import java.applet.*; 
import java.awt.*;
/**
* This class implements a drawing board.
* It captures the users mouseDown and mouseUp
* events setting the drawing boundaries, and
* draws a shape according to the user's 
* specifications obtained from the controlStrip
* object
*/
public class whiteBoard extends Panel {


  
  // These variables store the x and y coordinates
  // obtained upon the mouseDown and mouseUp events
  // generated by the user
  protected int startX=0, prevX=0, currX=0;
  protected int startY=0, prevY=0, currY=0;

  // These variables store the actual dimensions
  // of the area that holds the shape to be drawn
  protected int width=0,prevWidth = 0, height=0,prevHeight=0;
  // These variables help determine the direction the user is
  // dragging the cursor before releasing the mouse button
  protected boolean widthIsNeg = false, heightIsNeg = false;
  
  protected String drawShape = "Line", drawColor = "Green", fillColor = ""; 
  // initializes the class
  public void whiteBoard () {
 
    setBackground(Color.lightGray); //sets background to light gray
    setForeground(Color.green);     //and drawing color to green


  }

  /*---------------------------------------------*/
  /**
  * This function handles the mouse down event  
  * It registers coordinates of the mouse click 
  * within the applet space                    
  * It also sets the shapes color according to  
  * the user's choice                           
  */
  /*---------------------------------------------*/

  public boolean mouseDown(Event e, int x, int y) {
  
    // initialize variables upon mouseDown event
    startX = x;
    startY = y;
    currX = x;
    currY = y;
    prevX=0;
    prevY=0;
    prevWidth=0;
    prevHeight=0;

    // Check for the user's color choice
    // and set the foreground color accrodingly
    if (drawColor == "Green")
       setForeground(Color.green);

    else if (drawColor == "Blue")
       setForeground(Color.blue);

    else
       setForeground(Color.yellow);



    return(true);
  }

  /*-----------------------------------------------*/
  /**
  * This function handles the mouseUp event       
  * It registers coordinates of the mouse release 
  * within the applet space                       
  * It also checks for what type of shape the user
  * chose, and draws it                           
  */
  /*-----------------------------------------------*/

  public boolean mouseUp(Event e, int x, int y)  {
  
    // if it's a line, draw it 
    // (currX and currY hold the coordinates
    // from the mouseDown event  
    if (drawShape == "Line")
      getGraphics().drawLine(currX,currY,x,y);
    else {
    // It's either an ellipse or a rectangle

    // determine the shape's dimensions 
      width =  x - startX;
      height = y - startY;
   
    // if user is dragging from right to left
      if (width < 0){
          width = width * (-1);  // make the width a positive value
          currX = x; // currX holds the release x coordinate
          widthIsNeg = true; // set the flag to true
      }
    // if user is dragging from bottom to top
      if (height < 0){
           height= height * (-1); // make the height a positive value
           currY = y; // currY holds the release y coordinate
           heightIsNeg = true; // set the flag to true
      }
   
     // if shape is a rectangle
      if (drawShape == "Rectangle"){
	  // Determine fill style
        if (fillColor == "Hollow") 	 
          // draws a hollow rectangle
          getGraphics().drawRect(currX,currY,width,height);
        else
          // draws a filled rectangle
          getGraphics().fillRect(currX,currY,width,height);
      }
      // if shape is an ellipse
      else if (drawShape == "Ellipse"){
        // Detemine fill style
        if (fillColor == "Hollow") 	 
          // draws a hollow ellipse
          getGraphics().drawOval(currX,currY,width,height);
        else
          // draws a filled ellipse
          getGraphics().fillOval(currX,currY,width,height);
      }
     }  
    

   return(true);
  }
  
  /*------------------------------*/
  /**
  * This function is called upon 
  * changing the shape choice in 
  * the control strip            
  */
  /*------------------------------*/
  public void changeShape(String shape){
     drawShape = shape;  // shape: user's choice of shape 
  }
  /*------------------------------*/
  /**
  * This function is called upon 
  * changing the color choice in 
  * the control strip            
  */
  /*------------------------------*/
  public void changeColor(String color){
     drawColor = color;  // color: user's choice of color
  }
  /*------------------------------*/
  /**
  * This function is called upon 
  * changing the style choice in 
  * the control strip            
  */
  /*------------------------------*/
  public void changeFillColor(String color){
     fillColor = color; // color: user's choice of style (hollow or filled)
  }

  /*------------------------------*/
  /**
  * This function is called upon 
  * pushing the reset button     
  */
  /*------------------------------*/
  public void clearDrawingArea (){
     getGraphics().clearRect(0,0,500,500);
  }



}