PC Online 1997 May/PCO_5_97.ISO/FilesBBS/OS2/RDB084R2.ARJ/RDB084R2.ZIP/ScrollPanel.java

Java Source | 1997-02-10 | 5.4 KB | 205 lines

/*
 * @(#)ScrollPanel.java        0.1 96/01/09  Jesse Hammons
 *
 * Copyright (c) 1996 Jesse Hammons
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Contact author for use policy on software and documentation
 */
// package edu.princeton.jhammons.awt;


import java.awt.Panel;
import java.awt.GridBagLayout;
import java.awt.GridBagConstraints;
import java.awt.Dimension;
import java.awt.Scrollbar;
import java.awt.Image;
import java.awt.Graphics;
import java.awt.Component;
import java.awt.Event;
/**
  * ScrollPanel is a generic Panel with scrollbars.  If a client Component is
  * assigned to a ScrollPanel, The ScrollPanel will set up the scrollbars so
  * that the Component can be scrolled around if the size of the client is
  * larger than the inside of the ScrollPanel.
  *
  * @version 0.1, 09 Jan 1996
  * @author Jesse Hammons
  */
public class ScrollPanel extends Panel {
  RepaintScrollbar horiz, vert;
  Component client;
  int prevx=0, prevy=0;
  boolean first = true;
  GridBagLayout g;
  GridBagConstraints c;
  NoPaintPanel clientPanel;
  Image osimg = null;
  Image biggest = null;
  Dimension bigSize;
  Graphics off;
  Dimension imSize;

  /**
    * Creates a ScrollPanel with no client Component.
    */
  public ScrollPanel() {
    this(null);
  }

  /**
    * Creates a ScrollPanel with the specified client Componenent.
    * @param client the client Component
    */
  public ScrollPanel(Component client) {
    super();
    this.client = client;
    int gap = 0;
    horiz = new RepaintScrollbar(this, Scrollbar.HORIZONTAL);
    vert = new RepaintScrollbar(this, Scrollbar.VERTICAL);
    clientPanel = new NoPaintPanel();
    clientPanel.setLayout(null);

    setLayout(new java.awt.BorderLayout());
    add("West", vert);
    add("South", horiz);
    add("Center", clientPanel);
    setClient(client);
  }

  /**
    * Sets the client of this ScrollPanel to client
    * @param client the client Component to be scrolled
    */
  public void setClient(Component client) {
    this.client = client;
    if (client != null) {
      clientPanel.add("Center",  client);
    }
  }

  /*
   * returns the client of this ScrollPanel
   * @return Component the current client of this ScrollPanel
   */
  public Component getClient() {
    return client;
  }
  /**
    * Paints the ScrollPanel the the Graphics context g.
    * @param g the Graphics context to paint to
    */
  public void paint(Graphics g) {
    Dimension s = size();
    Dimension d;
    int x = horiz.getValue();
    int y = vert.getValue();
    int dx = x - prevx;
    int dy = y - prevy;
    if (client != null) {
      client.move(-x, -y);
      d = client.size();
      if (osimg == null || imSize.width < d.width ||
      imSize.height < d.height) {
    if (biggest != null && bigSize.width >= d.width &&
        bigSize.height >= d.height) {
      osimg = biggest;
      imSize = d;
    } else {
      try {
        osimg = createImage(d.width, d.height);
        off = osimg.getGraphics();
        imSize = d;
        biggest = osimg;
        bigSize = d;
      } catch(Exception e) { dbg(e.toString()); return; }
    }
      }
      if (osimg != null) {
    int vw = vert.size().width;
    int hh = horiz.size().height;
    off.clipRect(vw, 0, size().width-vw, size().height-hh);
    clientPanel.paint(off);
    g.copyArea(prevx, prevy, s.width-dx, s.height-dy, dx, dy);
    g.clipRect(-x, -y, dx, dy);
    g.drawImage(osimg, -x, -y, this);
      }
    }
    prevx = x;
    prevy = y;
  }// paint()
  /**
    * Updates the ScrollPanel using the Graphics context g.
    * equivalent to paint(g).
    * @param g the Graphics context to use
    * @see #paint
    */
  public void update(Graphics g) {
    paint(g);
  }

  private void dbg(String s) {
    System.out.println(s);
  }

  /**
    * Reshapes the ScrollPanel to the specified bounding box, and resets
    * the Scrollbars to the appropriate maximum values, page sizes, etc.
    * @param x    the X coordinate
    * @param y    the Y coordinate
    * @param w  the width of the bounding box
    * @param h    the height of the bounding box
    */
  public void reshape(int x, int y, int w, int h) {
    super.reshape(x, y, w, h);
    Dimension s = size();
    Dimension cs;
    int vpage, hpage;
    if (client != null) {
      cs = client.size();

      vpage = s.height;
      hpage = s.width;
      vert.setValues(vert.getValue(), vpage, 0, cs.height-s.height);
      horiz.setValues(horiz.getValue(), hpage, 0, cs.width-s.width);
    }
  } //reshape()
} // ScrollPanel
class RepaintScrollbar extends Scrollbar {
  Component callBack = null;

  public RepaintScrollbar(Component cb, int orientation) {
    super(orientation);
    callBack = cb;
  }
  public RepaintScrollbar(int orientation) {
    super(orientation);
  }
  public void setCallBack(Component cb) {
    callBack = cb;
  }

  public Component getCallBack() {
    return callBack;
  }
  public boolean handleEvent(Event e) {
    if (callBack != null)
      callBack.repaint();
    return true;
  }
}

class NoPaintPanel extends Panel {
  public NoPaintPanel() {
    super();
  }
  public void paint(Graphics g) {
  }
  public void update(Graphics g) {
  }
}