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Alex Rivera
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I am trying to implement position-sensitive zooming inside a JScrollPane . The JScrollPane contains a component with a customized paint that will draw itself inside whatever space it is allocated - so zooming is as easy as using a MouseWheelListener that resizes the inner component as required. But I also want zooming into (or out of) a point to keep that point as central as possible within the resulting zoomed-in (or -out) view (this is what I refer to as 'position-sensitive' zooming), similar to how zooming works in google maps. I am sure this has been done many times before - does anybody know the "right" way to do it under Java Swing?. Would it be better to play with Graphic2D 's transformations instead of using JScrollPanes ? Sample code follows: package test; import java.awt.*; import java.awt.event.*; import java.awt.geom.*; import javax.swing.*; public class FPanel extends javax.swing.JPanel { private Dimension preferredSize = new Dimension(400, 400); private Rectangle2D[] rects = new Rectangle2D[50]; public static void main(String[] args) { JFrame jf = new JFrame("test"); jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); jf.setSize(400, 400); jf.add(new JScrollPane(new FPanel())); jf.setVisible(true); } public FPanel() { // generate rectangles with pseudo-random coords for (int i=0; i<rects.length; i++) { rects[i] = new Rectangle2D.Double( Math.random()*.8, Math.random()*.8, Math.random()*.2, Math.random()*.2); } // mouse listener to detect scrollwheel events addMouseWheelListener(new MouseWheelListener() { public void mouseWheelMoved(MouseWheelEvent e) { updatePreferredSize(e.getWheelRotation(), e.getPoint()); } }); } private void updatePreferredSize(int n, Point p) { double d = (double) n * 1.08; d = (n
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