/*
Research Project:   Graphical Database for Category Theory
                    J. Bradbury, Dr. R. Rosebrugh, I. Rutherford
                    Mount Allison University 2001
File:               OffsetCanvas.java
                    (author: Larry Barowski, Auburn University, 5/29/96)
Description:	      This abstract class is used inside a ScrolledPanel, and
                    implements the required functionality to communicate with it.
*/

  //Import statement
   import java.awt.Dimension;
   import java.awt.Point;
   import java.awt.Canvas;
   import javax.swing.*;

   public abstract class OffsetCanvas extends LPanel
   {
   /**
    *	Event id for size change. Subclasses must post an event with this id
    *	when their contents or windows are resized.
    **/
      public static int	RESIZE = 32450;
   
   /**
    *	Event id for changing the label above the OffsetCanvas.
    *	The arg field of the event must contain the string.
    **/
      public static int	LABEL = 32451;
   
   
   
   
   /**
    *	Adjust the offset of the contents of the canvas. These must have the
    *	following meaning: screen position + offset = contents position.
    *	e.g. if xoffset is 10, contents starts 10 pixels to the left of the
    *	screen.
    *
    *@param xoffset horizontal offset
    *@param yoffset vertical offset
    **/
      abstract public void setOffsets(double xoffset, double yoffset, boolean redraw);
   
   
   
   
   
   /**
    *	Return the size of the contents.
    **/
      abstract public DDimension contentsSize();
   
   
   
   
   
   
      abstract public DPoint getOffset()
      ;
   }