import java.awt.*;

public class ScrollableScribble extends Panel {
	Canvas canvas;
	Scrollbar hbar,vbar;
	java.util.Vector lines = new java.util.Vector(100,100);
	int last_x,last_y;
	int offset_x,offset_y;
	int canvas_width,canvas_height;

	// Create a canvas and two scrollbars and lay them out in the panel.
	// Use a BorderLayout to get the scrollbarsflush against the
	// right and bottom sides of the canvas.  When the panel grows,
	// the convas and scrollbars will also grow appropriately.
	public ScrollableScribble() {
		// implicit super() call here creates the panel
		canvas = new Canvas();
		hbar = new Scrollbar(Scrollbar.HORIZONTAL);
		vbar = new Scrollbar(Scrollbar.VERTICAL);
		this.setLayout(new BorderLayout(0,0));
		this.add("Center",canvas);
		this.add("South",hbar);
		this.add("East",vbar);
	}

	// Draw the scribbles that weÕve saved in the Vector
	// the offset_x and offset_y variables specify which portion of
	// the larger (1000x1000) scribble is to be displayed in the 
	// relatively small canvas.  Moving the scrollbars changes these
	// variables, and thus scrolls the picture.  Note that the Canvas
	// component automatically does clipping; we canÕt accidentally
	// draw outside of its borders.
	public void paint(Graphics g) {
		Line L;
		Graphics canvas_g = canvas.getGraphics();
		for (int i=0; i<lines.size(); i++) {
			L = (Line)lines.elementAt(i);
			canvas_g.drawLine(L.x1 - offset_x, L.y1 - offset_y,
				L.x2 - offset_x,L.y2 - offset_y);
		}
	}

	// Handle userÕs mouse scribbles, Draw the scribbles
	// and save them in the vector for later redrawing.
	public boolean mouseDown(Event e,int x,int y)
	{
		last_x = x; last_y = y;
		return true;
	}

	public boolean mouseDrag(Event e, int x, int y)
	{
		Graphics g = canvas.getGraphics();
		g.drawLine(last_x,last_y,x,y);
		lines.addElement(new Line(last_x + offset_x, last_y + offset_y,
			x + offset_x,y + offset_y));
		last_x = x;
		last_y = y;
		return true;
	}

	// Handle mouse up, too, just for symmetry.
	public boolean mouseUp(Event e, int x, int y) { return true; }

	// This method handles the scrollbar events.  It updates the
	// offset_x and offset_y variables that are used by the paint()
	// method, and then calls update(), which clears the canvas and
	// invokes the paint() method to redraw the scribbles.
	public boolean handleEvent(Event e) {
		if (e.target == hbar) {
			switch(e.id) {
			case Event.SCROLL_LINE_UP:
			case Event.SCROLL_LINE_DOWN:
			case Event.SCROLL_PAGE_UP:
			case Event.SCROLL_PAGE_DOWN:
			case Event.SCROLL_ABSOLUTE:
				offset_x = ((Integer)e.arg).intValue(); break;
			}
			this.update(canvas.getGraphics());
			return true;
		}
		else if (e.target == vbar) {
			switch(e.id) {
			case Event.SCROLL_LINE_UP:
			case Event.SCROLL_LINE_DOWN:
			case Event.SCROLL_PAGE_UP:
			case Event.SCROLL_PAGE_DOWN:
			case Event.SCROLL_ABSOLUTE:
				offset_y = ((Integer)e.arg).intValue(); break;
			}
			this.update(canvas.getGraphics());
			return true;
		}

		// If we didn't handle it above, pass it on to the superclass
		// handleEvent routine, which will check its type and call
		// the mouseDown(), mouseDrag(), and other methods.
		return super.handleEvent(e);
	}

	// This method is called when our size is changed.  We need to 
	// know this so we can update the scrollbars
	public synchronized void reshape(int x, int y, int width, int height) {
		// do the real stuff
		super.reshape(x,y,width,height);
		// Update our scrollbar page size
		Dimension hbar_size = hbar.size();
		Dimension vbar_size = vbar.size();
		canvas_width = width - vbar_size.width;
		canvas_height = height - hbar_size.height;
		hbar.setValues(offset_x,canvas_width,0,1000-canvas_width);
		vbar.setValues(offset_y,canvas_height,0,1000-canvas_height);
		hbar.setPageIncrement(canvas_width/2);
		vbar.setPageIncrement(canvas_height/2);
		this.update(canvas.getGraphics());
	}
}

// This class stores the coordinates of one line of the scribble.
class Line {
	public int x1,y1,x2,y2;
	public Line(int x1, int y1, int x2, int y2) {
		this.x1 = x1; this.y1 = y1; this.x2 = x2; this.y2 = y2;
	}
}