import java.lang.reflect.Field;

import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.SashForm;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.layout.FormAttachment;
import org.eclipse.swt.layout.FormData;
import org.eclipse.swt.layout.FormLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Sash;
import org.eclipse.swt.widgets.Shell;

public class SashFormTest
{
    // Minimum width of right composite
    final static int MIN_WIDTH = 200;
    
    public static void main (String [] args)
    {
        Display display = new Display ();
        
        final Shell shell = new Shell(display);        
        shell.setLayout(new FormLayout());        
        shell.setText("SashFormTest");
        
        final SashForm sashForm = new SashForm(shell, SWT.HORIZONTAL);
        
        sashForm.setLayout(new FormLayout());
        {
            FormData formData = new FormData();
            formData.top = new FormAttachment(0, 0);            
            formData.bottom = new FormAttachment(100, 0);
            formData.left = new FormAttachment(0, 0);            
            formData.right = new FormAttachment(100, 0);
            sashForm.setLayoutData(formData);
        }
        
        Composite leftComposite = new Composite(sashForm, SWT.NONE);
        leftComposite.setLayout(new FormLayout());
        {
            FormData formData = new FormData();
            formData.top = new FormAttachment(0, 0);            
            formData.bottom = new FormAttachment(100, 0);
            formData.left = new FormAttachment(0, 0);            
            formData.right = new FormAttachment(100, 0);
            leftComposite.setLayoutData(formData);
        }
        leftComposite.setBackground(new Color(shell.getDisplay(), 255, 0, 0));
                
        Composite rightComposite = new Composite(sashForm, SWT.NONE);        
        rightComposite.setLayout(new FormLayout());
        {
            FormData formData = new FormData();
            formData.top = new FormAttachment(0, 0);            
            formData.bottom = new FormAttachment(100, 0);
            formData.left = new FormAttachment(0, 0);            
            formData.right = new FormAttachment(100, 0);
            rightComposite.setLayoutData(formData);
        }
        rightComposite.setBackground(new Color(shell.getDisplay(), 0, 255, 0));
        
        sashForm.setWeights(new int[] {30, 70});
        
        shell.setSize(500, 200);
        
        // Get sashes using reflection
        Sash[] sashes = getSashes(sashForm);
        
        Sash sash = sashes[0];
        
        // Composite on the right side of the sash
        // is always at least 200 px wide, when sash is moved
        sash.addSelectionListener(new SelectionAdapter ()
        {                     
            public void widgetSelected(SelectionEvent event)
            {   
                if (event.x >= shell.getBounds().width - MIN_WIDTH)
                {   
                    int shellWidth = shell.getBounds().width;
                    
                    // Calculate new ratio for sashes weights                    
                    double ratio = (double)shellWidth / Math.abs(shell.getBounds().width - MIN_WIDTH);                                            
                    double percent = 100 / ratio;                  
                    
                    int percentRounded = (int) Math.floor(percent);
                    
                    sashForm.setWeights(new int[]{percentRounded, 100 - percentRounded});                                      
                    sashForm.layout();                      
                }
            }
        });
        
        shell.open ();
        
        while (!shell.isDisposed ())
        {
            if (!display.readAndDispatch())
            {
                display.sleep ();
            }   
        }
        display.dispose ();
    }
    
    private static Sash[] getSashes(SashForm sf)
    {
        Field fields[] = sf.getClass().getDeclaredFields();
        for (int i = 0; i < fields.length; ++i)
        {            
            if (fields[i].getName().equals("sashes"))
            {   
                try
                {   
                    fields[i].setAccessible(true);
                    return (Sash[]) fields[i].get(sf);
                }
                catch (IllegalAccessException e)
                {
                    e.printStackTrace();
                }
            }
        }
        return null;
    }
}