clipped.java

exploring Java 2ed edition 附带的例子程序

import java.awt.*;
import java.awt.event.*;

public class Clipped extends TerribleFlicker { 
	int nextX, nextY;
	
	public void mouseDragged( MouseEvent e ) {
		nextX = e.getX(); nextY = e.getY();
		repaint();
	}

	void clipToAffectedArea( Graphics g, int oldx, int oldy, int newx, 
										int newy, int width, int height) {
		int x = Math.min( oldx, newx );
		int y = Math.min( oldy, newy );
		int w = ( Math.max( oldx, newx ) + width ) - x;
		int h = ( Math.max( oldy, newy ) + height ) - y;
		g.setClip( x, y, w, h );
	}

	public void update( Graphics g ) {
		int lastX = currentX, lastY = currentY;
		currentX = nextX; currentY = nextY;
		clipToAffectedArea( g, lastX, lastY, currentX, currentY, imgWidth, imgHeight );
		paint( g );
	}
}