/*   ダブルバッファ Canvas for MIDP  Ver 0.00   */
/*                                              */
/*                                              */
/*   by Atsushi                     2000/7/24   */


// package lib.midp;

import javax.microedition.lcdui.*;


public class DoubleBufferedCanvas extends Canvas
{
	/*   ---   Field   ---   */

	private Image buffer;
	private Graphics g;

	/*   ---   Constructor   ---   */

	public DoubleBufferedCanvas()
	{
	}

	/*   ---   バッファ情報   ---   */

	public Image getBuffer()
	{
		if (buffer==null)
		{
			initBuffer();
		}
		
		return buffer;
	}

	public Graphics getBufferGraphics()
	{
		if (buffer==null)
		{
			initBuffer();
		}
		
		return g;
	}

	/*   ---   描画処理   ---   */

	public void paint(Graphics g)
	{
		int x,y,bufferWidth,bufferHeight;
		int color;
	
		if (buffer==null)
		{
			initBuffer();
		}
		bufferWidth =buffer.getWidth ();
		bufferHeight=buffer.getHeight();
		if ((getWidth ()!=bufferWidth) ||
		    (getHeight()!=bufferHeight))
		{
			initBuffer();
		}
		
		x=(getWidth ()-bufferWidth )/2;
		y=(getHeight()-bufferHeight)/2;
		color=g.getColor();
		g.setColor(0,0,0);
		if (y>0) g.fillRect(0,0             ,bufferWidth , y);
		if (y<0) g.fillRect(0,bufferHeight+y,bufferWidth ,-y);
		if (x>0) g.fillRect(0             ,0, x,bufferHeight);
		if (x<0) g.fillRect(bufferWidth +x,0,-x,bufferHeight);
		g.setColor(color);
		paintBuffer(g,x,y);
	}

	protected void paintBuffer(Graphics g,int x,int y)
	{
		g.drawImage(buffer,x,y,Graphics.TOP | Graphics.LEFT);
	}

	private void initBuffer()
	{
		if (getWidth()<=0 || getHeight()<=0) return;
		
		buffer=Image.createImage(getWidth(),getHeight());
		g=buffer.getGraphics();
		
		initGraphics();
	}

	protected void initGraphics() {}
}