CSCI A201/A597 Lab Notes 9 Spring 2000

Use the lab to get help using appendix E or to start with your assignment.

A survey will be posted and be available from now until April 1st.

Here's another application that may or may not be presented in lecture.

1. Drawing one curve with the mouse.

import element.*;

public class Lab9 {
    public static void main(String[] args) {
	DrawingWindow d = new DrawingWindow(); 

  	Pt p = d.awaitMousePress(); 
        d.moveTo(p); 
	while (d.mousePressed()) {
	    d.lineTo(d.getMouse()); 
        } 

    } 
} 

import element.*;

public class Lab9 {
    public static void main(String[] args) {
	DrawingWindow d = new DrawingWindow(); 

        while (true) {  
    	    Pt p = d.awaitMousePress(); 
            d.moveTo(p); 
	    while (d.mousePressed()) {
	        d.lineTo(d.getMouse()); 
            } 
        }

    } 
} 

3. Making it somewhat more explicit.

import element.*;

public class Lab9 {
    public static void main(String[] args) {
	DrawingWindow d = new DrawingWindow(); 

	while (true) {
  	  Pt current = d.awaitMousePress(); 
          d.moveTo(current); 
	  while (d.mousePressed()) {
	      Pt next = d.getMouse();               
  	      d.lineTo(next);  
	  } 
	}

    } 
}

import element.*;

public class Lab9 {
    public static void main(String[] args) {
	DrawingWindow d = new DrawingWindow(); 

	while (true) {
  	  Pt current = d.awaitMousePress(); 
          d.moveTo(current); 
	  while (d.mousePressed()) {
	      Pt next = d.getMouse();               
  	      d.lineTo(next);  

	      Pt tnerruc = new Pt(current);      // [1]
	      tnerruc.x(2 * 100 - current.x());  // [1]

	      Pt txen = new Pt(next);            // [2]
	      txen.x(2 * 100 - next.x());        // [2]

	      d.moveTo(tnerruc);                 // [3]
	      d.lineTo(txen);                    // [3] 

	      d.moveTo(next);                    // [4] 

	      current = next;                    // [5] 
	  } 
	}

    } 
} 

1. this part creates the symmetric of current with respect to the vertical that goes through the middle of a default drawing window (with the x coordinate equals 100).

2. same thing for next

3. draw the line from tnerruc to txen

4. now the current position is in the symmetric drawing; fix that

5. update current. What happens otherwise?

Check page 78 in your textbook for more.