dvgraphicsinfox.java

来自「ALGAE是一个快速创建算法演示的框架。目前支持的算法实现语言包括java和c」· Java 代码 · 共 92 行

package edu.odu.cs.zeil.AlgAE.Client.DataViewer;

import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Image;

import edu.odu.cs.zeil.AlgAE.Client.DataViewer.DataGraph.GraphicsInfo;

/**
 *  Graphics context information, with support for double buffering.
 *
 *  @author Steven J. Zei */
public class DVGraphicsInfo extends GraphicsInfo
{
  /**
   *  The image that new drawing is written into.
   */
  Image drawTo;

  /**
   *  The image with old drawing that the canvas is repainted from.
   */
  Image repaintFrom;

  
  /**
   *  Build a graphics context.
   *
   *  @param c The canvas that this graphic information is associated with.
   */
  DVGraphicsInfo()
  {
    super();
    repaintFrom = drawTo = null;
    textOffset.width = 0;
  }
  






  /**
   *  Initialize the graphics data member <code>g</code> to a valid
   *  graphics context and sets the canvasSize and textOffset values.
   */
  public void openGraphics()
  {
    canvasSize = canvas.getSize();
    if (drawTo == null)
      {
	drawTo = canvas.createImage (canvasSize.width, canvasSize.height);
	g = drawTo.getGraphics();
	g.setColor(canvas.getBackground());
	g.fillRect(0, 0, canvasSize.width, canvasSize.height);
	g.setFont (font);
	if (textOffset.width == 0)
	  {
	    FontMetrics fm = g.getFontMetrics();
	    textOffset.width = (fm.charWidth('X') + 1) / 2;
	    textOffset.height = (fm.getAscent() + 1) / 2;
	  }
      }
  }
  


  /**
   *  Indicates that the graphics data member <code>g</code> is no longer
   *  in use.
   *
   *  @param wasWrittenTo  Input parameter, true if anything has been
   *     written to the graphics context since it was opened.
   *     False if we were "only looking".
   */
  public void closeGraphics(boolean wasWrittenTo)
  {
    if (wasWrittenTo)
      {
	repaintFrom = drawTo;
	drawTo = null;
      }
  }
  
  

}