:
th - canvasHeight);
//"visible" arg to setValues() has
//no effect after scrollbar is visible.
vert.setPageIncrement((int)(canvasHeight * 0.9));
return;
}
public void paint(Graphics g) {
//This method probably was called due to applet being resized.
resizeHorz();
resizeVert();
return;
}
}
back.