import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.ScrolledComposite;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Group;
import org.eclipse.swt.widgets.Listener;

/**
 * This class allows vertical mouse wheel scrolling without manual focus
 * It works with ScrolledComposite and sets focus to first control in child Composite
 * of ScrolledComposite with MouseEnter event (only if any of Composite controls not focused yet)
 */
public class EasyScroll {

	/**
	 * @param scrolledComposite Target ScrolledComposite
	 * @param setVerticalIncrementValue Allows setting vertical bar increment value 
	 *            
	 */
	public static final void addEasyMouseWheelScroll(
			final ScrolledComposite scrolledComposite, boolean setVerticalIncrementValue) {
		if (setVerticalIncrementValue)
			scrolledComposite.getVerticalBar().setIncrement(5);

		final ScrollControl scrollControl = new ScrollControl();
		
		// Getting child composite of ScrolledComposite
		Composite childComposite = null;
		if (scrolledComposite.getChildren()[0] instanceof Composite)
			childComposite = (Composite) scrolledComposite.getChildren()[0];		
		
		childComposite.addListener(SWT.MouseEnter, new Listener() {
			public void handleEvent(Event e) {
				if (!scrollControl.isAnotherControlInFocus)
					scrolledComposite.setFocus();
			}
		});

		scrollControl.checkControlsOnScroll(childComposite);
	}

}

/**
 * Need to control scrolling
 */
class ScrollControl {
	boolean isAnotherControlInFocus = false;

	/**
	 * Correcting some bug with wrong focusing
	 * @param composite
	 */
	public void checkControlsOnScroll(Composite composite) {
		for (final Control control : composite.getChildren()) {
			if (control instanceof Composite || control instanceof Group) {
				checkControlsOnScroll((Composite) control);
			} else {
				control.addListener(SWT.MouseDown, new Listener() {
					public void handleEvent(Event e) {
						control.addListener(SWT.MouseExit, new Listener() {
							public void handleEvent(Event e) {
								control.setFocus();
								isAnotherControlInFocus = true;
								control.removeListener(SWT.MouseExit, this);
							}
						});
						control.addListener(SWT.FocusOut, new Listener() {
							public void handleEvent(Event e) {
								isAnotherControlInFocus = false;
							}
						});
					}
				});

			}
		}
	}
}